Co-reporter:Cong Wu, Lu Zhang, Jingjing Liu, Yuan Li, Shuqin Yang, Baozhong Liu, Shumin Han
Journal of Alloys and Compounds 2017 Volume 693() pp:573-581
Publication Date(Web):5 February 2017
DOI:10.1016/j.jallcom.2016.09.206
•Re–Mg–Ni-based alloys with specific proportion of 3R-A2B7 and 2H-A2B7 phases are obtained.•3R-A2B7 phase can transfer into 2H-A2B7 phase by increasing annealing temperature.•3R-A2B7 phase is easier to become amorphous than 2H-A2B7 phase.•The 2H-A2B7 phase is favorable for the improvement of HRD and cyclic stability.A La0.59Nd0.14Mg0.27Ni3.3 alloy with 72 wt% Gd2Co7-type (3R-A2B7) and 28 wt% Ce2Ni7-type (2H-A2B7) phases is prepared by induction melting followed by the annealing at 1148 K. Upon further increasing the annealing temperature to 1248 K, the 3R-A2B7 phase transforms into the 2H-A2B7 phase, forming an alloy with a 97 wt% 2H-A2B7 phase and a 3 wt% 3R-A2B7 phase. Electrochemical measurement shows that the discharge capacity retention of the alloy electrode at the 100th cycle increases from 88.5% to 92.4% as the 2H-A2B7 phase increases from 28 wt% to 97 wt%. Compared to the 3R-A2B7 phase, the 2H-A2B7 phase shows a stronger ability to resist amorphousiation during dehydrogenation and has better structural stability. Therefore, the transformation from the 3R-A2B7 phase to the 2H-A2B7 phase stabilizes the structure of the alloy against amorphization and oxidation, thus improving the cyclic stability of the alloy. Electrochemical pressure–composition (P–C) isotherms contain two discharge plateaus; the higher plateau corresponds to the 3R-A2B7 phase and the lower one is associated with the 2H-A2B7 phase. As the 2H-A2B7 phase increases, the high-rate dischargeability of the alloy electrodes increases from 56.8% to 66.3%.
Co-reporter:Jin Wang, Dandan Ke, Yuan Li, Hongming Zhang, Chunxiao Wang, Xin Zhao, Yongjie Yuan, Shumin Han
Materials Research Bulletin 2017 Volume 95(Volume 95) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.materresbull.2017.07.039
•Three-dimensional graphene oxide is used as catalyst carrier.•3DGO facilitates to form highly dispersed cobalt.•Increasing alkalinity promotes hydrolysis but deteriorates recyclability.Highly dispersed cobalt nanoparticles supported on three-dimensional graphene oxide particles (Co@3DGO) have been successfully prepared by a chemical reduction method. Cobalt presents a dispersive morphology with an average diameter of 20 nm. 3DGO exhibits a stereo lamellar structure with oxygen containing functional groups which increases effective contact area and anchors the cobalt ions. Co carried on 3DGO induces a higher hydrogen generation rate (HGR) in NaBH4 hydrolysis up to 4394 mLH2min−1gcobalt−1 at 298 K. As well as the reaction activation energy is 37 kJ mol−1. Moreover, it was found that recycling performance is inverse to the concentration of NaOH. After five consecutive cycles, the recyclability retention percentage increases from 54% to 70% when the concentration of NaOH was reduced from 0.25 M to 0.05 M.Download high-res image (121KB)Download full-size image
Co-reporter:Jian-zheng Song;Zi-yang Zhao;Xin Zhao
International Journal of Minerals, Metallurgy, and Materials 2017 Volume 24( Issue 10) pp:1183-1191
Publication Date(Web):09 November 2017
DOI:10.1007/s12613-017-1509-z
To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH2 + 10wt%LaH3 + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H2 within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH3 and NbH upon dehydriding of MgH2. By contrast, pure MgH2, an MgH2 + 20wt%LaH3 composite, and an MgH2 + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H2, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH2 + 10wt%LaH3 + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH2. The introduction of LaH3 and NbH was beneficial to the hydrogen storage performance of MgH2.
Co-reporter:Dandan Peng, Yuan Li, Yang Liu, Lu Zhang, Hongming Zhang, Zhenmin Ding, Shumin Han
Journal of Alloys and Compounds 2017 Volume 711(Volume 711) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.jallcom.2017.03.263
•A new lamellar structure of CS was prepared by carbonizing starch.•MgH2@CS was prepared employing Mg powder and CS by hydrogenation.•Significant low onset dehydrogenation temperature of 2LiBH4–MgH2@CS at ca. 150 °C.•Capacity retention rate of 2LiBH4–MgH2@CS reaches 80.5% after five cycles.In this paper, a magnesium hydride-carbon composite (MgH2@CS) was successfully synthesized by hydrogenation, employing magnesium powder and carbonized-starch (CS) as the raw material. The as-prepared MgH2@CS was ball-milled with LiBH4 to constitute a novel Li–Mg–B–H system (2LiBH4–MgH2@CS). Compared with the primary 2LiBH4–MgH2, the 2LiBH4–MgH2@CS composite showed a significant improvement in hydrogen storage performance. Temperature programmed desorption (TPD) analyses show that the 2LiBH4–MgH2@CS composite starts to slowly release hydrogen at about 150 °C, which is 245 °C lower than that of the pure 2LiBH4–MgH2; the final hydrogen desorption capacity reaches 9.3 wt% (LiBH4 with a weight loss of 7.0 wt%). In particular, the capacity retention rate of 2LiBH4–MgH2@CS reaches 80.5% after five reversible de/hydrogenation cycles at 400 °C. Microstructure analyses reveal that the CS with lamellar structure could not only serve as a support for anchoring well-dispersed MgH2 nanoparticles, but could also effectively prevent the aggregation and growth of Mg and magnesium hydrides during de/hydrogenation. Furthermore, the homogeneous nanosized Mg that is generated from decomposition of MgH2@CS has high reactivity, which could accelerate the decomposition of LiBH4 and meanwhile shorten the incubation period of MgB2, thereby greatly enhancing the kinetics of dehydrogenation. These studies provide us with fundamental insights into the design of the Li–Mg–B–H system.
Co-reporter:Wei Zhang, Guang Xu, Lingjuan Chen, Shuyi Pan, ... Shumin Han
International Journal of Hydrogen Energy 2017 Volume 42, Issue 22(Volume 42, Issue 22) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.ijhydene.2017.05.018
•Novel 3D porous FG nano-sheets were synthesized and used to modify LiBH4.•LiBH4–20 wt.% FG composite onset desorption temperature was 120 °C lower than LiBH4.•The composite showed favorably cyclic uptake of 3.23 wt.% H2 at the 4th cycle.•Nano-modifying and functional anion jointly improved LiBH4 hydrogen storage properties.Novel fluorinated graphene (FG) nano-sheets with three-dimensional (3D) porous structure were synthesized by one-pot hydrothermal reaction, and then ball milled with LiBH4 to prepare the hydrogen storage composite material. The LiBH4 with 20 wt.% FG composite begins to release hydrogen at 204 °C, 120 °C lower than that of pure LiBH4. Moreover, it can release 3.45 wt.% hydrogen at 400 °C within 1000 s, which is 2.57 times faster than pure LiBH4. The reversibility of the LiBH4–FG composite also has been enhanced, its absorption capacity still reaches 78.6% of initial hydrogen uptake at the 4th cycle. According to the phase composition analyses, F– can partially substitute the anionic H in LiBH4 or LiH, resulting in a favorable thermodynamic modification. Additionally, the activation energy (Ea) of hydrogen desorption of LiBH4 is reduced from 181.80 kJ/mol to 130.87 kJ/mol. The remarkably improved hydrogen storage performances of LiBH4 are largely attributed to the combined effects of the nano-modifying and the function of F anion of the FG.The hydrogen storage performances of LiBH4 are significantly improved by modifying with novel 3D porous FG nano-sheets.Download high-res image (238KB)Download full-size image
Co-reporter:Yuan Li, Chunxiao Wang, Zhentao Dong, Jin Wang, ... Shumin Han
International Journal of Hydrogen Energy 2017 Volume 42, Issue 30(Volume 42, Issue 30) pp:
Publication Date(Web):27 July 2017
DOI:10.1016/j.ijhydene.2017.06.170
•Ni or Co coating layer forms at alloy surface under existence of N2H4·HSO4.•The coating layer remains at the alloy surface after 100 cycles.•The coating layer improves kinetics behavior of alloy electrodes.In order to make NdMgNi-based alloys more competitive as a candidate of negative electrode materials for nickel/metal hydride batteries, surface coating Ni and Co was performed on Nd0.7Mg0.3Ni3 surface via an electroless plating method. N2H4·H2SO4 in plating solution cleans the alloy surface and makes the coating layer adhere evenly and tightly to the alloy surface. Scanning electron microscopy and transmission electron microscopy images show that honeycomb-like Ni and flake-like Co deposited at the Ni-coated and the Co-coated alloy surface, respectively. The Ni-coating tends to form a denser and more stable surface layer than the Co-coating, and consequently Ni-coating brings more remarkable improvements in electrochemical properties. At a discharge current density of 1800 mA/g, the high rate dischargeability of the electrodes increases from 55.3% (untreated) to 75.7% (Ni-coated) and 73.6% (Co-coated), respectively. As well as, the initial discharge capacity is improved and the discharge capacity degradation is suppressed by surface coating. The improvement of electrochemical properties is ascribed to the higher catalytic activity and the protective function of the coating layers.M2+ = Ni2+ or Co2+. The Ni or Co-coating was formed at surface of the alloy. The coating layer improves electrochemical properties of NdMgNi-based hydrogen storage alloy electrodes.Download high-res image (210KB)Download full-size image
Co-reporter:Dandan Ke, Jin Wang, Hongming Zhang, Yuan Li, ... Shumin Han
International Journal of Hydrogen Energy 2017 Volume 42, Issue 43(Volume 42, Issue 43) pp:
Publication Date(Web):26 October 2017
DOI:10.1016/j.ijhydene.2017.09.121
•Pt–Co NPs are embedded in PG, forming a well dispersed catalyst.•Pt–Co@PG catalyst presents excellent catalytic activity for AB hydrolytic.•Hydrolysis reveal high TOF 461.17 molH2 min−1 molPt−1 and low Ea 32.17 kJ mol−1.•Pt–Co@PG catalyst exhibits good reusability with 81.2% after five runs.Nanoporous graphene (PG) supported Pt–Co bimetallic nanoparticles were prepared and their catalytic activity in hydrogen generation from hydrolysis of NH3·BH3 solution were examined. The synthesized Pt–Co@PG with a loading amount of 30 wt% Pt–Co (atomic ratio 1:9) exhibited a superior TOF value of 461.17 molH2 min−1 molPt−1 and an activation energy (Ea) value of 32.79 kJ mol−1 for NH3·BH3 hydrolysis. This remarkably enhanced activity was ascribed to the charge interaction between Pt–Co NPs and PG support. The defects and holes on PG acting as the anchoring sites for Pt–Co NPs was beneficial for achieving a uniform distribution and a decreased particle size for the NPs. The Pt–Co@PG catalysts also showed a well-established reusability, with 81.2% of their initial catalytic activity after five runs of reactions, demonstrating that they had high durability.
Co-reporter:Zeru Jia, Lu Zhang, Yumeng Zhao, Juan Cao, Yuan Li, Zhentao Dong, Wenfeng Wang, Shumin Han
Journal of Power Sources 2017 Volume 371(Volume 371) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.jpowsour.2017.10.041
•Single-phase PuNi3-, Gd2Co7-, and Pr5Co19-type Nd–Mg–Ni alloys have been obtained.•Self-discharge rate increases with higher [NdNi5]/[NdMgNi4] subunit ratio.•Hydride stability elevates, leading to less reversible self-discharge.•Oxidation/corrosion alleviates, leading to less irreversible self-discharge.•Reversible self-discharge is main factor leading to self-discharge of alloys.To decrease the self-discharge rate of the nickel metal hydride batteries, the self-discharge characteristic and mechanism of single-phase PuNi3-, Gd2Co7-, and Pr5Co19-type Nd–Mg–Ni-based alloys are studied from the perspective of structure in this work. It is found that the self-discharge rate of the alloy electrodes gradually increases with a rising [NdNi5]/[NdMgNi4] subunit ratio. The factors resulting in reversible and irreversible self-discharge are analyzed by electrochemical pressure-composition isotherms, Tafel and SEM measurements. Electrochemical P-C isotherms show that with the increasing [NdNi5]/[NdMgNi4] subunit ratio, the hydrogen desorption plateau pressure sharply elevates, leading to less stability of the corresponding hydride and more reversible self-discharge of the alloys; whereas, corrosion current density of the three alloy electrodes gradually decreases and SEM shows that the amount of hydroxide accumulating on the alloy surface diminishes, indicating the oxidation/corrosion degree alleviates and less irreversible self-discharge with the higher [NdNi5]/[NdMgNi4] ratio. By calculating the proportion of reversible and irreversible self-discharge in total capacity loss, we find that the reversible self-discharge is nearly more than 90% for the three single-phase alloys, while irreversible self-discharge is less than 10%, which illustrates that reversible self-discharge is the dominate factor in self-discharge of Nd–Mg–Ni-based alloys in this study.
Co-reporter:Jingjing Liu, Yongke Yan, Honghui Cheng, Shumin Han, Yifei Lv, Kang Li, Chen Lu
Journal of Power Sources 2017 Volume 351(Volume 351) pp:
Publication Date(Web):31 May 2017
DOI:10.1016/j.jpowsour.2017.03.064
•An A5B19-type single-phase alloy is obtained by a simple step-wise annealing method.•Phase transformation at different annealing stages is studied.•The A5B19 single-phase alloy has excellent structural stability.•Cycle life of the A5B19-type single-phase alloy is three times that of as-cast alloy.•The single-phase alloy exhibits superior kinetics property and high capacity.A (La,Mg)5Ni19 single-phase La0.78Mg0.22Ni3.73 alloy with superior overall electrochemical properties has been prepared by step-wise annealing the as-cast alloy sample. The as-cast alloy is composed of 2H-/3R-type (La,Mg)2Ni7 and (La,Mg)5Ni19 main phases as well as (La,Mg)Ni3 and LaNi5 minor phases. During step-wise annealing process, (La,Mg)Ni3 and LaNi5 minor phases are first consumed to form (La,Mg)2Ni7 and (La,Mg)5Ni19 phases at 800–850 °C. Then the 3R-type (La,Mg)2Ni7 phase transforms to (La,Mg)5Ni19 phase at 900 °C, followed by the transformation of 2H-type (La,Mg)2Ni7 phase to (La,Mg)5Ni19 phase which is completed at 950 °C, producing the alloy with (La,Mg)5Ni19 single phase. The (La,Mg)5Ni19 single-phase alloy possesses good structural stability and strong resistance against pulverization and corrosion/oxidation during repeated charge/discharge cycling, achieving a cycle life of above 400 cycles, nearly three times that of the as-cast alloy. Meanwhile, the (La,Mg)5Ni19-phase alloy electrode exhibits outstanding kinetics performance with a high rate dischargeability of 62.4% at 1500 mA g−1 compared with 51.2% of the as-cast alloy. The (La,Mg)5Ni19 single-phase alloy is considered a promising potential electrode material for high-power and long-lifetime Ni/MH batteries.Download high-res image (268KB)Download full-size image
Co-reporter:Yongjie Yuan, Zhentao Dong, Yuan Li, Lu Zhang, ... Shumin Han
Progress in Natural Science: Materials International 2017 Volume 27, Issue 1(Volume 27, Issue 1) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.pnsc.2017.01.004
LaFeO3-xwt% rGO composite (x = 8, 10, 12) was synthesized by ultraphonic stirring and lyophilization method. SEM, TEM and XRD results show that the perovskite-type LaFeO3 was dispersed by rGO to form special porous structure due to the gauze-shaped wrinkles and folds structure of rGO. It was found that the special porous structure can effectively increase the specific surface area and suppress particle aggregation of LaFeO3, thus improving the electrical conductivity and appreciably enhancing the electrochemical properties of LaFeO3. As compared with LaFeO3, the maximum discharge capacity of the composite (x=10) increased from 209.5 mAh g–1 to 334.6 mAh g–1. The High rate dischargeability at a discharge current density of 1500 mA g–1 (HRD1500) and the capacity retention rate after 100 charge/discharge cycles (S100) of the composite increased by 9% and 17%, respectively.
Co-reporter:Lu Zhang, Yanqiao Ding, Yuan Li, Yumeng Zhao, Xin Zhao, Baozhong Liu and Shumin Han
Journal of Materials Chemistry A 2016 vol. 4(Issue 24) pp:9419-9429
Publication Date(Web):23 May 2016
DOI:10.1039/C6TA02889F
In this paper, we report a new Gd2Co7-type Sm1.6Mg0.4Ni7 compound as a hydrogen storage material with a special hydrogen absorption/desorption process and good hydrogen storage ability. The Gd2Co7-type Sm1.6Mg0.4Ni7 compound absorbs 1.88 wt% H2 within 17 min at 298 K under 10 MPa H2. Meanwhile, the hydrogen absorption speed accelerates to 3.4 min after 20 hydrogenation/dehydrogenation cycles with a 1.44 wt% H2 under 3 MPa H2. Especially, the capacity retention of the compound is 99.3% at the 100th cycle. We found the hydrogen absorption/desorption of the compound undergoes two equilibrium stages, relating to the transformation of H2 between H-solid solution phase and hydride phase with a lower rate and higher enthalpy change at the lower concentration H2 stage, and the direct conversion between H2 and the hydride phase with a higher rate and lower enthalpy change at the higher concentration H2 stage. The two step mode lowers the inner-molecular strain and mismatch in subunit volumes of the compound in hydrogen absorption/desorption, caused by the transformation of H2 at the lower concentration of H2 stage, thus leading to good structural stability and excellent cycling stability. The new insights are expected to provide viable intermetallic materials as high-pressure tank materials for hydrogen storage with nice hydrogen storage properties.
Co-reporter:Yumeng Zhao, Shumin Han, Yuan Li, Jingjing Liu, Lu Zhang, Shuqin Yang, Juan Cao, Zeru Jia
Electrochimica Acta 2016 Volume 215() pp:142-149
Publication Date(Web):10 October 2016
DOI:10.1016/j.electacta.2016.08.089
In this work, we studied the structural phase transformation and electrochemical characteristics of AB4-type La–Mg–Ni-based alloys through zoning annealing of La0.78Mg0.22Ni3.90 polymorphic alloy. The as-cast La0.78Mg0.22Ni3.90 alloy contained two phases of LaNi5 (50.8 wt.%) and (La,Mg)2Ni7 (49.2 wt.%). When annealed at 1173 K, solid LaNi5 phase reacted with a liquid phase from (La,Mg)2Ni7 converting into the (La,Mg)5Ni19 phase. Increasing temperature to 1223 K, the residual LaNi5 phase continued to react with a liquid phase from (La,Mg)5Ni19 forming a new (La,Mg)6Ni24 phase in the alloy. Field-emission scanning electron microscope (FE-SEM) analysis found that the (La,Mg)6Ni24 phase showed diffuse distributing in the alloys and this particular morphology provided plenty of phase boundaries which offered more hydrogen diffusion routes. The high rate dischargeability (HRD) of the alloy electrodes increased with higher (La,Mg)6Ni24 phase abundance. When the abundance of (La,Mg)6Ni24 phase raised to 62.0 wt.%, the HRD of the alloy electrode at a discharge current density of 1500 mA g−1(HRD1500) reached 68.0%. Meanwhile, the surface exchange current density (I0) and hydrogen diffusion coefficient (D) increased to 360.35 mA g−1 and 2.450 × 10−11 cm2 s−1, respectively.
Co-reporter:Jiasheng Wang, Shumin Han, Zhibin Wang, Dandan Ke, Jingjing Liu and Mingzhen Ma
Dalton Transactions 2016 vol. 45(Issue 16) pp:7042-7048
Publication Date(Web):08 Mar 2016
DOI:10.1039/C6DT00045B
The 2LiBH4–MgH2 + 20 wt% BaTiO3 composite was prepared by ball-milling LiBH4, MgH2 and BaTiO3, and the effect of BaTiO3 on the hydrogen storage properties of the composite was investigated. TG-DSC results show that the onset dehydrogenation temperature of the composite is 299 °C, which is 124 °C lower than that of 2LiBH4–MgH2, and the dehydrogenation amount of the composite increases from 6.86 wt% to 7.48 wt% at 500 °C. Kinetic tests show that the dehydrogenation amount of 2LiBH4–MgH2 + 20 wt% BaTiO3 reaches 1.5 wt% within 400 seconds, almost 10 times that of 2LiBH4–MgH2. BaTiO3 reacts with LiBH4 during the dehydrogenation of the composite and generates BaB6 and TiO2. BaB6 is beneficial to lower the stability of LiBH4, while TiO2 has a catalytic effect in improving the hydrogenation/dehydrogenation kinetics of the reaction between Mg and LiBH4.
Co-reporter:Jingjing Liu, Shumin Han, Yuan Li, Lu Zhang, Yumeng Zhao, Shuqin Yang, Baozhong Liu
International Journal of Hydrogen Energy 2016 Volume 41(Issue 44) pp:20261-20275
Publication Date(Web):26 November 2016
DOI:10.1016/j.ijhydene.2016.08.149
•The latest study progress in La–Mg–Ni-based hydrogen storage alloys is reviewed.•Influential rules of preparation and elements on phase transformation are discussed.•Design theory and method of single-phase La–Mg–Ni-based alloys are summarized.•Effects of different alloy phases on the electrochemical performance are analyzed.•Challenges in further improvement of La–Mg–Ni-based alloys are proposed.La–Mg–Ni-based alloys with unique superlattice structures emerged as one of the most promising negative electrode materials for Ni/MH batteries because of their high discharge capacity, energy density and rate capability. They usually contain multiphase structures, and the phase composition plays a significant role in determining their electrochemical performance. This review aims to summarize the latest progresses in studying the phase composition and electrochemical properties of La–Mg–Ni-based alloys, thus to provide guidance for further studies, design and optimization of related negative electrode materials for Ni/MH power batteries. The review starts with the structural characteristics of the superlattice alloy phases in La–Mg–Ni-based alloys. Subsequent emphases are placed on the variations in phase composition of La–Mg–Ni-based alloys induced by different heat treatment procedures and elemental compositions, followed by the next two parts in which the electrochemical characteristics of AB3-, A2B7- and A5B19-type single-phase alloys are summarized, and the effects of phase composition and microstructure on the electrochemical properties are illustrated. Finally, perspectives and challenges in regard of the rational design and electrochemical improvement of La–Mg–Ni-based alloys as high-performance negative electrode materials for Ni/MH batteries are discussed.
Co-reporter:Cong Wu, Shuqin Yang, Yuan Li, Yufei Ma, Lu Zhang, Jingjing Liu, Shumin Han
Journal of Alloys and Compounds 2016 Volume 665() pp:231-239
Publication Date(Web):25 April 2016
DOI:10.1016/j.jallcom.2016.01.039
•Ultra-high pressure technique was applied on La–Mg–Ni-based alloy.•It tends to generate (La,Mg)Ni3 phase during the pressuring process.•Ultra-high pressure produce more crack on the surface of (La,Mg)Ni3 phase.•Ultra-high pressure impedes the hydrogen diffusion resulting in the decrease of HRD.This research highlighted the effects of ultra-high pressure (UHP) technique (1–5 GPa) on microstructural evolution and electrochemical performances of La0.70Mg0.30Ni3.3 alloy. Structure analysis showed that the as-cast alloy consisted of (La,Mg)Ni3, (La,Mg)2Ni7, (La,Mg)5Ni19, LaNi5 and LaMgNi4 phases. For all the UHP treated alloys, (La,Mg)5Ni19 phase disappeared via converting into (La,Mg)2Ni7 and LaNi5 phases. At 1 GPa, LaNi5 phase and LaMgNi4 phase fully transformed into (La,Mg)Ni3 and (La,Mg)2Ni7 phases by the peritectic reactions. However, when the pressure was 3 GPa and 5 GPa, the peritectic reactions were uncompleted for the atom diffusion was hindered, which not only caused the minor residual of LaNi5 and LaMgNi4 phases in the alloys, but also resulted in the increase of (La,Mg)Ni3 phase and the decrease of (La,Mg)2Ni7 phase. Electrochemical measurements displayed that the cyclic stability of alloy electrode treated at 1 GPa increased by 8.7% comparing with that of the as-cast alloy electrode, while the cyclic stability reduced when the pressure increased to 3 GPa and 5 GPa. This indicated that the appropriate UHP treatment was favorable for the improvement of the cycle life of alloy electrode. The high rate dischargeability (HRD) of alloy electrodes gradually decreased with the pressure increasing, which mainly resulted from the decrease of the hydrogen diffusion coefficient.
Co-reporter:Yufei Ma, Yuan Li, Ting Liu, Xin Zhao, Lu Zhang, Shumin Han, Yijing Wang
Journal of Alloys and Compounds 2016 Volume 689() pp:187-191
Publication Date(Web):25 December 2016
DOI:10.1016/j.jallcom.2016.07.313
•Li3BO3 as a novel additive was found to improve hydrogen storage properties of LiBH4.•Li3BO3 lowered the initial desorption temperature of LiBH4 to 105 °C.•LiBH4–Li3BO3 composite showed superiorly reversible 2.8 wt% H2 within 5 cycles.•Li3BO3 provided high-activity sites and catalyzed decomposition/formation of [BH4]−.LiBH4 is considered a promising hydrogen storage material for automotive applications; however, its usage is limited because of unfavorable reversibility and sluggish kinetics. In this paper, we have improved the hydrogen storage properties of LiBH4 by doping with a porous Li3BO3 additive, which was prepared by a solid state synthesis method. The LiBH4–33 wt% Li3BO3 composite was prepared via mechanical milling. The composite exhibited an acceptable hydrogenation/dehydrogenation rate, high hydrogen storage capacity and superior reversibility. The initial dehydrogenation temperature of the composite was 105 °C, which is 205 °C lower than that of the pristine LiBH4, and the hydrogen desorption capacity was 4.12 wt% at 450 °C within 2000 s. The composite maintained its hydrogen absorption capacity of 2.8 wt% with a narrow gap after 5 de/hydrogenation cycles at 400 °C and 5.0 MPa. The Li3BO3 additive clearly enhanced the hydrogen storage properties of LiBH4 and facilitated the decomposition and formation of [BH4]−, thus accelerating de/rehydrogenation of LiBH4. At the same time, Li3BO3 offered numerous porous channels that enhanced hydrogen circulation.
Co-reporter:Jiasheng Wang, Zhibin Wang, Yuan Li, Dandan Ke, Xiaozhu Lin, Shumin Han, Mingzhen Ma
International Journal of Hydrogen Energy 2016 Volume 41(Issue 30) pp:13156-13162
Publication Date(Web):10 August 2016
DOI:10.1016/j.ijhydene.2016.06.061
•A novel nano-sized Ce3S3 was synthesized and doped into LiBH4.•LiBH4 + 20 wt.% Ce3S3 exhibits favorable re-hydrogenation ability at the 4th cycle.•LiBH4 + 20 wt.% Ce3S3 onset dissociation temperature was 80 °C lower than LiBH4.•The generated Li2S and CeB6 have co-catalytic effects to the re-hydrogenation.Ce2S3 with a diameter ca. 100–200 nm was synthesized by a solvothermal method and doped into LiBH4. Ce2S3 reacts with LiBH4, forming Li2S and CeB6 as the dehydrogenated products, and they become active substances in the re-hydrogenation reaction to improve the reversibility of the LiBH4 system. The composite of LiBH4 with 20 wt.% Ce2S3 exhibits favorable re-hydrogenation ability, its hydrogen absorption still reaches 3.6 wt.% at the 4th cycle. After dehydrogenation, The initial dehydrogenation temperature of the LiBH4 + 20 wt.% Ce2S3 composite is decreased to 250 °C, which is 80 °C lower than that of the pristine LiBH4 system. Furthermore, within 3000 s, the LiBH4 + 20 wt.% Ce2S3 composite can release about 4.0 wt.% hydrogen at 400 °C, which is 1.67 times higher than that of the pristine LiBH4. The activation energy (Ea) of dehydrogenation reaction of LiBH4 is reduced from 181.80 kJ/mol to 157.82 kJ/mol.
Co-reporter:Dandan Ke, Yuan Li, Jin Wang, Lu Zhang, Jidong Wang, Xin Zhao, Shuqin Yang, Shumin Han
International Journal of Hydrogen Energy 2016 Volume 41(Issue 4) pp:2564-2574
Publication Date(Web):30 January 2016
DOI:10.1016/j.ijhydene.2015.11.142
•A novel PAMAM dendrimers-encapsulated Ag–Co catalyst is prepared.•Poly(amidoamine) dendrimers benefit AgCo NPs formation and dispersibility.•Catalytic activity of AgCo/PAMAM NPs is largely enhanced on AB hydrolytic reaction.•Initial turnover frequency (TOF) value reaches to 15.84 molH2·min−1·molM−1.•Synergistic effect of PAMAM-encapsulated AgCo on AB hydrolysis reaction is studied.Multifunctional poly(amidoamine) (PAMAM) dendrimers-encapsulated Ag–Co bimetallic nanoparticles (Ag–Co/PAMAM NPs) have been prepared via a facile co-complexation chemical reduction method. By exploiting the well-defined dendritic spatial construction of PAMAM dendrimers as NPs support and capping ligand, the as-synthesized NPs show unconspicuous agglomeration and uniformly distribution with average diameter of 5 nm. The Ag–Co/PAMAM NPs show the composition-dependent catalytic activity in catalytic dehydrogenation of ammonia borane (AB), with NPs in 30 atom.% Ag exhibiting the superior activity and yielding an initial turnover frequency (TOF) as high as 15.84 molH2·min−1·molM−1. Combined with the electro–transfer interaction between Ag and Co, the effective control of the NPs dispersibility and the electro-donating ability of PAMAM dendrimers with amounts of amide and amine groups facilitate the catalytic performances of Ag–Co/PAMAM catalyst on the hydrolysis of AB. The work also includes the kinetic studies on zero-order with respect to substrate concentration and first-order reaction with respect to catalyst concentration, as well as temperature effect to determine the apparent activation energy of the reaction (Ea = 35.66 kJ mol−1). Furthermore, the reusability tests reveal Ag–Co/PAMAM NPs still show good catalytic activity and magnetically reusability in successive runs, which make these dendrimers-stabilized bimetallic nanoparticles promising heterogeneous catalysts in practical application.
Co-reporter:Lu Zhang, Yanqiao Ding, Yumeng Zhao, Wenkai Du, Yuan Li, Shuqin Yang, Shumin Han
International Journal of Hydrogen Energy 2016 Volume 41(Issue 3) pp:1791-1800
Publication Date(Web):21 January 2016
DOI:10.1016/j.ijhydene.2015.12.049
•Single A2B7-type Sm-containing La0.60Sm0.15Mg0.25Ni3.4 alloy was obtained.•Sm element promotes formation of Gd2Co7-type phase, reaching 73.2 wt.%.•Single A2B7-type alloy shows superior HRD1500, achieving 40%.•Cycling stability of single A2B7-type alloy is enhanced to 87.7% at 100th cycle.•Slower inner strain growth during cycling of single alloy ascribes to improved S100.Improvement in cycling stability is a key issue for La–Mg–Ni-based alloys to be widely applied as anode electrode materials of nickel metal hydride batteries. In this paper, we report the phase structure and melioration of cycling stability of a Sm-containing A2B7-type La–Mg–Ni-based alloy. Sm element promotes the Gd2Co7-type phase formation with increasing annealing period, which the Ce5Co19-, CaCu5- and MgCu4Sn-type phases in as-cast La0.60Sm0.15Mg0.25Ni3.4 alloy are successively eliminated as the annealing time increases from 6 to 24 h at 950 °C and forms a single A2B7-type alloy with coexistence of 73.2 wt.% Gd2Co7- and 26.8 wt.% Ce2Ni7-type phases. The single A2B7-type La0.60Sm0.15Mg0.25Ni3.4 alloy is superior in discharge capacity (382 mAh g−1) and high rate dischargeability (40% at a 1500 mA g−1 discharge current density). Especially, the cycling stability of the alloy is enhanced to 87.7% at the 100th cycle. The improved cycling stability of the single A2B7-type alloy is mainly attributed to its slower growth of inner strain during charging/discharging, which improves anti-pulverization/amorphization ability, and drops oxidation degree of the alloy. Therefore, Sm is a positive element in improvement of the cycling stability property of the La–Mg–Ni-based alloys.
Co-reporter:Xiaocui Chen, ;Ruiyao Wang ;Yuan Li
Acta Crystallographica Section C 2016 Volume 72( Issue 1) pp:6-13
Publication Date(Web):
DOI:10.1107/S2053229615022779
Crystal engineering can be described as the understanding of intermolecular interactions in the context of crystal packing and the utilization of such understanding to design new solids with desired physical and chemical properties. Free-energy differences between supramolecular isomers are generally small and minor changes in the crystallization conditions may result in the occurrence of new isomers. The study of supramolecular isomerism will help us to understand the mechanism of crystallization, a very central concept of crystal engineering. Two supramolecular isomers of dichloridobis(1,10-phenanthroline-κ2N,N′)cobalt(II), [CoCl2(C12H8N2)2], i.e. (IA) (orthorhombic) and (IB) (monoclinic), and two supramolecular isomers of dichloridobis(1,10-phenanthroline-κ2N,N′)cobalt(II) N,N-dimethylformamide monosolvate, [CoCl2(C12H8N2)2]·C3H7NO, i.e. (IIA) (orthorhombic) and (IIB) (monoclinic), were synthesized in dimethylformamide (DMF) and structurally characterized. Of these, (IA) and (IIA) have been prepared and structurally characterized previously [Li et al. (2007). Acta Cryst. E63, m1880–m1880; Cai et al. (2008). Acta Cryst. E64, m1328–m1329]. We found that the heating rate is a key factor for the crystallization of (IA) or (IB), while the temperature difference is responsible for the crystallization of (IIA) or (IIB). Based on the crystallization conditions, isomerization behaviour, the KPI (Kitajgorodskij packing index) values and the density data, (IB) and (IIA) are assigned as the thermodynamic and stable kinetic isomers, respectively, while (IA) and (IIB) are assigned as the metastable kinetic products. The 1,10-phenanthroline (phen) ligands interact with each other through offset face-to-face (OFF) π–π stacking in (IB) and (IIB), but by edge-to-face (EF) C—H...π interactions in (IA) and (IIA). Meanwhile, the DMF molecules in (IIB) connect to neighbouring [CoCl2(phen)2] units through two C—H...Cl hydrogen bonds, whereas there are no obvious interactions between DMF molecules and [CoCl2(phen)2] units in (IIA). Since OFF π–π stacking is generally stronger than EF C—H...π interactions for transition-metal complexes with nitrogen-containing aromatic ligands, (IIA) is among the uncommon examples that are stable and densely packed but that do not following Etter's intermolecular interaction hierarchy.
Co-reporter:Lu Zhang, Yuan Li, Xin Zhao, Jingjing Liu, Dandan Ke, Wenkai Du, Shuqin Yang and Shumin Han
Journal of Materials Chemistry A 2015 vol. 3(Issue 26) pp:13679-13690
Publication Date(Web):21 May 2015
DOI:10.1039/C5TA02554K
A Ce2Ni7-type single-phase La0.78Mg0.22Ni3.45 alloy has been prepared by zoning annealing of the as-cast sample. It is found that at temperatures below 890 °C, non-super-stacking CaCu5- and MgCu4Sn-type phases disappear and super-stacking Ce5Co19-, Gd2Co7- and Ce2Ni7-type phases remain. The Ce5Co19-type phase can totally transform into the Ce2Ni7-type phase via a peritectic reaction at temperatures of 890–900 °C. At temperatures of 900–950 °C, the Gd2Co7-type phase melts and decomposes into the Ce5Co19-type phase, and the newly formed Ce5Co19-type phase subsequently reacts to form the Ce2Ni7-type phase. The Ce2Ni7-type single phase remains stable even at higher temperatures of 950–975 °C. The single-phase alloy shows a superior discharge capacity, close to 394 mA h g−1, and high electrochemical cycling stability, which can achieve 413 cycles as its discharge capacity reduces to 60% of the maximum value. We found that the capacity attenuation of the single-phase alloy is mainly due to the loss of active material at the alloy surface caused by oxidization of La and Mg, and the pulverization of the alloy is not severe with 100 charge/discharge cycles. The crystal structure of the single-phase alloy can be preserved well. Oxidation of La occurs prior to that of Mg. La hydroxide grows from nano-structured needles to larger-scaled rods then to unformed lamellar hydroxide, whereas the precipitation of Mg forms as irregular lamellae inlaid with hexagonal flakes.
Co-reporter:Jingjing Liu, Shumin Han, Da Han, Yuan Li, Shuqin Yang, Lu Zhang, Yumeng Zhao
Journal of Power Sources 2015 Volume 287() pp:237-246
Publication Date(Web):1 August 2015
DOI:10.1016/j.jpowsour.2015.04.059
•A2B7-type La–Mg–Ni-based alloys with A5B19-type minor phase are obtained.•Cell volumes of A2B7- and A5B19-type phases decrease with more A5B19-type phase.•A5B19-type phase enhances the structural stability of the alloys during cycling.•A5B19-type phase catalyzes the discharge process of the A2B7-type phase.•HRD and cycle stability are improved by the addition of A5B19-type phase.The A2B7-type lanthanum (La)–magnesium (Mg)–nickel (Ni)-based alloy with single (La,Mg)2Ni7 phase and different amounts of (La,Mg)5Ni19 minor phase was obtained by step-wise sintering. The impact of (La,Mg)5Ni19 phase on the alloy's microstructure and electrochemical performance was subsequently studied. It was found that the average subunit volume in (La,Mg)5Ni19 phase is smaller than that in (La,Mg)2Ni7 phase, resulting in increases of strains inside the alloys and decreases of cell volumes. During battery charge/discharge, the (La,Mg)5Ni19 phase network scattered in the alloys relieves internal stress, alleviates pulverization and oxidation of the alloys, stabilizes the stacking structures against amorphization, and finally improves the cycling stability of the alloys. Furthermore, (La,Mg)5Ni19 phase with higher Ni content desorbs hydrogen ahead of (La,Mg)2Ni7 phase. The reduced hydrogen pressure in (La,Mg)5Ni19 phase can subsequently lead to the fast discharge of (La,Mg)2Ni7 phase, thus making a remarkable improvement in high rate dischargeability at 1500 mA g−1 from 46.2% to 58.9% with increasing (La,Mg)5Ni19 phase abundance from 0 to 37.4 wt.%. Therefore, it is believed that A2B7-type La–Mg–Ni-based alloys with A5B19-type minor phase are promising prototypes for high-power and long-lifetime nickel/metal hydride battery electrode materials.
Co-reporter:Lu Zhang, Wenkai Du, Shumin Han, Yuan Li, Shuqin Yang, Yumeng Zhao, Cong Wu, Hanzhou Mu
Electrochimica Acta 2015 Volume 173() pp:200-208
Publication Date(Web):10 August 2015
DOI:10.1016/j.electacta.2015.05.049
•PuNi3-type single phase La2MgNi9, Pr2MgNi9 and Nd2MgNi9 alloys were obtained.•Mg enters into Pr2 sites of PuNi3 and reaches the maximum solid solubility to 1.0.•Phase transformation occurs to raise the phase with more [A2B4] as increasing Mg.•Pr2MgNi9 alloy exhibits preferable cycling stability and HRD.In this paper, via adjusting Mg content in Pr3−xMgxNi9 (x = 0.45 − 1.2) alloys, a PuNi3-type single-phase Pr2MgNi9 alloy was obtained by powder-sintering method. The solid solubility of Mg in PuNi3-type phase and phase transformation of Pr3−xMgxNi9 (x = 0.45 − 1.2) alloys at 1173 K sintering temperature, as well as hydrogen storage properties of single-phase RE2MgNi9 (RE = La, Pr, Nd) alloys were subsequently studied. We found that when x increased from 0.45 to 1.0, entrance of Mg into Pr2 sites of PuNi3-type phase resulted in a phase transformation from Gd2Co7-type to PuNi3-type, reaching the maximum solid solubility at x = 1.0 with a PuNi3-type single phase at 1173 K. As x further increased to 1.2, an MgCu4Sn-type secondary phase formed. That was the phase transformation occurs to increase the super-stacking phase possessing more [A2B4] slabs with increase of Mg content. Electrochemical results showed that single-phase alloy had good discharge capacity and superior cycling stability. Comparing with PuNi3-type single-phase La2MgNi9 and Nd2MgNi9 alloys, PuNi3-type single-phase Pr2MgNi9 alloy also exhibited preferable cycling stability and high rate dischargeability (HRD), which were 86.3% (at 100 cycles) and 56.7% (at a current density of 1500 mA g−1), respectively.
Co-reporter:Yumeng Zhao, Shumin Han, Yuan Li, Jingjing Liu, Lu Zhang, Shuqin Yang, Dandan Ke
Electrochimica Acta 2015 Volume 152() pp:265-273
Publication Date(Web):10 January 2015
DOI:10.1016/j.electacta.2014.11.137
•Pr5Co19-type single-phase La0.84Mg0.16Ni3.80 alloy was prepared.•The La0.84Mg0.16Ni3.80 alloy shows superior HRD.•Ce2Ni7 or LaNi5 phase was introduced to improve electrochemical properties•Ce2Ni7 phase benefits discharge capacity and cycling stability.•LaNi5 phase enhances HRD.To determine the structure and electrochemical properties of La–Mg–Ni-based Pr5Co19-type super-stacking structure alloys, a La0.84Mg0.16Ni3.80 alloy was designed and synthesized by step-wise powder sintering. X-ray diffraction (XRD) analysis and Rietveld refinement show that the alloy consists of a single Pr5Co19-type phase. Electrochemical studies show that the alloy has a mediocre discharge capacity of 338 mAh g−1 and good cycling stability. High rate dischargeability at 1500 mA g−1(HRD1500) reaches 51.5% and the corresponding discharge capacity remains 174 mAh g−1. To improve overall electrochemical properties of the alloy, especially the discharge capacity, Ce2Ni7-type or LaNi5 secondary phase was introduced into the single-phase alloy by adjusting molar ratio of precursors. When the content of Ce2Ni7-type phase increases from 0 to 40.6 wt.%, the maximum discharge capacity enhances from 338 to 388 mAh g−1 and the discharge capacity retention at the 100th cycle is improved from 77.0% to 85.3%. With the presence of 20.7 wt.% LaNi5 phase in the alloy, the HRD1500 increases to 56% and the surface exchange current density (i0) increases from 275.50 mA g−1 to 354.16 mA g−1.
Co-reporter:Jingjing Liu, Shumin Han, Yuan Li, Shuqin Yang, Xiaocui Chen, Cong Wu, Chunping Ma
Electrochimica Acta 2015 Volume 184() pp:257-263
Publication Date(Web):1 December 2015
DOI:10.1016/j.electacta.2015.10.055
•Pr is found to prefer forming [AB5] subunits to [A2B4] subunits.•Pr substitution for La increases the (La,Mg)5Ni19 phase network.•(La,Mg)5Ni19 network increases anti-pulverization and anti-amorphization resistance.•La0.6Pr0.2Mg0.2Ni3.4Al0.1 alloy shows cycle stability of 90.7% after 100 cycles.Fast capacity degradation is a significant drawback hindering La–Mg–Ni-based alloys from wide application as anode electrode materials of nickel metal hydride batteries. Herein, the effect of Pr element on the phase structure and cycling stability of La0.8−xPrxMg0.2Ni3.4Al0.1 (x = 0, 0.1, 0.2 and 0.3) alloys is investigated. All the alloys contain (La,Mg)2Ni7 and (La,Mg)5Ni19 main phases as well as LaNi5 minor phase. It is found that Pr tends to form [AB5] subunits more than [A2B4] subunits, thus increasing the content of (La,Mg)5Ni19 phase with higher [AB5]/[A2B4] ratio in sacrifice of (La,Mg)2Ni7 phase. The increased (La,Mg)5Ni19 phase network with good structural stability increases the anti-pulverization and anti-amorphization resistance of the alloys. After 100 charge/discharge cycles, part of the superlattice phases in La0.6Mg0.2Ni3.4Al0.1 alloy decomposes into amorphous phase and LaNi5 phase, leading to the decrease in superlattce phase abundance; while little amorphization is observed for La0.6Pr0.2Mg0.2Ni3.4Al0.1 alloy and its phase contents remain almost unchanged. Correspondingly La0.6Pr0.2Mg0.2Ni3.4Al0.1 alloy electrode has a slighter oxidation degree after 100 cycles in alkaline electrolyte and exhibits good electrochemical cycling stability with a discharge capacity of 340 mAh g−1 and a cycling stability of 90.7% at the 100th cycle.
Co-reporter:Yaru Pei, Wenkai Du, Yuan Li, Wenzhuo Shen, Yunchai Wang, Shuqin Yang and Shumin Han
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 27) pp:18185-18192
Publication Date(Web):09 Jun 2015
DOI:10.1039/C5CP02395E
An efficient carbon–polyaniline (PANI)-coated method was applied for perovskite-type oxide LaFeO3 to enhance its high-temperature electrochemical performance. Transmission electron microscopy (TEM) results reveal that LaFeO3 particles are evenly coated with carbon and PANI hybrid layers after carbon–PANI treatment. The carbon layers prevent the nanosized LaFeO3 particles from aggregation and allow the electrolyte to penetrate in every direction inside the particles. The PANI layers also enhance the electrocatalytic activity, facilitating hydrogen protons transferring from the electrolyte to the electrode interface. The cooperation of carbon and PANI hybrid layers results in a significant enhancement of the electrochemical performance at high temperatures. At an elevated temperature (60 °C), the maximum discharge capacity of the LaFeO3 electrodes remarkably increases from 231 mA h g−1 to 402 mA h g−1 and the high rate dischargeability at a discharge current density of 1500 mA g−1 (HRD1500) increases from 22.7% to 44.3%. Moreover, the hybrid layers mitigate the corrosion of LaFeO3 electrodes by reducing the loss of active materials in the alkaline electrolyte, leading to increase in the capacity retention rate from 67.1% to 77.6% after 100 cycles (S100).
Co-reporter:Dandan Ke, Yang Tao, Yuan Li, Xin Zhao, Lu Zhang, Jidong Wang, Shumin Han
International Journal of Hydrogen Energy 2015 Volume 40(Issue 23) pp:7308-7317
Publication Date(Web):22 June 2015
DOI:10.1016/j.ijhydene.2015.04.041
•Mo-modified Co–B catalyst decreases particle size and enlarges specific surface area.•Catalytic activity of Mo-modified Co–B is largely enhanced on NaBH4 hydrolysis.•The maximum hydrogen generation rate reaches to 4200mLH2min−1gcatalyst−1.•Induced Mo facilitates dissociation of water and promotes whole hydrolysis reaction.Mo-modified Co–B nanoparticles have been prepared by the co-deposition chemical reduction method. The relationship between microstructure, catalytic activity and kinetics performance for H2 generation by hydrolysis of alkaline NaBH4 is studied. Compared to unmodified Co–B nanoparticles, the synthesized Co–Mo–B nanoparticles exhibit smaller particle size with average diameter of 30 nm, more uniform distribution with unconspicuous agglomeration, and larger specific surface area. The induced Mo in the Co–Mo–B catalyst exists as molybdenum oxides, which facilitates the dissociation of water due to weakening of the bond strength of the H–OH bond and promote the hydrolysis reaction of NaBH4. As a result, the maximum hydrogen generation rate and the activation energy of the hydrolysis reaction catalyzed by Mo-modified Co–B catalyst reach to 4200mLH2min−1gcatalyst−1 and 43.7 kJ mol−1, respectively, which are superior to those of the Co–B catalyst. Kinetic studies show that, in low concentration of NaBH4, first-order reaction is observed with respect to NaBH4 concentration, indicating that surface adsorption of BH4− is the rate-limiting step. At high NaBH4 concentration, hydrolysis reaction is zero-order, and the hydrolysis rate depends on surface reaction of adsorbed molecules.
Co-reporter:Yuan Li, Yang Tao, Dandan Ke, Yufei Ma, Shumin Han
Applied Surface Science 2015 Volume 357(Part B) pp:1714-1719
Publication Date(Web):1 December 2015
DOI:10.1016/j.apsusc.2015.09.220
Highlights
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The Co–Ni composite coating was prepared by electroplating.
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The alloy treated at 10 mA/cm2 has superior kinetic performances.
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The Co–Ni layer accelerates the charge transfer rate on the surface of the alloy.
Co-reporter:Lu Zhang, Jinding Wang, Wenkai Du, Yanqiao Ding, Yuan Li, Shuqin Yang, Shumin Han, Yanping Fan
Journal of Alloys and Compounds 2015 Volume 653() pp:498-505
Publication Date(Web):25 December 2015
DOI:10.1016/j.jallcom.2015.09.049
•Increase of Mg content in Nd1−xMgxNi3 cause phase transformations.•The maximum solid solubility of Mg in PuNi3-type (Nd,Mg)Ni3 phase is 0.36 at 1183 K.•Single-phase Nd0.64Mg0.36Ni3 alloy exhibits excellent HRD1800 of 55.7%.•Single-phase Nd0.64Mg0.36Ni3 alloy has superior S100 of 84.5%.•More or less than Mg maximum solid solubility damage the electrochemical properties.In this paper, Nd1−xMgxNi3 (x = 0.10–0.50) alloys as anode electrode materials of nickel metal hydride batteries were prepared by the powder sintering method. The solid solubility of Mg and electrochemical properties of the Nd1−xMgxNi3 (x = 0.10–0.50) alloys were studied. It is found that when x increases from 0.1 to 0.36, the multiphase structure with Ce2Ni7-, PuNi3- and MgCu4Sn-type phases of the alloy changes to PuNi3-type single-phase structure. As x further increases to 0.5, the extra Mg can not further enter into the PuNi3-type structure and forms an MgNi2 secondary phase. It indicates that the maximum solid solubility of Mg in the PuNi3-type (Nd,Mg)Ni3 phase is 0.36 at 1183 K. Electrochemical studies show the PuNi3-type single-phase Nd0.64Mg0.36Ni3 alloy exhibits good discharge capacity, close to 341 mAh g−1, and superior high rate dischargeability, which remains 151 mAh g−1 at a current density of 1800 mA g−1, respectively. Especially, the single-phase alloy exhibits excellent cycling property, which 288 mAh g−1 retained after cycling 100 cycles. The content of Mg is a key factor that affects the phase structure and electrochemical properties for Nd–Mg–Ni-based alloy. Less than or more than the maximum solid solubility value of Mg are disadvantageous to the cycling stability of the alloy due to the formation of impurity phase in the alloys.
Co-reporter:Jingjing Liu, Shumin Han, Yuan Li, Xin Zhao, Shuqin Yang, Yumeng Zhao
International Journal of Hydrogen Energy 2015 Volume 40(Issue 2) pp:1116-1127
Publication Date(Web):12 January 2015
DOI:10.1016/j.ijhydene.2014.11.024
•Cooperative effect of Sm and Mg on A-site is meaningful but scarcely reported.•Super-stacking phase abundance is increased and crystal grains are refined.•Cycling stability and HRD is remarkably improved.•Grain refinement and stacking phase increase contribute to good properties.The cooperative effects of Sm and Mg on the electrochemical properties of La0.85−x(Sm0.75Mg0.25)xMg0.15Ni3.65 (x = 0, 0.1, 0.15, 0.2, 0.25) alloys were investigated. It was found that the alloys mainly contained (La,Mg)2Ni7, (La,Mg)5Ni19 and LaNi5 phases. Partial replacement of Sm and Mg for La increased the total abundance of (La,Mg)2Ni7 and (La,Mg)5Ni19 super-stacking phases, refined crystal grains and decreased cell volumes. It was proved that Mg contributed to increasing the total abundance of super-stacking phases so that the discharge capacity and high rate dischargeability (HRD) were enhanced. Sm was favorable to the refinement of crystal grains, which contributed to better HRD and cycling stability. The joint effects of Sm and Mg in improving the overall electrochemical properties of the alloy electrodes were remarkable. The electrochemical cycle life for the alloy with x = 0.20 reached 280 cycles, more than two times that of the pristine alloy. Meanwhile the HRD1500 was increased by 12.3% and the maximum discharge capacity was also improved.
Co-reporter:Yaru Pei, Yuan Li, Jerry Yinghui Che, Wenzhuo Shen, Yunchai Wang, Shuqin Yang, Shumin Han
International Journal of Hydrogen Energy 2015 Volume 40(Issue 28) pp:8742-8749
Publication Date(Web):27 July 2015
DOI:10.1016/j.ijhydene.2015.05.047
•Carbon-coated LaFeO3 materials were prepared by PANI pyrolysis.•PANI was formed on LaFeO3 surface uniformly by chemical deposition.•High-temperature electrochemical performance was improved due to carbon coatings.•The carbon layers enhanced the electrocatalytic activity of LaFeO3.•The carbon coatings hindered the LaFeO3 particles from aggregating into stacks.To further improve the high-temperature electrochemical performance of perovskite-type oxides, the LaFeO3 carbon-coated composites used as the negative materials for MH-Ni batteries were obtained using the polyaniline (PANI) pyrolysis method. Transmission electron microscopy (TEM) results revealed that LaFeO3 particles were evenly coated with carbon layers, forming a core–shell structure. The carbon layers could enhance the conductivity and electrocatalytic activity, speeding up hydrogen protons transferring from electrolyte to electrode interface. Furthermore, the carbon coatings hindered the LaFeO3 particles from aggregating into stacks and reduced the corrosion of the LaFeO3 electrodes. At an elevated temperature (60 °C), owing to the carbon coatings, the maximum discharge capacity of the LaFeO3 electrodes remarkably increased from 211 mAh g−1 to 358 mAh g−1, and charge retention (CR) increased from 85.4% to 94.6%. Also, the high rate dischargeability at a discharge current density of 1500 mA g−1 (HRD1500) increased from 21.0% to 37.6%, and the capacity retention rate after 100 cycles (S100) increased from 63.0% to 70.9%.
Co-reporter:Jidong Wang, Kehong Guo, Dandan Ke, Shumin Han
Chemical Physics Letters 2015 Volume 618() pp:11-13
Publication Date(Web):2 January 2015
DOI:10.1016/j.cplett.2014.10.059
•CdS quantum dots were synthesized in ODE/glycerol interfaces at 140, 160 and 180 °C.•The monodisperse CdS quantum dots were synthesized via a one-pot route.•The growth mechanism of CdS quantum dots in ODE/glycerol interfaces was described.The present letter reports a facile synthetic strategy in octadecene(ODE)/glycerol interfaces to prepare CdS quantum dots (QDs) with bright bandgap emission. In this synthesis, the precursors were not synthesized as a preceding step, but all chemicals were reacted simultaneously in a one-pot reaction. The monodispersed CdS QDs were synthesized in ODE/glycerol interfaces at 140, 160 and 180 °C, respectively. The thermodynamic equilibrium was proposed to explain the growth mechanism of CdS QDs in the ODE/glycerol interfaces.The monodisperse CdS quantum dots were synthesized in ODE/glycerol interfaces via one-pot route.
Co-reporter:Zhiping LIU, Shuqin YANG, Yuan LI, Mingzhen MA, Shumin HAN
Journal of Rare Earths 2015 Volume 33(Issue 4) pp:397-402
Publication Date(Web):April 2015
DOI:10.1016/S1002-0721(14)60432-4
Yttrium (Y) has been used as the partial substitution element for lanthanum (La) to improve the electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys. La0.80–xYxMg0.20Ni2.85Mn0.10Co0.55Al0.10 (x=0.00, 0.05 and 0.10) alloys were prepared by the inductive melting technique. The alloys were composed of LaNi5 and (La,Mg)2Ni7 phases, the introduction of Y promoted the formation of (La,Mg)2Ni7 phase, and thus the Y-substituted alloy electrodes exhibited higher discharge capacities. Y substitution was also found to be effective to improve the discharge kinetics of the alloy electrodes. When the Y content x increased from 0.00 to 0.10, the high-rate dischargeability of the alloy electrodes at a discharge current density of 1800 mA/g (HRD1800) increased from 23.6% to 39.7% at room temperature. In addition, the measured HRD1800 showed a linear dependence on both the exchange current density and the hydrogen diffusion coefficient at different temperatures, respectively.HRD of La0.80–xYxMg0.20 Ni2.85Mn0.10Co0.55Al0.10 alloy electrodes at 298 K
Co-reporter:Xiaocui Chen;Yue Wang, ;Yongju Wei ;Ruiyao Wang
Acta Crystallographica Section C 2015 Volume 71( Issue 5) pp:357-362
Publication Date(Web):
DOI:10.1107/S2053229615006336
4,4′-Bipyridine-1,1′-diium (H2bipy) acetylenedicarboxylate, C10H12N22+·C4O42−, (1), is a new member of a family of related structures with similar unit-cell parameters. The structures in this family reported previously [Chen et al. (2012). CrystEngComm, 14, 6400–6403] are (H2bipy)[Cu(ox)2] (ox is oxalate), (2), (H2bipy)[NaH(ox)2], (3), and (H2bipy)[H2(ox)2], (4). Compound (1) has a one-dimensional structure, in which H2bipy2+ cations and acetylenedicarboxylate (ADC2−) anions are linked through a typical supramolecular synthon, i.e.R22(7), and form linear `–cation–anion–' ribbons. Through an array of nonclassical C—H...O hydrogen bonds, adjacent ribbons interact to give two-dimensional sheets. These sheets stack to form a layered structure viaπ–π interactions between the H2bipy2+ cations of neighbouring layers. The supramolecular isostructurality of compounds (1)–(4) is ascribed to the synergistic effect of multiple interactions in these structures. The balanced strong and weak intermolecular interactions stabilizing this structure type include strong charge-assisted N—H...O hydrogen bonds, C—H...O contacts and π–π interactions.
Co-reporter:Xin Zhao;Shu-min Han;Yuan Li
International Journal of Minerals, Metallurgy, and Materials 2015 Volume 22( Issue 4) pp:423-428
Publication Date(Web):2015 April
DOI:10.1007/s12613-015-1089-8
A composite of LiBH4-Mg2NiH4 doped with 10wt% CeH2.29 was prepared by ball milling followed by dynamic interspace vacuum treatment at 573 K. The introduction of CeH2.29 caused a transformation in the morphology of Mg from complex spongy and lamellar to uniformly spongy, resulting in refined particle size and abundant H diffusion pathways. This LiBH4-Mg2NiH4 + 10wt% CeH2.29 composite exhibited excellent hydrogen storage properties. The starting temperature of rapid H absorption decreased to 375 K in the doped composite from 452 K for the unmodified material, and the onset decomposition temperature of its hydride was reduced from 536 K to 517 K. In addition, the time required for a hydrogen release of 1.5wt% (at 598 K) was 87 s less than that of the un-doped composite.
Co-reporter:Yunchai Wang;Yuan Li;Wenzhuo Shen;Yaru Pei
Journal of Solid State Electrochemistry 2015 Volume 19( Issue 5) pp:1419-1425
Publication Date(Web):2015 May
DOI:10.1007/s10008-015-2755-5
In order to improve the electrochemical kinetics of La–Mg–Ni-based alloy, the chemical modification of polypyrrole (PPy) doped with sodium sulfate (Na2SO4) has been applied on the surface of the La0.80 Mg0.20Ni2.70Mn0.10Co0.55Al0.10 alloy particles. SEM, TEM, and FT-IR results indicate that the spongy nano-PPy successfully forms on the surface of the alloy particles and that the PPy nanoparticles distribute uniformly. Owing to the nano-PPy, which possesses excellent electrochemical redox reversibility, electrocatalytic activity, and high conductivity, electrochemical kinetics of the alloy electrode is remarkably ameliorated. The high-rate dischargeability (HRD) of the treated alloy electrode at 1800 mA g−1 reaches two times of that for the bare alloy, meanwhile the discharge voltages increase obviously. The charge transfer resistance (Rct) of treated alloy electrode markedly decreases; the limiting current density (IL) and the hydrogen diffusion coefficient (D) increase.
Co-reporter:Jiasheng Wang 王家盛;Wei Zhang;Ying Cheng
Journal of Wuhan University of Technology-Mater. Sci. Ed. 2015 Volume 30( Issue 4) pp:670-673
Publication Date(Web):2015 August
DOI:10.1007/s11595-015-1209-3
The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH2- WS2 composites were investigated. The TPD (Temperature-Programmed-Desorption) curves showed that the onset dehydrogenation temperature of the MgH2 + 20wt% WS2 composite was 615 K, 58 K lower than that of the pristine MgH2. The kinetic measurements showed that within 21 min, the MgH2 + 20wt% WS2 composite could absorb 2.818wt% at 423 K, and release 4.244 wt% of hydrogen at 623 K, while the hydriding/dehydriding capacity of MgH2 reached only 0.979wt% and 2.319wt% respectively under identical conditions. The improvement of hydrogenation/dehydrogenation performances for the composite was attributed to the cocatalytic effect between the new phases W and MgS which formed during the ball-milling process.
Co-reporter:Lu Zhang, Junling Zhang, Shumin Han, Yuan Li, Shuqin Yang, Jingjing Liu
Intermetallics 2015 Volume 58() pp:65-70
Publication Date(Web):March 2015
DOI:10.1016/j.intermet.2014.11.009
•Rising annealing temperature increases La3MgNi14 mass via phase transformations.•LaNi5 and LaMgNi4 phases can be eliminated at lower temperature.•La3MgNi14 phase benefits discharge capacity.•La4MgNi19 phase enhances high rate dischargeability (HRD).In this study, phase transformation and electrochemical properties of super-stacking La0.70Mg0.30Ni3.3 alloys obtained by annealing the induction melting samples were systematically studied. XRD and Rietveld refinement results show that the as-cast alloy consists of LaNi5, La4MgNi19, La3MgNi14, La2MgNi9 and LaMgNi4 phases, and the gradual rising annealing temperature effectively increases La3MgNi14 phase abundance via phase transformations. At 1123 K, LaNi5 and LaMgNi4 are eliminated, transforming to super-stacking phases. Further increase the temperature to 1173 K, partial La4MgNi19 and La2MgNi9 phases transform to La3MgNi14 phase and La4MgNi19 phase is depleted completely at 1223 K, resulting in La3MgNi14 as the main phase and La2MgNi9 as the surplus phase. Electrochemical results show that increasing abundance of La3MgNi14 phase makes a significant improvement on the discharge capacity of the alloy electrode, enhancing from 370 to 401 mAh g−1. And ascribing to the formation of La4MgNi19 phase, the high rate dischargeability (HRD1800) of the alloy electrode is ameliorated by 10%. Based on the phase transformation, purposeful controlling the alloy phase composition by annealing could efficiently improve the electrochemical properties of the super-stacking metal hydride alloys.
Co-reporter:Lu Zhang, Shumin Han, Da Han, Yuan Li, Xin Zhao, Jingjing Liu
Journal of Power Sources 2014 Volume 268() pp:575-583
Publication Date(Web):5 December 2014
DOI:10.1016/j.jpowsour.2014.06.093
•Ce2Ni7-type single phase La1.6Mg0.4Ni7 alloy is obtained by annealing treatment.•Cell volume change rate of [La1.22Mg0.78Ni4] is larger than of [LaNi5] (I and II).•Ce2Ni7-type phase decomposes into amorphous La and Mg, nano Ni and LaNi5.•Phase decomposition contributes to decrease of discharge capacity.•Single phase alloy electrode has superior discharge capacity and cycling stability.The Ce2Ni7-type (hexagonal, 2H) single phase La1.6Mg0.4Ni7 alloy has been obtained by annealing the induction melting as-cast sample at 1223 K for 12 h. The relationship between phase structural stability and volume change rate of the three kinds of slabs in Ce2Ni7-type structure is studied. It is found that the volume change rate of Mg-containing [La1.22Mg0.78Ni4] slab after hydrogenation/dehydrogenation is larger than that of [LaNi5] I (outer) and [LaNi5] II (inner) slabs, and the consecutive cell volume change of [La1.22Mg0.78Ni4] slab ultimately results in the decomposition of Ce2Ni7-type phase La1.6Mg0.4Ni7 to amorphous La and Mg phases, nanocrystalline Ni, and CaCu5-type LaNi5 phases, as well as the reduction of electrochemical discharge capacity. Electrochemical studies show that the single phase alloy electrode possesses good discharge capacity (400 mAh g−1) and cycling stability (84.2% after 100 cycles). The improvement in phase structure stability and the cycling stability of the superlattice structure alloys can be achieved by inhibiting the significant volume change of Mg-containing slabs during hydrogenation/dehydrogenation.
Co-reporter:Yuan Li, Yang Tao, Dandan Ke, Shuqin Yang, Shumin Han
Journal of Alloys and Compounds 2014 Volume 615() pp:91-95
Publication Date(Web):5 December 2014
DOI:10.1016/j.jallcom.2014.06.112
•We synthesized nano-Mo–Ni particles by a facile method.•The particles improve charge transfer rate at surface of metal hydride electrode.•HRD of electrodes with Mo–Ni particles increases remarkably.A simple method was developed to synthesize Mo–Ni compounds using a chemical reduction method. The compound was then added to La–Mg–Ni-based alloy electrodes in order to improve the electrochemical kinetics of the electrodes. Scanning electron microscopy and transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed that the as-synthesized compound consisted of nanoparticles with a chemical composition of MoNi2.5. X-ray diffraction analysis revealed that the compound mainly consisted of a MoNi3 and a Ni phase. The Mo–Ni particles were added to the La–Mg–Ni-based alloy electrode material and uniformly distributed on the alloy surface. An improvement in initial discharge capacity and high rate dischargeability (HRD) could be observed, as well as an enhancement of cycle stability. At 1500 mA/g the HRD increased by 10.2%, and the initial discharge capacity increased from 286 mA h/g to 307 mA h/g. After adding the particles to the alloy, the Mo–Ni particles showed a high electro-catalytic activity due to a charge transfer reaction on the alloy surface, thereby decreasing the charge transfer resistance and increasing the exchange current density. Consequently, the kinetics of the electrode reaction was significantly improved due to an enhancement of the electro-catalytic activity.
Co-reporter:Jinding Wang, Shumin Han, Yuan Li, Jingjing Liu, Linda Che, Lu Zhang, Junling Zhang
Journal of Alloys and Compounds 2014 Volume 582() pp:552-557
Publication Date(Web):5 January 2014
DOI:10.1016/j.jallcom.2013.08.099
•Gd2Co7 phase abundance increases with Nd substitution dramatically.•Nd substitution results in the depletion of the minor CaCu5-type phase.•The equilibrium plateau is elevated and broadened with Nd substitution.An investigation of the phase formation mechanism and electrochemical properties of the La0.75−xNdxMg0.25Ni3.3 (x = 0, 0.15) alloys has been conducted in this paper. As explored by Rietveld analysis of the XRD data, the La0.75Mg0.25Ni3.3 alloy is composed of Ce2Ni7-type and Gd2Co7-type phases accompanied by minor CaCu5-type phase. The partial substitution Nd for La benefits the formation of Gd2Co7-type phase, indicating that the atoms with smaller radius favor the formation of the Gd2Co7-type phase. However, CaCu5-type phase disappears with Nd substitution. Because part of the replaced La atoms transform into [A2B4] subunits with the Ni atoms, and the formed [A2B4] subunits crystallize with [AB5] subunits to produce A2B7-type phase, resulting in the depletion of the minor CaCu5-type phase. The electrochemical P–C isotherms present that the La0.60Nd0.15Mg0.25Ni3.3 alloy only containing A2B7-type phase has one single plateau while the La0.75Mg0.25Ni3.3 alloy which contains minor LaNi5 phase has two plateaus. It is beneficial for the elevation of equilibrium plateau pressure ascribing to the contraction in cell volumes by Nd substitution. Electrochemical measurements show that the substitution of La by Nd improves the discharge capacity and the high rate dischargeability owing to the increase of A2B7-type phase abundance.
Co-reporter:Xilin ZHU, Shumin HAN, Xin ZHAO, Yuan LI, Baozhong LIU
Journal of Rare Earths 2014 Volume 32(Issue 5) pp:429-433
Publication Date(Web):May 2014
DOI:10.1016/S1002-0721(14)60089-2
Hydrogen storage properties of 2LiNH2-MgH2 system were improved by adding lanthanum hydride (LaH3), and the role of LaH3 in hydrogen sorption process of Li-Mg-N-H system was investigated. Temperature programmed sorption results showed that the addition of lanthanum hydride reduced the dehydriding/hydriding onset temperature of 2LiNH2-MgH2 system by at least 15 K. Moreover, A 0.053 wt.%/min average rate was determined for the hydrogen desorption of 2LiNH2-MgH2-0.05LaH3 composite, while it was only 0.035 wt.%/min for 2LiNH2-MgH2 system. Hydrogen absorption capacity increased from 1.62 wt.% to 2.12 wt.% within 200 min by adding LaH3 into 2LiNH2-MgH2 system at 383 K. In the dehydrogenation of 2LiNH2-MgH2-0.05LaH3 composite, LaH2 transferred to LaN phase, which reversed to LaH2 in the following hydrogen adsorption process. The reversible reaction of LaH2 effectively promoted the hydrogen sorption of Li-Mg-N-H system. Moreover, the homogenous distribution of fine La hydride was favorable to improving effect of lanthanum hydride.XRD patterns of 2LiNH2-MgH2-0.05LaH3 system after dehydrogenation at different temperatures
Co-reporter:Jingjing Liu, Shumin Han, Yuan Li, Yifei Lv, Shuqin Yang, Junling Zhang, Jinding Wang
Electrochimica Acta 2013 Volume 111() pp:18-24
Publication Date(Web):30 November 2013
DOI:10.1016/j.electacta.2013.07.227
•A novel high-pressure sintering method was used to prepare La–Mg–Ni-based alloys.•Phase composition and electrochemical property are related to sintering pressure.•Increase in sintering pressure promotes formation of Ce2Ni7-type phase.•The alloy sintered at 2 GPa shows optimum electrochemical and kinetic properties.A novel method high-pressure sintering was applied to prepare La0.25Mg0.75Ni3.5 alloy as negative electrode material for nickel/metal hydride battery. The phase structures, electrochemical performance and electrochemical kinetics of the alloys sintered with various pressures have been investigated. When sintered within 1.5–2.5 GPa, the alloys have Ce2Ni7-type and Pr5Co19-type main phases and LaNi5 minor phase. Pressurizing promotes the formation of Ce2Ni7-type phase with higher crystalline density. But when the sintering pressure reaches 4 GPa, the atomic diffusion is hindered, leading to the rise of LaNi5 phase, appearance of MgNi2 phase, and decrease of Ce2Ni7-type and Pr5Co19-type phases. Electrochemical measurements show that when the sintering pressure changes from 1.5 to 4 GPa, the maximum discharge capacity first increases then decreases. The alloy electrode sintered at 2 GPa shows superior high rate dischargeability and the gentlest capacity decrease with increasing discharge current density. Furthermore, kinetic study demonstrates that the reaction of alloy electrodes is controlled by charge-transfer step. Cycling stability is deteriorated as the sintering pressure increases due to higher expansion ratio of the cell volume and denser structures of the alloy.
Co-reporter:Lu Zhang, Shumin Han, Yuan Li, Jingjing Liu, Junling Zhang, Jinding Wang, Shuqin Yang
International Journal of Hydrogen Energy 2013 Volume 38(Issue 25) pp:10431-10437
Publication Date(Web):21 August 2013
DOI:10.1016/j.ijhydene.2013.05.129
•La–Mg–Ni-based alloys with specific phase composition were prepared.•LaNi5 reacts with LaMgNi4, generating (La,Mg)Ni3 and (La,Mg)2Ni7 phases.•Alloy with (La,Mg)2Ni7 main and (La,Mg)Ni3 minor phases has better stability.•Alloy with (La,Mg)2Ni7 main and LaNi5 minor phases has better kinetics.Starting from two precursors LaNi5 and LaMgNi4, four alloys with different phase structures were prepared by powder sintering technique. The results suggest that LaNi5 phase can consecutively react with LaMgNi4 phase generating (La,Mg)Ni3 and (La,Mg)2Ni7 phases, and the mole ratio of precursors LaNi5/LaMgNi4 (x) affects the phase structures of alloys significantly. XRD and Rietveld refinement results demonstrate that the alloys mainly consist of (La,Mg)Ni3 and (La,Mg)2Ni7 phases (x = 0.28 and 0.59) or (La,Mg)2Ni7 and LaNi5 phases (x = 0.87 and 1.47). When x increases from 0.28 to 0.59, the main phase becomes (La,Mg)2Ni7 phase with Ce2Ni7- and Gd2Co7-type from PuNi3-type (La,Mg)Ni3 phase. As x rises from 0.59 to 0.87, the secondary phase (La,Mg)Ni3 disappears with CaCu5-type LaNi5 phase emerging. When x grows from 0.87 to 1.47, the content of LaNi5 phase increases from 17.88 to 60.72 wt.% with (La,Mg)2Ni7 phase content declining. The alloy with (La,Mg)2Ni7 as the main phase and (La,Mg)Ni3 as the secondary phase is conducive to cyclic stability and the alloy with (La,Mg)2Ni7 as the main phase and LaNi5 as the secondary phase is beneficial to the high-rate dischargeability.
Co-reporter:Jiasheng Wang, Shumin Han, Wei Zhang, Dan Liang, Yuan Li, Xin Zhao, Ruibing Wang
International Journal of Hydrogen Energy 2013 Volume 38(Issue 34) pp:14631-14637
Publication Date(Web):13 November 2013
DOI:10.1016/j.ijhydene.2013.08.129
•MoS2 addition lowers the onset dehydrogenation temperature by 113 °C.•The total dehydrogenating amount increases from 9.26 wt.% to 10.47 wt.% at 500 °C.•Li2S and MoB2 act as catalysts and improve the hydrogen storage properties.•The addition of MoS2 accelerates the dehydrogenation rate.A 2LiBH4–MgH2–MoS2 composite was prepared by solid-state ball milling, and the effects of MoS2 as an additive on the hydrogen storage properties of 2LiBH4–MgH2 system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS2, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH4–MgH2 system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B2H6 and H2S are released. Furthermore, MoS2 improves the dehydrogenation kinetics, and lowers the activation energy (Ea) 34.49 kJ mol−1 of the dehydrogenation reaction between Mg and LiBH4 to a value lower than that of the pristine 2LiBH4–MgH2 sample. According to the XRD test, Li2S and MoB2 are formed by the reaction between LiBH4 and MoS2, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH4–MgH2 system.
Co-reporter:Yanhong Jia, Shumin Han, Wei Zhang, Xin Zhao, Pengfei Sun, Yanqing Liu, He Shi, Jiasheng Wang
International Journal of Hydrogen Energy 2013 Volume 38(Issue 5) pp:2352-2356
Publication Date(Web):19 February 2013
DOI:10.1016/j.ijhydene.2012.12.018
The catalytic effect of MoS2 and MoO2 on the hydrogen absorption/desorption kinetics of MgH2 has been investigated. It is shown that MoS2 has a superior catalytic effect over MoO2 on improving the hydrogen kinetic properties of MgH2. DTA results indicated that the desorption temperature decreased from 662.10 K of the pure MgH2 to 650.07 K of the MgH2 with MoO2 and 640.34 K of that with MoS2. Based on the Kissinger plot, the activation energy of the hydrogen desorption process is estimated to be 101.34 ± 4.32 kJ mol−1 of the MgH2 with MoO2 and 87.19 ± 4.48 kJ mol−1 of that with MoS2, indicating that the dehydriding process energy barrier of MgH2 can be reduced. The enhancement of the hydriding/dehydriding kinetics of MgH2 is attributed to the presence of MgS and Mo or MgO and Mo which catalyze the hydrogen absorption/desorption behavior of MgH2. The detailed comparisons between MoS2 and MoO2 suggest that S anion has superior properties than O anion on catalyzing the hydriding/dehydriding kinetics of MgH2.Highlights► MoS2 and MoO2 ameliorate the hydriding/dehydriding kinetics of MgH2. ► MoS2 is superior over MoO2 on improving the hydrogen kinetics of MgH2. ► The dehydriding process energy barrier of MgH2 was reduced by MoS2 and MoO2.
Co-reporter:Jingjing Liu, Shumin Han, Yuan Li, Shuqin Yang, Wenzhuo Shen, Lu Zhang, Yu Zhou
Journal of Alloys and Compounds 2013 Volume 552() pp:119-126
Publication Date(Web):5 March 2013
DOI:10.1016/j.jallcom.2012.09.102
In this paper, the phase transformation and electrochemical characteristics of the as-cast and annealed La0.75Mg0.25Nix (x = 3.0, 3.3, 3.5, 3.8) alloys were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), pressure composition isotherm (PCI) and electrochemical measurements. The as-cast alloys were composed of LaNi5, (La,Mg)2Ni7 and (La,Mg)Ni3 phases. Phase transformation of LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase occurred during annealing treatment, leading to the increase of the (La,Mg)2Ni7 phase and decrease or even depletion of the LaNi5 and (La,Mg)Ni3 phases. The two plateaus observed in P–C isotherms of the as-cast alloys tended to become single and the plateau pressure dropped after the phase transformation by annealing. Electrochemical study showed that for the alloy electrodes with and without annealing treatment, the maximum discharge capacity and HRD initially increased then decreased with x increasing from 3.0 to 3.8. The transformation of the LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase favored the maximum discharge capacity and cycling stability but suppressed the activation as well as HRD of the La0.75Mg0.25Nix (x = 3.0, 3.3, 3.5, 3.8) alloy electrodes. The annealing treatment significantly improved the cycling stability of the alloy electrodes by alleviating the pulverization and oxidation degree of the electrode alloys.Highlights► The mechanism of phase transformation during annealing is illustrated. ► Double pressure plateau tends to single after phase transformation by annealing. ► Cycling stability is dramatically improved after phase transformation by annealing. ► The improvement of cycling stability is due to less pulverization and oxidation.
Co-reporter:Xin Zhao, Shumin Han, Xilin Zhu, Baozhong Liu, Xiaocui Chen, Yanqing Liu, Ruibing Wang
Journal of Alloys and Compounds 2013 Volume 581() pp:270-274
Publication Date(Web):25 December 2013
DOI:10.1016/j.jallcom.2013.05.053
•The LaH3–TiH2 composite additive for the Mg2Ni alloys is created.•The catalysis of La and Ti is included in the composite additive.•Hydrogen kinetic properties of Mg2Ni alloys at low temperature are improved.•Hydrogen decomposing onset temperature of the composites is decreased to 464.05 K.A novel LaH3–TiH2 composite additive was prepared by ball milling LaH3 and TiH2 at a 1:1 weight ratio. Kinetic measurements on the hydrogenation reaction indicated that the LaH3–TiH2 composite additive could significantly improve the hydrogen absorption properties of Mg2Ni. In comparison with that of a pure Mg2Ni alloy and a composite material combining Mg2Ni + 10 wt.% LaH3, the hydrogen storage capacity of the Mg2Ni + 10 wt.% (LaH3–TiH2) composite was 0.251 wt.% and 0.559 wt.% higher at 423 K within 100 s, respectively. Moreover, the composite additive revealed an excellent effect on ameliorating the thermodynamic properties of the Mg2Ni hydride. The decomposition onset temperature of the Mg2Ni + 10 wt.% (LaH3–TiH2) composite hydride was 17 and 13 K lower than that of the pure Mg2NiH4 and Mg2Ni + 10 wt.% TiH2 composite, respectively. X-ray diffraction (XRD) results indicated that the LaH3 in the LaH3–TiH2 composite additive were converted to LaH2 by the catalytic effect of TiH2 during the hydrogenation cycles and that the process enhanced the kinetic properties of hydrogen storage for Mg2Ni alloy.
Co-reporter:Shuqin Yang, Hongping Liu, Shumin Han, Yuan Li, Wenzhuo Shen
Applied Surface Science 2013 Volume 271() pp:210-215
Publication Date(Web):15 April 2013
DOI:10.1016/j.apsusc.2013.01.161
Abstract
In order to improve the overall electrochemical performances of La–Mg–Ni-based hydrogen storage alloy, electroless composite plating Ni–Cu–P treatment was applied to La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 alloy powders. SEM observation showed that the composite treatment resulted in spherical particles more densely depositing on the alloy surface, and subsequently EDS analysis indicated that the particles should be Ni–Cu-P compounds. These particle coatings enhanced the conductivity and the catalytic activity, besides acting as a protective layer, thereby improving the electrochemical properties of the alloy. The discharge capacity of the alloy electrode noticeably increased from 338 mA/g to 361 mA/g. The capacity retention after 200 charge/discharge cycles and the high rate dischargeability (HRD) at 1500 mA/g discharge current density of the alloy electrode increased from 76.0% and 27.7% to 84.8% and 37.0%, respectively. The superior HRD value is believed to be ascribed to the improved kinetics from the compact metallic layers on the surface.
Co-reporter:Xilin Zhu, Lichao Pei, Ziyang Zhao, Baozhong Liu, Shumin Han, Ruibing Wang
Journal of Alloys and Compounds 2013 Volume 577() pp:64-69
Publication Date(Web):15 November 2013
DOI:10.1016/j.jallcom.2013.04.062
•The catalysis mechanism of La hydrides on MgH2 has been investigated.•The hydrogen desorption content of MgH2 + 20 wt.% LaH3 is 5.1 wt.% at 548 K.•The rate-controlling step of MgH2 is altered due to the addition of LaH3.•The LaH2.3 phase distributes homogeneously throughout the Mg phase.•And the Mg crystals are coated with LaH2.3 crystals in the matrix.A systematic investigation was performed on the hydrogen storage properties of composites which were prepared by ball milling MgH2 with different amounts of LaH3 and the catalysis mechanism of La hydride on MgH2 was reported in this paper. Pressure–Composition–Temperature (P–C–T) curves showed that the reversible hydrogen storage capacity of MgH2 + 20 wt.% LaH3 composite was 5.1 wt.% at 548 K, while the pure MgH2 hardly released any H2 under the same conditions. The addition of LaH3 also significantly improved the hydriding/dehydriding kinetics, and led to the rate-controlling steps of MgH2 becoming altered from a three-dimensional interfacial reaction to a one-dimensional diffusion process. The XRD pattern indicated that the LaH3 phase partially transformed to LaH2.3 phase during the dehydriding process. TEM micrograph images revealed that the LaH2.3 phase was distributed homogeneously throughout the Mg phase and that the Mg crystals were coated with LaH2.3 crystals in the matrix. This microstructure exhibited an obvious volume contraction and resulted in a distinct strain of MgH2 when the LaH3 phase released H2. DSC curves proved that the addition of LaH3 could decrease the temperature at which the onset of the dehydrogenation of MgH2 occurred by approximately 20.4 K.
Co-reporter:Yanqing LIU, Shumin HAN, Lin HU, Baozhong LIU, Xin ZHAO, Yanhong JIA
Journal of Rare Earths 2013 Volume 31(Issue 8) pp:784-789
Publication Date(Web):August 2013
DOI:10.1016/S1002-0721(12)60358-5
REMg8.35Ni2.18Al0.21 (RE=La, Ce, Pr, and Nd) alloys were prepared by induction melting and following annealing. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the alloys were composed of Mg2Ni, (La, Pr, Nd)Mg2Ni, (La, Ce)2Mg17, (Ce, Pr, Nd)Mg12 and Ce2Ni7 phases. The above phases were disproportioned into Mg2NiH4, MgH2 and REHx (x=2.51 or 3) phases in hydriding. CeH2.51 phase transformed into CeH2.29 phase in dehydriding, whereas LaH3, PrH3 and NdH3 phases remained unchanged. The PrMg8.41Ni2.14Al0.20 alloy had the fastest hydriding kinetics and the highest dehydriding plateau pressure while the CeMg8.35Ni2.18Al0.21 alloy presented the best hydriding/dehydriding reversibility. The onset hydrogen desorption temperature of the CeMg8.35Ni2.18Al0.21 hydride decreased remarkably owing to the phase transformation between the CeH2.51 and the CeH2.29.DTA curves of the hydrogenated REMg8.35Ni2.18Al0.21 alloys from 400 to 700 K at the heat rate of 10 K/min in an Ar atmosphere
Co-reporter:Shuqin Yang, Shumin Han, Yuan Li, Jingjing Liu
Materials Science and Engineering: B 2013 Volume 178(Issue 1) pp:39-44
Publication Date(Web):1 January 2013
DOI:10.1016/j.mseb.2012.10.010
The phase structures, surface morphologies and electrochemical kinetic properties of MmNi4.50−xMnxCo0.45Al0.30 (Mm is the mischmetal, x = 0.25, 0.30, 0.35, 0.40 and 0.45) hydrogen storage alloys have been investigated in this paper. The X-ray diffraction (XRD) shows that all the alloys mainly consist of LaNi5 phase with CaCu5-type structure, which belongs to P6/mmm space group (central symmetry). Scanning electron microscopy (SEM) tests indicate that there are partial element segregations in the alloys. Meanwhile, energy dispersive spectrum (EDS) results display that the elements constituting Mm exist in the matrix phase in relatively larger proportion, while Mn, Al and Co tend to appear in precipitate phase. For the alloy with x = 0.35, the electrochemical performances, including discharge capacity, high-rate dischargeability (HRD) and cycling life, of the alloy electrode are better than that of other alloy electrodes. With the increase of Mn content, the exchange current density (I0) of the alloy electrodes first increases and then decreases, the hydrogen diffusion coefficient (D) of alloy electrodes gradually decreases. There is a linear correlation between HRD at a discharge current density of 1500 mA/g and I0.Highlights► La, Ce, Pr and Nd present more in the matrix phase and Mn, Al and Co appear more in the precipitate phase. ► The alloy with x = 0.35 exhibits better overall electrochemical properties. ► The electrochemical reaction on alloy surface is the rate-determining step.
Co-reporter:Wenzhuo Shen, Shumin Han, Yuan Li, Shuqin Yang, Qi Miao
Applied Surface Science 2012 Volume 258(Issue 17) pp:6316-6320
Publication Date(Web):15 June 2012
DOI:10.1016/j.apsusc.2012.03.029
Abstract
A new polyaniline (PANI)-coated technique is adopted for the La–Mg–Ni-based alloy La0.80Mg0.20Ni2.70Mn0.10Co0.55Al0.10 in order to advance its electrochemical kinetic characteristics. In this treatment, the aniline monomers are electroplated on the alloy particles to form polyaniline films. FE-SEM observation and UV–vis analysis results revealed that the coral-like atrovirens PANI particles are deposited on the surface of the alloy. Through the PANI-coating the capacity retention rate at the 200th cycle of the La–Mg–Ni-based alloy electrodes amounts up from original 82.3% to 86.4% and the high rate discharge ability increased from 24.7% to 35.6% at a discharge current density of 1500 mA g−1. Linear polarization, anodic polarization and cyclic voltammetry measurements suggest that charge-transfer resistance decreases and the hydrogen absorption rate of the alloys increases after PANI-coating.
Co-reporter:Baozhong Liu, Jinhua Li, Shumin Han, Lin Hu, Lichao Pei, Mingzhi Wang
Journal of Alloys and Compounds 2012 Volume 526() pp:6-10
Publication Date(Web):15 June 2012
DOI:10.1016/j.jallcom.2012.02.085
Herein, we prepared a new type of magnesium and transition metal-based alloys with the formula of LaMg8.40Ni2.34−xAlx (x = 0 and 0.20). Their phase structures, morphologies and hydrogen storage properties were studied by different methods. The XRD patterns show that LaMg8.40Ni2.34−xAlx alloys are made of La2Mg17, LaMg2Ni and Mg2Ni phases. The SEM images indicate that the phase distributions in LaMg8.40Ni2.14Al0.20 alloy are more uniform compared with LaMg8.40Ni2.34 alloy. In addition, the reversible hydrogen storage capacity of LaMg8.40Ni2.14Al0.20 alloy is 3.22 wt.% at 558 K, which is higher than that of LaMg8.40Ni2.34 alloy. The partial substitution of Al for Ni effectively improves the hydrogen storage capacity, as well as the hydriding/dehydriding kinetics of the alloys, with the evidence that 89% hydrogen in the saturated state in LaMg8.40Ni2.14Al0.20 alloy was released in 1500 s at 573 K, while only 74% hydrogen in the saturated state in LaMg8.40Ni2.34 alloy was released at the same conditions. Consequently, we believe that the alloying of aluminum in the magnesium-rare earth-transition metal-based alloys can effectively improve their hydrogen storage performance.Highlights► LaMg8.40Ni2.34 and LaMg8.40Ni2.14Al0.20 alloys consist of La2Mg17, LaMg2Ni and Mg2Ni phases. ► The distribution of initial phases in LaMg8.40Ni2.14Al0.20 alloy is more uniform. ► Reversible capacity of LaMg8.40Ni2.14Al0.20 alloy is higher than that of LaMg8.40Ni2.34 alloy. ► Mg hydride in LaMg8.40Ni2.14Al0.20 alloy is less stable, the stability of Mg2Ni hydride is similar. ► The better kinetics is due to the more uniform distribution of initial phases.
Co-reporter:Wenzhuo Shen, Shumin Han, Yuan Li, Jing Yang, Kun Xiao
Materials Chemistry and Physics 2012 Volume 132(2–3) pp:852-857
Publication Date(Web):15 February 2012
DOI:10.1016/j.matchemphys.2011.12.023
Polyaniline (PANI) electroless-deposition is applied onto La–Mg–Ni-based La0.80Mg0.20Ni2.70Mn0.10Co0.55Al0.10 hydrogen storage alloy powders in order to improve electrochemical and kinetic properties. FE-SEM and FT-IR results reveal that coral-like PANI particles are deposited on the surface of the alloy. Owing to the PANI coating the initial discharge capacity of the alloy electrodes increases from original 174 mAh g−1 to 226 mAh g−1, the capacity retention rate at 200 cycles (S200) increases from 85% to 88%, and the high rate discharge ability (HRD) is scaled up by 18% at discharge current density of 1500 mA g−1. Linear polarization, EIS, anodic polarization and potential static step discharge measurements indicate that charge transfer resistance decreases and the hydrogen diffusion rate increases after PANI-coating.Highlights► We study the effect of PANI on electrochemical properties of La–Mg–Ni-based alloys. ► The PANI improves the initial activation property. ► It enhances HRD remarkably.
Co-reporter:Ji Dong Wang, Shu Min Han, Dan Dan Ke
Chinese Chemical Letters 2012 Volume 23(Issue 12) pp:1407-1410
Publication Date(Web):December 2012
DOI:10.1016/j.cclet.2012.11.006
Family 373 and 406 of CdS magic-sized nanocrystals (MSNCs) were synthesized by a one-pot non-injection approach and white-light emission was generated from the coexistence of them. This light had excellent color characteristics, as defined by their pure white CIE (Commission International de l’Eclairage) color coordinates (0.328, 0.343), and it correlated with a color temperature of 5696 K. A probable thermodynamic equilibrium was proposed to explain the white-light emission behavior in this letter.
Co-reporter:Lichao Pei, Shumin Han, Jiasheng Wang, Lin Hu, Xin Zhao, Baozhong Liu
Materials Science and Engineering: B 2012 Volume 177(Issue 18) pp:1589-1595
Publication Date(Web):1 November 2012
DOI:10.1016/j.mseb.2012.08.003
RMg2Ni alloys were prepared by inductive melting where R is rare earth (R = La, Ce, Pr, Nd). X-ray diffraction (XRD) patterns revealed a single-phase composition of RMg2Ni phase when R was one of the three elements (La, Pr, Nd), and a double-phase composition of CeMg2Ni and CeMg3 phases when R was Ce. In the hydriding process, RMg2Ni phases transformed to rare earth hydrides (R-H) and Mg2NiH4 phase, and for CeMg3 phase, it is decomposed to CeH2.74 and MgH2 phases. The enthalpy change of Mg2Ni phase in RMg2Ni alloys during the hydriding/dehydriding process was smaller compared with that of pristine Mg2Ni alloy, which could be attributed to the existence of R-H. The hydrogen storage properties of RMg2Ni alloys changed with different R compositions in R-H. At 573 K, the NdMg2Ni alloy had the highest hydrogen storage capacity and dehydriding plateau, and the descending order of hysteresis was PrMg2Ni < NdMg2Ni < CeMg2Ni < LaMg2Ni, which suggested that the PrMg2Ni alloy exhibited a better cycling stability and reversibility than the other three alloys. At 523 K, the uptake time of RMg2Ni alloys to reach 90% of the maximum hydrogen storage capacity was 75 s, 34 s, 65 s and 52 s, respectively, compared with 110 s of pristine Mg2Ni alloy. Therefore, we believed the R-H in the alloys not only improved their thermodynamic properties but also accelerated their hydriding kinetics.Highlights► RMg2Ni (R = La, Ce, Pr, Nd) alloys show different phase structures and properties. ► R-H reduces the enthalpy of Mg2Ni phase and accelerates its hydriding rate. ► NdMg2Ni alloy has the highest hydrogen storage capacity and dehydriding plateau. ► And the hysteresis of PrMg2Ni alloy is the smallest at 573 K among these alloys. ► The hydriding rate of CeMg2Ni alloy is faster than the other alloys at 523 K.
Co-reporter:Suxia Yang;Zhiping Liu;Wei Zhang;Jianzheng Song
Rare Metals 2011 Volume 30( Issue 5) pp:
Publication Date(Web):2011 October
DOI:10.1007/s12598-011-0414-2
The effects of annealing treatment on the microstructure and electrochemical properties of low-Co LaNi3.55Mn0.35Co0.20Al0.20Cu0.75Fe0.10 hydrogen storage alloys were investigated. X-ray diffraction (XRD) analysis indicated that annealing treatment remarkably reduced the lattice strain and defects, and increased the unit-cell volume. The optical microscope analysis showed that the as-cast alloy had a crass dendrite microstructure with noticeable composition segregation, which gradually disappeared with increasing annealing temperature, and the microstructure changed to an equiaxed structure after annealing the alloy at 1233 K. The electrochemical tests indicated that the annealed alloys demonstrated much better cycling stability compared with the as-cast one. The capacity retention at the 100th cycle increased from 90.0% (as-cast) to 94.7% (1273 K). The annealing treatment also improved the discharge capacity. However, the high rate dischargeability (HRD) value of the annealed alloy slightly dropped, which was believed to be ascribed to the decreased exchange current density and the hydrogen diffusion coefficient in alloy bulk.
Co-reporter:Jinhua Li;Baozhong Liu;Lin Hu;Xin Zhao;Mingzhi Wang
Rare Metals 2011 Volume 30( Issue 5) pp:
Publication Date(Web):2011 October
DOI:10.1007/s12598-011-0413-3
The phase structure and hydrogen storage properties of LaMg3.70Ni1.18 alloy were investigated. The LaMg3.70Ni1.18 alloy consists of main LaMg2Ni phase, minor La2Mg17 and LaMg3 phases. The alloy can be activated in the first hydriding/dehydriding process, and initial LaMg2Ni, La2Mg17, and LaMg3 phases transfer to LaH2.34, Mg, and Mg2Ni phases after activation. The reversible hydrogen storage capacity of the LaMg3.70Ni1.18 alloy is 2.47 wt.% at 558 K, which is higher than that of the LaMg2Ni alloy. The pressure-composition-temperature (PCT) curves display two hydriding plateaus, corresponding to the formation of MgH2 and Mg2NiH4. However, only one dehydriding plateau is observed, owing to the synergetic effect of hydrogen desorption between MgH2 and Mg2NiH4. The uptake time for hydrogen content to reach 99% of saturated state is less than 250 s, and 90% hydrogen can be released in 1200 s in the experimental conditions, showing fast kinetics in hydriding and dehydriding. The activation energies of the LaMg3.70Ni1.18 alloy are −51.5 ± 1.1 kJ/mol and −57.0 ± 0.6 kJ/mol for hydriding and dehydriding, respectively. The hydriding/dehydriding kinetics of the LaMg3.70Ni1.18 alloy is better than that of the Mg2Ni alloy, owing to the lower activation energy values.
Co-reporter:Shuqin Yang, Shumin Han, Yuan Li, Suxia Yang, Lin Hu
Materials Science and Engineering: B 2011 Volume 176(Issue 3) pp:231-236
Publication Date(Web):25 February 2011
DOI:10.1016/j.mseb.2010.11.013
In this paper, the structure and electrochemical kinetic properties of MmNi3.70−xMn0.35Co0.60Al0.25Bx (x = 0.00, 0.10, 0.15, 0.20, 0.25) hydrogen storage alloys prepared by inductive melting have been systematically studied. The X-ray diffraction (XRD) shows that the alloys with B have not only LaNi5 phase, but the secondary phase with CeCo4B-type structure. The amount of the secondary phase and the plateau pressure of pressure–composition (P–C) isotherms gradually increase with the increase of B content. As x increases from 0.00 to 0.25, the high-rate dischargeability (HRD) of alloy electrodes first increases and then decreases. When x = 0.20, the HRD value reaches the maximum—63.1% at 1500 mA/g discharge current density. Electrochemical kinetic measurements indicate that the superior HRD of alloy electrodes is ascribed to their high surface electrocatalytic activity and fast hydrogen transfer in the bulk of alloys. The substitution of Ni with B in suitable amount could improve the kinetic properties of rare earth-based AB5-type alloys because of the formation of the secondary phase.
Co-reporter:Yuan Li, Shumin Han, Xilin Zhu, Huiling Ding
Journal of Power Sources 2010 Volume 195(Issue 1) pp:380-383
Publication Date(Web):1 January 2010
DOI:10.1016/j.jpowsour.2009.06.093
In order to improve overall electrochemical properties of AB3-type hydrogen storage alloy electrodes, especially the cycling stability, CuO was added to the electrode. Electrochemical properties of the electrodes with and without additives were studied. Cyclic voltammetry and SEM results show that CuO is reduced to Cu during the charging process and the fine Cu particles deposit at surface of the alloy particles. The as-deposited Cu particles form a protective layer to increase electronic and heat conductivity of the electrodes and thus improve maximum discharge capacity, high rate dischargeability, cycling stability and dischargeability at high temperature of the electrodes. The maximum discharge capacity increases from 314 mAh g−1 (blank electrode) to 341 mAh g−1 (3.0 wt.% CuO) and the capacity retention rate at the 200th cycle increases from 71.6% to 77.2% (2.5 wt.% CuO).
Co-reporter:Wenzhuo Shen, Shumin Han, Yuan Li, Jianzheng Song, Qi Tong
Electrochimica Acta 2010 Volume 56(Issue 2) pp:959-963
Publication Date(Web):30 December 2010
DOI:10.1016/j.electacta.2010.09.040
A new polyaniline (PANI)-coated technique was adopted for a AB5-type alloy (La0.64Ce0.25Pr0.03Nd0.08Ni4.19Mn0.31Co0.42Al0.23) in order to improve its electrochemical and kinetic properties. FE-SEM observation and FT-IR analysis results revealed that the PANI electroless deposited to the surface of alloy particles. Through the PANI-coating the initial discharge capacity increased from 299 to 331 mAh/g and the high rate discharge ability (HRD) increased from 8.5 to 45.0% at discharge current density of 1440 mA/g. For kinetic properties, linear polarization, EIS, anodic polarization and cyclic voltammetry measurements suggested that charge-transfer resistance decreased and the hydrogen absorption rate of the alloys increased after PANI-coating.
Co-reporter:Yuan Li, Shumin Han, Zhiping Liu
International Journal of Hydrogen Energy 2010 Volume 35(Issue 23) pp:12858-12863
Publication Date(Web):December 2010
DOI:10.1016/j.ijhydene.2010.08.141
In order to improve kinetic properties of La–Mg–Ni-based hydrogen storage alloys, Mo–Ni treatment was applied to La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 alloy powders. FESEM results showed that after Mo–Ni treatment some network-shaped substance with nano-size formed on the surface of the alloy particles. The EDS results revealed increase in Ni content and emerge of Mo element. EIS and Linear polarization showed that charge-transfer resistance decreased and exchange current density increased for the treated alloy electrode, and the high rate dischargeability (HRD) was consequently improved. HRD at 1500 mA/g increased from 22.5% to 39.5%. Mo- and Ni-single treatments were performed compared with the Mo–Ni treatment, and the results showed that the single treatment improved HRD slightly, far less than the Mo–Ni treatment.
Co-reporter:Shumin Han, Zhonghou Feng, Lin Hu, Yuan Li, Jiansheng Hao, Jingwu Zhang
Materials Chemistry and Physics 2010 Volume 124(Issue 1) pp:17-20
Publication Date(Web):1 November 2010
DOI:10.1016/j.matchemphys.2010.06.034
A novel electro-active material was synthesized by precipitation under high levels of supersaturation. The compound was pure β-Co(OH)2 with hexagonal crystal structure by XRD analysis, and it was flake-shaped, 50–200 nm in particle size and ∼20 nm in thickness by FE-SEM observation. The quasireversible electrochemical reaction between β-Co(OH)2 and Co upon charging/discharging produced a maximum discharge capacity of 462 mAh g−1, and furthermore the discharge capacity retained 97.6% of the initial capacity at the 100th cycle. These findings highlight the potential for β-Co(OH)2 compound in applications to negative electrode materials of alkaline rechargeable batteries.
Co-reporter:Jiansheng Hao;Peng Gao;Yuan Li
Journal of Applied Electrochemistry 2010 Volume 40( Issue 9) pp:1683-1687
Publication Date(Web):2010 September
DOI:10.1007/s10800-010-0165-z
Metal oxides (TiO2, Er2O3 and ZnO) were added to La–Mg–Ni-based hydrogen storage alloy electrodes and their effects on the structural and electrochemical properties were studied. The charge efficiency, especially at high charge current density was greatly ameliorated, and the high rate charge capability at 1440 mA g−1 increased from 85.1% (blank) to 94.1% (TiO2), 93.3% (Er2O3) and 90.5% (ZnO). The high temperature dischargeability was also improved in case of TiO2, Er2O3 and ZnO additives. These additives suppressed formation of Mg(OH)2 and La(OH)3 during charge/discharge process and therefore the cycling stability was improved. The discharge capacity retention at the 200th cycle increased from 72.9% (blank) to 79.6% (TiO2), 87.5% (Er2O3) and 77.9% (ZnO).
Co-reporter:Lin Hu, Shumin Han, Jinhua Li, Cheng Yang, Yuan Li, Mingzhi Wang
Materials Science and Engineering: B 2010 Volume 166(Issue 3) pp:209-212
Publication Date(Web):15 February 2010
DOI:10.1016/j.mseb.2009.11.028
LaMg2Cu alloy was prepared by inductive melting and then was annealed at 723 K for 10 h in 0.1 MPa argon atmospheres. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the alloy consisted of LaMg2Cu2 phase, LaMg3 phase and a few of unknown phases. The annealing treatment improved the equilibrium pressure and hydrogen absorption capacity of LaMg2Cu alloy. The hydrogen absorption capacity of the as-cast and annealed alloys at 473 K were 2.86 and 3.33 wt.%, and the equilibrium pressure were 1 and 3 MPa, respectively. The enthalpy and entropy of LaMg2Cu–H hydriding reaction were determined. LaMg2Cu alloy could absorb hydrogen with rapid hydriding kinetics, the hydrogen absorption rate of LaMg2Cu increased from 423 K to 498 K and the uptake time for hydrogen content to reach 90% of the maximum storage capacity for annealed alloy was less than 550 s at 498 K. The experimental curves of hydrogen absorption kinetics could be fitted with good accuracy by Jander equation. It suggested that the hydriding of LaMg2Cu alloy was a three-dimensional diffusion-controlled process. And the activation energy and pre-exponential factor of LaMg2Cu alloy were also calculated.
Co-reporter:Wencui Zhang, Shumin Han, Jiansheng Hao, Yuan Li, Taoyu Bai, Jingwu Zhang
Electrochimica Acta 2009 Volume 54(Issue 4) pp:1383-1387
Publication Date(Web):30 January 2009
DOI:10.1016/j.electacta.2008.09.019
The structure and electrochemical kinetics properties of La0.90−xCexPr0.05Nd0.05Ni3.90Co0.40Mn0.40Al0.30 (x = 0.10, 0.20, 0.30, 0.40, 0.50) hydrogen storage alloys have been investigated. XRD shows that the alloys consist of LaNi5 phase with hexagonal CaCu5 structure. With increase in Ce content, the parameter a and cell volume decrease remarkably, but the parameter c increases slightly. The limiting current density IL and the hydrogen diffusion coefficient D increase, and the exchange current density I0 increases firstly from 201.4 mA/g (x = 0.10) to 277.9 mA/g (x = 0.30) and then decreases to 208.5 mA/g (x = 0.50). Meanwhile, high rate dischargeability (HRD) at 1440 mA/g increases from 44.1% (x = 0.10) to 59.9% (x = 0.30), and then decreases to 44.2% (x = 0.50). As the amount of Ce increases, the plateau pressure of P–C isotherms increases gradually, the capacity retention of the alloys increases firstly and then decreases, the alloy with x = 0.30 has the higher capacity retention and cycling stability, but the maximum discharge capacity of alloys decreases. Ce is a vital element in favor of kinetics properties of rare earth-based AB5-type alloys, and the substitution of La with Ce in suitable amount could improve the HRD by increasing kinetics.
Co-reporter:Huiling Ding, Shumin Han, Yi Liu, Jiansheng Hao, Yuan Li, Jingwu Zhang
International Journal of Hydrogen Energy 2009 Volume 34(Issue 23) pp:9402-9408
Publication Date(Web):December 2009
DOI:10.1016/j.ijhydene.2009.09.082
A novel electroplating treatment was applied onto La–Mg–Ni-based La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 alloy powders. The effect of cobalt or nickel metallic coating on morphological and electrochemical properties was studied. FESEM results showed that a dense layer of spherical cobalt particles with uniform radius and an undulate layer of lamellar nickel formed on the surface of the Co- and Ni-coated alloys, respectively. These coatings enhanced the conductivity and the catalytic activity, besides acting as a protective layer, thereby improving the electrochemical properties. The maximum discharge capacity increased from original 316 mAh/g to 335 mAh/g on Co-coated alloys and 336 mAh/g on Ni-coated ones, the cycling stability was enhanced and the self-discharge was suppressed. The high rate dischargeability (HRD) was ameliorated remarkably, and the HRD value at 1500 mA/g rose by 10% and 17%, for cobalt- and nickel-coated alloy electrodes respectively, which is believed to be ascribed to the improved kinetics from the metallic coatings on the surface.
Co-reporter:Yuan Li, Da Han, Shumin Han, Xilin Zhu, Lin Hu, Zhong Zhang, Yuwen Liu
International Journal of Hydrogen Energy 2009 Volume 34(Issue 3) pp:1399-1404
Publication Date(Web):February 2009
DOI:10.1016/j.ijhydene.2008.11.049
La0.60R0.20Mg0.20(NiCoMnAl)3.5 (R = La, Ce, Pr, Nd) alloys were prepared by inductive melting. Variations in phase structure and electrochemical properties due to partial replacement of La by Ce, Pr and Nd, were investigated. The alloys consist mainly of LaNi5 phase, La2Ni7 phase and LaNi3 phase as explored by XRD and SEM. The maximum discharge capacity decreases with Ce, Pr and Nd substitution for La. However, the cycling stability is improved by substituting Pr and Nd at La sites, capacity retention rate at the 100th cycle increases by 13.4% for the Nd-substituted alloy. The electrochemical kinetics measurements show that Ce and Pr substitution improves kinetics and thus ameliorates the high rate dischargeability (HRD) and low temperature dischargeability. The HRD at 1200 mA g−1 increases from 22.1% to 61.3% and the capacity at 233 K mounts up from 90 mAh g−1 to 220 mAh g−1 for the Ce-substituted alloy.
Co-reporter:Taoyu Bai, Shumin Han, Xilin Zhu, Yue Zhang, Yuan Li, Wencui Zhang
Materials Chemistry and Physics 2009 Volume 117(Issue 1) pp:173-177
Publication Date(Web):15 September 2009
DOI:10.1016/j.matchemphys.2009.05.031
A new surface treatment technique, i.e. HF etching-Ni coating duplex surface treatment was applied to modify AB3-type La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 hydrogen storage alloy. Surface structure and electrochemical properties were investigated. SEM and EDS indicated that Ni deposited on the alloy surface, forming a porous Ni-rich layer. And thus initial activation ability and kinetics properties of the alloy electrode were improved significantly. The ratio C1st/Cmax increased from 68.0% to 89.3%, the middle discharge voltage is 0.025 V higher, the high rate dischargeability (HRD) was about 10% higher at a current density of 1080–1800 mA g−1, and the cycling stability was improved slightly after duplex surface treatment. In addition, the exchange current density I0, the limiting current density IL, the oxidation peak current and the peak area of cyclic voltammograms were also increased obviously after the duplex surface treatment.
Co-reporter:Shumin Han;Yuan Li;Zhong Zhang;Xilin Zhu;Jinhua Li
Frontiers of Chemistry in China 2009 Volume 4( Issue 1) pp:48-51
Publication Date(Web):2009 March
DOI:10.1007/s11458-009-0007-x
The Ml-Mg-Ni-based (Ml = La-rich mixed lanthanide) hydrogen storage alloy Ml0.88Mg0.12Ni3.0-Mn0.10Co0.55Al0.10 was prepared by inductive melting. The micro-structure was analyzed by XRD and SEM. The alloy consists mainly of CaCu5-type phase, Ce2Ni7-type phase and Pr5Co19-type phase. The electrochemical measurements show that the maximum discharge capacity is 386 mAh/g, 16.3% higher than that of the commercial AB5-type alloy (332 mAh/g). At discharge current density of 1 100 mA/g, high rate dischargeability is 62%, while that of the AB5-type alloy is only 45%. The discharge capacity decreases to 315 mAh/g after 300 charge/ discharge cycles, 81.5% of the maximum discharge capacity.
Co-reporter:Yuan Li, Shumin Han, Jinhua Li, Xilin Zhu, Lin Hu
Journal of Alloys and Compounds 2008 Volume 458(1–2) pp:357-362
Publication Date(Web):30 June 2008
DOI:10.1016/j.jallcom.2007.03.106
The low-Co content La0.80−xNdxMg0.20Ni3.20Co0.20Al0.20 (x = 0.20, 0.30, 0.40, 0.50, 0.60) alloys were prepared by inductive melting and the effect of Nd content on the electrochemical properties was investigated. XRD shows that the alloys consist mainly of LaNi5 phase, La2Ni7 phase and minor LaNi3 phase. The electrochemical P–C–T test shows hydrogen storage capacity increases first and then decreases with increasing x, which is also testified by the electrochemical measurement that the maximum discharge capacity increases from 290 mAh/g (x = 0.20) to 374 mAh/g (x = 0.30), and then decreases to 338 mAh/g (x = 0.60). The electrochemical kinetics test shows exchange current density I0 increases with x increasing from 0.20 to 0.50 followed by a decrease for x = 0.60, and hydrogen diffusion coefficient D increases with increasing x. Accordingly high rate dischargeability increases with a slight decrease at x = 0.60 and the low temperature dischargeability increases with increase in Nd content. When x is 0.50, the alloy exhibits a better cycling stability.
Co-reporter:Yuan Li, Shumin Han, Jinhua Li, Xilin Zhu, Lin Hu
Materials Chemistry and Physics 2008 Volume 108(Issue 1) pp:92-96
Publication Date(Web):15 March 2008
DOI:10.1016/j.matchemphys.2007.09.009
In our endeavor to obtain hydrogen storage alloys with high discharge capacity and good cycling stability, the Ml0.70Mg0.30(Ni3.95Co0.75Mn0.15Al0.15)x (x = 0.60, 0.64, 0.68, 0.70, 0.76) (where Ml denotes La-rich misch metal) alloys with Ml substitution for La and B-side multi-alloying have been prepared by inductive melting, and the effect of stoichiometry x on the electrochemical properties has been investigated systematically. XRD analysis shows that the alloys are mainly composed of LaNi5 phase and LaNi3 phase. The electrochemical test shows that the maximum discharge capacity, kinetics, high rate dischargeability (HRD) and low temperature dischargeability (LTD) all increase and then decrease with increasing x. The alloy with x = 0.64 has larger maximum discharge capacity, 372 mAh g−1. As the case of x = 0.70, the alloy exhibits better kinetics, HRD and LTD. The testing alloys exhibit good cycling stability, and the capacity retention of the alloys at the 100th cycles increases from 78.0% (x = 0.60) to 90.3% (x = 0.76).
Co-reporter:Lin HU, Shumin HAN, Jinhua LI, Xilin ZHU, Yuan LI
Rare Metals 2008 Volume 27(Issue 4) pp:429-433
Publication Date(Web):August 2008
DOI:10.1016/S1001-0521(08)60157-6
A commercial AB5 hydrogen storage alloy was used as an additive to improve the electrochemical properties of Ml-Mg-Ni-based hydrogen storage alloys. The effect of AB5 alloy addition on the phase structure, charge/discharge characteristics, and electrochemical kinetics of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy was investigated. The maximum discharge capacity of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 + 4 wt.% AB5 electrode reaches 406 mAh/g. The anodic polarization, cyclic voltammetry, and potential step discharge experiments show that the electrochemical kinetics of the electrode with additives was promoted, with the LaNi5 phase of AB5 alloy acting as electro-catalytic sites in the electrode alloy. The high-rate dischargeability of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 + 4 wt.% AB5 alloy electrode at 1100 mA/g reaches 60.9%, which is 9.4% higher than that of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy electrode. The cycling stability of the electrode with 4 wt.% AB5 alloy has also been improved.
Co-reporter:Yuan Li, Shumin Han, Jinhua Li, Lin Hu
Electrochimica Acta 2007 Volume 52(Issue 19) pp:5945-5949
Publication Date(Web):25 May 2007
DOI:10.1016/j.electacta.2007.03.040
Phase structure and electrochemical properties of the Ml1−xMgxNi2.80Co0.50Mn0.10Al0.10 (x = 0.08, 0.12, 0.20, 0.24, 0.28) (Ml = La-rich mixed lanthanide) alloys were studied. X-ray diffraction (XRD) analysis and Rietveld refinement show that the alloys consist mainly of LaNi5 and (La,Mg)Ni3 phase. Due to variation in phases of the alloys, the maximum discharge capacity, the high rate dischargeability (HRD), and the low temperature dischargeability increase first and then decrease. The maximum discharge capacity increases from 322 mAh g−1 (x = 0.08) to 375 mAh g−1 (x = 0.12), and then decreases to 351 mAh g−1 (x = 0.28) with increasing x. As the case of x = 0.20, HRD at 1200 mA g−1 and discharge capacity at 233 K reaches 41.7% and 256 mAh g−1, respectively. The cycling stability is improved by substituting La with Ml and B-site multi-alloying, and the capacity retention of Ml0.72Mg0.28Ni2.80Co0.50Mn0.10Al0.10 at the 200th cycle is 71%.
Co-reporter:Zhong Zhang, Shumin Han, Yuan Li, Tianfu Jing
Journal of Alloys and Compounds 2007 Volume 431(1–2) pp:208-211
Publication Date(Web):4 April 2007
DOI:10.1016/j.jallcom.2006.05.032
The Ml1−xMgxNi3.0Mn0.10Co0.55Al0.10 (x = 0.05, 0.10, 0.15, 0.20, 0.30) (where Ml denotes La-rich mischmetal) alloys were prepared by inductive melting. The prepared alloys consist of LaNi5 phase and (La,Mg)Ni3 phase; the LaNi5 phase decreases and (La,Mg)Ni3 phase increases as x increases. Due to the change of the phase structure, the maximum discharge capacity, high rate dischargeability (HRD) and low temperature dischargeability (LTD) of the alloys increase and then decrease with increasing x. The maximum discharge capacity reaches up to 363 mAh/g at x = 0.20, and at x = 0.15, HRD and LTD reach 58.0% at 1200 mA/g and 75.8% at 233 K, respectively. The cycle stability decreases with increasing Mg content. However, by using Ml substitution for La as A-side component and multi-substituted B-side metals, the cycle stability is improved. The capacity retention of the alloys at the 200th cycle is up to 74.9% when x is 0.05.
Co-reporter:Z. Zhang;S. M. Han;W. Guan;Y. Li;Y. W. Liu
Journal of Applied Electrochemistry 2007 Volume 37( Issue 3) pp:311-314
Publication Date(Web):2007 March
DOI:10.1007/s10800-006-9241-9
The effect of magnesium content on the phase structure and electrochemical properties of Ml1−xMgxNi2.78Co0.50Mn0.11Al0.11 (x = 0.05, 0.10, 0.20, 0.30) hydrogen storage alloys was investigated. The results of X-ray diffraction reveal that all the alloys consist of the major phase (La, Mg)Ni3 and the secondary phase LaNi5. With increase in x, the relative content of the (La, Mg)Ni3 phase increases gradually, and the maximum capacity and low temperature dischargeability of the alloy electrodes first increase and then decrease. When x is 0.20, the discharge capacity of the alloy electrode reaches 363 mAh g−1 at 293 K and 216 mAh g−1 at 233 K, respectively. The high rate dischargeability of the alloy electrodes increases with increase in x. When the discharge current density is 1200 mA g−1, the high rate dischargeability of the alloy electrodes increases from 22.0% to 50.4% with x increasing from 0.05 to 0.30. The cycling stability of the electrodes decreases gradually with increase in magnesium content.
Co-reporter:M. Li, S.M. Han, Y. Li, W. Guan, L.R. Mao, L. Hu
Electrochimica Acta 2006 Volume 51(Issue 26) pp:5926-5931
Publication Date(Web):15 August 2006
DOI:10.1016/j.electacta.2006.03.037
In our endeavor to improve overall properties of the La–Mg–Ni–Co type alloys, RE0.93Mg0.07Ni2.96Co0.60Mn0.37Al0.17 hydrogen storage electrode alloy with low magnesium content was obtained by inductive melting. The phase structure and electrochemical characteristics of the alloy were investigated by XRD and electrochemical measurement. The results indicate that RE0.93Mg0.07Ni2.96Co0.60 Mn0.37Al0.17 alloy has multi-phase microstructure containing the CaCu5 structure of LaNi5 phase as matrix phase and a little of LaNi3 phase as the secondary phase. The maximum discharge capacity of RE0.93Mg0.07Ni2.96Co0.60Mn0.37Al0.17 alloy reaches 359 mAh/g, which is 7.2% higher than that of commercial AB5 alloy electrode. The discharge capacity of RE0.93Mg0.07Ni2.96Co0.60Mn0.37Al0.17 alloy electrode at 233 K is up to 147 mAh/g, which is 308.3% higher than that of commercial AB5 alloy electrode. Meanwhile, the discharge capacity of RE0.93Mg0.07Ni2.96Co0.60Mn0.37Al0.17 alloy can reach 92.7% of commercial AB5 alloy after 100 charge/discharge cycles.
Co-reporter:Zhong Zhang, Shumin Han, Yuan Li, Tianfu Jing, Xiaotie Wang
Journal of Alloys and Compounds 2006 Volume 421(1–2) pp:289-293
Publication Date(Web):14 September 2006
DOI:10.1016/j.jallcom.2005.11.031
In order to investigate the effect of sintering temperature on phase structure and electrochemical properties of AB5–5 mass% LaMg3, as a part of our systematic studies, the AB5–5 mass% LaMg3 composite alloys were prepared by sintering AB5 and LaMg3 powders at 973 K, 1073 K, 1123 K, 1173 K and 1273 K, respectively. Phase structure and electrochemical properties of the composites were investigated. The results show that the composite alloys were composed of matrix AB5 phase and secondary LaNi3 phase. The maximum discharge capacity, high rate dischargeability (HRD) and dischargeability at low temperature increase first and then decrease with increasing sintering temperature. AB5–5 mass% LaMg3 composite alloy sintered at 1123 K has the best overall electrochemical properties. For example, it exhibits as high a discharge capacity as 358 mAh g−1, which is 7.2% higher than that of AB5 alloy, a better HRD and a better dischargeability at low temperature. However, cyclic stability of AB5–5 mass% LaMg3 becomes better with increasing sintering temperature. AB5–5 mass% LaMg3 sintered at 1273 K has the best cyclic stability and its capacity retention after 100 cycles is 94.3%, which is 3.7% higher than that of the commercial AB5 alloy.
Co-reporter:Shu-Min Han, Zhong Zhang, Min-Shou Zhao, Yang-Zeng Zheng
International Journal of Hydrogen Energy 2006 Volume 31(Issue 5) pp:563-567
Publication Date(Web):April 2006
DOI:10.1016/j.ijhydene.2005.06.008
AB2–x%LaNi5(x=0,1,5,10) composite alloys were prepared by melting Zr0.9Ti0.1Ni1.1Mn0.6V0.3Zr0.9Ti0.1Ni1.1Mn0.6V0.3 with a small amount of LaNi5LaNi5 alloy as addition. The microstructure and electrochemical characteristics of the composite alloys were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that LaNi5LaNi5 addition does not change the basic hexagonal C14 Laves phase of AB2AB2 alloys, but some second phases have segregated. It was found that the addition of LaNi5LaNi5 greatly improves the activation property, high-rate dischargeability (HRD) and charge–discharge cycling stability of AB2AB2 Laves phase alloy. At current density of 1200 mA/g, HRD of the alloy increases from 38.92% (x=0x=0) to 60.09% (x=10x=10). The capacity retention of the alloy after 200 charge–discharge cycles increases from 57.10% (x=0x=0) to 83.86% (x=5x=5) and 67.31% (x=10x=10). The improvement of the electrochemical characteristics caused by LaNi5LaNi5 addition seems to be related to formation of the second phases.
Co-reporter:Shu-Min Han, Min-Shou Zhao, Zhong Zhang, Yang-Zeng Zheng, Tan-Fu Jing
Journal of Alloys and Compounds 2005 Volume 392(1–2) pp:268-273
Publication Date(Web):19 April 2005
DOI:10.1016/j.jallcom.2004.08.091
Hypo-stoichiometric AB5−α (α > 0)-type LaNi5–x%AB2 (x = 1, 5, 10, 20) composite alloys were successfully prepared by sintering the powder mixtures of LaNi5 and AB2-type Laves phase alloy Zr0.9Ti0.1(Mn0.35Ni0.55V0.15)2 as addition. The phase structure and electrochemical characteristics of the composite alloys were investigated by means of XRD, EDS and electrochemical measurements. It was shown that LaNi5–x%AB2 (x = 1, 5, 10, 20) composite alloys have multi-phase structure, the matrix phase is CaCu5 structure of LaNi5 alloy, the second phase is Zr-rich phase which dispersed in the matrix phase as strips. The discharge capacity and rate discharge capacity of LaNi5 alloy electrodes were greatly improved after composite treated by adding AB2 alloy. The maximum discharge capacity of the composite alloy electrodes increased from 188 mAh/g for x = 0 to 305 mAh/g for x = 10, and the rate discharge capacity of the composite alloy for x = 5 at the current density of 300 and 2040 mA/g was 97 and 55% of that of the alloy at 60 mA/g, respectively. The electrochemical characteristics of LaNi5 alloy at low temperature were also significantly improved by adding AB2 alloy. The discharge capacity of LaNi–5%AB2 composite alloy electrode at 233 K was up to 215 mAh/g.
Co-reporter:Liangliang Guo, Yuan Li, Yufei Ma, Yang Liu, Dandan Peng, Lu Zhang, Shumin Han
International Journal of Hydrogen Energy (26 January 2017) Volume 42(Issue 4) pp:
Publication Date(Web):26 January 2017
DOI:10.1016/j.ijhydene.2016.11.184
•The LiBH4@CNCs composite with special pentagram structure was obtained.•Confinement and catalysis form a synergetic effect on hydrogen storage properties.•Hydrogen desorption temperature reduces to 320 °C with an 200 °C onset temperature.•Rehydrogenation of LiBH4 is achieved under 400 °C and 50 bar H2.In this work, we first obtained carbon nanocages (CNCs) with nanoporous structure and high specific surface area via a template synthesis method, and then prepared a LiBH4@CNCs hydrogen storage composite by combining melting LiBH4 into the CNCs. Temperature programmed desorption (TPD) analyses show that the composite starts to release hydrogen at 200 °C, with the maximal desorption peak occurs at about 320 °C, which is 180 °C lower than that of the pure LiBH4. Also, the final hydrogen desorption capacity reaches 7.5 wt.%. We also see enhanced reversible properties of the composite, of which 78% initial hydrogen is absorbed after five de/rehydrogenation cycles at 400 °C. The further studies show that the LiBH4 can react with the oxygen-containing group of CNCs to form LiBO2 during the infiltration process. The LiBO2 dispersed on the scaffold of CNCs further reacts with LiBH4 to release more hydrogen, and the reaction product Li3BO3 as an efficient catalyst can significantly improve the reversible hydrogen storage properties of the LiBH4. The synergetic effect of nanoconfinement of CNCs and catalysis of Li3BO3 is proved to be largely beneficial for the decomposition process and reversible hydrogen absorption of LiBH4.
Co-reporter:Jiasheng Wang, Shumin Han, Zhibin Wang, Dandan Ke, Jingjing Liu and Mingzhen Ma
Dalton Transactions 2016 - vol. 45(Issue 16) pp:NaN7048-7048
Publication Date(Web):2016/03/08
DOI:10.1039/C6DT00045B
The 2LiBH4–MgH2 + 20 wt% BaTiO3 composite was prepared by ball-milling LiBH4, MgH2 and BaTiO3, and the effect of BaTiO3 on the hydrogen storage properties of the composite was investigated. TG-DSC results show that the onset dehydrogenation temperature of the composite is 299 °C, which is 124 °C lower than that of 2LiBH4–MgH2, and the dehydrogenation amount of the composite increases from 6.86 wt% to 7.48 wt% at 500 °C. Kinetic tests show that the dehydrogenation amount of 2LiBH4–MgH2 + 20 wt% BaTiO3 reaches 1.5 wt% within 400 seconds, almost 10 times that of 2LiBH4–MgH2. BaTiO3 reacts with LiBH4 during the dehydrogenation of the composite and generates BaB6 and TiO2. BaB6 is beneficial to lower the stability of LiBH4, while TiO2 has a catalytic effect in improving the hydrogenation/dehydrogenation kinetics of the reaction between Mg and LiBH4.
Co-reporter:Yaru Pei, Wenkai Du, Yuan Li, Wenzhuo Shen, Yunchai Wang, Shuqin Yang and Shumin Han
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 27) pp:NaN18192-18192
Publication Date(Web):2015/06/09
DOI:10.1039/C5CP02395E
An efficient carbon–polyaniline (PANI)-coated method was applied for perovskite-type oxide LaFeO3 to enhance its high-temperature electrochemical performance. Transmission electron microscopy (TEM) results reveal that LaFeO3 particles are evenly coated with carbon and PANI hybrid layers after carbon–PANI treatment. The carbon layers prevent the nanosized LaFeO3 particles from aggregation and allow the electrolyte to penetrate in every direction inside the particles. The PANI layers also enhance the electrocatalytic activity, facilitating hydrogen protons transferring from the electrolyte to the electrode interface. The cooperation of carbon and PANI hybrid layers results in a significant enhancement of the electrochemical performance at high temperatures. At an elevated temperature (60 °C), the maximum discharge capacity of the LaFeO3 electrodes remarkably increases from 231 mA h g−1 to 402 mA h g−1 and the high rate dischargeability at a discharge current density of 1500 mA g−1 (HRD1500) increases from 22.7% to 44.3%. Moreover, the hybrid layers mitigate the corrosion of LaFeO3 electrodes by reducing the loss of active materials in the alkaline electrolyte, leading to increase in the capacity retention rate from 67.1% to 77.6% after 100 cycles (S100).
Co-reporter:Lu Zhang, Yuan Li, Xin Zhao, Jingjing Liu, Dandan Ke, Wenkai Du, Shuqin Yang and Shumin Han
Journal of Materials Chemistry A 2015 - vol. 3(Issue 26) pp:NaN13690-13690
Publication Date(Web):2015/05/21
DOI:10.1039/C5TA02554K
A Ce2Ni7-type single-phase La0.78Mg0.22Ni3.45 alloy has been prepared by zoning annealing of the as-cast sample. It is found that at temperatures below 890 °C, non-super-stacking CaCu5- and MgCu4Sn-type phases disappear and super-stacking Ce5Co19-, Gd2Co7- and Ce2Ni7-type phases remain. The Ce5Co19-type phase can totally transform into the Ce2Ni7-type phase via a peritectic reaction at temperatures of 890–900 °C. At temperatures of 900–950 °C, the Gd2Co7-type phase melts and decomposes into the Ce5Co19-type phase, and the newly formed Ce5Co19-type phase subsequently reacts to form the Ce2Ni7-type phase. The Ce2Ni7-type single phase remains stable even at higher temperatures of 950–975 °C. The single-phase alloy shows a superior discharge capacity, close to 394 mA h g−1, and high electrochemical cycling stability, which can achieve 413 cycles as its discharge capacity reduces to 60% of the maximum value. We found that the capacity attenuation of the single-phase alloy is mainly due to the loss of active material at the alloy surface caused by oxidization of La and Mg, and the pulverization of the alloy is not severe with 100 charge/discharge cycles. The crystal structure of the single-phase alloy can be preserved well. Oxidation of La occurs prior to that of Mg. La hydroxide grows from nano-structured needles to larger-scaled rods then to unformed lamellar hydroxide, whereas the precipitation of Mg forms as irregular lamellae inlaid with hexagonal flakes.
Co-reporter:Lu Zhang, Yanqiao Ding, Yuan Li, Yumeng Zhao, Xin Zhao, Baozhong Liu and Shumin Han
Journal of Materials Chemistry A 2016 - vol. 4(Issue 24) pp:NaN9429-9429
Publication Date(Web):2016/05/23
DOI:10.1039/C6TA02889F
In this paper, we report a new Gd2Co7-type Sm1.6Mg0.4Ni7 compound as a hydrogen storage material with a special hydrogen absorption/desorption process and good hydrogen storage ability. The Gd2Co7-type Sm1.6Mg0.4Ni7 compound absorbs 1.88 wt% H2 within 17 min at 298 K under 10 MPa H2. Meanwhile, the hydrogen absorption speed accelerates to 3.4 min after 20 hydrogenation/dehydrogenation cycles with a 1.44 wt% H2 under 3 MPa H2. Especially, the capacity retention of the compound is 99.3% at the 100th cycle. We found the hydrogen absorption/desorption of the compound undergoes two equilibrium stages, relating to the transformation of H2 between H-solid solution phase and hydride phase with a lower rate and higher enthalpy change at the lower concentration H2 stage, and the direct conversion between H2 and the hydride phase with a higher rate and lower enthalpy change at the higher concentration H2 stage. The two step mode lowers the inner-molecular strain and mismatch in subunit volumes of the compound in hydrogen absorption/desorption, caused by the transformation of H2 at the lower concentration of H2 stage, thus leading to good structural stability and excellent cycling stability. The new insights are expected to provide viable intermetallic materials as high-pressure tank materials for hydrogen storage with nice hydrogen storage properties.
