Co-reporter:Shangfeng Jiang;Baolian Yi;Qing Zhao;Zhigang Shao
RSC Advances (2011-Present) 2017 vol. 7(Issue 19) pp:11719-11723
Publication Date(Web):2017/02/13
DOI:10.1039/C7RA00194K
Ordered titanium dioxide nanorod arrays are prepared by a hydrothermal method and applied to the catalyst supports of the palladium–nickel catalysts (Pd2Ni3–TiO2) for formic acid oxidation. Due to the three-dimensional catalytic structure and alloying effect, the Pd2Ni3–TiO2 exhibits superior mass activity and long-term stability than those of Pd–TiO2 and commercial PdC catalysts. The present work opens a new approach to design catalysts with superior catalytic performance and durability for direct formic acid fuel cells with three-dimensional catalytic structure.
Co-reporter:Xueqiang Gao;Jia Jia;Jinkai Hao;Feng Xie;Jun Chi;Bowen Qin;Li Fu;Wei Song;Zhigang Shao
RSC Advances (2011-Present) 2017 vol. 7(Issue 31) pp:19153-19161
Publication Date(Web):2017/03/28
DOI:10.1039/C7RA01980G
The anion exchange ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) enhances anion transport in the catalyst layer of the electrode, and thus improves performance and durability of the AEMFC. In this work, a novel ionomer based on a triblock copolymer with high conductivity and good durability is synthesized successfully. The spectroscopy (such as 1H-NMR, FT-IR) results of the ionomer indicate that the functional group is grafted onto the poly(styrene-ethylene/butylene-styrene) (SEBS) successfully and the OH− conductivity of the ionomer is 30 mS cm−1 at 75 °C. Besides, quaternary ammonium SEBS (QASEBS) is used as the ionomer in a H2/O2 AEMFC and exhibits a significant durability of 500 h at a constant current density of 100 mA cm−2, moreover, the degradation rate of voltage is only 0.22 mV h−1 during the 500 h durability test. In addition, the peak power density of the membrane electrode assembly (MEA) with the QASEBS ionomer reaches 375 mW cm−2 at 50 °C, which is 3 times than that of the MEA using the commercially available Acta I2 ionomer (124 mW cm−2) for comparison.
Co-reporter:Yachao Zeng;Xiaoqian Guo;Zhiqiang Wang;Jiangtao Geng;Hongjie Zhang;Wei Song;Zhigang Shao;Baolian Yi
Nanoscale (2009-Present) 2017 vol. 9(Issue 20) pp:6910-6919
Publication Date(Web):2017/05/25
DOI:10.1039/C7NR01491K
Proton exchange membrane fuel cells are promising candidates for the next-generation power sources; however, poor durability and high cost impede their widespread application. To address this dilemma, a nanostructured membrane electrode assembly (MEA) based on Pt/Nb2O5 nanobelts (NBs) was constructed through hydrothermal synthesis and the physical vapour deposition method. Pt/Nb2O5 NBs were directly aligned with Nafion membrane without ionomer as a binder. The prepared catalyst layer is ultrathin and has ultralow Pt loading. A single cell performance of 5.80 kW gPt−1 (cathode) and 12.03 kW gPt−1 (anode) was achieved by the Pt/Nb2O5 NBs-based MEA (66.0 μgPt cm−2). The accelerated durability test indicates that the Pt/Nb2O5 NBs-based MEA is far more stable than conventional Pt/C-based MEA.
Co-reporter:Jun Chi, Hongmei YuBowen Qin, Li Fu, Jia Jia, Baolian Yi, Zhigang Shao
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 1) pp:
Publication Date(Web):December 14, 2016
DOI:10.1021/acsami.6b13360
Employing a low-cost and highly efficient electrocatalyst to replace Ir-based catalysts for oxygen evolution reaction (OER) has drawn increasing interest in renewable energy storage. In this work, a vertically aligned FeOOH/NiFe layered double hydroxides (LDHs) nanosheets supported on Ni foam (VA FeOOH/NiFe LDHs-NF) is prepared as a highly effective OER electrode in alkaline electrolyte. The VA FeOOH/NiFe LDHs-NF represents nanosheet arrays on nickel foam with some interspace among them. The vertically aligned and interlayer-structured architecture is binder-free and contributes to facile strain relaxation, relieving the exfoliation of the catalysts layer caused by the oxygen evolution process. The as-prepared electrode shows current densities of 10 and 500 mA cm–2 at overpotentials of 208 and 288 mV, and good stability in a half-cell electrolyzer. Besides, the alkaline polymer electrolyte water electrolyzer (APEWE) with this electrode showed 1.71 V at 200 mA cm–2, and 2.041 V at 500 mA cm–2, exhibiting the corresponding energy efficiency of 86.0% and 72.0% (based on the lower heating value of hydrogen), which is better than the typical commercial alkaline water electrolyzer.Keywords: alkaline polymer electrolyte water electrolyzer; binder-free; layered double hydroxides; oxygen evolution reaction; water splitting;
Co-reporter:Bowen Qin;Jun Chi;Jia Jia;Xueqiang Gao;Dewei Yao;Baolian Yi;Zhigang Shao
RSC Advances (2011-Present) 2017 vol. 7(Issue 50) pp:31574-31581
Publication Date(Web):2017/06/16
DOI:10.1039/C7RA03675B
Alkaline anion exchange membrane fuel cells have faster kinetics for the oxygen reduction reaction (ORR) than proton exchange membrane fuel cells; however, the hydrogen oxidation reaction (HOR) at anodes with precious metals is more sluggish under alkaline conditions than that under acidic conditions, which hinders the further development of fuel cells. Herein, a novel catalyst, iridium nanoparticle-supported ceria–carbon black (10% Ir/CeO2–C), was developed for use in the hydrogen oxidation reaction (HOR) under basic conditions. Cyclic voltammetry reveals that the electrochemical surface area of 10% Ir/CeO2–C is 1.5 times that of 10% Ir/C. The RDE measurement suggests that the exchange current density of 10% Ir/CeO2–C is 2.4 times that of 10% Ir/C, and the mass activity and specific activity of 10% Ir/CeO2–C for HOR are greater than those of 10% Ir/C by 2.8 fold and 1.8 fold, respectively. The effective prevention of the agglomeration of the highly dispersed Ir nanoparticles could be ascribed to the strong metal–support interaction between Ir and CeO2, and the promoted electrocatalytic activity would benefit from the oxophilic effect due to the higher oxygen storage-release capacity of ceria. Thus, 10% Ir/CeO2–C would be a good candidate for use at the anode of alkaline anion exchange membrane fuel cells.
Co-reporter:Jia Jia;Xueqiang Gao;Jun Chi;Bowen Qin;Wei Song;Zhigang Shao;Baolian Yi
Journal of Materials Chemistry A 2017 vol. 5(Issue 28) pp:14794-14800
Publication Date(Web):2017/07/18
DOI:10.1039/C7TA02437A
A novel cathode architecture using vertically aligned Cu nanoneedle arrays (NNAs) as an ordered support for alkaline anion-exchange membrane fuel cell (AAEMFC) application is developed. Cu NNAs are directly grown on a GDL via three steps of electrochemical reaction. After depositing a Pd layer on the surface of Cu by a pulse electrodeposition method to form Pd/CuNNAs, the cathode catalyst layer is formed. The AAEMFC prepared without alkaline ionomer in the cathode catalyst layer shows an enhanced performance with ultra-low Pd loading down to 47 μg cm−2, which is much higher than that of a conventional cathode electrode with the Pt loading of 100 μg cm−2. This is the first report where three-dimensional Cu NNAs are applied as the cathode support in an AAEMFC, which is able to deliver a higher power density without an alkaline ionomer than conventional MEAs.
Co-reporter:Guangfu Li, Hongmei Yu, Donglei Yang, Jun Chi, Xunying Wang, Shucheng Sun, Zhigang Shao, Baolian Yi
Journal of Power Sources 2016 Volume 325() pp:15-24
Publication Date(Web):1 September 2016
DOI:10.1016/j.jpowsour.2016.06.004
•Surfactant effect on synthesis of IrSn bimetallic oxides has been illustrated.•Structure-performance correlation for oxygen evolution is well comprehended.•An as-prepared sample shows 2-time higher activity than commercial Ir black.•Superior stability is observed both in half-cell and electrolyser tests.•Fabricated IrSn catalyst is economically feasible for large scale applications.Addressing major challenges from the material cost, efficiency and stability, it is highly desirable to develop high-performance catalysts for oxygen evolution reaction (OER). Herein we explore a facile surfactant-assisted approach for fabricating IrSn (Ir/Sn = 0.6/0.4, by mol.) nano-oxide catalysts with good morphology control. Direct proofs from XRD and X-ray photoelectron spectra indicate hydrophilic triblock polymer (TBP, like Pluronic® F108) surfactant can boost the formation of stable solid-solution structure. With the TBP hydrophilic and block-length increase, the fabricated IrSn oxides undergoing the rod-to-sphere transition obtain the relatively lower crystallization, decreased crystallite size, Ir-enriched surface and incremental available active sites, all of which can bolster the OER activity and stability. Meanwhile, it is observed that the coupled Ir oxidative etching takes a crucial role in determining the material structure and performance. Compared with commercial Ir black, half-cell tests confirm F108-assistant catalysts with over 40 wt% Ir loading reduction show 2-fold activity enhancement as well as significant stability improvement. The lowest cell voltage using 0.88 mg cm−2 Ir loading is only 1.621 V at 1000 mA cm−2 and 80 °C with a concomitant energy efficiency of 75.8% which is beyond the DOE 2017 efficiency target of 74%.
Co-reporter:Shangfeng Jiang, Baolian Yi, Longsheng Cao, Wei Song, Qing Zhao, Hongmei Yu, Zhigang Shao
Journal of Power Sources 2016 Volume 329() pp:347-354
Publication Date(Web):15 October 2016
DOI:10.1016/j.jpowsour.2016.08.098
•Vertically aligned PPy NWs were employed as the ordered catalyst supports.•PtPd-PPy electrode without additional proton conducting ionomer.•PtPd-PPy show better mass-transfer than that of commercial Pt/C based electrode.The degradation of carbon supports significantly influences the performance of proton exchange membrane fuel cells (PEMFCs), particularly in the cathode, which must be overcome for the wide application of fuel cells. In this study, advanced catalytic layer with electronic conductive polymer–polypyrrole (PPy) nanowire as ordered catalyst supports for PEMFCs is prepared. A platinum–palladium (PtPd) catalyst thin layer with whiskerette shapes forms along the long axis of the PPy nanowires. The resulting arrays are hot-pressed on both sides of a Nafion® membrane to construct a membrane electrode assembly (without additional ionomer). The ordered thin catalyst layer (approximately 1.1 μm) is applied in a single cell as the anode and the cathode without additional Nafion® ionomer. The single cell yields a maximum performance of 762.1 mW cm−2 with a low Pt loading (0.241 mg Pt cm−2, anode + cathode). The advanced catalyst layer indicates better mass transfer in high current density than that of commercial Pt/C-based electrode. The mass activity is 1.08-fold greater than that of DOE 2017 target. Thus, the as-prepared electrodes have the potential for application in fuel cells.
Co-reporter:Shangfeng Jiang; Baolian Yi;Hongjie Zhang; Wei Song;Yangzhi Bai; Hongmei Yu; Zhigang Shao
ChemElectroChem 2016 Volume 3( Issue 5) pp:734-740
Publication Date(Web):
DOI:10.1002/celc.201500571
Abstract
The degradation of the carbon supports and high platinum (Pt) loading significantly hinder the wide adoption of proton exchange membrane fuel cells. In conventional electrodes, the ionomer binders introduce an undesirable, high oxygen-transport resistance and cover the catalysts active sites. Herein, an advanced catalytic layer based on vertically aligned titanium nitride nanorod arrays (TiN NRs) is prepared, without additional ionomer or binders in the cathode. After supporting the thin-film platinum–palladium–cobalt (PtPdCo) catalyst (Pt loading: 66.9 μm cm−2) onto TiN NRs, the ordered electrodes were investigated as the cathode of a single cell without additional ionomer in the catalytic layer. With this electrode architecture, the as-synthesized electrode performs with a maximum power density of 390.5 mW cm−2 and cathode mass-specific power density of 5.84 W mgPt−1. The 2000 potential cycles accelerated degradation test shows that the PtPdCo–TiN electrode is more stable than the commercial gas diffusion electrode.
Co-reporter:Shangfeng Jiang; Baolian Yi;Hongjie Zhang; Wei Song;Yangzhi Bai; Hongmei Yu; Zhigang Shao
ChemElectroChem 2016 Volume 3( Issue 5) pp:
Publication Date(Web):
DOI:10.1002/celc.201600168
Co-reporter:Changkun Zhang, Hongmei Yu, Li Fu, Yu Xiao, Yuan Gao, Yongkun Li, Yachao Zeng, Jia Jia, Baolian Yi, Zhigang Shao
Electrochimica Acta 2015 Volume 153() pp:361-369
Publication Date(Web):20 January 2015
DOI:10.1016/j.electacta.2014.10.090
An oriented ultrathin catalyst layer (UTCL) has been prepared for fuel cells application based on the high electrical conductivity TiO2 nanotube (TNTs). The electrical conductivity of TNTs was improved by the deposited C via a plasma enhanced chemical vapor deposition (PECVD) technique. Pt catalysts were deposited on the high electrical conductivitve TNTs by the radio frequency (RF) sputtering to form the oriented C-TNTs-Pt electrode. The mass activity of C-TNTs-Pt-1 at 0.85 V was about 0.44 A mgPt−1. The prepared oriented UTCL based on the C-TNTs-Pt electrode displayed a maximum power density of 206 and 305 mW cm−2 at an ultralow Pt loading resulting in a relatively high Pt utilization of 8.3 and 6.0 kW g−1Pt. A 2D symmetry model based on the parameters of the oriented UTCL was established. In the model, the performance of fuel cell was improved along with the decreasing of CL thickness. Meanwhile, it is found that there is little effect on the cell performance when the electrical conductivity of CL is larger than 3 S cm−1. The study in this work gave effectual evidence on the possibility of using the oriented UTCL for developing low cost fuel cells.
Co-reporter:Yun Zhao, Hongmei Yu, Feng Xie, Yanxi Liu, Zhigang Shao, Baolian Yi
Journal of Power Sources 2014 Volume 269() pp:1-6
Publication Date(Web):10 December 2014
DOI:10.1016/j.jpowsour.2014.06.026
•The pore-filled anion exchange membranes are successfully prepared.•The membranes exhibit high ionic conductivity and excellent alkaline durability.•The fuel cell with the resulting membranes shows excellent high power out.A series of composite anion exchange membranes are successfully synthesized by thermal polymerization of chloromethyl monomer in a porous polyethylene (PE) substrate followed by amination with trimethylamine for alkaline anion exchange membrane fuel cells (AAEMFCs) application. These membranes exhibit excellent alkaline durability and high ionic conductivity. The resulting alkaline anion exchange membranes (AAEMs) show a hydroxide conductivity up to 0.057 S cm−1 at 30 °C in deionized water and do not exhibit significant changes in the ionic conductivity and the IEC in 1 M KOH solution at 60 °C for around 1000 h. The maximum power density of 370 mW cm−2 is obtained at 50 °C for H2/O2 AAEMFC.High durability and hydroxide ion conducting pore-filled anion exchange membranes is developed.
Co-reporter:Guangfu Li, Hongmei Yu, Xunying Wang, Donglei Yang, Yongkun Li, Zhigang Shao, Baolian Yi
Journal of Power Sources 2014 Volume 249() pp:175-184
Publication Date(Web):1 March 2014
DOI:10.1016/j.jpowsour.2013.10.088
•Ir–Sn oxide is synthesized by an advanced soft-material assistant method.•Ir–Sn oxide properties depend on the F127 content.•Ir–Sn oxide shows significantly high activity and stability for O2 evolution.•The noble-metal loading in the water electrolysis anode is only 0.77 mg cm−2.Over the past several decades, tremendous effort has been put into developing cost-effective, highly active and durable electrocatalysts for oxygen evolution reaction (OER) in the proton exchange membrane water electrolyzer. This report explores an advanced and effective “soft” material-assistant method to fabricate Ir0.6Sn0.4O2 electrocatalysts with a 0.6/0.4 ratio of Ir/Sn in precursors. Adopting a series of characterization methods, the collective results suggest that the surfactant-material F127 content, as an important factor, can efficiently control the formation of Ir–Sn oxides with varying surface properties and morphologies, such as the grainy and rod-shaped structures. Associating with the half-cell and single electrolyzer, it is affirmed that the optimal ratio of (Ir + Sn)/F127 is 100 for the preparation of S100-Ir0.6Sn0.4O2 with obviously enhanced activity and sufficient durability under the electrolysis circumstances. The lowest cell voltages obtained at 80 °C are 1.631 V at 1000 mA cm−2, and 1.820 V at 2000 mA cm−2, when applying S100-Ir0.6Sn0.4O2 OER catalyst and Ti-material diffusion layer on the anode side and Nafion® 115 membrane. Furthermore, the noble-metal Ir loading in the same cell decreases to 0.77 mg cm−2. These results highlight that Ir–Sn oxide synthesized by the soft-material method is a promising OER electrocatalyst.
Co-reporter:Donglei Yang, Hongmei Yu, Guangfu Li, Yun Zhao, Yanxi Liu, Changkun Zhang, Wei Song, Zhigang Shao
Journal of Power Sources 2014 Volume 267() pp:39-47
Publication Date(Web):1 December 2014
DOI:10.1016/j.jpowsour.2014.04.053
•Microstructure of electrode with anion-exchange ionomer is studied and improved.•The colloidal anion-exchange ionomer is prepared and evaluated for the first time.•A high performance of 407 mW cm−2 in the alkaline fuel cell is obtained.The electrode fabrication and resulting microstructure are the main determinates of the performance of alkaline anion exchange membrane fuel cells (AAEMFCs). In the present work, the electrode microstructure is adjusted by the ionomer content in catalyst layers as well as the dispersion solvent for catalyst inks. The ionomer content shows a strong influence on the cell active, ohmic and mass-diffusion polarization losses. Especially, an in-suit proof for the ionomer as the hydroxide conductor is first given by the cell cycle voltammogram, and the optimum content is 20 wt.%. Meanwhile, it is found that the ionomer either dissolves in the dielectric constant ɛ = 18.3–24.3 solutions (including ethanol, propanol and isopropanol) or disperses in the n-butyl acetate (ɛ = 5.01) colloid. Compared with these electrodes using the solution method, the colloidal electrode tends to form the larger catalyst/ionomer agglomerates, increased pore volume and pore diameter, continuous ionomer networks for hydroxide conduction, and correspondingly decreased ohmic and mass-diffusion polarization losses. Ultimately, when employing the optimum ionomer content and the colloid approach, the highest peak power density we achieved in AAEMFC is 407 mW cm−2 at 50 °C, which can be taken as a considerable success in comparison to the current results in publications.
Co-reporter:Li Fu, Hongmei Yu, Changkun Zhang, Zhigang Shao, Baolian Yi
Electrochimica Acta 2014 Volume 136() pp:363-369
Publication Date(Web):1 August 2014
DOI:10.1016/j.electacta.2014.05.094
Hydrogen production from solar and photoelectrochemical water splitting based on modified nanostructure hematite is investigated for sustainable energy development. Herein, nanorod hematite arrays are prepared by adjusted-hydrothermal method with a diameter of 30 nm. Phosphate group and cobalt ions are deposited on the surface of hematite by chemical immersion process to improve its photoelectrochemical performance and speed up the oxygen evolution reaction in water splitting. The CoPi-modified α-Fe2O3 nanorod arrays (NAs) show a greatly enhanced electrochemical and photoelectrochemical property with a photocurrent density 270 μA cm−2 at 1.23 V (vs. RHE) for FeCoPi-4 compared with 20 μA cm−2 for untreated α-Fe2O3 NAs. The effect of phosphate groups and cobalt ions on the α-Fe2O3 NAs are both investigated. The Co (II) ion is connected closely with the α-Fe2O3 surface through phosphate groups by XPS detection. The phosphate enhances the transport of electron from α-Fe2O3 to Co ion. The high performance demonstrated in photoelectrochemical test indicates that CoPi-modified α-Fe2O3 NAs is a potential photoelectrocatalyst for water splitting.
Co-reporter:Li Fu, Hongmei Yu, Yongkun Li, Changkun Zhang, Xunying Wang, Zhigang Shao and Baolian Yi
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 9) pp:4284-4290
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3CP54240H
We reported a facile adjusted method for the synthesis of high surface area nanorod hematite film as a photoanode for application in water splitting. Crystalline hematite nanorods (EG-α-Fe2O3) are fabricated by electrodeposition in Fe2+ precursor solution with the addition of ethylene glycol (EG) and followed by annealing at 450 °C. The nanorod hematite film fabricated by the modified electrodeposition approach exhibits a more uncompact structure than α-Fe2O3 obtained by directly electrodepositing on the FTO substrate. The optical and structural characteristics of the obtained film are also tested. The results infer that EG can tune the morphology of hematite and improve the photoabsorption in the visible light region due to its inducement of one-dimensional growth of crystal hematite. It also enhances the photoresponse activity of hematite in water splitting by improving the activities at the semiconductor/solution interface. The photocurrent density of EG-α-Fe2O3 nanorods increased to 0.24 mA cm−2 at 1.4 V vs. RHE in 1 M KOH (pH = 13.6), almost 5 times higher than the original α-Fe2O3 (0.05 mA cm−2, measured under the same conditions).
Co-reporter:Changkun Zhang, Hongmei Yu, Li Fu, Yuan Gao, Jia Jia, Shangfeng Jiang, Baolian Yi and Zhigang Shao
RSC Advances 2014 vol. 4(Issue 102) pp:58591-58595
Publication Date(Web):29 Oct 2014
DOI:10.1039/C4RA09759A
Wheat ear-like catalysts were prepared on Co–OH–CO3 nanowires to design an ultra-thin catalyst layer (UTCL). Without any ionomers, the UTCL exhibited a maximum power density of 481 mW cm−2 at an ultra-low Pt loading of 43 μg cm−2Pt, resulting in a relatively high Pt utilization of 11.2 kW g−1Pt. It is expected that the nanostructured thin film materials will lead to further technological advancements in fuel cells and other applications.
Co-reporter:Changkun Zhang, Hongmei Yu, Yongkun Li, Li Fu, Yuan Gao, Wei Song, Zhigang Shao and Baolian Yi
Nanoscale 2013 vol. 5(Issue 15) pp:6834-6841
Publication Date(Web):15 May 2013
DOI:10.1039/C3NR01086D
Herein the Pt nanocrystals were synthesized by a high-pressure methanol reduction method onto the hydrogenated TiO2 nanotube arrays pre-treated by Sn/Pd. Then Sn/Pd/Pt ternary catalysts were fabricated by hydrogen treatment. The composite catalysts with a diameter of about 18 nm were located uniformly at the inner nanotubes. The novel catalyst combined with hydrogenated TiO2 nanotube arrays exhibits excellent electro-catalytic activity and high durability. The electrochemical performance of the catalysts after 18000 potential cycles between 0 and 1.2 V vs. RHE could reach the maximum, and the electrochemical surface area of the catalyst at 18000 cycles is about 136 m2 g−1Pt+Pd, which is 1.3 folds than the commercial JM Pt/C (104 m2 g−1Pt). Furthermore, there is little decrease in the electrochemical surface area for the catalyst after additional 7300 potential cycles (total 24300 cycles). In a full cell testing, the fabricated novel electrode with extra-low Pt loading (0.043 mg cm−2) generated power as 1.21 kW g−1Pt when it is used as the cathode in a fuel cell.
Co-reporter:Yun Zhao, Hongmei Yu, Donglei Yang, Jin Li, Zhigang Shao, Baolian Yi
Journal of Power Sources 2013 Volume 221() pp:247-251
Publication Date(Web):1 January 2013
DOI:10.1016/j.jpowsour.2012.08.053
A crosslinked composite anion exchange membrane was first prepared for anion exchange membrane fuel cell (AEMFC) application by a feasible route. The membrane exhibited high ionic conductivity, excellent dimensional and thermal stability. An AEMFC assembled with the crosslinked composite membrane showed high power output and promising cell durability. This result indicates that the crosslinked composite membrane has potential for AEMFC application.Graphical abstractHigh-performance alkaline anion exchange membrane fuel cell using novel crosslinked composite anion exchange membrane is developed.Highlights► A crosslinked composite membrane is successfully prepared by a feasible route. ► The composite membrane exhibits high ionic conductivity and excellent stability. ► The fuel cell with the crosslinked composite membrane shows excellent high power out.
Co-reporter:Yongkun Li, Hongmei Yu, Changkun Zhang, Wei Song, Guangfu Li, Zhigang Shao, Baolian Yi
Electrochimica Acta 2013 Volume 107() pp:313-319
Publication Date(Web):30 September 2013
DOI:10.1016/j.electacta.2013.05.090
•A novel PEC cell with a membrane electrode assembly is proposed and investigated.•The alkaline anion exchange membrane used in this PECs separate the evolved gases.•Influence of water on the morphology of the TiO2NTs is investigated and discussed.•Effect of annealing treatment of TiO2NTs on the hydrogen production is carried out.An efficient and economical technology for hydrogen production via solar water splitting in a newly designed photoelectrochemical (PEC) cell is reported. The core of the PEC cell is a membrane electrode assembly (MEA) that consisted of a TiO2 nanotube photoanode, a Pt/C cathode and alkaline membrane. The TiO2 nanotube arrays (NTs) were prepared by electrochemical anodization of titanium mesh in a mixed electrolyte solution of glycol and NH4F and then calcined at different temperature to transform the amorphous structure into crystalline. Effect of water content on the morphology of the TiO2NTs is investigated, and the optimal amount of water in the electrolyte is between 10 wt% and 80 wt%. Emphasis was the effect of the annealing temperature of anodized TiO2NTs on the hydrogen production in the PEC cell. The results indicate that the crystal phase and morphology of TiO2NTs are stable at 450 °C, which exhibits the best photocatalytic activity. Photocurrent generation of 1.55 mA/cm2 under UV-light irradiation under applied bias (0.6 V vs. Normal Hydrogen Electrode, NHE) shows good performance on hydrogen production.
Co-reporter:Guangfu Li, Hongmei Yu, Xunying Wang, Shucheng Sun, Yongkun Li, Zhigang Shao and Baolian Yi
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 8) pp:2858-2866
Publication Date(Web):18 Dec 2012
DOI:10.1039/C2CP44496H
We developed an advanced surfactant-assistant method for the IrxSn1−xO2 (0 < x ≤ 1) nanoparticle (NP) preparation, and examined the OER performances by a series of half-cell and full-cell tests. In contrast to the commercial Ir black, the collective data confirmed the outstanding activity and stability of the fabricated IrxSn1−xO2 (x = 1, 0.67 and 0.52) NPs, which could be ascribed to the amorphous structure, good dispersion, high pore volume, solid-solution state and Ir-rich surface for bi-metal oxides, and relatively large size (10–11 nm), while Ir0.31Sn0.69 exhibited poor electro-catalytic activity because of the separated two phases, a SnO2-rich phase and an IrO2-rich phase. Furthermore, compared with highly active IrO2, the improved durability, precious-metal Ir utilization efficiency and correspondingly reduced Ir loading were realized by the addition of Sn component. When the Ir0.52Sn0.48O2 cell operated at 80 °C using Nafion® 115 membrane and less than 0.8 mg cm−2 of the noble-metal Ir loading, the cell voltages we achieved were 1.631 V at 1000 mA cm−2, and 1.821 V at 2000 mA cm−2. The IR-free voltage at the studied current density was very close to the onset voltage of oxygen evolution. The only 50 μV h−1 of voltage increased for the 500 h durability test at 500 mA cm−2. In fact, these results are exceptional compared to the performances for OER in SPEWE cells known so far. This work highlights the potential of using highly active and stable IrO2–SnO2 amorphous NPs to enhance the electrolysis efficiency, reduce the noble-metal Ir loading and thus the cost of hydrogen production from the solid polymer electrolyte water electrolysis.
Co-reporter:Yun Zhao, Jing Pan, Hongmei Yu, Donglei Yang, Jin Li, Lin Zhuang, Zhigang Shao, Baolian Yi
International Journal of Hydrogen Energy 2013 Volume 38(Issue 4) pp:1983-1987
Publication Date(Web):12 February 2013
DOI:10.1016/j.ijhydene.2012.11.055
The quaternary ammonia polysulfone (QAPS) alkaline anion exchange membrane (AAEM) was previously prepared successfully. The QAPS membrane showed good ionic conductivity but poor mechanical strength and high swelling ratio. This study focused on membrane mechanical strength and dimensional stability by PTFE membrane enhancement, which increases the mechanical strength by five times and decreases the swelling ratio by 50%. The fuel cell with the resulted thinner QAPS/PTFE composite membrane with catalyst coated membrane (CCM) as the electrode showed a high power output, and the peak power density of 315 mW cm−2 was achieved at 50 °C.Highlights► The QAPS/PTFE composite membrane was prepared by a facile procedure. ► The composite membrane increases mechanical strength and decreases swelling ratio. ► SEM results indicate that the pores of PTFE membrane are completely filled. ► The fuel cell with the resulting thinner composite membrane showed high power out.
Co-reporter:Yongkun Li, Hongmei Yu, Changkun Zhang, Li Fu, Guangfu Li, Zhigang Shao, Baolian Yi
International Journal of Hydrogen Energy 2013 Volume 38(Issue 29) pp:13023-13030
Publication Date(Web):30 September 2013
DOI:10.1016/j.ijhydene.2013.03.122
•Au nanoparticles decorated TiO2 nanorods modified electrode was synthesized.•The modified electrode shows excellent photoactivity toward water splitting.•The Au amount can be well controlled by changing the deposition time.•The Au underlayers assisted the vectorial transfer of the photogenerated charges.We report on the design and synthesis of a novel Au/TiO2/Au heterostructure and its implementation as a photoanode for photoelectrochemical (PEC) application. The Au/TiO2/Au heterostructure was produced by assembling Au nanoparticles and TiO2 nanorods (NRs) onto FTO substrate, followed by electrodepositing Au nanoparticles on the TiO2NRs. Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods were adopted to characterize the prepared photoanodes. Compared to the system involving Au nanoparticles directly linked to TiO2, this Au/TiO2/Au heterostructure exhibits significant improved photoresponse as a photoanode, as demonstrated good performance in PECs. This study illustrates the importance of pre-deposited Au underlayers in influencing PEC properties of hybrid assembled nanostructures. As the Au/TiO2NRs/Au photoanodes are easily fabricated and highly stable, Au/TiO2NRs/Au can serve as a good substitution for TiO2 in a variety of solar energy driven applications including PEC water splitting, photocatalysis, and solar cells.
Co-reporter:Changkun Zhang, Hongmei Yu, Yongkun Li, Li Fu, Yuan Gao, Wei Song, Zhigang Shao, Baolian Yi
Journal of Electroanalytical Chemistry 2013 Volume 701() pp:14-19
Publication Date(Web):15 July 2013
DOI:10.1016/j.jelechem.2013.04.012
•A simple and efficient strategy was used for the preparation of Pt/TiO2 nanotube.•The electrode exhibited good electrochemical performance and excellent stability.•The performance of electrode is still stable after holding at 1.6 V vs.NHE for 100h.A simple and efficient method was demonstrated for preparing the Pt/TiO2 nanotube arrays by H2 reduction. The effects of the reduction atmospheres and temperatures on Pt catalysts preparation were investigated. The well dispersion of Pt catalysts supported onto the TiO2 nanotube array exhibited favorable electrochemical performance and excellent durability. After 2000 potential cycles between 0 and 1.2 V vs. RHE, the electrochemical surface area of 350-Pt–H–TNTs electrode (Pt catalysts reduced by high purity H2 at 350 °C) decreased by 26% compared with 68% for JM 20% Pt/C after 800 cycles. Meanwhile, the 450-Pt–H–TNTs electrode (Pt catalysts reduced by high purity H2 at 450 °C) showed no decrease in the electrochemical surface area except for a little loss in the reduction of surface oxides after 2000 potential cycles. Furthermore, the electrochemical performance of 450-Pt–H–TNTs electrode is still stable after holding at 1.6 V vs. RHE for 100 h.
Co-reporter:Yongkun Li, Hongmei Yu, Changkun Zhang, Li Fu, Guangfu Li, Zhigang Shao, Baolian Yi
Journal of Electroanalytical Chemistry 2013 Volume 688() pp:228-231
Publication Date(Web):1 January 2013
DOI:10.1016/j.jelechem.2012.10.023
The photoelectrochemical water splitting into hydrogen and oxygen using sun light is a potentially clean and renewable source of hydrogen fuel. TiO2 nanotubes (NTs) grown by anodization in a fluoride based electrolyte were loaded with Ni oxide nanoparticles by a pulse electrodeposition method. The fabricated NiOx/TiO2NTs electrodes were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoemission spectroscopy (XPS). The photoelectrochemical property of fabricated NiOx/TiO2NTs electrodes was characterized by using a compartment cell. It was found that the Ni oxide nanoparticles loaded enhanced the visible spectrum absorption of the TiO2 nanotube arrays, as well as their solar-spectrum induced photocurrents, while a reverse result was obtained under UV-light illumination.Highlights► TiO2 nanotubes grown by anodization in a fluoride based electrolyte were loaded with Ni oxide nanoparticles by a pulse electrodeposition method. ► The nanoparticles inside of the tube wall have a comparably uniform size distribution with an average size of approximately 80 nm. ► The Ni oxide nanoparticles loaded enhanced the visible spectrum absorption of the TiO2 nanotube arrays, as well as their solar-spectrum induced photocurrents.
Co-reporter:Changkun Zhang; Hongmei Yu;Yongkun Li;Yuan Gao;Yun Zhao;Dr. Wei Song; Zhigang Shao; Baolian Yi
ChemSusChem 2013 Volume 6( Issue 4) pp:659-666
Publication Date(Web):
DOI:10.1002/cssc.201200828
Abstract
Hydrogen-treated TiO2 nanotube (H–TNT) arrays serve as highly ordered nanostructured electrode supports, which are able to significantly improve the electrochemical performance and durability of fuel cells. The electrical conductivity of H–TNTs increases by approximately one order of magnitude in comparison to air-treated TNTs. The increase in the number of oxygen vacancies and hydroxyl groups on the H–TNTs help to anchor a greater number of Pt atoms during Pt electrodeposition. The H–TNTs are pretreated by using a successive ion adsorption and reaction (SIAR) method that enhances the loading and dispersion of Pt catalysts when electrodeposited. In the SIAR method a Pd activator can be used to provide uniform nucleation sites for Pt and leads to increased Pt loading on the H-TNTs. Furthermore, fabricated Pt nanoparticles with a diameter of 3.4 nm are located uniformly around the pretreated H–TNT support. The as-prepared and highly ordered electrodes exhibit excellent stability during accelerated durability tests, particularly for the H–TNT-loaded Pt catalysts that have been annealed in ultrahigh purity H2 for a second time. There is minimal decrease in the electrochemical surface area of the as-prepared electrode after 1000 cycles compared to a 68 % decrease for the commercial JM 20 % Pt/C electrode after 800 cycles. X-ray photoelectron spectroscopy shows that after the H–TNT-loaded Pt catalysts are annealed in H2 for the second time, the strong metal–support interaction between the H–TNTs and the Pt catalysts enhances the electrochemical stability of the electrodes. Fuel-cell testing shows that the power density reaches a maximum of 500 mW cm−2 when this highly ordered electrode is used as the anode. When used as the cathode in a fuel cell with extra-low Pt loading, the new electrode generates a specific power density of 2.68 kW gPt−1. It is indicated that H–TNT arrays, which have highly ordered nanostructures, could be used as ordered electrode supports.
Co-reporter:Guangfu Li, Hongmei Yu, Wei Song, Xunying Wang, Yongkun Li, Zhigang Shao, Baolian Yi
International Journal of Hydrogen Energy 2012 Volume 37(Issue 22) pp:16786-16794
Publication Date(Web):November 2012
DOI:10.1016/j.ijhydene.2012.08.087
IrxRu1−xO2(1 ≥ x ≥ 0) with nanorod structure were successfully synthesized by employed pre-filling the Ir and/or Ru guest species into the peripheral-pore of NH2-modified as-synthesized SBA-15 and explored as electrocatalyst for oxygen evolution reaction (OER) in water electrolyzers. Various physicochemical parameters for zeolite template and/or IrxRu1−xO2 were obtained by SEM, TEM, XRD, EDX and N2 gas absorption/desorption measurements. The morphology for prepared IrxRu1−xO2 samples with individual and/or cluster nanorods was changed with the component difference. Cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, steady state polarization curves and stability tests were performed to investigate the catalytic activity and stability of these electrocatalysts for OER. The cell with catalyst RuO2 showed best catalytic performance with the lowest onset potential (1.374 V at 10 mA cm−2), which may be ascribed to regular nanoclusters and larger outer active surface area. Meanwhile, the cell stability tests suggested that the addition of IrO2 in IrxRu1−xO2 improved the stability of the RuO2 catalyst.Graphical abstractHighlights► IrxRu1−xO2 nanorods are successfully synthesized by a zeolite-template method. ► Zeolite-template method has obvious advantage for good morphology control. ► RuO2 shows excellent catalytic activity for oxygen evolution reaction. ► IrO2 addition in IrxRu1−xO2 improves the electrochemical stability of RuO2.
Co-reporter:Changkun Zhang, Hongmei Yu, Yongkun Li, Wei Song, Baolian Yi, Zhigang Shao
Electrochimica Acta 2012 80() pp: 1-6
Publication Date(Web):
DOI:10.1016/j.electacta.2012.05.162
Co-reporter:Guangfu Li;Dr. Wei Song;Meiling Dou;Yongkun Li; Zhigang Shao; Baolian Yi
ChemSusChem 2012 Volume 5( Issue 5) pp:858-861
Publication Date(Web):
DOI:10.1002/cssc.201100519
Co-reporter:Yun Zhao, Hongmei Yu, Danmin Xing, Wangting Lu, Zhigang Shao, Baolian Yi
Journal of Membrane Science 2012 s 421–422() pp: 311-317
Publication Date(Web):
DOI:10.1016/j.memsci.2012.07.034
Co-reporter:Junbo Hou, Hongmei Yu, Min Yang, Wei Song, Zhigang Shao, Baolian Yi
International Journal of Hydrogen Energy 2011 Volume 36(Issue 19) pp:12444-12451
Publication Date(Web):September 2011
DOI:10.1016/j.ijhydene.2011.06.100
This study correlates the post start cell performance and impedance with the cold start process in the subzero environment. The sequential failed cold starts are deliberately conducted as well as the start at small current density. Here the failed cold start means the cell voltage drops to or below zero within very short time during the start process. It is found that there are reversible performance losses for the sequential failed cold starts, while not obvious degradation and no recovery happen for the start at small current density. Using the thin film and agglomerate model, it is confirmed that this is due to the water blocking effect. Comparing the results from different start processes, a model with respect to the shifting of reactive region within the catalyst layer is applied to explain that the reversible performance loss is associated with the amount of the generated water or ice and the water location or distribution during cold start. The relationship of the cold start performance at high current density and the pore volume in the catalyst layer is also discussed.Highlights► The post start performance is correlated with the cold start process. ► Water blocking effect within CL is the reason for the reversible performance loss. ► The loss depends on the water amount and distribution during the start process. ► The findings encourage two strategies for the cold start of PEM fuel cells.
Co-reporter:Yongkun Li, Hongmei Yu, Wei Song, Guangfu Li, Baolian Yi, Zhigang Shao
International Journal of Hydrogen Energy 2011 Volume 36(Issue 22) pp:14374-14380
Publication Date(Web):November 2011
DOI:10.1016/j.ijhydene.2011.08.026
A photoelectrochemical (PEC) cell with an innovative design for hydrogen generation via photoelectrocatalytic water splitting is proposed and investigated. It consisted of a TiO2 nanotube photoanode, a Pt/C cathode and a commercial asbestos diaphragm. The PEC could generate hydrogen under ultraviolet (UV) light-excitation with applied bias in KOH solution. The Ti mesh was used as the substrate to synthesize the self-organized TiO2 nanotubular array layers. The effect of the morphology of the nanotubular array layers on the photovoltaic performances was investigated. When TiO2 photocatalyst was irradiated with UV-excitation, it prompted the water splitting under applied bias (0.6 V vs. Normal Hydrogen Electrode, NHE.). Photocurrent generation of 0.58 mA/cm2 under UV-light irradiation showed good performance on hydrogen production.Highlights► A novel PEC cell with an innovative design is proposed and investigated. ► The designed PEC cell was effective for hydrogen production. ► Pt/C carbon paper as the cathode rather than Pt foil minimized the catalyst loading. ► The new PEC cell takes less space than a typical three-arm reactor.
Co-reporter:Wei Song, Hongmei Yu, Lixing Hao, Baolian Yi, Zhigang Shao
International Journal of Hydrogen Energy 2010 Volume 35(Issue 20) pp:11129-11137
Publication Date(Web):October 2010
DOI:10.1016/j.ijhydene.2010.07.041
Effect of catalytic ink on sub-freezing endurance of proton exchange membrane fuel cells (PEMFCs) was investigated in this paper. By direct spraying method, a catalyst-coated membrane (CCM) was fabricated with isopropyl alcohol as organic solvent (CCM-A), and CCM-B was fabricated with isopropyl alcohol and butyl acetate. The hydrophobicity of the two CCMs was similar proved by contact angle tests, and CCM-B showed larger pore volume demonstrated by mercury intrusion tests. Initial cell performance and relevant electrochemical characteristics of the two CCMs were measured and compared. CCM-B showed better performance and larger electrochemical active surface area (ECA). By analyzing the electrochemical impedance spectra (EIS) at low current densities, the ionic resistances of the catalyst layers were calculated. Results indicated that adding butyl acetate to the catalytic ink benefited the ionic resistance. Then, the fuel cells with the two CCMs were subzero stored at −20 °C with saturated residual water. After 20 freeze–thaw cycles, the CCM prepared with isopropyl alcohol and butyl acetate showed less degradation in terms of polarization curves and EIS. And the ionic resistances of the both CCMs decreased to a certain extent.
Co-reporter:Zhili Miao, Hongmei Yu, Wei Song, Lixing Hao, Zhigang Shao, Qiang Shen, Junbo Hou, Baolian Yi
International Journal of Hydrogen Energy 2010 Volume 35(Issue 11) pp:5552-5557
Publication Date(Web):June 2010
DOI:10.1016/j.ijhydene.2010.03.045
In this study, a novel strategy is reported to improve the cold start performance of proton exchange membrane (PEM) fuel cells at subzero temperatures. Hydrophilic nano-oxide such as SiO2 is added into the catalyst layer (CL) of the cathode to increase its water storing capacity. To investigate the effect of nanosized SiO2 addition, the catalyst coated membranes (CCMs) with 5 wt.% and without nanosized SiO2 are fabricated. Although at normal operation conditions the cell performance with nanosized SiO2 was not so good as that without SiO2, cold start experiments at −8 °C showed that the former could start and run even at 100 mA cm−2 for about 25 min and latter failed very shortly. Even at −10 °C, the addition of SiO2 dramatically increased the running time before the cell voltage dropped to zero. These results further experimentally proved the cold start process was strongly related with the cathode water storage capacity. Also, the performance degradation during 8 cold start cycles was evaluated through polarization curves, cyclic voltammetry (CV) and electrochemical impedance spetra (EIS). Compared with the cell without SiO2 addition, the cell with 5 wt.% SiO2 indicated no obvious degradation on cell performance, electrochemical active surface area and charge transfer resistance after experiencing cold start cycles at −8 °C.
Co-reporter:Wei Song, Hongmei Yu, Lixing Hao, Zhili Miao, Baolian Yi, Zhigang Shao
Solid State Ionics 2010 Volume 181(8–10) pp:453-458
Publication Date(Web):29 March 2010
DOI:10.1016/j.ssi.2010.01.022
A new hydrophobic thin film catalyst layer (CL) was prepared by the decal method in this work. Polytetrafluoroethylene (PTFE) was introduced to the catalyst ink with 1 wt.% Nafion® ionomer as the hyperdispersant. Aluminum foil was adopted as the transferring medium which enabled the sintering process of PTFE. Then an appropriate amount of Nafion® ionomer was sprayed onto the CL for proton conduction. At last, the CL was transferred onto a Nafion® membrane and the catalyst-coated membrane (CCM) was formed. Contact angle measurement and mercury intrusion porosimetry test were conducted to characterize the hydrophobicity and porosity of the thin film CL. The results showed that PTFE addition favored the CL hydrophobicity and porosity. The optimal PTFE content was also deduced by comparing the fuel cell performance under different PTFE contents. Electrochemical analysis revealed that PTFE addition decreased the electrochemical active area (ECA) but enhanced the diffusion process in the CL.
Co-reporter:Zhili Miao, Hongmei Yu, Wei Song, Dan Zhao, Lixing Hao, Baolian Yi, Zhigang Shao
Electrochemistry Communications 2009 Volume 11(Issue 4) pp:787-790
Publication Date(Web):April 2009
DOI:10.1016/j.elecom.2009.01.010
Hydrophilic nanosized SiO2 and sulfonated SiO2 particles were added to the cathode catalyst layer (CL) to improve the water wettability and the performance of a proton exchange membrane fuel cell (PEMFC) at low humidity. It was found that both nanosized SiO2 and sulfonated SiO2 additive improved the hydrophilicity of the cathode CL by the contact angle measurement. Contrary to nanosized SiO2, sulfonated SiO2 improved the conductivity of the cathode CL. Increased wettability of the cathode CL from SiO2 maintained fuel cell at hydration conditions. This phenomenon had a profound influence on electrode performance at low humidity. Since the sulfonic groups in sulfonated SiO2 improved the proton conductivity of the cathode CL, the cell with sulfonated SiO2 showed better performance.
Co-reporter:Wei Song;Junbo Hou;Lixing Hao
Journal of Applied Electrochemistry 2009 Volume 39( Issue 5) pp:609-615
Publication Date(Web):2009 May
DOI:10.1007/s10800-008-9700-6
The sub-freezing endurance of proton exchange membrane (PEM) fuel cells with hydrophobic and hydrophilic catalyst-coated membranes (CCMs) was investigated. The polarization curves, electrochemical characteristics and physical structures of the CCMs were measured. The cells were frozen at −20 °C with saturated residual water after operating at 60 °C. After eight freeze/thaw cycles, no evident negative effect on the performance of the cell with a hydrophobic CCM was observed, while the cell with a hydrophilic CCM degraded severely. By analyzing the polarization curves, it was concluded that the mass transport limitation was the main reason for the performance loss of the hydrophilic cell. The electrochemical active surface area (ECA) results suggest that the hydrophobicity of the catalyst layer (CL) has an apparent impact on the residual water distribution of the membrane electrode assembly (MEA). A larger water content in the hydrophilic CL has a negative effect on the subzero endurance. From the polarization resistance obtained from electrochemical impedance spectroscopy (EIS) the origin of degradation was further clarified. Mercury intrusion porosimetry showed that the pore size of the hydrophilic catalyst layer changed significantly after freezing; the mean pore size increased from 5.68 to 6.71 nm. However, with a water removal method, namely, gas purging, it was possible to prevent degradation effectively.
Co-reporter:Shucheng Sun, Hongmei Yu, Junbo Hou, Zhigang Shao, Baolian Yi, Pingwen Ming, Zhongjun Hou
Journal of Power Sources 2008 Volume 177(Issue 1) pp:137-141
Publication Date(Web):15 February 2008
DOI:10.1016/j.jpowsour.2007.11.012
Fuel cells for automobile application need to operate in a wide temperature range including freezing temperature. However, the rapid startup of a proton exchange membrane fuel cell (PEMFC) at subfreezing temperature, e.g., −20 °C, is very difficult. A cold-start procedure was developed, which made hydrogen and oxygen react to heat the fuel cell considering that the FC flow channel was the characteristic of microchannel reactor. The effect of hydrogen and oxygen reaction on fuel cell performance at ambient temperature was also investigated. The electrochemical characterizations such as I–V plot and cyclic voltammetry (CV) were performed. The heat generated rate for either the single cell or the stack was calculated. The results showed that the heat generated rate was proportional to the gas flow rate when H2 concentration and the active area were constant. The fuel cell temperature rose rapidly and steadily by controlling gas flow rate.
Co-reporter:Junbo Hou, Hongmei Yu, Liang Wang, Danmin Xing, Zhongjun Hou, Pingwen Ming, Zhigang Shao, Baolian Yi
Journal of Power Sources 2008 Volume 180(Issue 1) pp:232-237
Publication Date(Web):15 May 2008
DOI:10.1016/j.jpowsour.2008.01.052
Stable proton exchange membrane (PEM) with good proton conductivity at subzero temperatures is important for the development of PEM fuel cell cold start. In this work, subfreezing conductivity was reported for several aromatic-based PEMs including sulfonated polyimides (SPIs) with three values of ion-exchange capacity (IEC), sulfonated poly(ether ether ketone) (SPEEK) and disulfonated poly(arylene ether sulfone) copolymer (SPSU) as well as Nafion® 212. Measurements were performed using the electrochemical impedance spectroscopy (EIS) technique. The results showed that only fully hydrated SPEEK (IEC, 1.75) and SPSU (IEC, 2.08) had comparable conductivities with Nafion® 212 at subzero temperatures. Considering implement of gas purge before subzero storage of PEM fuel cell, the conductivity for those PEMs humidified by water vapor at activity of 0.75 was also investigated. The state of water in aromatic-based PEMs was quantified by differential scanning calorimetry (DSC), and its correlation with conductivity of the membrane was also discussed.
Co-reporter:Lixing Hao, Hongmei Yu, Junbo Hou, Wei Song, Zhigang Shao, Baolian Yi
Journal of Power Sources 2008 Volume 177(Issue 2) pp:404-411
Publication Date(Web):1 March 2008
DOI:10.1016/j.jpowsour.2007.11.034
The effect of water generation on the performance of proton exchange membrane fuel cell (PEMFC) was investigated by using a periodical linear sweep method. Three different kinds of I–V curves were obtained, which reflected different amount of water uptake in the fuel cell. The maximum water uptake that could avoid flooding in the fuel cell and the hysteresis of water diffusion were also discussed. Quantitative analysis of water uptake and water transport phenomena in this study were conducted both experimentally and theoretically. Results showed that the water uptake capacity for the fuel cell under no severe flooding was 27.837 mg cm−2. The transient response of the internal resistance indicated that the high frequency resistance (HFR) lagged the current with a value of about 20 s. The effect of purging operation on the internal resistance of the fuel cell was also explored. Experimental data showed that the cell experienced a continuous 8-min purging process can maintain at a relatively steady and dry state.
Co-reporter:Junbo Hou, Wei Song, Hongmei Yu, Yu Fu, Lixing Hao, Zhigang Shao, Baolian Yi
Journal of Power Sources 2008 Volume 176(Issue 1) pp:118-121
Publication Date(Web):21 January 2008
DOI:10.1016/j.jpowsour.2007.10.035
With electrochemical impedance spectroscopy (EIS), the ionic resistances of the catalyst layer (CL) were measured at different current densities after the proton exchange membrane (PEM) fuel cell suffered the subfreezing temperature. Compared with those of the CL before being frozen, the ionic resistances unexpectedly decreased a little, which accorded well with the polarization results. Considering that the frequency-dependent penetration depth was small in the high frequency region, a semi-quantitative method based on the finite transmission-line equivalent circuit was followed to investigate the ionic resistance profile across the whole CL. The results indicated that the change of the ionic resistance profile was not uniform across the CL after the cell experienced freeze/thaw cycles, which was more evident at the higher current densities.
Co-reporter:Wei Song, Junbo Hou, Hongmei Yu, Lixing Hao, Zhigang Shao, Baolian Yi
International Journal of Hydrogen Energy 2008 Volume 33(Issue 18) pp:4844-4848
Publication Date(Web):September 2008
DOI:10.1016/j.ijhydene.2008.06.057
A three-electrode system with 2 M H2SO4 as the electrolyte was developed to investigate the oxygen reduction kinetics on Pt/C catalyst at sub-freezing temperatures. This system successfully avoided the ice formation above −10 °C. Furthermore, the influence of different membrane electrode assembly (MEA) status, i.e. the membrane hydration and the electrode structure, on the kinetic results in a sub-freezing fuel cell was diminished in this method. By cyclic voltammetry (CV) test, the electrochemical active surface area (ECA) of Pt/C catalyst at sub-freezing temperatures was obtained. Results showed that the ECA at sub-freezing temperatures was almost the same as that at room temperature, either the H-desorption or the H-adsorption process at subzero temperatures still took place in the same way. According to the analysis of the linear scan voltammetry (LSV), the kinetics of oxygen reduction on Pt/C catalyst at sub-freezing temperatures was explored. The limiting current density decreased as temperature dropped and the exchange current density at subzero temperatures still obeyed the Arrhenius theory.
Co-reporter:Junbo Hou, Wei Song, Hongmei Yu, Yu Fu, Zhigang Shao, Baolian Yi
Journal of Power Sources 2007 Volume 171(Issue 2) pp:610-616
Publication Date(Web):27 September 2007
DOI:10.1016/j.jpowsour.2007.07.015
Polarization losses of the fuel cells with different residual water amount frozen at subzero temperature were investigated by electrochemical impedance spectroscopy (EIS) taking into account the ohmic resistance, charge transfer process, and oxygen mass transport. The potential-dependent impedance before and after eight freeze/thaw cycles suggested that the ohmic resistance did not change, while the change of the charge transfer resistance greatly depended on the residual water amount. Among the four cells, the mass transport resistance of the cell with the largest water amount increased significantly even at the small current density region. According to the thin film-flooded agglomerate model, the interfacial charge transfer process and oxygen mass transport within the agglomerate and through the ionomer thin film in the catalyst layer both contributed to the high frequency impedance arc. From the analysis of the Tafel slopes, the mechanism of the oxygen reduction reaction (ORR) was the same after the cells experienced subzero temperature. The agglomerate diffusion changed a little in all cells and the thin film diffusion effect was obvious for the cell with the largest residual water amount. These results indicated that the slower oxygen diffusion within the catalyst layer (CL) was the main contributor for the evident performance loss after eight freeze/thaw cycles.
Co-reporter:Junbo Hou, Baolian Yi, Hongmei Yu, Lixing Hao, Wei Song, Yu Fu, Zhigang Shao
International Journal of Hydrogen Energy 2007 Volume 32(Issue 17) pp:4503-4509
Publication Date(Web):December 2007
DOI:10.1016/j.ijhydene.2007.05.004
The effects of the residual water in the PEM fuel cell after cold start on the performance, electrode electrochemical characteristics, and cell components were investigated by controlling the cold-start processes of three cells at -5∘C. Neither the cell performance loss nor the cell resistance increase with the start number was observed. There was no change in the electrochemical active surface area (ECA) and charge transfer resistance at low current density. The correlation between the amount of the residual water and the ohmic polarization and cell resistance showed mass-transport process slightly changed with the water amount in the cell. This trend correlated well with the charge transfer resistance at high current density. The change of mass-transport process came from the gas diffusion layer by the analysis of ECA. It was found that hydrogen crossover rate of the membrane at the three hydrated states did not change through eight start-ups at -5∘C. Based on the analysis of SEM and water-storage capacity, it was believed that less water was stored in the catalyst layer even though much water resided in the cell.
Co-reporter:Junbo Hou, Hongmei Yu, Shengsheng Zhang, Shucheng Sun, Hongwei Wang, Baolian Yi, Pingwen Ming
Journal of Power Sources 2006 Volume 162(Issue 1) pp:513-520
Publication Date(Web):8 November 2006
DOI:10.1016/j.jpowsour.2006.07.010
Proton exchange membrane fuel cell (PEMFC) freeze degradation was investigated using 20 freeze/thaw cycles of two cells with gases purged immediately after operation. The cell purged by gas with an RH 58.0% at 25 °C was found to have no performance loss after the 20 freeze/thaw cycles. From the cell resistances and the electrochemical impedance spectra (EIS), the electrolyte conductivity and interfacial charge transfer resistance were unchanged. The electrochemical active surface area (ECSA) from the cyclic voltammetry (CV) measurements indicated that the amount of water in the catalyst layer of the cell was reduced to an extent that the damage in the freeze/thaw cycles was avoided. Another cell was purged by RH 64.9% gas in the first cycle, and then was purged with RH 45.0% gas in 19 freeze/thaw cycles. Although the cell easily became flooded at high current densities after the first cycle, no further performance loss was found. The pore size distribution data from mercury intrusion porosimetry measurements suggested that the gas diffusion layer was changed by the first freeze cycles. The micrographs (SEM) further proved no membrane electrode assembly (MEA) delamination. These results shed some light on the relationship of the water amount in the cell to subzero temperature exposure.
Co-reporter:Hongmei Yu, Zhongjun Hou, Baolian Yi, Zhiyin Lin
Journal of Power Sources 2002 Volume 105(Issue 1) pp:52-57
Publication Date(Web):5 March 2002
DOI:10.1016/S0378-7753(01)00957-0
Fuel of proton exchange membrane fuel cells (PEMFC) mostly comes from reformate containing CO, which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC is studied in this paper. Several electrode structures are investigated for CO containing fuel. The experimental results show that thin-film catalyst electrode has higher specific catalyst activity and traditional electrode structure can stand for CO poisoning to some extent. A composite electrode structure is proposed for improving CO tolerance of PEMFCs. With the same catalyst loading, the new composite electrode has improved cell performance than traditional electrode with PtRu/C electrocatalyst for both pure hydrogen and CO/H2. The EDX test of composite anode is also performed in this paper, the effective catalyst distribution is found in the composite anode.
Co-reporter:Yachao Zeng, Zhigang Shao, Hongjie Zhang, Zhiqiang Wang, Shaojing Hong, Hongmei Yu, Baolian Yi
Nano Energy (April 2017) Volume 34() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.nanoen.2017.02.038
•A nanostructured ultrathin catalyst layer (NUCL) has been constructed for PEMFCs.•The NUCL is based on open walled Co-doped Pt nanotube arrays (NTAs).•The Co-doped Pt NTAs is prepared from a template-assisted deposition and etching strategy.•Single cell test manifests that NUCL has a pronounced catalyst utilization and durability.Nanostructured ultrathin catalyst layer based on open-walled PtCo bimetallic nanotube arrays has been designed and constructed through a hydrothermal and physical vapor deposition method for proton exchange membrane fuel cells (PEMFCs). The open-walled PtCo bimetallic NTAs with a diameter ca. 100 nm were directly aligned with proton exchange membrane, forming an ultrathin catalyst layer with a thickness ca. 300 nm. The incorporation of Co in Pt is realized by a facile thermal annealing method, endowing the catalyst layer with improved activity. During the purification of catalyst-coated-membrane (CCM) electrode, the sealed off PtCo nanotubes cracked into open-walled nanotubes, making both the interior and exterior surfaces exposed to the surroundings. The catalyst layer is binder-free and beneficial for exposing catalytic active sites, enhancing mass transport during the operation of PEMFCs. Serving as cathode, a maximum power density of 14.38 kW gPt−1 was achieved with a cathodic Pt loading of 52.7 μg cm−2, which is 1.7 fold higher than the conventional CCM. Accelerated degradation test (ADT) manifests that the prepared nanostrucutred ultrathin catalyst layer is more stable than the conventional CCM. The proposed catalyst layer structure and also its preparation method hold great potential for PEMFCs and other applications.Nanostructured ultrathin catalyst layer based on open-walled PtCo bimetallic nanotube arrays has been designed and constructed for fuel cells. The concept is realized by hydrothermal synthesis and physical vapor deposition method. Beneficial from its structural advantages, a power density of 17.02 kW gPt−1 (anode) and 14.38 kW gPt−1 (cathode) has been achieved. And the advanced catalyst layer presented enhanced durability over the conventional catalyst layer.
Co-reporter:Jia Jia, Hongmei Yu, Xueqiang Gao, Jun Chi, Bowen Qin, Wei Song, Zhigang Shao and Baolian Yi
Journal of Materials Chemistry A 2017 - vol. 5(Issue 28) pp:NaN14800-14800
Publication Date(Web):2017/06/15
DOI:10.1039/C7TA02437A
A novel cathode architecture using vertically aligned Cu nanoneedle arrays (NNAs) as an ordered support for alkaline anion-exchange membrane fuel cell (AAEMFC) application is developed. Cu NNAs are directly grown on a GDL via three steps of electrochemical reaction. After depositing a Pd layer on the surface of Cu by a pulse electrodeposition method to form Pd/CuNNAs, the cathode catalyst layer is formed. The AAEMFC prepared without alkaline ionomer in the cathode catalyst layer shows an enhanced performance with ultra-low Pd loading down to 47 μg cm−2, which is much higher than that of a conventional cathode electrode with the Pt loading of 100 μg cm−2. This is the first report where three-dimensional Cu NNAs are applied as the cathode support in an AAEMFC, which is able to deliver a higher power density without an alkaline ionomer than conventional MEAs.
Co-reporter:Guangfu Li, Hongmei Yu, Xunying Wang, Shucheng Sun, Yongkun Li, Zhigang Shao and Baolian Yi
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 8) pp:NaN2866-2866
Publication Date(Web):2012/12/18
DOI:10.1039/C2CP44496H
We developed an advanced surfactant-assistant method for the IrxSn1−xO2 (0 < x ≤ 1) nanoparticle (NP) preparation, and examined the OER performances by a series of half-cell and full-cell tests. In contrast to the commercial Ir black, the collective data confirmed the outstanding activity and stability of the fabricated IrxSn1−xO2 (x = 1, 0.67 and 0.52) NPs, which could be ascribed to the amorphous structure, good dispersion, high pore volume, solid-solution state and Ir-rich surface for bi-metal oxides, and relatively large size (10–11 nm), while Ir0.31Sn0.69 exhibited poor electro-catalytic activity because of the separated two phases, a SnO2-rich phase and an IrO2-rich phase. Furthermore, compared with highly active IrO2, the improved durability, precious-metal Ir utilization efficiency and correspondingly reduced Ir loading were realized by the addition of Sn component. When the Ir0.52Sn0.48O2 cell operated at 80 °C using Nafion® 115 membrane and less than 0.8 mg cm−2 of the noble-metal Ir loading, the cell voltages we achieved were 1.631 V at 1000 mA cm−2, and 1.821 V at 2000 mA cm−2. The IR-free voltage at the studied current density was very close to the onset voltage of oxygen evolution. The only 50 μV h−1 of voltage increased for the 500 h durability test at 500 mA cm−2. In fact, these results are exceptional compared to the performances for OER in SPEWE cells known so far. This work highlights the potential of using highly active and stable IrO2–SnO2 amorphous NPs to enhance the electrolysis efficiency, reduce the noble-metal Ir loading and thus the cost of hydrogen production from the solid polymer electrolyte water electrolysis.
Co-reporter:Li Fu, Hongmei Yu, Yongkun Li, Changkun Zhang, Xunying Wang, Zhigang Shao and Baolian Yi
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 9) pp:NaN4290-4290
Publication Date(Web):2014/01/06
DOI:10.1039/C3CP54240H
We reported a facile adjusted method for the synthesis of high surface area nanorod hematite film as a photoanode for application in water splitting. Crystalline hematite nanorods (EG-α-Fe2O3) are fabricated by electrodeposition in Fe2+ precursor solution with the addition of ethylene glycol (EG) and followed by annealing at 450 °C. The nanorod hematite film fabricated by the modified electrodeposition approach exhibits a more uncompact structure than α-Fe2O3 obtained by directly electrodepositing on the FTO substrate. The optical and structural characteristics of the obtained film are also tested. The results infer that EG can tune the morphology of hematite and improve the photoabsorption in the visible light region due to its inducement of one-dimensional growth of crystal hematite. It also enhances the photoresponse activity of hematite in water splitting by improving the activities at the semiconductor/solution interface. The photocurrent density of EG-α-Fe2O3 nanorods increased to 0.24 mA cm−2 at 1.4 V vs. RHE in 1 M KOH (pH = 13.6), almost 5 times higher than the original α-Fe2O3 (0.05 mA cm−2, measured under the same conditions).
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