•The Ag NPs/CFs is firstly used in the photocatalytic reduction of CO2.•The formation mechanism of spherical Ag NPs on CFs is proposed.•A mechanism of photocatalysis over Ag NPs/CFs is proposed.Carbon fibers (CFs) decorated with Ag nanoparticles (Ag NPs), hereafter denoted as Ag NPs/CFs, have been successfully synthesized via a simple solution dipping combined with an ultrasonic treatment. CFs are decorated by spherical Ag NPs with 20–50 nm diameters mainly consisted of the Ag nanocrystals, which is reduced from Ag+ by both CFs and polyviylpyrrolidone (PVP). The aggregation of Ag NPs on the surface of CFs via Ostwald ripening and from the solution are the primarily responsible for the formation of spherical Ag NPs. The as-prepared Ag NPs/CFs Exhibits 4-time higher of photocatalytic activity than the pure Ag NPs, meanwhile enhancing the selectivity to convert CO2 into CH3OH. A possible visible light photocatalytic mechanism for the better performance and selectivity of Ag NPs/CFs is discussed. The significant enhancement of the CO2 photocatalytic reduction is primarily attributed to the increase of CO2 adsorption and the efficient electron transfer to CO2 as well as the active site splitting of CO2 reduction and H2O decomposition.Download high-res image (222KB)Download full-size image
•An environmentally benign method is used for synthesizing Cu/SiO2.•The catalysts prepared by new method exhibit better performance.•The Cu2O in the reduced catalysts with new method is stable in the reaction.Dimethyl oxalate (DMO) hydrogenation for ethylene glycol (EG) production is problematic due to environmental concerns and safety regulations. Therefore, development of improved methods for diethyl oxalate (DEO) hydrogenation based EG production is desirable. The objective of this research was to develop a cost-effective and environmentally benign approach for the synthesis of highly active and stable Cu/SiO2 catalysts for selective hydrogenation of diethyl oxalate (DEO) to ethylene glycol (EG). Here, ammonium carbonate is used to prepare Cu/SiO2 catalysts through deposition precipitation instead of the conventional pollution-producing evaporation process associated with the use of ammonia. The Cu/SiO2 catalysts prepared with the new method achieved 6.9–13.1% higher selectivity and showed better stability. The improved stability and selectivity resulted from increased chemical adsorption of DEO and H2 due to the high Cu2O concentration and Cu+/(Cu0 + Cu+) ratio (reduced from ion-exchanged CuOSi units), and reduced carbon deposition on the Cu/SiO2 catalyst. The Cu2O reduced from CuOSi units in the Cu/SiO2 catalyst prepared by the new method was more stable than the Cu+ species reduced from copper phyllosilicate in the Cu/SiO2 catalyst prepared by the conventional method. Therefore, the new Cu/SiO2 catalyst preparation method appears most promising.Download high-res image (115KB)Download full-size image
Co-reporter:Shipeng Wan, Qin Zhong, Man Ou, Shule Zhang, Wei Cai
Journal of Photochemistry and Photobiology A: Chemistry 2017 Volume 340(Volume 340) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.jphotochem.2017.03.015
•A series of sheet-like CNs was first-ever synthesized using C, M and Mm as precursors.•C-M-Mm CNs possess large surface areas and high separation rate of e−−h+ pairs.•The NO conversion rate in the presence of C1-M0-Mm1 CN reaches 94.9%.•Reasons for the tremendous enhanced PCO performance on C-M-Mm CNs were analyzed.•Reaction product and possible mechanism of the PCO of NO were investigated.In this paper, a series of sheet-like carbon nitride (CN) semiconductor photocatalysts was synthesized by facial supramolecular method using cyanuric acid (C), melamine (M) and 2,4-diamino-6-methyl-1,3,5-triazine (Mm) as precursors. It is the first report where the latter monomer was used in such synthetic route. The prepared C-M-Mm CNs possess higher specific surface areas, stronger light absorption as well as lower recombination rate of photogenerated electron-hole pairs in comparison with bulk CN. They were used on the photocatalytic oxidation (PCO) of NO (∼ 400 ppm) with injected H2O2 solution (0.044 mL min−1) under simulated solar-light irradiation. The results indicate that the C-M-Mm CNs exhibit tremendous enhanced photocatalytic activity, wherein the C1-M0-Mm1 CN possesses the highest photocatalytic activity (94.86%). The enhanced photocatalytic performance belongs to the synergic effect of large specific surface area, wide solar-light absorption edge and high separation and transfer efficiency of photogenerated electron-hole pairs. The presence of H2O2 is also essential in the improvement of the photocatalytic efficiency via production of more active species. The main product in the PCO of NO is NO3−, which was confirmed by Ion Chromatography. In addition, the mechanism of PCO is also discussed in detail. The results indicate that O2− plays a leading role in the process of PCO of NO.Download high-res image (121KB)Download full-size image
Co-reporter:Yang Song, Qin Zhong, Dongyu Wang, Yalin Xu, Wenyi Tan
International Journal of Hydrogen Energy 2017 Volume 42, Issue 34(Volume 42, Issue 34) pp:
Publication Date(Web):24 August 2017
DOI:10.1016/j.ijhydene.2017.04.216
•The products of H2S electrochemical oxidation over SFCM were detected.•The way anode SFCM interact with fuel gas containing H2S be explained.•The maximum power density could reach 45.69 mW cm−2 in 0.05% H2S/N2 at 800 °C.•The conversion efficiency of the H2S oxidation in the SFCM catalytic will increase to 96%.Symmetrical Solid Oxide Fuel Cells (SSFCs) are highly competitive options for a sustainable energy future, however, its application is hindered by the development of more surfer tolerance and highly efficient electrodes. Sr2FeCo0.5Mo0.5O6−δ (SFCM) was investigated as potential electrode materials for SSFCs using H2S as a fuel directly. SFCM powders, before and after exposure to 0.05% H2S/N2, were carried out to analyze the structure and morphology by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). A maximum power density of 45.69 mW cm−2 was obtained in the configuration of SSFC (SFCM/LSGM/SFCM) in 0.05% H2S/N2 at 800 °C. SFCM had high catalytic activity in converting H2S into SO2 without obviously deactivation. After cell test, X-ray photoelectron spectroscopy (XPS) was used to reveal the distribution of valence state of sulfur. There founding demonstrated that the SSCM has a certain surfer tolerance ability, and that understanding how the electrodes works and impact the cell performance is critical to the design of highly stable double perovskite electrodes.
Co-reporter:Man Ou, Shipeng Wan, Qin Zhong, Shule Zhang, Yanan Wang
International Journal of Hydrogen Energy 2017 Volume 42, Issue 44(Volume 42, Issue 44) pp:
Publication Date(Web):2 November 2017
DOI:10.1016/j.ijhydene.2017.09.047
•The single Pt atoms supported on g-C3N4 nanosheets photocatalysts were obtained.•The single Pt atoms are uniformly embedded into the surface of g-C3N4 nanosheets.•The Pt-SA-CN exhibits both higher photocatalytic H2 evolution and PCO of NO.•The reasons for the enhanced photoactivity of Pt-SA-CN samples are also discussed.Generally, the outstanding photoactivity of the semiconductor photocatalyst often attributes to the loaded Pt or H2PtCl6 solution. However, the utilization efficiency of Pt is relatively low due to the agglomeration during the loading or photocatalytic reaction process. Here, we have successfully synthesized the single Pt atoms supported on g-C3N4 nanosheets (Pt-SA-CN) with dilute amounts of Pt (<0.3 wt% Pt) by a facile incipient wetness impregnation. The single Pt atoms are uniformly embedded into the g-C3N4 nanosheets via PtN coordination bonds. Surprisingly, with the introduction of single Pt atoms, the Pt-SA-CN photocatalysts exhibit both higher photocatalytic H2 evolution and photo-oxidation of NO to NO3−. Especially, the Pt0.2-SA-CN photocatalyst displays the most excellent photocatalytic performance in the series of Pt-SA-CN samples, and even higher than that of the g-C3N4 nanosheets in H2PtCl6 (1 wt% Pt) solution and the Pt loaded on g-C3N4 surface by photodeposition method. The utilization efficiency of Pt has a considerable enhancement and the photoactivity is also improved. The reasons for the enhanced photocatalytic performance of Pt-SA-CN samples are also further discussed.
•Nanocrystalline Ce0.90 Co0.10 O2-δ and Ce0.90-x Cux Co0.10 O2-δ (x = 0.03, 0.07, 0.10) catalysts were synthesized.•A novel catalyst-duct separation system for NOX removal by catalytic ozonation was developed.•The hydroxyl radical could be “transferred” from catalyst surface to the duct through its reproduction reaction.•Ce0.83 Cu0.07 Co0.10 O2-δ significantly enhanced catalytic performance for NOX removal.•The activation bridging O played an important role in promoting the generation of OH radicals.A series of Ce0.90Co0.10O2 − δ and Ce0.90 − xCuxCo0.10O2 − δ (x = 0.03, 0.07 and 0.10) catalysts synthesized by an alkaline hydrothermal method were utilized as ozonation catalysts for the NOX (x = 1, 2) removal at low temperatures. A novel catalyst-duct separation apparatus for denitrification by catalytic ozonation was developed by our group. Ce0.83Cu0.07Co0.10O2 − δ exhibits the highest catalytic activity (91.5% removal at 120 °C), whereas Ce0.80Cu0.10Co0.10O2 − δ presents the lowest (74.1% removal at 120 °C). Only NO3− is detected in the tail solutions. The catalytic performance presents a positive relationship with the corresponding OH concentration. OH radical can be “transferred” from catalyst surface to the duct, prolonging activation time through its own reproduction reaction. The surface –OH activation, not the surface –OH density determines the OH concentration in the present method. Ce0.83Cu0.07Co0.10O2 − δ contains a large number of high-activation bridging –OH, whereas the bridging –OH is absent in Ce0.80Cu0.10Co0.10O2 − δ. Therefore, Ce0.83Cu0.07Co0.10O2 − δ shows much higher activation for promoting the formation of OH than Ce0.80Cu0.10Co0.10O2 − δ.Download high-res image (213KB)Download full-size image
Co-reporter:Li Zhu, Yiqing Zeng, Shule Zhang, Jinli Deng, Qin Zhong
Journal of Environmental Sciences 2017 Volume 54(Volume 54) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.jes.2016.09.014
A series of cobalt doped TiO2 (Co-TiO2) and CoOx loaded TiO2 (Co/TiO2) catalysts prepared by sol–gel and impregnation methods respectively were investigated on selective catalytic reduction with NH3 (NH3-SCR) of NO. It was found that Co-TiO2 catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD, TEM, Raman and FT-IR, Co species were proved to be doped into TiO2 lattice by replaced Ti atoms. After being characterized and analyzed by NH3-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH3-SCR activities of Co-TiO2 catalysts, compared with Co/TiO2 catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions (O2−). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates (NO3−) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH3-SCR activity of Co-TiO2 catalysts.The Co species doped TiO2 catalysts had a better catalytic performance than CoOx loaded TiO2 catalysts for having more oxygen vacancies and superoxide ions which could promote the SCR reaction.Download high-res image (156KB)Download full-size image
Co-reporter:Lu Gan, Qin Zhong, Xiaolu Zhao, Yang Song, Yunfei Bu
Journal of Alloys and Compounds 2016 Volume 655() pp:99-105
Publication Date(Web):15 January 2016
DOI:10.1016/j.jallcom.2015.09.136
•Conventional cathode material La0.7Sr0.3MnO3 is modified by B-site Mg doping.•The effects of Mg doping are explored on structure and electrochemical properties.•LSMM20 has the potential as a cathode candidate material for IT-SOFCs.A series of La0.7Sr0.3Mn3−δ (LSM)-based perovskite cathode material with B-site Mg-doped composition La0.7Sr0.3Mn1−xMgxO3−δ (LSMM, x = 0, 0.1, 0.2) was successfully synthesized by a combined EDTA-citrate complexing method. The effect of the introduction of Mg into the Mn-site of La0.7Sr0.3MnO3 on the structural characteristics and electrochemical properties of the samples was specifically investigated. Among all the samples, La0.7Sr0.3Mn0.8Mg0.2O3−δ (LSMM20) showed larger BET surface areas (8.72 m2/g), a lower thermal expansion coefficient of ∼10.6 × 10−6 K−1 in a temperature range of 50–900 °C and a higher oxygen vacancy concentration. The good electrochemical performance of LSMM20 was manifested from its lower polarization resistance (Rp), resulting in a maximum power density of 187 mW cm−2 for an electrolyte supported single cell at 800 °C. This study indicates the potential of LSMM20 as a cathode candidate material for IT-SOFCs.
Co-reporter:Jie Ding, Jiandong Lin, Junjun Xiao, Yi Zhang, Qin Zhong, Shule Zhang, Lina Guo, Maohong Fan
Journal of Alloys and Compounds 2016 Volume 665() pp:411-417
Publication Date(Web):25 April 2016
DOI:10.1016/j.jallcom.2016.01.040
•The NOX removal is determined by the concentration of OH radicals.•The surface –OH linked to Ce atoms plays an important role.•The adsorption of H2O over Ce atoms is critical.Nanostructure cerium–titanium catalysts including fluoride (F−) doped ones were prepared by impregnation (Ce/TiO2 and Ce/F–TiO2) and co-precipitation (CeTi and CeTiF) method, and tested as ozonation catalysts for low-temperature NOX removal ranging from 40 to 180 °C. Interestingly, the doping of F− promotes the NOX removal for CeTi whereas inhibits the removal for Ce/TiO2. The NOX removal presents linear relationship with the concentration of hydroxyl radicals (OH). The surface –OH linked to Ce atoms as well as the H2O adsorption over Ce atoms play the important role in the generation of ·OH radicals. The doping of F− into CeTi improves the activation of Ce–OH linkage bonds and the adsorption of H2O over Ce atoms, thus increasing the concentration of OH radicals and catalytic activities. Although the doping of F− into Ce/TiO2 enhances the density of surface –OH, the ones linked to Ce atoms remain constant and the H2O adsorption over Ce atoms are declined, finally declining the catalytic activities.
Co-reporter:Yang Yu, Lei Zhong, Qin Zhong and Wei Cai
RSC Advances 2016 vol. 6(Issue 56) pp:50680-50687
Publication Date(Web):05 May 2016
DOI:10.1039/C6RA04678A
This study describes the synthesis of cobalt–ceria catalysts with octahedron and nanosphere shapes via a facile and surfactant-free hydrothermal method. The morphology of the products could be controlled by adjusting the proportion of solvent. The products evolved from nanospheres to octahedra with decreasing ethylene glycol/water volume fraction ratio in the reaction system. The formation process of the nanospheres involved dissolution–recrystallization-assembly and Ostwald ripening processes. Furthermore, the sizes of the obtained ceria–cobalt nanospheres were about 30 to 150 nm; these were composed of many crystallites with sizes of approximately 7 to 9 nm. The size of the ceria–cobalt nanospheres could be controlled by changing the cobalt doping amount in the mixed water–glycol system. These synthesized catalysts were applied for NO oxidation. The catalytic performance is closely related to the oxygen vacancy and the NO adsorption ability. In the low cobalt doping amount, NO adsorption and desorption played an important role in the oxidation process. However, the adsorption and activation O2 was the key step when the NO adsorption and desorption ability was similar.
Microporous and Mesoporous Materials 2016 Volume 234() pp:303-309
Publication Date(Web):1 November 2016
DOI:10.1016/j.micromeso.2016.07.041
•Solvent-free method was used to prepared copper contained SAPO-34 directly.•The method reduced the waste production, increased the yield, accelerated the crystallization.•The so-prepared sample show outstanding performance in NH3-SCR.•Comparison between solvent-free and ion-exchange method was made.With the introduction of solvent-free method, copper-contained SAPO-34 zeolite was synthesized by mixing, grinding and heating the raw materials with Cu-TEPA added in the precursor. Compared to conventional method of hydrothermal synthesis along with ion-exchange, the direct synthesis with the absence of solvent has effectively reduced the waste production, increased the yield and accelerated the crystallization period as well. The so-prepared sample exhibited absolute symmetry of isolated Cu2+ by incorporating into the cativy of SAPO-34. The ion-exchange process produced some bulk CuO on zeolite surface, and it might affect the crystallinity of zeolite. The addition of copper led to changes in surface area, pore structure, redox performance and acid sites for SAPO-34. The exchanged sample show wide active temperature and excellent low temperature NOx conversion, but the activity and selectivity decreased significantly at a high temperature. The direct synthesized sample exhibited remarkable NOx conversion rate and high N2 selectivity with a more efficient preparation, it also retained the excellent hydrothermal stability of chabazite structure.
Co-reporter:Man Ou, Qin Zhong, Yanxiao Zhao, Yuxiang Xue, Fujiao Song
Materials Letters 2016 Volume 184() pp:227-231
Publication Date(Web):1 December 2016
DOI:10.1016/j.matlet.2016.08.025
•Double-layer half-open flower BVO-GS sample was obtained by solvothermal route.•The size of BVO-GS composite is about 2 times reduced after the addition of GO.•Photoactivity of BVO and BVO-GS composite was evaluated by removing NO and RhB.•Reasons for the enhanced photoactivity with BVO-GS composite were analyzed.Graphene decorated 3D double-layer half-open flower BiVO4 composite (BVO-GS) was prepared via a facile solvothermal route. It was found that the size of the 3D BiVO4 could be reduced from 4.5 µm to 2 µm with the addition of graphene oxide (GO). And the transportation and separation of the photo-generated electrons-holes were also significantly improved. Photocatalytic performances of BiVO4 and BVO-GS have been evaluated by removing gaseous NO and RhB in liquid under visible light (VL) irradiation, where BVO-GS sample displayed enhanced photoactivity. The conversion of NO (~400 ppm) was about 60% and the RhB degradation ratio was about 90% for BVO-GS under VL irradiation. The boosted performance was attributed to the synthesized effect of size, shape and high photo-generated electrons-holes. The present study reveals that the role of graphene is not only a capping agent to controlling the size, but also a catalyst promoter for the photocatalytic performance.
The sulfur resistance and performance of Sr- and Mn-doped yttrium chromite (YSCM)-samaria-doped ceria (SDC) composite material were investigated for potential use as anodes in solid oxide fuel cells (SOFCs). The anode was well adhered to the electrolyte, which was ascribed to their similar coefficient of thermal expansion (TEC). The electro-catalytic activity of YSCM-SDC anodes in yttria-stabilized zirconia (YSZ) electrolyte-supported cells toward hydrogen oxidation was superior to that of the La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) anode. Sr depletion in the YSCM structure and the formation of SrSO4 in the presence of sulfur led to performance degradation of the anode. Irreversible and reversible performance degradation suggested that YSCM and SDC played a respective role during the anode deactivation process. The voltage decreased at a rate of 31 mV/h and stabilized at 0.49 V under a 3000 ppm H2S atmosphere. In addition, the sulfur tolerance of YSCM-SDC anode was better than SDC under strictly identical conditions.
Co-reporter:Lemeng Yu, Qin Zhong, Zhiyong Deng, Shule Zhang
Journal of Molecular Catalysis A: Chemical 2016 Volume 423() pp:371-378
Publication Date(Web):November 2016
DOI:10.1016/j.molcata.2016.07.040
•H2-pretreatment was used to Ce-Ti catalyst which had a significantly enhancement on NH3-SCR DeNOX.•Differences on physical and chemical properties on catalyst caused by pretreatment was compared.•The existence and role of superoxide ions was tested and certified.Hydrogen pretreatment was processed on the amorphous Ce-Ti catalyst which notably enhanced its NH3-SCR performance. We concluded that 3-h and 400 °C were the most suitable and efficient pretreatment conditions, whereas the NOx conversion rate was above 95% from 210 °C to 360 °C for such pretreated catalyst. XRD, PL, H2-TPR, XPS and Raman analyses found that the enhancement was attributed to the effects generated by the pretreatment: Ce4+ reduced to active Ce3+, the incerase of the oxygen vacancies, the chemisorbed oxygen, and the formation of superoxide ions. The NO adsorption oxidation capability, and the acid sites were also promoted by the pretreatment, which were favorable for the SCR reaction. The reaction among NO, O2 and NH3 on catalysts were studied by in-situ DRIFT. The adsorption of NH3 was dominant under the SCR reaction conditions The enhancement demonstrated good durability. The stability of catalyst under water vapor and sulfur dioxide were also tested.
Co-reporter:Wenkai Zhao, Shule Zhang, Jie Ding, Zhiyong Deng, Lina Guo, Qin Zhong
Journal of Molecular Catalysis A: Chemical 2016 Volume 424() pp:153-161
Publication Date(Web):1 December 2016
DOI:10.1016/j.molcata.2016.08.007
•Catalytic ozonation technology was developed for low-temperature denitrification.•CuFe2O4 nanoparticles show superior catalytic activity.•Further mechanism of the catalytic ozonation of NOx was investigated.In this paper, copper ferrite(CuFe2O4), prepared by a hydrothermal method, was successfully utilized in catalytic ozonation for NOx removal. CuFe2O4 shows higher activity (83%) than both CuO (79%) and Fe2O3 (70%). Hydroxyl radicals (OH) have been detected in the catalytic ozonation process, which has been confirmed to determine the catalytic performance of NOx removal. Compared to CuO and Fe2O3, CuFe2O4 exhibits more surface hydroxyl groups and oxygen vacancies, indicating that the synergetic effect of the surface hydroxyl groups and oxygen vacancies plays an important role in the enhancement of the generation of hydroxyl radicals, thus the catalytic activity. A possible mechanism for the catalytic ozonation of NOx was proposed.
Co-reporter:Man Ou, Haoyu Nie, Qin Zhong, Shule Zhang and Lei Zhong
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 43) pp:28809-28817
Publication Date(Web):02 Oct 2015
DOI:10.1039/C5CP04730G
A surfactant-free solvothermal method was developed for the controlled synthesis of diverse 3D ms-BiVO4 superstructures, including a flower, a double-layer half-open flower and a hollow tube with square cross-sections, via facilely adjusting the pH values with the aid of NH3·H2O. The effects of the morphologies of the prepared 3D ms-BiVO4 superstructure on the photocatalytic oxidation of NO were investigated, indicating that the enhanced photoactivity was not related to the surface area, but associated with the unique morphology, surface structure and good crystallinity. Moreover, the flower-like ms-BiVO4 photocatalyst with a more (040) reactive crystal plane exhibited higher photoactivity than those of other samples. The unique morphology helped with flushing the oxidation products accumulated on the surface of photocatalysts in the H2O2 system, and further improved the photoactivity. A trapping experiment was also conducted to examine the effects of the active species involved in the PCO of NO intuitively.
Co-reporter:Lei Zhong, Yang Yu, Wei Cai, Xinxin Geng and Qin Zhong
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 22) pp:15036-15045
Publication Date(Web):06 May 2015
DOI:10.1039/C5CP00896D
The performances of Cr/Ti-PILC catalysts, which were prepared by the pre-modification method, are studied for the selective catalytic oxidation of NO. The aim of this paper is to elucidate the detailed relationship between physical nanoparticle structure and chemical properties. The maximum NO conversion over the Cr-HP(3)/TP catalyst reached 71.4% at 280 °C. The catalysts were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of H2 (H2-TPR), temperature-programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. The characterization results demonstrated that the enhanced catalytic activity was ascribed to several beneficial effects, which were caused by the pre-modification such as the inhibition of crystallite size, improvement of Cr species dispersion and increase of the amount of active sites. XPS and FTIR experiments indicated that two Cr(VI) species, oxidized state CrO3 and chromate species with the anionic form, were generated via pre-modification, which played different roles in the catalytic reaction. In addition, the TPR and TPD results suggest that the increased active sites (Cr(VI) species) were conducive for the preferential adsorption and activation of NO. Furthermore, DRIFTS results revealed that the intermediates, NO+ and nitrates, interacted quickly to generate gaseous NO2.
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 7) pp:2012
Publication Date(Web):January 20, 2015
DOI:10.1021/ie504100b
Amorphous cerium and titanium mixed oxides (Am-CeTi) and crystalline cerium and titanium mixed oxides (Ct-CeTi), prepared by coprecipitation and impregnation methods, respectively, were successfully utilized in catalytic ozonation for NOx removal. The catalytic activity has been confirmed to be determined by the concentration of ·OH radicals. Am-CeTi shows higher activity than Ct-CeTi. Ce–O–Ti linkage bonds, with an interaction between Ce and Ti on an atomic scale, are confirmed for the first time to be an active site for catalytic ozonation to remove NOx. The incorporation of more Ce results in an amorphous structure (Am-CeTi) and a higher number of Ce–O–Ti linkage bonds as compared to that of Ct-CeTi, and the Ce–O–Ti structure is directly observed by HR-TEM. Moreover, such incorporation is responsible for less surface defects and lower densities of surface hydroxyl groups because of the elimination of crystalline defects. The higher catalytic activity of Am-CeTi indicates the small effect of surface defects and surface groups.
Co-reporter:Yang Yu, Lei Zhong, Jie Ding, Wei Cai and Qin Zhong
RSC Advances 2015 vol. 5(Issue 30) pp:23193-23201
Publication Date(Web):25 Feb 2015
DOI:10.1039/C4RA15439H
A series of ceria oxides doped with 20 mol% of Zr, Sn and Ti were prepared by a citric sol–gel method throughout the thermal decomposition of the corresponding metallic propionates. Furthermore, cobalt oxides were loaded on the supports by a one-step sol–gel method. The results showed a solid solution when doping with Zr and Ti and SnO2 surface segregation in the case of Sn. We demonstrated that cobalt dispersion states were influenced by the doping metals. The Ce–Co metal-oxide catalyst possessed a higher amount of finely dispersed cobalt species, more oxygen vacancies and excellent redox ability. These features may be responsible for improving the catalytic activity of Ce–Co metal-oxides for NO oxidation.
Chemical Engineering & Technology 2015 Volume 38( Issue 5) pp:797-803
Publication Date(Web):
DOI:10.1002/ceat.201300590
Abstract
The kinetics of sulfite oxidation in the simultaneous desulfurization and denitrification of the oxidation-absorption process was investigated with a bubbling apparatus under the conditions of varying pH, sulfite concentration, nitrite concentration, temperature, and air flow. The results indicate that the oxidation of sulfite is promoted dramatically by mixing with nitrite, due to the decline of the apparent energy of activation and the initiation of nitric dioxide decomposition by nitrite. An increase of the nitrite concentration, the air flow, the reaction temperature, or the pH supports the decomposition of nitrite and the production of nitric dioxide, thus leading to an enhancement of the sulfite oxidation rate. A kinetic model is established according to the experimental results. A satisfactory agreement between the calculated and the experimental values is obtained.
Journal of Molecular Catalysis A: Chemical 2015 Volume 399() pp:18-24
Publication Date(Web):April 2015
DOI:10.1016/j.molcata.2015.01.015
•The preparation method affected the dispersion of cobalt in the Ce–Zr systems.•Co/Zr1−xCexO2 catalysts prepared by citrate complexation showed high catalytic activity.•The surface concentration of Ce3+ was favorable to high catalytic performance.•The addition of large amount of Zr had a negative effect on catalytic activity.A series of cobalt supported on Zr1−xCexO2 catalysts were synthesized by citrate complexation method (CC-series) and impregnation method (IM-series) and their catalytic performance of the NO oxidation to NO2 were tested. CC-series exhibited higher catalytic activity than IM-series. These prepared samples were characterized by various techniques such as XRD, Raman spectroscopy, BET, TEM, H2-TPR, UV–vis DRS and XPS. CC-series was found to possess easier reducibility, lower crystallite size and higher relative amount of Ce3+ compared with IM-series, which in turn led to their higher catalytic activity. The effect of Ce/Zr ratio on the catalytic activity of samples was also investigated. The results showed that adding large amount of Zr into Co/CeO2 system had a negative effect on the activity because of the corresponding decreasing of the surface Ce3+ concentration which was related with the production of oxygen vacancy.
Journal of Molecular Catalysis A: Chemical 2015 Volume 398() pp:344-352
Publication Date(Web):March 2015
DOI:10.1016/j.molcata.2015.01.002
•We prepared CoOx/N-doped CeO2 via a g-C3N4 decorated sol–gel method.•The CoOx crystallites were encapsulated by CeO2.•Compared to CoOx/CeO2, the N-doped samples showed better catalytic performance.A series of neoteric CoOx/N-doped CeO2 catalysts were synthesized by partly substituting the lattice oxygen of CeO2 with nitrogen by a simple g-C3N4-modified sol–gel method and comprehensively characterized by XRD, H2-TPR, XPS, BET, TEM, TG, UV–vis DRS, PL, EIS, NO(O2)-TPD and EPR. The results demonstrated that: (1) The N-doped catalysts showed larger surface areas and pore volumes, which were favorable for the adsorption of reactant gas; (2) Replacing O with N could promote the reduction of resultant catalysts and assist cobalt oxide in changing the valence and the support in supplying the oxygen; (3) By a sol–gel method, the CoOx crystallites in these catalysts were encapsulated by CeO2 with only a small fraction of Co ions on the surface and strongly interacting with CeO2. Such structure maximized the interaction between CoOx and CeO2 in three dimensions, resulting in unique redox properties. Moreover, the prepared materials were evaluated in the selective catalytic oxidation of NO. The results showed that the N-doped materials exhibited higher catalytic activity than the un-doped one due to those physicochemical changes. An enhanced mechanism on the improvement of catalytic performance was proposed, and this could pave the way for the designed and synthesis of new highly catalytic activity catalysts.This research studied the N-doped CeO2 supported CoOx on the process of NO oxidation. The resulting catalysts were comprehensively characterized and the results showed that the N-doped catalysts exhibited higher catalytic activity than undoped one due to a series of physicochemical changes. An enhanced mechanism on the improvement of catalytic performance was proposed, and this could pave the way for the designed and synthesis of new highly catalytic activity catalysts.
Research on Chemical Intermediates 2015 Volume 41( Issue 6) pp:3479-3490
Publication Date(Web):2015 June
DOI:10.1007/s11164-013-1465-9
The objective of this study was to investigate the promoting effect of F-doping of CeO2–TiO2 catalysts on low-temperature selective catalytic reduction (SCR) of NOX with NH3. A series of F-doped Ce–Ti mixed-oxide catalysts were prepared by the co-precipitation method. The experimental results showed that the best F-doped Ce–Ti mixed-oxide catalyst, with an F loading of 1.5 %, resulted in almost 97 % NOX conversion at 180 °C. The catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, and temperature-programmed desorption of NH3. The high activity might be because of F-induced strong interaction between Ce and Ti facilitating formation of Ce3+, which was important for improving chemisorption of oxygen. Addition of F could enhance the redox potential, resulting in more active adsorbed NH3 species, which simultaneously enhanced catalytic activity for NH3-SCR of NOX.
Co-reporter:Yang Song, Qin Zhong, Wenyi Tan, Cai Pan
Electrochimica Acta 2014 Volume 139() pp:13-20
Publication Date(Web):1 September 2014
DOI:10.1016/j.electacta.2014.07.022
Double-perovskite Sr2Fe1.5Mo0.5O6-δ with high performance has been investigated as potential symmetrical electrode materials for Solid Oxide Fuel Cells (SOFCs). In order to enhance its catalytic activity and electrochemical performance, a series of cobalt-substituted Sr2Fe1.5-xCoxMo0.5O6-δ (SFCM, x = 0, 0.5, 0.75 and 1) were synthesized in this work. XRD, BET, XPS, PL, O2-TPD (H2-TPR), SEM and electrochemical performance tests have been conducted to characterize the improved performances. XRD and BET measurements indicate SFCM with the double-perovskite structure, and smaller grain size is 30.51 nm, as well as the larger BET surface areas 9.51 m2/g for cobalt-rich sample x = 0.75. The redox couples Fe3+/Fe2+, Co3+/Co2+ and Mo6+/Mo5+ are revealed by XPS, and more oxygen vacancy δ=0.46 is detected by PL and iodometry for sample x = 0.75, which is conducive to the redox catalytic activity and ionic conductivity yielding highest 59.48 S·cm−1 at 800 °C. Sample x = 0.5 with the lowest conductance activation energy 0.42 eV also exhibits best electrochemical performance with the highest power density of 42.6 mW·cm−2 for the configuration of SFCM/LSGM/SFCM in 0.5% H2S-3% H2 at 800 °C.
•A novel technology is proposed to simultaneous SO2 and NOX removal.•The NOX removal reaches 95%, and the SO2 is about 99%.•The method acquires good environmental and economic implications.•The NOX and SO2 are mainly removed by OH radicals and O3, respectively.A novel oxidation-removal process for simultaneous removal of NOX and SO2 was developed, which utilized the catalytic ozonation over Ce–Ti catalyst and assisted with a glass made ammonia-based washing tower. Compared with conventional flue gas treatment, the present method acquires non-secondary pollution, minimal waste production and low operating costs. The main byproducts, ammonia sulfate and nitrate, are important fertilizers and industrially raw materials. A maximum removal of 95% for NOX and nearly complete SO2 removal were obtained with the assistance of washing tower under the following experimental conditions: O3 concentration, 8.5 mg·L− 1; flow of oxidant mixtures, 100 mL·min− 1; simulated flue gas temperature, 120 °C; H2O flow, 2.4 mL·min− 1; and total gas flow, 400 mL·min− 1. The reaction mechanisms are discussed, and the final oxidation products are characterized. The experimental results show that the OH radicals from catalytic ozonation have an oxidation-removal effect of NOX and SO2. The multipollutant capacity of the washing tower is largely enhanced with the Ce–Ti catalyst. And the present method performs better stability with the assistance of the washing tower.
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 24) pp:12560-12566
Publication Date(Web):08 May 2014
DOI:10.1039/C4CP00809J
H2 or CO pretreatment had been processed on the Ag/γ-Al2O3 catalyst which significantly enhanced its NH3-SCR activity. The main purpose of this study was to prove that the impacts of pretreatment on silver species caused the enhancement. XRD, UV-vis, XPS, in situ FTIR and NO-TPD results showed the relationship between pretreatment, Ag species, NOX adsorption and NOX conversion. Extra nitrates were adsorbed on the Ag clusters which were produced by the pretreatment, thereby enhancing the activity. The reactivities between NO and NH3 had been studied. The difference between CO-pretreatment and H2-pretreatment had also been discussed. Furthermore, the durability and stability of the pretreated sample were tested. Therefore, a modified Ag2O/Al2O3 catalyst for NH3-SCR was researched.
Oxygen vacancies are omnipresent on an oxide surface under ambient conditions. The addition of fluorine to V2O5/TiO2 increases the number of oxygen vacancies which can react with O2 to form a superoxide species. The adsorption of NO and NH3 on the surface of the F-doped V2O5/TiO2 catalyst is investigated by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Active oxygen species formed on the surface of the catalyst are detected by EPR. At 513 K, the adsorption of NO and NH3 possibly lies in the vicinity of the surface superoxide radicals, and leads to a change in the nearby electronic structure of these sites. The present results show that F-doping can form more oxygen vacancies on the surface of the catalyst. The oxygen vacancies play an important role in the catalytic conversion of the nitrogen oxides, because they can improve the adsorption and activation of NO, NH3 and O2. Additionally, the results of NO-TPD and NH3-TPD demonstrate that there is a close correlation between the adsorption amounts of NO or NH3 and the oxygen vacancy concentrations of the catalysts. The stability and lifetime of the surface O2− anions are directly correlated to the structure of the adsorption site on the catalyst surface and influence the catalytic ability of the catalyst to adsorb reaction gases under the NH3-SCR operating conditions.
International Journal of Hydrogen Energy 2014 Volume 39(Issue 25) pp:13694-13700
Publication Date(Web):22 August 2014
DOI:10.1016/j.ijhydene.2014.03.179
•The crystallite size of LSCCM gets smaller with ceria-substitution on the A-site.•The surface adsorption oxygen content of LSCCM is higher compared with LSCM.•The total conductivity of LSCCM increases in air and humidified H2 compared with LSCM.•The maximum power density enhances markedly after doping ceria in wet H2–H2S.12.5 wt.% ceria-substituted on the A-sites of La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) for La0.75Sr0.125 Ce0.125Cr0.5Mn0.5O3−δ (LSCCM) has been synthesized by the sol–gel process and evaluated as the electrode materials of symmetric solid oxide cells. The orthorhombic perovskite-type structure was demonstrated using X-ray diffraction (XRD) and part of cerium has been successfully doped to LSCM and presents two valence states (+3 and +4). In addition, the surface adsorption oxygen content increases due to ceria-doping using X-ray photoelectron spectroscopy (XPS). The measured electrical conductivity shows that the addition of ceria yields increase in total conductivity in air and humidified H2. Electrochemical performance test of yttria-stabilized zirconia (YSZ) electrolyte-supported symmetric solid oxide fuel cell with the configuration of LSCCM|YSZ|LSCCM was performed, and shows peak power density of 33.12 mW cm−2 at 1173 K when operating in wet 3% H2–1% H2S, far greater than the one of LSCM in the same test conditions.
A series of cerium modified Cr/Ti-PILC catalysts were evaluated, which showed a remarkable increase in the activity of NO oxidation. The aim of this novel design was to investigate the mechanism of cerium modification over the Cr/Ti-PILC catalyst. Physicochemical characteristics were investigated in detail by various techniques such as BET, TPD (NO and O2), XPS, PL, EPR and DRIFTS. The analysis results demonstrated that cerium modification could facilitate the generation of oxygen vacancy via charge transfer, promote the formation of surface superoxide ions (O2−), and increase the amount of surface nitrates. Furthermore, the original oxidation pathway of Cr/Ti-PILC was maintained by cerium modification. The experimental results showed that the NO conversion of CrCe(0.25)/Ti-PILC catalyst was increased to nearly 66.9% at 300 °C.
The oxidation of NO to NO2 was investigated on Co–Ce–Zr solid solutions prepared by the sol–gel method. An improvement of the catalytic activities of the samples was observed for Co-contained catalysts compared to Ce–Zr solid solution. The ZCCo0.36 catalyst exhibited more than 50 % NO conversion rate in the temperature range from 250 to 350 °C. The chemico-physical properties of catalysts were characterized by XRD, Raman spectroscopy, BET, XPS and NO-TPD. The results indicated that the introduction of cobalt into the lattice of Ce–Zr solid solution increased the amount of Ce3+ and facilitated the oxygen mobility. The features may be responsible for the improving of catalytic activities of Co–Ce–Zr metal-oxides for NO oxidation.
A series of Ce0.85Ca0.15−xSrxO2–δ(x = 0, 0.03 and 0.06) were synthesized via citrate–nitrate combustion method. Samples were first characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD and SEM results showed that a complete solid solution formed in fluorite structure and Ce0.85Ca0.15−xSrxO2−δ had homogeneous distribution of particle with grain size in the range of 2.5 to 3 μm. The electrical conductivities of Ce0.85Ca0.15−xSrxO2−δ were evaluated for its use as a solid electrolyte in the intermediate-temperature solid oxide fuel cells by complex plane impedance measurements. Impedance measurements were made in the frequency range 1 MHz–0.1 Hz and temperature range 300–700 °C. It was found that Ce0.85Ca0.12Sr0.03O2−δ showed highest conductivity.
Journal of Sol-Gel Science and Technology 2014 Volume 72( Issue 3) pp:443-454
Publication Date(Web):2014 December
DOI:10.1007/s10971-014-3454-x
Novel visible-light-driven g-C3N4/BiVO4 composite photocatalysts were fabricated via sol–gel and simple mixing and heating methods. The photocatalysts were characterized by X-ray diffraction, thermogravimetric, Fourier transform infrared, transmission electron microscope, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, and photoluminescence spectra. The results indicated that BiVO4 was well dispersed on g-C3N4 sheet and an interaction between g-C3N4 and BiVO4 was confirmed, which were facile to the electron transfer from g-C3N4 to BiVO4 species. The mechanism was further induced to the heterojunction effect to improve the photocatalytic efficiency. The g-C3N4/BiVO4 heterojunction at a weight ratio of 80 % calcined at 500 °C exhibited the most excellent photocatalytic ability for RhB decolorization under visible-light irradiation (λ > 420 nm) which was extraordinary more active than that of pure components.
Journal of Molecular Catalysis A: Chemical 2014 Volume 393() pp:222-231
Publication Date(Web):1 November 2014
DOI:10.1016/j.molcata.2014.06.018
•The amorphous iron oxides to hematite mechanism with the calcination temperature rising was investigated.•The effect of oxygen vacancy on the catalytic efficiency of H2O2 decomposition for NOX removal was studied.•The promotional mechanism of the oxygen vacancy on the catalytic decomposition of H2O2 for NOX removal was proposed.Iron oxide catalysts were used for the study of catalytic decomposition of H2O2 into OH radicals for simultaneous oxidation-removal of NOX and SO2. These catalysts were prepared by Fe(NO3)3·9H2O calcined at different temperatures. The objects were to determine the catalytic efficiency toward the oxidation-removal of SO2 and NOX in relation to the calcination temperature. 100% SO2 removal is achieved in all conditions, but NOX removal increases with the calcination temperature rising. SEM and TEM analyses indicated that the pellet-type particles containing hematite were firstly formed on the surface of large aggregates, and then peeled off from the surface layer by layer as the calciantion temperature increased from 100 to 300 °C. This separating process led to the increase of specific surface areas and the transformation from iron composition to hematite, thus benefiting the catalytic removal efficiency. At higher temperatures (>300 °C), the iron nitrate was gradually melted, dramatically reducing the specific surface areas. However, higher calcination temperature benefits the generation of oxygen vacancies, which had a more apparent promotional effect on the catalytic efficiency. And finally, the promotional mechanism of oxygen vacancies is deduced in this paper.
Co-reporter:Xiufang Zhu, Qin Zhong, Dandan Xu, Han Yan, Wenyi Tan
Journal of Alloys and Compounds 2013 Volume 555() pp:169-175
Publication Date(Web):5 April 2013
DOI:10.1016/j.jallcom.2012.11.186
Ce0.9Sr0.1Cr0.5Fe0.5O3±δ as a potential anode for solid oxide fuel cell has been described in previous work, such as the conductivities in H2 and H2S, electrochemical properties and longevity of the cell with fuelled 3% H2 or 5% H2S, et al. In the further research, an interesting phenomenon is found that the mass increases when temperature rising over 680 °C in TG–DTA. The reason is the formation of nitrides by the analysis of thermodynamics calculation. Therefore, the synthesized process is optimized to reduce and cool down in 100% H2 for avoiding forming nitrides. Then, the fluorite structure Ce0.9Sr0.1Cr0.5Fe0.5O4±δ (CSCFe) is obtained. Thermal expansion coefficient (TEC) shows that anode CSCFe and electrolyte Ce0.8Sm0.2O1.9 (SDC) have a good matching. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) are used to describe the electron changes of every element in CSCFe before and after cell test. The results indicate that some electrons transfer from Ce3+ to Fe3+, which causes the intensity of EPR weaker, and increases the electron conductivity of CSCFe. After the cell operating in 5% H2S, XPS patterns indicate that some lattice oxygen migrate from the bulk to the surface releasing oxygen vacancies. The triple phase boundary (TPB) of the reaction between H2S and O2− is magnified, and the efficiency of the single cell is enhanced. Compared the electrochemical properties of the cell which fluorite structure Ce0.9Sr0.1Cr0.5Fe0.5O4±δ as anode with previous perovskite structure Ce0.9Sr0.1Cr0.5Fe0.5O3±δ as anode, the results demonstrate that the former is more suitable as anode for SOFC fuelled with H2S due to more content of Ce3+ in the material.Highlights► Fluorite structure CSCFe was obtained after 100% H2 reduction. ► The maximum current density and power density are 87.21 mA/cm2 and 19.23 mW/cm2 for cell test in 5% H2S at 600 °C. ► XPS indicates the electrons easily transfer from Ce3+ to Fe3+ increasing the electronic conduction. ► The formation of oxygen vacancies magnifies the TPB, which enhance the cell efficiency.
Co-reporter:Yang Song, Wenyi Tan, Dandan Xu, Yunfei Bu, Qin Zhong
Journal of Alloys and Compounds 2013 Volume 576() pp:341-344
Publication Date(Web):5 November 2013
DOI:10.1016/j.jallcom.2013.05.219
•A series of materials La0.75Sr0.25−xCexCr0.5Mn0.5 were synthesized at 1100 °C as potential electrode materials for SFCs.•H2-TPR and O2-TPD indicate that the material with high cerium is more suitable for used as the symmetric electrode.•FTIR results show the material with high cerium content is not resistant to sulfur.•The maximum power density of LSC0.13CM|YSZ|LSC0.13CM cell is 17.86 mW cm−2 for SFC test in 5% H2S–5% wet H2 at 900 °C.A series of materials La0.75Sr0.25−xCexCr0.5Mn0.5O3−δ (LSCCM, x = 0, 0.1, 0.13 and 0.15) were synthesized by the sol–gel process, and their structures were demonstrated using X-ray diffraction (XRD). The best ratio of ceria-substitution in LSCCM series was studied in detail by H2 temperature programmed reduction (H2-TPR), O2 temperature programmed desorption (O2-TPD), and Fourier transform infrared (FTIR). The catalytic activity results of H2-TPR and O2-TPD prove that ceria-substitution x = 0.15 for La0.75Sr0.25−xCexCr0.5Mn0.5O3−δ has the best catalytic activity, but the FTIR results show the material with high ceria content is not resistant to sulfur. Taking account both catalytic activity and sulfur tolerance, ceria-substitution x = 0.13 is an optimum for La0.75Sr0.25−xCexCr0.5Mn0.5O3−δ, with which maximal power density of 17.86 mW cm−2 can be attained in 5% H2S–5% wet H2 at 900 °C.
Co-reporter:Yunfei Bu, Qin Zhong, Dandan Xu, Wenyi Tan
Journal of Alloys and Compounds 2013 Volume 578() pp:60-66
Publication Date(Web):25 November 2013
DOI:10.1016/j.jallcom.2013.05.020
•The redox and sulfur stability of SSCF was examined firstly.•These materials have tendency to recapture oxygen when exposed to air after reduction.•There is no other work report the role of lattice oxygen in deactivation of SSCF.Sm0.9Sr0.1Cr0.5Fe0.5O3−δ was used as a promising anode catalyst for the conversion of H2S-containing fuel by SOFC in our previous research. A further research about the redox stability and sulfur resistance of the series of Sm0.9Sr0.1CrxFe1−xO3−δ (x = 0.2, 0.5, 0.8) was carried out through XRD, TEM, BET, and H2-TPR in this work. It was found the different doping amount of SSCF were stable at the temperature below 800 °C under reduction conditions. XPS was used to compare the fresh sample with the treated one. The reduction treatment tended to decrease the concentration of lattice oxygen but the surface adsorbed oxygen amount was found to be higher in reduced samples comparing with fresh samples. It was suggested that these materials had tendency to recapture oxygen when exposed to air after reduction. The role of lattice oxygen in deactivation of SSCF as anode catalyst was also studied after the sample was reduced to 1000 ppm H2S (balanced by N2) at 800 °C for 2 h.The Sm0.9Sr0.1Cr0.5Fe0.5O3−δ is demonstrated to be a potential anode material for SOFCs running on H2S-containing fuel in our previous research, so in this work we synthesized a series of perovskite materials with formula Sm0.9Sr0.1CrxFe1−xO3−δ. XRD, XPS, TEM, BET, and H2-TPR were used to study the resulting perovskites in terms of their redox stability of both bulk and H2S stability. The role of lattice oxygen in deactivation of SSCF as anode catalyst was also studied.
Journal of Chemical Technology and Biotechnology 2013 Volume 88( Issue 4) pp:623-628
Publication Date(Web):
DOI:10.1002/jctb.3875
Abstract
BACKGROUND: For a microbial fuel cell (MFC), the anode material plays a crucial role in power output.
RESULTS: A dual-chamber MFC was constructed using carbon cloth (CC) anodes treated by concentrated nitric acid (CC-A) and heated in a muffle furnace (CC-H), respectively. The experiment results showed that the stable maximum voltages were 0.42–0.46 V for CC, 0.52–0.58 V for CC-A and 0.80 V for CC-H under the condition of a 1000 Ω external resistance, which were much higher than those reported in the literature so far. Moreover, the maximum power density of the CC-H anode (687 mW m−2) was larger than for the CC-A anode (480 mW m−2) and the CC anode (333 mW m−2). Electrochemical impedance spectroscopy (EIS) results revealed that the internal resistance was 251 Ω for CC anode, 202 Ω for CC-A anode and 162 Ω for CC-H anode. Scanning electron microscopy (SEM) results indicated that the increase of power generation was attributed to the increase of bacteria counts attached to anodes. The power output of the MFC increased along with the increase of the N1s/C1s ratio, which was proved by X-ray photoelectron spectroscopy (XPS) analysis.
Co-reporter:Wei Cai, Qin Zhong, Shule Zhang and Jingxin Zhang
RSC Advances 2013 vol. 3(Issue 19) pp:7009-7015
Publication Date(Web):06 Mar 2013
DOI:10.1039/C3RA40226F
CrOx, Ce0.5Zr0.5O2 and 10Cr/Ce0.5Zr0.5O2 catalysts were prepared to investigate the separate effect of Cr and Ce0.5Zr0.5O2 for selective catalytic oxidation of NO. It was found that the co-actions of CrOx and Ce0.5Zr0.5O2 exhibited the higher catalytic activity than separate effect of CrOx or Ce0.5Zr0.5O2. The separate effects of Cr and Ce0.5Zr0.5O2 on the structure of the catalysts were systematically examined by XRD, TEM, BET, XPS, NO-TPD and O2-TPD. The XPS results showed that Cr species were enriched on the surface and the amount of Cr6+ increased after Cr was loaded on the Ce0.5Zr0.5O2. TPD results showed that NO was adsorbed on the sites of Cr, and O2 was adsorbed and activated on the ceria–zirconia solid solution. Finally, the adsorbed NO interacted with the adsorbed O2 to generate NO2 in the Langmuir–Hinshelwood mechanism.
The novel carbon dioxide (CO2) adsorbents with high capture efficiency were prepared through impregnating TiO2 nanotubes (TiNT) with four kinds of amines, namely monoethanolamine (MEA), ethylenediamine (EDA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), respectively. The samples were characterized by thermogravimetric analysis, low temperature N2 adsorption and transmission electron microscopy. CO2 capture was investigated in a dynamic packed column. The TEPA-loaded sample showed a better adsorption capacity due to its higher amino-groups content. In condition, TiNT-TEPA-69 shows the highest CO2 adsorption capacity among the four TEPA-loaded samples, approximately 4.37 mmol/g at 60 °C. The adsorption capacity was enhanced to 5.24 mmol/g under moisture conditions. TiNT-TEPA-69 was selected as adsorbent to study the adsorption/desorption behavior in the absence of moisture and in the presence of moisture. While the former is fairly stable after 5 adsorption/desorption cycles, the latter decreases dramatically.
The aim of this paper is to examine the feasibility of Y0.9Sr0.1Cr1−xFexO3−δ for potential use as anode materials in solid oxide fuel cells (SOFCs) fed with fuel gas containing H2S, as well as other electrochemical devise. Y0.9Sr0.1Cr1−xFexO3−δ (x = 0.1, 0.3, 0.5) were synthesized by gel combustion method and had single-phase orthorhombic perovskite structure. These materials were all stable in reducing atmosphere (10%, v/v H2/N2) up to 800 °C. By the comparison of the O 1s peaks assigned to Y0.9Sr0.1Cr1−xFexO3−δ before and after reduction in H2/N2, lower content of lattice oxygen and higher content of adsorbed oxygen were observed for Y0.9Sr0.1Cr0.9Fe0.1O3−δ, while others appeared opposite results. This phenomenon suggested that reduced Y0.9Sr0.1Cr0.9Fe0.1O3−δ could capture oxygen when exposure to air, which is essential for anode materials. Moreover, Y0.9Sr0.1Cr0.9Fe0.1O3−δ maintained good chemical stability under H2S-containing atmosphere through XRD and FT-IR analysis. So Y0.9Sr0.1Cr0.9Fe0.1O3−δ was suggested as a promising anode material for SOFCs fed with fuel gas containing H2S.
A series of chromium-ceria doped on TiO2-pillared clay nanocomposites catalysts with various Cr/Ce ratios were investigated in the oxidation of NO. This study aimed to not only synthesize the CrCe/TiO2-PILC nanocomposites, but also figure out the promotion effect of Ce in the oxidation process and the interaction between chromium and ceria on the surface of TiO2-PILC. The samples were characterized by XRD, SEM, TEM, XPS and H2-TPR methods. The best catalyst Cr(1)Ce(0.25)/TiO2-pillared clay yielded 69% NO to NO2 conversion at 350 °C (in the condition of GHSV = 35,400 h−1). With the content of ceria increasing, the NO conversion increased significantly while when the Cr/Ce equaled 1:1, the activity decreased. The chromium oxides were well dispersed on the surface of the support. Analysis of XPS indicated that the addition of ceria oxides could promote the formation of chemisorbed oxygen and raise the quantivalency of Cr. The powerful electron withdrawing ability of Ce made the electron density around Ti atoms decrease. The result showed that CeOx enhanced the metal–support interaction. H2-TPR indicated that the proper addition of CeOx increased the reducible phase that was beneficial to the reaction. Moreover, the catalysts showed a good resistance to SO2 and H2O. When SO2 and H2O were added in the feed gas, the catalytic activity decreased but when removed, the activity recovered. The deactivation was not totally irreversible.
Co-reporter:Wenyi Tan, Han Yan, Dandan Xu, Qin Zhong
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16552-16557
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.08.085
•Effect of Y as dopant on electro-catalytic activity for LSCY was investigated.•Electro-catalytic activity of LSCY still needs improvements.•EIS indicates polarization loss for LSCY dominates in the total resistance loss.•A hypothesis about choice of doping cation is proposed.Fuel gas containing sulfur to feed solid oxide fuel cell is a challenge for extending the application of SOFC. Yttrium doped into LaxSr1−xCrO3 as potential anode tolerant to H2S was investigated by XRD, XPS and electrochemical impedance spectra (EIS). Good sinter characteristic for (La,Y)0.7Sr0.3CrO3−δ (LYSC) observed by SEM contributes to the low ohmic loss (high conductivity) in SOFC fueled by H2(3%)–H2S(1%). Maximum power density of 20 mW/cm2 and open circuit voltage of 0.95 V for SOFC with LYSC can be obtained at 700 °C. The results by EIS indicate charge transfer loss in polarization resistance dominates in the total resistance, especially lower than 650 °C. Compared to ohmic loss, polarization resistance in LYSC is still the main cause to hinder the improvement of SOFC performance. Thus, LYSC with doped non-variant valence Y maintains good sulfur tolerance determined by XPS without improved electro-catalytic activity as EIS suggest.
Journal of Fluorine Chemistry 2013 Volume 153() pp:26-32
Publication Date(Web):September 2013
DOI:10.1016/j.jfluchem.2013.05.027
•Investigate the site location of F above TiO2 (0 0 1).•Oxygen vacancies could form at the position of bridging oxygen.•W species could interact with oxygen vacancies by one trapped electron.•The reduced value of W species could form over WTiF and VWTiF catalyst.•V species improved the formation of reduced value of W species.Cluster molecular modeling of F-doped V2O5–WO3/TiO2 catalyst was studied using density functional theory and first principles molecular dynamics simulations. The results showed that (i) site location of F above TiO2 (0 0 1) was that F atom instead bridging oxygen of TiO2; (ii) oxygen vacancies could form at the position of bridging oxygen over F-doped TiO2 supporter; (iii) oxygen vacancies by F doping showed higher activity and W species could interact with oxygen vacancies by one trapped electron; (iv) the reduced value of W species could form over WTiF and VWTiF catalyst; (v) V species improved the formation of reduced value of W species. These results facilitated the formation of reduced W species that was important to improve the formation of superoxide ions.Cluster molecular modeling of F-doped V2O5–WO3/TiO2 catalyst was studied using density functional theory and first principles molecular dynamics simulations. The results showed that (i) site location of F above TiO2 (0 0 1) was that F atom instead bridging oxygen of TiO2; (ii) oxygen vacancies could form at the position of bridging oxygen over F-doped TiO2 supporter; (iii) oxygen vacancies by F doping showed higher activity and W species could interact with oxygen vacancies by one trapped electron; (iv) the reduced value of W species could form over WTiF and VWTiF catalyst; (v) V species improved the formation of reduced value of W species. These results facilitated the formation of reduced W species that was important to improve the formation of superoxide ions.
Korean Journal of Chemical Engineering 2013 Volume 30( Issue 4) pp:836-841
Publication Date(Web):2013 April
DOI:10.1007/s11814-013-0008-9
TiO2 nanotubes (TNT) were prepared by hydrothermal method at 140 °C for 23 h. The V2O5/TNT (VTNT) catalysts were obtained by impregnation in NH4VO3 solution. The VTNTs exhibited much higher denitration efficiency than those supported on the raw TiO2, and satisfactory resistance to water and sulfur. Results from BET, TEM, XRD, NH3-TPD and EPR verified that V2O5 was dispersed well on TNT, thus favoring NH3 adsorption, promoting the transformation from V5+ to V4+, conducing to the formation of oxygen vacancies and superoxide radicals in the presence of NH3 and O2, and then resulting in the high catalytic activity of VTNTs.
Co-reporter:Dandan Xu;Xiufang Zhu;Yunfei Bu;Han Yan;Wenyi Tan
Ionics 2013 Volume 19( Issue 3) pp:491-497
Publication Date(Web):2013 March
DOI:10.1007/s11581-012-0751-7
Sm0.9Sr0.1Cr0.5Fe0.5O3 (SSCF) was successfully synthesized by gel combustion method. The structure and physicochemical properties of SSCF were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). The results showed that SSCF had orthorhombic perovskite-type structure and a homogeneous distribution of pores and particles with grain size in the range 200–300 nm. Meanwhile, SSCF exhibited good chemical compatibility with electrolyte Ce0.8Sm0.2O1.9 (SDC), and no additional diffraction peaks associated with impurities were observed after exposure to 10 % v/v H2/N2 and 1 % v/v H2S/N2. The conductivities of SSCF were evaluated with DC four-probe method in various atmospheres at 400–800 °C. The highest conductivities of SSCF were 0.56, 0.26 and 0.12 S cm−1 in air, 10 % v/v H2/N2 and 1 % v/v H2S/N2, respectively. The electrochemical properties were measured for the cell with configuration of SSCF-SDC/SDC/Ag at different temperatures. Electrochemical impedance spectroscopy (EIS) revealed that with the increase in temperature, the ohmic and total interfacial resistances of the cell decreased and the ohmic resistance gradually became the main factor affecting the performance of the cell.
A series of BaCe0.8 − xZrxY0.2O3 − δ (BCZYx) (x = 0, 0.2, 0.4, 0.6, 0.8) powders were prepared by EDTA–citrate complexing sol–gel process in this paper. The electrical conducting behavior, as well as chemical stability, was investigated. X-ray diffraction (XRD) results reveal that all samples are homogenous perovskite phases. Observed from XRD patterns and thermogravimetric curves, the samples with x ≥ 0.4 survive in the pure CO2, while samples with various Zr contents all present structurally stable against steam at 800 °C. The Zr-free sample of BaCe0.8Y0.2O3 − δ possesses the maximum bulk conductivity, 4.25 × 10−2 S/cm, but decomposes into Ba(OH)2 and Ce0.8Y0.2O3 − δ in steam. A negative influence of increasing Zr content on the conductivity of BCZYx can be observed by impedance tests. Considering the effect of temperature on the bulk conductivity, BCZY0.4 is preferred to be applied in SOFC as a protonic conductor, ranging from 1.52 × 10−4 to 1.51 × 10−3 S/cm (500–850 °C) with Ea = 0.859 eV, which is proved to be a good protonic conductor with tH+ ≥ 0.9.
Journal of Molecular Catalysis A: Chemical 2013 Volume 373() pp:108-113
Publication Date(Web):July 2013
DOI:10.1016/j.molcata.2013.03.011
•Investigation of the role of tungsten species in the ternary V2O5/WO3/TiO2 catalysts for SCR of NO with NH3.•WO3 improves the electrons transfer of the catalysts to facilitate the formation of reduced vanadium oxide.•The reduced vanadium oxide improves the formation of superoxide ions.Promotional effect of WO3 on the formation of O2− over V2O5/TiO2 catalyst for selective catalytic reduction of NO with NH3 was studied. The aim of this novel design was to investigate the role of tungsten species in electrons transfer over the ternary VWTi catalysts. Analysis by XRD, XPS, PL and EPR showed that WO3 species improved the electrons transfer of the catalysts to facilitate the formation of reduced V2O5 that was important to improve the formation of superoxide ions. This property was remarkably different from that of the VTi catalyst and it could contribute to a new understanding of the catalytic behavior of VWTi catalyst in low-temperature SCR processes.
Energy & Fuels 2012 Volume 26(Issue 8) pp:4903-4909
Publication Date(Web):July 13, 2012
DOI:10.1021/ef3005256
The objective of this study was to investigate the effects of fly ash (FA) and Mn and Fe modified FA on elemental mercury capture under air at 120 °C. X-ray fluorescence spectrometry (XRF), Brunauer–Emmett–Teller (BET) surface area, scanning electron micrographs (SEMs), X-ray diffraction (XRD), thermogravimetric (TG) analysis, and X-ray photoelectron spectroscopy (XPS) were employed to characterize the samples. The results showed that the cooperation of Mn and Fe loaded on FA improved the performance of elemental mercury capture in a laboratory packed-bed reactor. In the presence of O2, Mn(2)–Fe(3)–FA (FA modified with an Mn/Fe molar ratio of 2/3) possessed the best reactivity and its Hg0 removal efficiency stayed around 98% within 8 h. The heterogeneous mercury reaction could be speculated as: Hg0 was physically adsorbed on the cation vacancies and then was oxidized to HgO by Mn4+ and Fe3+ cations. The reduced forms of Mn3+ and Fe2+ reoxidized under air, and HgO was finally adsorbed on the surface of the catalysts.
Co-reporter:Tan Wenyi, Zhong Qin, Yan Han, Zhu Xiufang, Li Hongyi
International Journal of Hydrogen Energy 2012 Volume 37(Issue 9) pp:7398-7404
Publication Date(Web):May 2012
DOI:10.1016/j.ijhydene.2012.02.008
The role of lattice oxygen in deactivation of La0.75Sr0.25Cr0.5Mn0.5O3±δ (LSCM55) as anode catalyst was studied in a solid oxide fuel cell (SOFC), where hydrogen sulfide (H2S) was utilized as fuel. After LSCM55 treated in H2S or H2-H2S, XRD patterns show that some impurities similar to La2O2S and MnOS are present. XPS spectra identify that S species in the impurities dominate on the anode catalysts in form of sulfate (SO42−), which depends on the treatments. S2p and O1s regions in XPS reveal that in the absence of oxygen, lattice oxygen not only on the surface but also in the bulk contributes to the formation of sulfate. Oxygen vacancies induced by H2 pre-reduction may provide the channel for lattice oxygen migrating from the bulk to the surface. Furthermore, it is found that LSCM55 with H2 pre-reduction achieves better lifespan of SOFC fueled by H2S than LSCM55 without H2 pre-reduction, which alleviates deactivation of anode catalyst, due to incomplete oxidation of H2S by residual lattice oxygen on the surface after H2 pre-reduction. However, improvement of H2 pre-reduction on anode catalysts LSCM55 is influenced to a certain degree after short-term operation under closed circuit.Promotions between H2S and lattice oxygen on the surface of anode catalysts under closed circuit.Highlights► Identification of sulfur distribution on the catalyst surface after treatments. ► Lattice oxygen in the bulk contributes to the sulfate formation. ► H2 pre-reduction improves sulfur tolerance of catalyst. ► Deactivation extent also depends on lattice oxygen migrating from the bulk. ► Deactivation is aggravated after short-term operation under closed circuit mode.
Co-reporter:Wei Zhao, Qin Zhong, Tianjiao Zhang and Yanxiao Pan
RSC Advances 2012 vol. 2(Issue 20) pp:7906-7914
Publication Date(Web):03 Jul 2012
DOI:10.1039/C2RA20987J
V2O5/TiO2 catalysts were prepared in the presence of (NH4)2TiF6 with controlled fluorine to titanium molar ratios (RF/Ti × 100) (0, 0.5, 1, 1.35 and 2) for selective catalytic reduction of nitrogen oxides (NOx) by NH3 (SCR process). It was found that the NOx conversion over F-doping V2O5/TiO2 was greatly improved compared with pure V2O5/TiO2. The effects of F-doping on the structure of the catalysts were systematically examined using XRD, Raman spectrum, BET, TEM, H2-TPR,NO-TPD, XPS and EPR. The XPS results showed that F ions were incorporated into the TiO2 lattice. The high catalytic activity was ascribed to several beneficial effects produced by F-doping – preventing of grain growth, inhibiting of phase transformation from anatase to rutile, higher reducibility of good dispersion of vanadia species, creation of oxygen vacancies, and increasing active sites. It was interesting to point out that the better catalytic activity of F-doped V2O5/TiO2 was achieved by the creation of surface oxygen vacancies.
Adsorption with solid sorbents is one of the most promising options for postcombustion carbon dioxide (CO2) capture. In this study, aminated graphite oxide used for CO2 adsorption was synthesized, based on the intercalation reaction of graphite oxide (GO) with amines, including ethylenediamine (EDA), diethylenetriamine (DETA) and triethylene tetramine (TETA). The structural information, surface chemistry and thermal behavior of the adsorbent samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), transmission electron microscope (TEM), elemental analysis, particle size analysis, nitrogen adsorption as well as differential thermal and thermogravimetric analysis (DSC–TGA). CO2 capture was investigated by dynamic adsorption experiments with N2CO2 mixed gases at 30 °C. The three kinds of graphite oxide samples modified by excess EDA, DETA and TETA showed similar adsorption behaviors seen from their breakthrough curves. Among them, the sample aminated by EDA exhibited the highest adsorption capacity with the longest breakthrough time of CO2. Before saturation, its adsorption capacity was up to 53.62 mg CO2/g sample. In addition, graphite oxide samples modified by different amount of EDA (EDA/GO raw ratio 10 wt%, 50 wt% and 100 wt%) were prepared in the ethanol. Their CO2 adsorption performance was investigated. The experimental results demonstrated that graphite oxide with 50 wt% EDA had the largest adsorption capacity 46.55 mg CO2/g sample.
Journal of Inclusion Phenomena and Macrocyclic Chemistry 2012 Volume 72( Issue 1-2) pp:1-14
Publication Date(Web):2012 February
DOI:10.1007/s10847-011-9983-9
Cyclodextrins have been widely used in organic syntheses, which can bind substrates and catalyze chemical reactions with high selectivity as well as transfer hydrophobic molecules into environmental friendly medium by supramolecular interaction through reversible formation of host–guest complexes. Herein we provide an overview of the recent developments of native and modified cyclodextrins as catalyst in several reactions. These reactions are classified into twelve types involving oxidation, reduction, addition, Tsuji-Trost reaction, cyclization, protection, bromination, coupling, oxygen–sulfur exchange, ring-opening, hydrolysis and photochemical reaction.
Y-doped La0.7Sr0.3CrO3−δ is a promising anode catalyst for solid oxygen fuel cell (SOFC). The performances of chemical and physical are measured by SEM, XRD and FT-IR. The conductivities of catalyst are measured by DC four-probe method in 20% H2S–N2, 3% H2–N2 and air from 573 K to 1173 K, respectively. The results show that Y-doped La0.7Sr0.3CrO3−δ powders have perfect perovskite phase structure with no extra peaks and exhibit good chemical compatibility with Ce0.8Sm0.2O1.9 (as electrolyte) in air. Through XRD and FT-IR analysis no sulfur-containing species is detected after exposure to the 20% H2S at 1173 K for 5 h. Meanwhile, Y-doped La0.7Sr0.3CrO3−δ shows that the highest conductivity is 0.21 S/cm at 1173 K in H2S. The open circuit voltages are 0.85 V at 1173 K in H2S and 1.04 V at 823 K in H2. The maximal power densities are 12.4 mW/cm2 in H2S and 1.59 W/cm2 in H2 for cells comprising Y-doped La0.7Sr0.3CrO3−δ–Sm0.2Ce0.8O1.9/Sm0.2Ce0.8O1.9/Ag.
Korean Journal of Chemical Engineering 2011 Volume 28( Issue 4) pp:
Publication Date(Web):2011 April
DOI:10.1007/s11814-010-0472-4
A mathematical model of ammonia-based wet flue gas desulfurization process was developed based on the double film theory. The calculated results of the desulfurization system for two 220 t·h−1 boilers per unit by this model were compared to that of corresponding measured data. It was found that the calculated results agree well with the measured data for the operating conditions of pH, liquid/gas ratio and SO2 concentration. This model can provide predictions of the absorption performance of an ammonia-based wet flue gas desulfurization process and appears to be helpful for designing scrubbers for SO2 absorption with ammonia absorbent.
Co-reporter:Fujiao Song, Qin Zhong, Qunyao Chen, Xiaojiao Rong, Bin Wang
Journal of CO2 Utilization (March 2015) Volume 9() pp:23-28
Publication Date(Web):1 March 2015
DOI:10.1016/j.jcou.2014.11.005
•TEPA modified titanate display superior CO2 adsorption performance.•TPD demonstrates a low desorption temperature range.•The CO2 adsorption on T-TEPA-n is attributed to weak chemical adsorption.Porous sulfur-doped titanate was synthesized by hydrothermal method as the support of amine for CO2 capture. Tetraethylenepentamine (TEPA) was selected as the modifier to enhance CO2 adsorption capacity and selectivity by the introduction of chemisorptions. The physicochemical properties of raw and TEPA modified sulfur-doped titanate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), as well as low temperature N2 adsorption. CO2 adsorption and desorption were investigated by a fixed bed reactor system and temperature programmed desorption (TPD), respectively. With the maximum TEPA loading of 45 wt%, the maximum CO2 adsorption capacity reached 3.58 mmol/g at 70 °C. The adsorption capacity for CO2 remained almost the same after cyclic regeneration experiments. Ultimately, the results of characterization and experiments were summarized to understand the CO2 adsorption–desorption mechanism.Download full-size image
Journal of Energy Chemistry (July 2014) Volume 23(Issue 4) pp:468-474
Publication Date(Web):1 July 2014
DOI:10.1016/S2095-4956(14)60173-X
Metal-organic frameworks (MOFs) have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-1(also named Cu-BTC or MOF-199) was chemically reduced by doping it with alkali metals (Li, Na and K) and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction (XRD), thermo-gravimetric analysis (TGA) and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li+, Na+ and K+, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST-1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.Alkali-metal cation doping of HKUST-1 are used to capture CO2 from flue gas. The surface areas of modified HKUST-1 materials are correlated to their CO2 adsorption capacities. The modified HKUST-1 is well-maintained in the presence of moist air.Download full-size image
Co-reporter:Yang Yu, Yunfei Bu, Qin Zhong, Wei Cai
Catalysis Communications (5 December 2016) Volume 87() pp:62-65
Publication Date(Web):5 December 2016
DOI:10.1016/j.catcom.2016.08.037
•Carbon nanofibers (PCNFs) decorated with g-C3N4 was prepared by electrospinning.•The modified sample has a conversion of 47.6%, which is much higher than that of PCNFs (23.6%).•The physicolchemical changes are favorable for the improvement of the catalytic performance.•NO will adsorb on the sample to form nitrites followed by the formation of NO2 and nitrates.Here we prepared a novel PAN-based carbon nanofibers (PCNFs) by electrospinning using g-C3N4 as a sacrificial template for oxidizing NO to NO2 at room temperature. The results show that g-C3N4 modified PCNFs can reach a steady conversion of 47.6%, which is much higher than that of PCNFs (23.6%). It is proposed that the g-C3N4 induces some physicolchemical changes that can be responsible for the excellent catalytic performance.Download full-size image
Co-reporter:Shule Zhang, Xiaoxiao Liu, Qin Zhong, Yao Yao
Catalysis Communications (5 August 2012) Volume 25() pp:7-11
Publication Date(Web):5 August 2012
DOI:10.1016/j.catcom.2012.03.026
A Y-doped TiO2-supported MnOX has been developed by partly substituting the Ti4+ of the catalyst with Y3+ to promote oxygen vacancies for charge compensation. The aim of this study was to improve the activity of low-temperature SCR of NO with NH3 in the presence of excess oxygen by means of increasing the amount of oxygen vacancies. Analysis by PL spectra, XPS and EPR showed that Y doping increased the amount of oxygen vacancies and superoxide ions. The catalytic activity of NO removal was promoted by Y doping.Download full-size imageHighlights► NO removal is enhanced on the Y-doped MnOX/TiO2 catalysts for low-temperature SCR. ► Y doping can increase oxygen vacancies for charge compensation on the catalysts. ► Oxygen vacancies by Y doping are responsible for the high catalytic activity.
Journal of Hazardous Materials (11 February 2015) Volume 283() pp:252-259
Publication Date(Web):11 February 2015
DOI:10.1016/j.jhazmat.2014.09.034
•It is a new idea to investigate the removal of elemental mercury over Mn/MgO at low temperature.•The amorphous MnO2 and chemisorbed O2 played key roles on the removal of elemental mercury.•Combined in situ FTIR with XPS and TG, the possible oxidation and adsorption mechanism is proposed and MnHgO3 is the product of elemental mercury oxidation over Mn/MgO.Mn modified the commercial magnesite powder prepared by wet impregnation method has been shown to be effective for gas-phase elemental mercury (Hg0) removal at low temperatures. The prepared samples are characterized in detail across multiform techniques: XRF, BET, SEM-EDX, XRD, H2-TPR, and XPS, and all the results show that the amorphous MnO2 impregnated on magnesite powder improves the removal efficiency of Hg0. Through further analysis by TG and in situ FTIR, the reasonable removal mechanism is also speculated. The results indicate that chemisorbed oxygen is an important reactant in the heterogeneous reaction, and gas-phase Hg0 is adsorbed and then oxidized to solid MnHgO3 on the surface of the adsorbent.Download full-size image
Co-reporter:Jie Ding, Qin Zhong, Shule Zhang, Wei Cai
Journal of Hazardous Materials (11 February 2015) Volume 283() pp:633-642
Publication Date(Web):11 February 2015
DOI:10.1016/j.jhazmat.2014.10.010
•The size- and shape-controllable synthesis of NIAO(x/y) is introduced.•The catalytic decomposition of H2O2 on NIAO(x/y) is utilized for NOX and SO2 removal.•NIAO(7/3) shows highest NOX (80%) and SO2 (100%) removal.•The aluminum dramatically improves the structure and surface properties of catalysts.•The catalytic mechanism and well stability is investigated.A novel, simple, reproducible and low-cost strategy is introduced for the size- and shape-controlled synthesis of iron–aluminum mixed oxide nanoparticles (NIAO(x/y)). The as-synthesized NIAO(x/y) catalyze decomposition of H2O2 yielding highly reactive hydroxyl radicals (OH) for NOX and SO2 removal. 100% SO2 removal is achieved. NIAO(x/y) with Fe/Al molar ratio of 7/3 (NIAO(7/3)) shows the highest NOX removal of nearly 80% at >170 °C, whereas much lower NOX removal (<63%) is obtained for NIAO(3/7). The melting of aluminum oxides in NIAO(7/3) promotes the formation of lamellar products, thus improving the specific surface areas and mesoporous distribution, benefiting the production of OH radicals. Furthermore, the NIAO(7/3) leads to the minor increase of points of zero charges (PZC), apparent enhancement of FeOH content and high oxidizing ability of Fe(III), further improving the production of OH radicals. However, the NIAO(3/7) results in the formation of aluminum surface-enriched spherical particles, thus decreasing the surface atomic ratio of iron oxides, decreasing OH radical production. More importantly, the generation of FeOAl causes the decline of active sites. Finally, the catalytic decomposition of H2O2 on NIAO(x/y) is proposed. And the well catalytic stability of NIAO(7/3) is obtained for evaluation of 30 h.Download full-size image
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 24) pp:NaN12566-12566
Publication Date(Web):2014/05/08
DOI:10.1039/C4CP00809J
H2 or CO pretreatment had been processed on the Ag/γ-Al2O3 catalyst which significantly enhanced its NH3-SCR activity. The main purpose of this study was to prove that the impacts of pretreatment on silver species caused the enhancement. XRD, UV-vis, XPS, in situ FTIR and NO-TPD results showed the relationship between pretreatment, Ag species, NOX adsorption and NOX conversion. Extra nitrates were adsorbed on the Ag clusters which were produced by the pretreatment, thereby enhancing the activity. The reactivities between NO and NH3 had been studied. The difference between CO-pretreatment and H2-pretreatment had also been discussed. Furthermore, the durability and stability of the pretreated sample were tested. Therefore, a modified Ag2O/Al2O3 catalyst for NH3-SCR was researched.
Co-reporter:Man Ou, Haoyu Nie, Qin Zhong, Shule Zhang and Lei Zhong
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 43) pp:NaN28817-28817
Publication Date(Web):2015/10/02
DOI:10.1039/C5CP04730G
A surfactant-free solvothermal method was developed for the controlled synthesis of diverse 3D ms-BiVO4 superstructures, including a flower, a double-layer half-open flower and a hollow tube with square cross-sections, via facilely adjusting the pH values with the aid of NH3·H2O. The effects of the morphologies of the prepared 3D ms-BiVO4 superstructure on the photocatalytic oxidation of NO were investigated, indicating that the enhanced photoactivity was not related to the surface area, but associated with the unique morphology, surface structure and good crystallinity. Moreover, the flower-like ms-BiVO4 photocatalyst with a more (040) reactive crystal plane exhibited higher photoactivity than those of other samples. The unique morphology helped with flushing the oxidation products accumulated on the surface of photocatalysts in the H2O2 system, and further improved the photoactivity. A trapping experiment was also conducted to examine the effects of the active species involved in the PCO of NO intuitively.
Co-reporter:Lei Zhong, Yang Yu, Wei Cai, Xinxin Geng and Qin Zhong
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 22) pp:NaN15045-15045
Publication Date(Web):2015/05/06
DOI:10.1039/C5CP00896D
The performances of Cr/Ti-PILC catalysts, which were prepared by the pre-modification method, are studied for the selective catalytic oxidation of NO. The aim of this paper is to elucidate the detailed relationship between physical nanoparticle structure and chemical properties. The maximum NO conversion over the Cr-HP(3)/TP catalyst reached 71.4% at 280 °C. The catalysts were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of H2 (H2-TPR), temperature-programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. The characterization results demonstrated that the enhanced catalytic activity was ascribed to several beneficial effects, which were caused by the pre-modification such as the inhibition of crystallite size, improvement of Cr species dispersion and increase of the amount of active sites. XPS and FTIR experiments indicated that two Cr(VI) species, oxidized state CrO3 and chromate species with the anionic form, were generated via pre-modification, which played different roles in the catalytic reaction. In addition, the TPR and TPD results suggest that the increased active sites (Cr(VI) species) were conducive for the preferential adsorption and activation of NO. Furthermore, DRIFTS results revealed that the intermediates, NO+ and nitrates, interacted quickly to generate gaseous NO2.
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