Acceleration of the oxygen reduction reaction at the cathode is paramount in the development of low-temperature solid oxide fuel cells.At low operating temperatures between 450 and 600℃,the interactions between the s...Acceleration of the oxygen reduction reaction at the cathode is paramount in the development of low-temperature solid oxide fuel cells.At low operating temperatures between 450 and 600℃,the interactions between the surface and the bulk of the cathode materials greatly impact the electrode kinetics and consequently determine the overall efficacy and long-term stability of the fuel cells.This review will provide an overview of the recent progress in the understanding of surface-bulk interactions in perovskite oxides as well as their impact on cathode reactivity and stability.This review will also summarize current strategies in the development of cathode materials through bulk doping and surface functionalization.In addition,this review will highlight the roles of surface segregation in the mediation of surface and bulk interactions,which have profound impacts on the properties of cathode surfaces and the bulk and therefore overall cathode performance.Although trade-offs between reactivity and stability commonly exist in terms of catalyst design,opportunities also exist in attaining optimal cathode performance through the modulation of both cathode surfaces and bulk using combined strategies.This review will conclude with future research directions involving investigations into the role of oxygen vacancy and mobility in catalysis,the rational modulation of surface-bulk interactions and the use of advanced fabrication techniques,all of which can lead to optimized cathode performance.展开更多
Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)...Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.展开更多
A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combusti...A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The aver-age thermal expansion coefficient （TEC） of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9 （SDC）-based anode-supported SOFC by using humidified （~3%H2O） hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.展开更多
To explore highly active and thermomechanical stable air electrodes for intermediate-temperature solid oxide fuel cells(ITSOFCs),10mol%Ta5+doped in the B site of strontium ferrite perovskite oxide(SrTa_(0.1)Fe_(0.9)O_...To explore highly active and thermomechanical stable air electrodes for intermediate-temperature solid oxide fuel cells(ITSOFCs),10mol%Ta5+doped in the B site of strontium ferrite perovskite oxide(SrTa_(0.1)Fe_(0.9)O_(3-δ),STF)is investigated and optimized.The effects of Ta^(5+)doping on structure,transition metal reduction,oxygen nonstoichiometry,thermal expansion,and electrical performance are evaluated systematically.Via 10mol%Ta^(5+)doping,the thermal expansion coefficient(TEC)decreased from 34.1×10^(-6)(SrFeO_(3-δ))to 14.6×10^(-6) K^(-1)(STF),which is near the TEC of electrolyte(13.3×10^(-6) K^(-1) for Sm_(0.2)Ce_(0.8)O_(1.9),SDC),indicates excellent thermomechanical compatibility.At 550-750℃,STF shows superior oxygen vacancy concentrations(0.262 to 0.331),which is critical in the oxygen-reduction reaction(ORR).Oxygen temperature-programmed desorption(O_(2)-TPD)indicated the thermal reduction onset temperature of iron ion is around 420℃,which matched well with the inflection points on the thermos-gravimetric analysis and electrical conductivity curves.At 600℃,the STF electrode shows area-specific resistance(ASR)of 0.152Ω·cm^(2) and peak power density(PPD)of 749 mW·cm^(-2).ORR activity of STF was further improved by introducing 30wt%Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)powder,STF+SDC composite cathode achieving outstanding ASR value of 0.115Ω·cm2 at 600℃,even comparable with benchmark cobalt-containing cathode,Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF).Distribution of relaxation time(DRT)analysis revealed that the oxygen surface exchange and bulk diffusion were improved by forming a composite cathode.At 650℃,STF+SDC composite cathode achieving an outstanding PPD of 1117 mW·cm^(-2).The excellent results suggest that STF and STF+SDC are promising air electrodes for IT-SOFCs.展开更多
基金the financial support from the China Scholarship Council(CSC).M.Li acknowledges the financial support from the HBIS Group and the Australian Research Council(ARC)Linkage Project(LP160101729)Z.Zhu acknowledges the financial support from the ARC Discovery Projects(DP170104660 and DP190101782).
文摘Acceleration of the oxygen reduction reaction at the cathode is paramount in the development of low-temperature solid oxide fuel cells.At low operating temperatures between 450 and 600℃,the interactions between the surface and the bulk of the cathode materials greatly impact the electrode kinetics and consequently determine the overall efficacy and long-term stability of the fuel cells.This review will provide an overview of the recent progress in the understanding of surface-bulk interactions in perovskite oxides as well as their impact on cathode reactivity and stability.This review will also summarize current strategies in the development of cathode materials through bulk doping and surface functionalization.In addition,this review will highlight the roles of surface segregation in the mediation of surface and bulk interactions,which have profound impacts on the properties of cathode surfaces and the bulk and therefore overall cathode performance.Although trade-offs between reactivity and stability commonly exist in terms of catalyst design,opportunities also exist in attaining optimal cathode performance through the modulation of both cathode surfaces and bulk using combined strategies.This review will conclude with future research directions involving investigations into the role of oxygen vacancy and mobility in catalysis,the rational modulation of surface-bulk interactions and the use of advanced fabrication techniques,all of which can lead to optimized cathode performance.
基金supported by the National Natural Science Foundation of China(22279025,21773048)the Natural Science Foundation of Heilongjiang Province(LH2021A013)+1 种基金the Sichuan Science and Technology Program(2021YFSY0022)the Fundamental Research Funds for the Central Universities(2023FRFK06005,HIT.NSRIF202204)。
文摘Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.
基金Project supported by the National Natural Science Foundation of China(51102107,51202080)Anhui Science and Technology Project(1206c0805038)
文摘A layered perovskite oxide Y0.8Ca0.2BaCoFeO5＋δ（YCBCF） was synthesized as a novel cathode material for intermedi-ate-temperature solid oxide fuel cells （IT-SOFCs） by citric acid-nitrates self-propagating combustion method. The phase and micro-structure of YCBCF were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The aver-age thermal expansion coefficient （TEC） of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 mW/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9 （SDC）-based anode-supported SOFC by using humidified （~3%H2O） hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.
基金financially supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.2018ND133J)the National Natural Science Foundation of China(Nos.22309067 and 22101150)the Natural Science Foundation of Jiangsu Province,China(No.BK20190965).
文摘To explore highly active and thermomechanical stable air electrodes for intermediate-temperature solid oxide fuel cells(ITSOFCs),10mol%Ta5+doped in the B site of strontium ferrite perovskite oxide(SrTa_(0.1)Fe_(0.9)O_(3-δ),STF)is investigated and optimized.The effects of Ta^(5+)doping on structure,transition metal reduction,oxygen nonstoichiometry,thermal expansion,and electrical performance are evaluated systematically.Via 10mol%Ta^(5+)doping,the thermal expansion coefficient(TEC)decreased from 34.1×10^(-6)(SrFeO_(3-δ))to 14.6×10^(-6) K^(-1)(STF),which is near the TEC of electrolyte(13.3×10^(-6) K^(-1) for Sm_(0.2)Ce_(0.8)O_(1.9),SDC),indicates excellent thermomechanical compatibility.At 550-750℃,STF shows superior oxygen vacancy concentrations(0.262 to 0.331),which is critical in the oxygen-reduction reaction(ORR).Oxygen temperature-programmed desorption(O_(2)-TPD)indicated the thermal reduction onset temperature of iron ion is around 420℃,which matched well with the inflection points on the thermos-gravimetric analysis and electrical conductivity curves.At 600℃,the STF electrode shows area-specific resistance(ASR)of 0.152Ω·cm^(2) and peak power density(PPD)of 749 mW·cm^(-2).ORR activity of STF was further improved by introducing 30wt%Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)powder,STF+SDC composite cathode achieving outstanding ASR value of 0.115Ω·cm2 at 600℃,even comparable with benchmark cobalt-containing cathode,Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF).Distribution of relaxation time(DRT)analysis revealed that the oxygen surface exchange and bulk diffusion were improved by forming a composite cathode.At 650℃,STF+SDC composite cathode achieving an outstanding PPD of 1117 mW·cm^(-2).The excellent results suggest that STF and STF+SDC are promising air electrodes for IT-SOFCs.
基金The Key-Area Research and Development Program of Guangdong Province(2022B0111130004)National Natural Science Foundation of China(52272257)Innovation Team of Jiangsu Province(JSSCTD202241)。
