硅酸盐学报2025，Vol.53Issue(10)：3022-3030,9.DOI:10.14062/j.issn.0454-5648.20240682
固体氧化物燃料电池PrBaFe2O5+δ阴极材料的结构和氧还原反应机理
Structure and Oxygen Reduction Reaction Mechanism of PrBaFe2O5+δ Cathode Material for Solid Oxide Fuel Cells
摘要
Abstract
Introduction Compared to Co-based cathode materials,Fe-based perovskite materials exhibit superior thermal stability and electrochemical stability,but they have lower conductivity and redox activity.The Fe-based perovskite materials are regarded as one of the cathode materials with a great development potential for SOFCs due to their lower thermal expansion coefficient and cost.In the LnBaFe2O5+δ(Ln=lanthanide elements,Y)double perovskite materials,PrBaFe2O5+δ(PBF)has the lowest activation energy for the redox reaction,making it a promising alternative material for SOFC cathodes.For the PBF materials,there are a few reports on their crystal structure and redox reaction mechanisms.There is still a debate regarding the tetragonal and cubic structures of PBF materials.Also,the mechanism of the redox reaction remains unclear and requires a further in-depth investigation.This study was to prepare the PBF cathode materials by a sol-gel method.In addition,the synthesis process,crystal structure,and redox reaction mechanisms of PBF materials were also investigated. Methods The average binding energy of the possible structures of PBF was calculated by the Cambridge Sequential Total Energy Package(CASTEP)module in Material Studio software.The reflex module in Materials Studio was used to simulate the X-ray diffraction(XRD)patterns after optimizing the structures.The PBF powder was prepared by a sol-gel method,and the precursors were analyzed by thermgravity-differential thermal analysis(TG-DTA),X-ray diffraction(XRD)and transmission electron microscopy(TEM).The calcined samples were treated in air,20％(in volume)H2(H2+N2)atmosphere,and pure H2 at 800 ℃ for 20 h.In addition,the electrochemical impedance spectra of the PBF|SDC|PBF symmetrical cell were measured,and analyzed via distribution of relaxation times(DRT). Results and discussion The simulated XRD patterns show distinct differences in the XRD peaks of the four PBF structures with the main difference between the tetragonal and simple cubic structures after 80°.The characteristic double peak of the double perovskite is attributed to an increased lattice distortion caused by an increase in oxygen vacancy defects,while its structural symmetry remains unchanged.The tetragonal structure has the lowest average binding energy,while the simple cubic structure has the highest.This indicates that the likelihood of PBF adopting a simple cubic structure is minimal,whereas the likelihood of it adopting a tetragonal structure is maximal. The results of TG-DTA and XRD indicate that the precursors form BaFeC3 and PrFeO3 heat-treated at 800 ℃and a subsequent two-phase solid solution process after 800 ℃.Pure PBF is obtained after roasting in air at 1200 ℃ for 5 h.In a 20％H2(H2+N2)atmosphere,pure PBF can be achieved at 800 ℃,indicating that the 20％H2(H2+N2)treatment accelerates the solid solution of BaFeO3 and PrFeO3.The PBF is structurally stable in both air and a 20％H2(H2+N2)atmosphere,but decomposes into Fe,BaFeO3,and Pr2O3 in pure H2,indicating that PBF material decomposes under pure hydrogen and is not suitable for use on the anode side.Also,the occupancy of O in the[Pr-O]layer decreases,indicating that more oxygen vacancies are generated after reduction.The analysis of the crystal structure shows that the unit cell is elongated in a 20％H2(H2+N2)atmosphere due to the formation of more oxygen vacancies in the[Pr-O]layer. Based on the different relaxation times of various cathodic reactions,the DRT analysis indicates that the limiting step of the ORR at 400-550 ℃ involves the ionization of oxygen atoms and the transport of oxygen ions,while that at 600-700 ℃ involves the chemisorption of oxygen and the dissociation of oxygen molecules.At 700-800 ℃,the limiting step is related to the physisorption of oxygen.Clearly,the conclusions drawn from time-domain analysis differ from those obtained through conventional impedance spectroscopy.At 750-800 ℃,time-domain analysis indicates that the limiting step affecting the ORR is the physisorption of oxygen,whereas conventional impedance spectroscopy indicates that it is the ionization of oxygen atoms and the transport of oxygen ions.This study posits that both sets of results can serve as a basis for optimizing the oxygen catalytic performance of PBF materials. Conclusions This study investigated the formation process,structure,stability,and oxygen catalytic performance of PBF materials by DFT calculations,XRD,TEM,EIS,and DRT analysis.The PBF synthesized through the solid solution formation of PrFeO3 and BaFeO3 at 800 ℃ exhibited a tetragonal structure(i.e.,space group:P4/mmm).The crystal structure remained stable in air and 20％H2(H2+N2)atmosphere,but partially decomposed into Fe,BaFeO3,and Pr2O3 in pure hydrogen.The limiting steps of the oxygen reduction reaction(ORR)were identified as the ionization of oxygen atoms and the transport of oxygen ions at 400-550 ℃,chemisorption of oxygen and dissociation of oxygen molecules at 600-700 ℃,and physisorption of oxygen at 700-800 ℃.关键词
固体氧化物燃料电池/双钙钛矿/阴极/氧还原反应Key words
solid oxide fuel cell/double perovskite/cathode/oxygen reductive reaction分类
信息技术与安全科学引用本文复制引用
薛柯,蔡长焜,谢满意,李舒婷,安胜利..固体氧化物燃料电池PrBaFe2O5+δ阴极材料的结构和氧还原反应机理[J].硅酸盐学报,2025,53(10):3022-3030,9.基金项目
国家自然科学基金(51974167). （51974167）
