Effect Of B-site Doping On Chemical Compatibility Of (La_0.25Sr_0.75)_0.9Ti_0.9X_0.1O_3-? And Stabilized Zirconia Electrolyte

As an important branch of new energy fuel cell has the advantages of clean and efficient.Solid oxide fuel cell?SOFC?has attracted more attention because of its fuel flexibility and full solid-state components which can avoid the corrosion problems caused by the using of liquid electrolyte.The components of SOFC include anode,electrolyte and cathode.Ni/YSZ cermet anode as a traditional anode material with advantages of high conductivity,good catalytic activity and superior electrochemical performance fuelled by H₂ has been widely used.However,serious carbon deposition occurred to Ni/YSZ cermet anode when nature gas and coal syngas were used as fuel.The Ni/YSZ cermet also has poor tolerance to H₂S contained in hydrocarbon fuels.La-substituted SrTiO₃?LST?becomes a potential anode material for SOFC owing to its high electrical conductivity,matching thermal expansion to zirconia electrolyte and good chemical and physical stability under oxidizing and reducing atmospheres.No obvious carbon deposition phenomenon was observed on the surface of anode containing LST when fuelled by hydrocarbon fuel.LST anode also showed excellent tolerance to sulfur.The disadvantages of LST are poor catalytic activity and the possible interaction between stabilized zirconia electrolyte?YSZ or ScSZ?.It has been found that stoichiometric LST can react with ScSZ to form La₂Zr₂O₇ with poor catalytic activity and low electrical conductivity,which significantly reduced the electrochemical performance of the LST anode.Though A-site deficient LST can effectively suppress the interfacial reactions occurred between LST and ScSZ,the inter-diffusion between A-site deficient LST and ScSZ still existed.The inter-diffusion changed the composition of anode located at TPB area and seriously degraded the performance of the anode.In this study,in order to improve the high temperature chemical compatibility between A-site deficient LST and ScSZ,doping at B-site of(La_0.25Sr_0.75)?0.9?TiO₃-? was proposed to suppress the inter-diffusion phenomenon.The chemical compatibility between different B-site doped(La_0.25Sr_0.75)_0.9Ti_0.9X_0.1O₃-? with ScSZ was deeply investigated.The electrochemical performance of the B-site doped LST anode with better chemical compatibility was performed.?1??LS?_0.9T,?LS?_0.9T_0.9A_0.1,?LS?_0.9T_0.9G_0.1,?LS?_0.9T_0.9S_0.1 were synthesized by sol-gel method.According to XRD results,uniform perovskite phase was formed in each powders and no additional phase was observed.Good crystallinity was observed in sample after sintered at 1200 ?.SEM images indicated that all of as-prepared samples have good sintering ability.?4?High temperature chemical compatibility between?LS?_0.9T,?LS?_0.9T_0.9A_0.1,?LS?_0.9T_0.9G_0.1,?LS?_0.9T_0.9S_0.1 and ScSZ was investigated though annealing test at 1200 ? in air for 30 hours.Annealing test results indicated that each B-site doping obviously influenced the chemical compatibility of?LS?_0.9T.?LS?_0.9T_0.9A_0.1 shows the best chemical compatibility in four samples.No obvious interaction was observed in annealing test pellet of?LS?_0.9T_0.9A_0.1/ScSZ,and both?LS?_0.9T_0.9A_0.1 and ScSZ remained cubic phase after 30 h annealing test.?2?Electrochemical performance tests were carried out for the cell with?LS?_0.9T/ScSZ anode and?LS?_0.9T/ScSZ anode,respectively.Current density degradation was observed in the cell with?LS?_0.9T/ScSZ anode during 5 h potential static test.The output current density of the cell with?LS?_0.9T_0.9A_0.1/ScSZ anode was low at initial state,which increased with the increasing of the testing time.Electrochemical impedance spectroscopy showed that polarization impedance decreased remarkably after 5h test.The electrochemical performance test and the chemical compatibility investigation indicate that?LS?_0.9T_0.9A_0.1 is a good potential anode material.