Research On H₂S Poisoning And Regeneration Of La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-? Based Solid Oxide Fuel Cellanode

Solid oxide fuel cell?SOFC?has the advantages of high efficiency,low pollution fuel flexibility and broad application.La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-??LSCrM?is a perovskite oxide anode material for SOFC with stable electrochemical performance and high sulfur tolerance.It can be regenerated by chemical or electrochemical oxidation after sulfur poisoning for its redox stability.In this dissertation,the short time cycles of sulfur poisoning and following chemical or electrochemical regenerattion of LSCrM anode were conducted under three H₂S concentration conditions of 5ppm,10 ppm and 50 ppm.The mechanism of sulfur poisoning and the mechanisms of poisioning and regeneration were studied.The effects of composition and microstructures the composite anode by introducing?ZrO₂?_0.92?Y₂O₃?_0.08?8YSZ?,Ce_0.8Sm_0.2O_1.9?SDC?and Ce_0.9Gd_0.1O_1.95?GDC?electrolytes were investigated,respectively,in order to improve the sulfur tolerance of the anodes as well as to study the regularity of a short time multiple sulfur poisoning-chemical oxidation cycles at different H₂S concentrations.The results show that the electrochemical performance of LSCrM anode poisoned by three H₂S concentrations of a fuel cell with YSZ electrolyte and LSM-YSZ cathode can be regeranated.The oxidation regeneration method is feasible for the regeneration of LSCrM with different concentrations of H₂S,but the effect of electrochemical oxidation regeneration on LSCrM of lower concentration H₂S?5ppm,10ppm?is less obvious than that of chemical oxidation regeneration method.The higher concentration of H₂S and the longer poisoning time cause more the covering products on anode particle surface.The composite anode with a LSCrM/YSZ ratio of 5:5 decreases 0.05 V during 10 h poisoning,and the decline rate is 6.4%,which is better than that of 8:2.The composite anode shows the best effect of during the 3^rdd to 6^thh poisioning-regeneration cycles during repeated poisoning-chemical oxidation regeneration cycles.By removing H₂S from the fuel gas,the performance of the fuel cell can also be regenerated after a relative long period,which is conducive to prolonging the life of fuel cell.The compoiste anodes of LSCrM and doped ceria SDC or GDC electrolyte can significantly improve the electrochemical performance of the LSCrM anode.The sulfur tolerance of the composite anode with SDC is better than the one with GDC.The poisoned LSCrM/DCO composite anode can also be regenerated by chemical oxidation regeneration and the sulfur tolerance of the LSCrM/CeO₂ composite anode is better than LSCrM/YSZ composite anode.