A review of sulfur poisoning of solid oxide fuel cell cathode materials for solid oxide fuel cells

To widespread solid oxide fuel cell (SOFC) implementation, it is essential to overcome issues of cost and lifetime, simultaneously. Sulfur poisoning of cathode materials, which comes from a trace amount of SO2 in air, is one of important factors to cause cathode performance degradation resulting in shortening lifetime of SOFC. Present review aims at providing state-of-art understanding of sulfur poisoning behaviors of cathode materials: the equilibrium considerations as well as the kinetic considerations are made on the chemical reactions of perovskite oxides with SO2 (g). Furthermore, the plausible sulfur poisoning mechanism of perovskite cathode materials is clarified; that is, the relationship between features of chemical reactions and cathode performance degradation is discussed in terms of the effects of electrochemical aspects on chemical reaction. In particular, some interesting differences in sulfur poisoning between (La, Sr)CoO3-delta (LSC) and (La, Sr)(Co, Fe)O3-delta (LSCF), can be well correlated with those differences in fundamental steps in oxygen reduction reactions; namely the availability of adsorption of O-2 molecule on the perovskite oxide surface. Finally, this review concludes with some generalized discussions on strategy of selecting elements and their compositions in the rare earth-transition metal perovskite oxides with alkali earth dopant.