Synergistic catalysis for oxygen reduction reaction via in situ nanoparticle exsolution-induced perovskite phase transformation

Perovskite-type SrFeO 3- δ (SF) is a promising cathode material for solid oxide fuel cells (SOFCs) owing to its high ionic and electronic conductivities. Moreover, it is necessary to enhance the electrocatalytic activity for oxygen reduction reaction (ORR) in the intermediate operating-temperature range. In this study, the tunable synthesis of Ce, Ni dual-doped SF-based materials enables the in situ exsolution of CeO 2 and NiO nanoparticles, thereby inducing the transformation from a simple tetragonal perovskite into a rod-like Ruddlesden–Popper (RP) phase. Compared to SF, the multi-catalyst with a nominal composition of Sr 0.9 Ce 0.1 Fe 0.8 Ni 0.2 O 3– δ exhibits improved ORR activity with only 37 % polarization resistance at 800 °C. Theoretical calculation reveals that the exposure of CeO 2 (220) and NiO (111) crystal planes facilitates the oxygen adsorption and that the formation of the RP phase increases the oxygen vacancy concentration in the lattice and promotes the oxygen dissociation.