(418c) Strain-Driven Exsolution in Perovskite Oxide for Improved Catalytic Activity at the Anode of Solid Oxide Fuel Cell

Redox ex-solution, in-situ synthesis process of metal nanoparticles upon high-temperature reduction has widely been studied as a way to fabricate metal nanocatalyst-decorated oxide electrodes for solid oxide electrochemical cells. However, the underlying mechanisms related to this phenomenon are not completely understood and the practical solutions that effectively accelerate B-site cation ex-solutions in perovskite oxide (ABO₃) have not yet been proposed. Here, we control the degree of Co enrichment at the surface of SrTi_0.75Co_0.25O_3-δ epitaxial thin films through lattice strain. Combined theoretical and experimental analyses show that the tensile strain that plays a role in stretching B-O bond length promotes the Co ex-solution in SrTi_0.75Co_0.25O_3-δ. To practically make use of these findings, we introduce a Ba cation, which is a large-sized isovalent dopant instead of a Sr cation, to expand the B-O bond length in the perovskite lattice. We successfully demonstrate that this approach can facilitate the ex-solution of B-site cations, suggesting a new strategy for improving the surface reactivity of perovskite-type oxides.