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

Han, J. W., Pohang University of Science and Technology (POSTECH)
Kim, K., Pohang University of Science and Technology (POSTECH)
Jung, W., KAIST
Koo, B., Korea Advanced Institute of Science and Technology (KAIST)
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 SrTi0.75Co0.25O3-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 SrTi0.75Co0.25O3-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.