Novel Catalysts Synthesized by High-Pressure Method and Reaction Mechanism Based on First-Principles Calculation

Recent advances in high-pressure synthesis and theoretical investigation of novel transition metal oxide catalysts for oxygen evolution/reduction reactions (OER/ORRs) are reviewed. Valence dependence of OER catalysis for perovskite oxides are demonstrated by comparative study of iron perovskite oxides synthesized under high pressure. Structure effects on OER catalytic activity are investigated in manganese oxides with simple ABO3-type and quadruple AA′3B4O12-type structures. In addition to intrinsic high ORR activities, electrochemical experiments display that OER activities of quadruple perovskites AMn7O12 (A=Ca, La) are superior to those of simple perovskite AMnO3 counterparts, leading to OER/ORR bifunctional catalysis. Theoretical calculations propose a OER mechanism for quadruple manganese perovskite oxide, in which adsorption sites bridging between A′- and B-site Mn atoms play a crucial role in lowering OER overpotentials.