Advances in Understanding Mechanisms of Perovskites and Pyrochlores as Electrocatalysts using In-Situ X-ray Absorption Spectroscopy.

Metal oxides are some of the most promising candidates as electrocatalysts for electrical-energy-storage (EES) systems. Particularly, perovskite and pyrochlore oxides have been intensively investigated as bifunctional electrocatalysts because of their superior catalytic activities during the oxygen-reduction and -evolution reactions. However, the origin of the outstanding catalytic activities and structural changes of the materials are not clear, in part due to the difficulty in identification during electrocatalysis. In this Minireview, we present a critical overview of recent progress in understanding catalytic mechanisms of perovskite and pyrochlore oxides, highlighting the innovative in-situ X-ray absorption spectroscopy (XAS) analysis for electrochemical tests.