Oxygen Evolution Reaction Activity of Sr₂Ta₂O₇ and Sr₂Nb₂O₇ Surfaces

摘要: Oxide materials with a perovskite-derived layered structure often show better photocatalytic performance compared to non-layered materials of similar composition. Here we investigate the catalytic activity for the oxygen evolution reaction (OER) on surfaces of the layered Carpy-Galy oxides Sr2Ta2O7 and Sr2Nb2O7. We find that the (010) surface parallel to the layering shear plane is not relevant for photocatalysis. The (100) surface perpendicular to this plane, on the other hand, can catalyze the OER, at least for Sr2Ta2O7, whereas Sr2Nb2O7 is inactive for the OER without a cocatalyst, both in agreement with experiment. The OER activity of Sr2Ta2O7 (100) is, however, only retained while the surface does not assume a reconstructed stepped structure via Sr dissolution which we predict to be thermodynamically favored. Engineering Sr2Ta2O7 into long-lasting photoelectrodes thus has to focus on exposing (100) facets as well as preventing Sr dissolution, for example via a high Sr concentration in the electrolyte.