Ba-leaching-initiated structural destabilization of perovskite Ruthenates during the oxygen evolution reaction

Abstract

The destabilization of a lattice structure during the oxygen evolution reaction (OER) is one of the most essential aspects for designing and realizing highly efficient electrocatalysts. However, the underlying mechanism of structural evolution or degradation at the microscopic scale on the electrocatalyst surface during the OER has not been elucidated because of the sluggish yet dynamic character of the reaction. To address this issue, the direct observation of the unstable electrocatalytic activity is necessary. In this study, we demonstrate that the structural destabilization of epitaxial cubic perovskite BaRuO3 thin films during the OER originates from Ba leaching, Ru dissolution, and oxygen vacancy. A thin film geometry is adopted to selectively visualize the structural decomposition at the well-defined sample surface. The cubic BaRuO3 thin film initially exhibits high OER activity, which drastically decreases even during the first cyclic voltammetry cycle and is completely lost after the first cycle. The OER activity loss is closely related to the generation of structural defects on the surface, indicating the absence of the Ba and Ru atoms. This study proposes the mechanism underlying the OER activity that can be extended to elucidate the structural destabilization in various Ru- and Ir-based oxide catalysts.