Ordering and Phase Control in Epitaxial Double-Perovskite Catalysts for the Oxygen Evolution Reaction

The complex oxide compound praseodymium barium cobalt oxide (PBCO) is an efficient catalyst for the oxygen evolution reaction (OER) during electrochemical water splitting, with an activity that is mainly ascribed to PBCO’s inherent atomic structure and band alignment. Here, we report on epitaxial PBCO thin films showing electrocatalytic properties, with current densities of up to 10 mA/cm2 at 1.8V vs. RHE. Dense PBCO thin films are synthesized in a disordered perovskite phase as well as in an coherently oxygen vacancy-ordered (double-)perovskite phase, in which oxygen vacancies are incorporated in every second CoO2-δ atomic plane along the out-of-plane direction. The transition from disordered to ordered growth occurs temperature-controlled during the growth process and can be directly monitored in-situ by means of reflection high-energy electron diffraction. The epitaxial fabrication process allows the control of structure and phase of the oxide catalysts, providing model systems for exploring structure-...