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Several coordination motifs of cobalt and manganese ions were obtained in various transition metal oxides, which enabled different oxidation and spin states. Combined high-resolution transmission electron microscopy (HRTEM) and X-ray absorption spectroscopy (XAS) confirmed the presence of coordination environments such as Co2+ in disordered prisms and Co4+/Mn4+ in face-shared octahedra. The influence of cobalt and manganese coordination on the oxygen evolution reaction (OER) activity and oxide stability in alkaline solution was studied. Under cycling, the surface of perovskites that consists of Co2+ in prisms was amorphized and the activity was similar to that of LaCoO3, which has a stable surface composed of Co3+ in octahedral coordination. These findings highlight the critical role of the electronic structure of transition metal oxides on the OER activity and stability.
Grimaud et al. (Wed,) studied this question.