Temperature-dependent electronic structure of bixbyite ?-Mn₂O₃ and the importance of a subtle structural change on oxygen electrocatalysis

Bixbyite ?-Mn2O3 is an inexpensive Earth-abundant mineral that can be used to drive both oxygen evolution (OER) and reduction reactions (ORR) in alkaline conditions. It possesses a subtle orthorhombic ? cubic phase change near room temperature suppresses Jahn–Teller distortions presents unique opportunity study how atomic structure affects the electronic catalytic activity at range easily accessible OER/ORR experiments. Previously, we observed heat-treated had better performance as bifunctional catalyst (Dalton Trans. 2016, 45, 18,494–18,501). We hypothesized heat-treatment pinned material into more electrochemically active phase. In this manuscript, use high-resolution X-ray diffraction collect temperature-dependent structures of ?-Mn2O3, then input them ab initio calculations. The calculations indicate transition causes Mn 3d O 2p bands overlap mix covalently, transforming from semiconductor semimetal. This also modifies Mn-O-Mn bond distances, which may improve electrochemistry. OER ORR experiments were performed using same electrode various temperatures. They show jump exchange current density temperature, demonstrating higher