Development of a MnCO3-based Electrocatalyst for Water Oxidation from Rhodochrosite Ore

Abstract An electrocatalyst based on a manganese carbonate mineral and intended to promote the water oxidation reaction was obtained by simply ball milling rhodochrosite ore. This material was found to catalyze the water oxidation reaction in a stable manner. Mn K-edge and O K-edge X-ray absorption fine structure (XAFS) analyses combined with theoretical simulations showed that the catalyst was composed of MnCO3 with slight distortions of the surface structure. Operando UV-vis absorption spectroscopy and linear combination fitting of XAFS spectra established that a portion of the MnCO3 surface was oxidized to MnO2. The MnO2 generated on the surface of this material likely provided active sites for the water oxidation reaction.