Development of a MnOOH Mineral Electrocatalyst for Water Splitting by Controlling the Surface Defects of a Naturally Occurring Ore

A MnOOH-based mineral electrocatalyst for the oxygen evolution reaction was developed using a natural ore that is typically insulating, simply by applying a ball milling treatment. This material catalytically decomposed water molecules to generate oxygen. Mn K-edge X-ray absorption spectroscopy analyses in the bulk and surface sensitive modes indicated that structural distortion at the surface provided the catalytically active sites. The formation of oxygen vacancies on natural ore surfaces is likely to be the key to developing efficient mineral electrocatalysts.