Significance of Surface Trivalent Manganese in the Electrocatalytic Activity of Water Oxidation in Undoped and Doped MnO2 Nanowires

Abstract The oxygen‐evolution reaction (OER) is a bottleneck reaction because of a significant overpotential loss in water electrolysis. Currently, MnO 2 ‐based materials are promising candidates for OER electrocatalysts owing to their abundance and excellent properties. Herein, a hydrothermal method was used to prepare MnO 2 nanowires with different diameters. Furthermore, an impregnation method was applied to dope MnO 2 nanowires with Ca and Ag ions. Characterization by TEM, XRD, Raman, X‐ray photoelectron spectroscopy (XPS), N 2 adsorption, and linear‐scanning voltammogram analysis were performed on these materials. It was found that the OER activity of as‐prepared and doped MnO 2 nanowires is highly dependent on the fraction of surface trivalent manganese in MnO 2 nanowires. Density functional theory calculations of doped MnO 2 revealed the delicate change of the electronic properties of MnO 2 nanowires after doping.