Computational Screening of Doped alpha-MnO2 Catalysts for the Oxygen Evolution Reaction

Minimizing energy and materials costs for driving the oxygen evolution reaction (OER) is paramount for the commercialization of water electrolysis cells and rechargeable metal-air batteries. Structural stability, catalytic activity, and electronic conductivity of pure and doped alpha-MnO2 for the OER are studied using density functional theory calculations. As model surfaces, we investigate the (110) and (100) facets, on which three possible active sites are identified: a coordination unsaturated, a bridge, and a bulk site. For pure and Cr-, Fe-, Co-, Ni-, Cu-, Zn-, Cd-, Mg-, Al-, Ga-, In-, Sc-, Ru-, Rh-, Ir-, Pd-, Pt-, Ti-, Zr-, Nb-, and Sn-doped -MnO2, the preferred valence at each site is imposed by adding/subtracting electron donors (hydrogen atoms) and electron acceptors (hydroxy groups). From a subset of stable dopants, Pd-doped alpha-MnO2 is identified as the best catalyst and the only material that can outperform pristine alpha-MnO2. Different approaches to increase the bulk electron conductivity of semiconducting alpha-MnO2 are discussed.