First-Principles Modeling of Electrochemical Water Oxidation on MnO:ZnO(001)

The demand for renewable hydrogen derived from CO₂-neutral water-splitting processes spurs efforts to develop new catalysts, including those inspired by nature. A first-principles quantum mechanics (Kohn-Sham density functional theory + U) approach has been used to model electrocatalytic water oxidation on the visible-light-absorbing transition-metal oxide alloy, MnO:ZnO; a material that can be considered a heterogeneous analogue to the photosystemII photocatalyst. Ab-initio-derived U values were used to correct self-interaction errors in the highly correlated material. It has been confirmed that previously established scaling relationships between the binding energies of reaction intermediates are valid. The predicted electrochemical overpotential for water oxidation under experimentally relevant conditions (0.82V versus the standard hydrogen electrode) is slightly higher than those values reported for manganese oxides and comparable to those previously calculated values for hematite photoanodes. Time to split! First-principles quantum mechanics studies on visible-light-absorbing MnO:ZnO alloy photoanodes for catalytic water oxidation are described. The computed overpotential of 0.82V for the oxidation of 0.5monolayers of H₂O on Mn:ZnO(001) under vacuum conditions (see picture) is comparable to calculated values for hematite.