Band Gap Engineering of MnO via ZnO Alloying: A Potential New Visible-Light Photocatalyst

Practical implementation of solar-powered water splitting and CO2 reduction to fuels requires the discovery of efficient and inexpensive photocatalytic (PC) materials. One possible materials design strategy aims to tune properties of relatively inexpensive transition metal oxide catalysts to increase sunlight absorption while preserving potential redox reactivity. Here we consider MnO for PC use by alloying it with ZnO in solid solutions. A combined density functional theory and GW scheme is used to study the band gap and band edge placements as a function of composition. We predict that alloying MnO with ZnO in varying amounts reduces MnO's band gap for more efficient light absorption while maintaining advantageous band edge placements. The 1:1 alloy of MnO and ZnO is identified as a new (2.6 eV band gap) visible-light-absorbing material with band edges suitably placed with respect to both water-oxidation and CO2-reduction reactions, making it a compelling candidate for solar PC chemistry.