Ab-initio calculation of band positions for transition metal oxides reveals potential materials for photoelectrochemistry

The position of the band edges is an essential property that characterizes a material's capability to function in a solar energy conversion device. Particularly, the placement of the valence band maximum and conduction band minimum must be in proximity to reduction-oxidation potentials of reactions taking place in a photoelectrochemical cell. We present calculations of the band edge positions of transition metal oxides and discuss the feasibility of using these materials in cells that produce fuel, including hydrogen and methanol. The valence band maximum is determined within the framework of periodic hybrid density functional theory and the conduction band minimum is found by adding the quasiparticle gap obtained from a non-self-consistent GW calculation built upon hybrid DFT input. The calculations are demonstrated on several materials including wüstite, hematite, cuprous (D) oxide, as well as manganese oxide and nickel oxide alloyed with zinc oxide.