Electronic and Optical Properties of CoX2O4 (X=Al, Ga, In) Alloys

The electronic and optical properties of Co based spinel oxides, CoX ₂O ₄ (X = Al, Ga, In) are calculated using first-principle density functional theory. We show that the desirable properties for solar photoconversion can be obtained by controlling the alloy compositions. The ability to manipulate the electronic and optical properties is attributed to the different s-orbital energies and sizes of the cations. Our calculated bandgaps as function of composition provide detailed practical guidance for synthesizing Co based spinel oxides with electronic and optical properties necessary to achieve high efficiency photoelectrochemical decomposition of water for hydrogen production by sunlight.