Polar-nonpolar Oxide heterostructures for photocatalysis

The discovery of two-dimensional electron gas (2DEG) at the interface of polar LaAlO$_{3}$ (LAO) and non-polar SrTiO$_{3}$ (STO) open the research field of layered oxide heterostructures. In this study, we propose new application of oxide heterostructures for photocatalysis. We take a sandwich-like heterostructure STO/LAO/STO as an example and prove it to be a promising photocatalyst which is active for near-infrared light. Because the sandwiched LAO is polarized and generates a build-in electrostatic field, the valance band and conduction band locates on two opposite STO surfaces. First principles calculations prove that the band gap is reduced and the absorption of near-infrared to visible light is improved distinctly. Simultaneously, the build-in electric field in LAO accelerates the electrons and holes into opposite directions, preventing the recombination, and generates an electron doped surface and a hole doped STO surface, which could be used for H$_{2}$O reduction and oxidation separately. Our study gives a new perspective into the applications of oxide heterostructures in solar energy conversion.