Alignment of Redox Levels at Semiconductor–Water Interfaces

Abstract

We determine the band alignment between various semiconductors and liquid water by combining molecular dynamics (MD) simulations of atomistic interface models, electronic-structure calculations at the hybrid-functional and GW level, and a computational standard hydrogen electrode. Our study comprises GaAs, GaP, GaN, CdS, ZnO, SnO2, rutile TiO2, and anatase TiO2. For each semiconductor, we generate atomistic interface models with liquid water at the pH corresponding to the point of zero charge. The molecular dynamics are started from two kinds of initial configurations, in which the water molecules are either molecularly (m) or dissociatively (d) adsorbed on the semiconductor surface. The calculated band offsets are found to be strongly influenced by the adsorption mode at the semiconductor–water interface, leading to differences larger than 1 eV between m and d models of the same semiconductor. We first assess the accuracy of various ab initio electronic-structure schemes. The use of a standard hybrid fun...