Computational Assessment of Nonpolar and Polar GaP Terminations for Photoelectrochemical Water Splitting

With photoelectrochemical water splitting being one of the most promising approaches for clean energy production and storage, the search for efficient photoelectrode materials is greater than ever. Gallium phosphide (GaP) is a well-established semiconductor with suitable band edge positions that has already been successfully employed in photoelectrochemical solar cells. However, to utilize it as efficiently as possible, a proper understanding of its properties when interfaced with water is required, and this is currently lacking. In this work we use ab initio molecular dynamics simulations to study the properties of the aqueous interfaces of various GaP nonpolar (110) and polar (001) terminations. We calculate their band alignment with respect to the standard hydrogen electrode potential and investigate their interfacial structural properties. Based on these properties we assess the capability of the various terminations to catalyze the reactions associated with water splitting and propose approaches for improving the performance of GaP for application in PECs.