Ab Initio Investigation of the Interfaces between III-V Semiconductors and Electrolytes

In the search for ideal electrodes for photoelectrochemical water splitting, III-V semiconductors, such as GaP, GaAs, and InP, have gained substantial attention, due to advantageous properties, such as suitable bandgaps and favorable alignment of their electronic levels with the relevant redox potentials. By growing such materials epitaxially, their composition, orientation, and surface termination, and therefore their properties, can be controlled with great precision. Identifying the most appropriate surface terminations for the intended application requires a good understanding of those surfaces and the effects of their interaction with water. To shed light on this intricate interaction, we employ ab initio molecular dynamics simulations to study various III-V surfaces in contact with water. We monitor the effect this interaction has on the electronic levels of the semiconductors with respect to the standard hydrogen electrode potential, as well as on the interfacial water structure, the formation of surface dipoles, and the charge exchange at the interfaces. Based on these results, the most suitable terminations for the water splitting redox reactions can be established.