Ab-initio modeling of water-semiconductor interfaces for direct solar-to-chemical energy conversion

We perform extensive density-functional theory total-energy calculations and ab-initio molecular dynamics simulations to evaluate the stability and reactivity of surface oxides and hydroxides of InP(001) for photoelectrochemical water cleavage. In order to achieve maximal accuracy, our simulations include the full interface between the semiconductor surface and liquid water. Certain oxide contaminants are found to have a dramatic impact on the surface reactivity, pointing to the importance of surface oxide and hydroxide intermediates in facilitating the water-dissociation component of the hydrogen evolution process. Our results are used to relate the chemical activity of the surface towards water dissociation to the oxygen bond topology. The importance of the liquid hydrogen-bond network near the interface is discussed, particularly in relation to the generation of local configurations favorable for dissociative water adsorption on InP(001).