Ab Initio Modeling of Semiconductor-Water Interfaces

Abstract

Semiconductor-water interfaces play a crucial role in (photo)electrochemistry. Since electrochemical interfaces are qualified as a complex chemical system, exploring the interfacial properties only by experimental measurements is challenging. It, therefore, requires an additional theoretical investigation on the microscopic atomic-scale features of the interface. In this chapter, the physical chemistries of semiconductor-water interfaces are discussed based on a method combing density functional theory based molecular dynamic (DFTMD) and free energy perturbation (FEP) theory. We introduce the calculations of the band alignments at electrochemical interfaces and the surface acidity constants (pKa) of semiconductors, which are the primary factors in determining the catalytic activities of semiconductors and the adsorption behavior of interfacial waters, respectively. Additionally, we present the construction of a fully atomistic model of a Helmholtz electric double layer at the semiconductor-water interface, which is the fundamental theoretical model to study the chemical reactivity of the surface. Semiconductor (photo)electrocatalytic reactions involve photogenerated electrons and holes. Have a knowledge of the excess electron and hole states in semiconductors and the proton-coupled electron transfer (PCET) reaction mechanisms can help us design catalysts with high efficiency of photocatalytic or photoelectrochemical water splitting. Combining these theoretical studies, the understanding of semiconductor-water interfaces will become gradually clear.