Band Alignment of 2D Material–Water Interfaces

Two-dimensional (2D) materials are presently being extensively studied in photo(electro)catalysis due to their excellent light absorption, high specific surface area, and readily tunable electronic properties. Electronic structure calculations are of great importance for improving our understanding of the activities of 2D materials. In this work, we perform density functional theory based molecular dynamics (DFTMD) simulations to simulate the explicit 2D material–water interfaces and study the water effects on band gaps and band edge positions in detail. Nine 2D materials with three kinds of typical surface structures are considered, including BN, MoS2, WS2, Black-P, GaSe, GaTe, CrCl3, MoO3, and V2O5. We find that the band gap will decrease when interacting with water, which is induced by a combination of structural and electronic effects. Especially, overlaps between electron densities of solid surfaces and liquid water molecules may change the band gap significantly. The band edge shifts are mainly determined by the net orientation of water molecules at the interfaces. More importantly, our results show that water dipoles are related to surface structures and may not be negligible. Our findings emphasize the water effects on electronic structures and pave the way to screen low-cost and high-efficiency 2D material photocatalysts.