Enhanced solar-to-hydrogen efficiency for photocatalytic water splitting based on a polarized heterostructure: The role of intrinsic dipoles in heterostructures

Inspired by natural photosynthesis, direct Z-scheme heterostructures are considered as promising photocatalysts for solar-driven water splitting and attract ever-growing interest. To date, it is still a challenge to achieve a high efficiency based on direct Z-scheme photocatalysts for overall water splitting, because suitable band gaps and overpotentials for both half-reactions and spatially separated catalytic sites should be fulfilled simultaneously in a photocatalytic system. These challenges can be solved by taking advantage of the intrinsic dipole effect for polarized materials. Here, we propose a new strategy to achieve this goal by constructing van der Waals (vdW) heterostructures based on two-dimensional (2D) polarized materials. Using density functional theory calculations, we predict a promising photocatalyst In₂Se₃/SnP₃heterostructure, with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) taking place separately on the SnP₃and In₂Se₃layers. It is found that the intrinsic dipole of the In₂Se₃monolayer effectively enhances the redox abilities for both the HER and OER. Moreover, the intrinsic dipole can promote the spatial separation of photogenerated carriers, and also contributes to a high solar-to-hydrogen (STH) efficiency of 19.26%, which is quite promising for commercial applications. This work opens up an avenue for the design of highly efficient Z-scheme photocatalysts for overall water splitting.