Mechanism of photocatalytic water splitting of 2D WSeTe/XS2 (X = Hf, Sn, Zr) van der Waals heterojunctions under the interaction of vertical intrinsic electric and built-in electric field

Finding photocatalytic materials with high hydrogen production efficiency is an effective way to solve the problem of the energy crisis. We use density functional theory (DFT) to predict the 2D WSeTe/XS2 (X = Hf, Sn, Zr) van der Waals (vdW) heterojunctions as the potential direct Z-scheme heterojunction photocatalysts and discuss the mechanism of photocatalytic water splitting under the interaction of vertical intrinsic electric field and built-in electric field. The WSeTe/XS2 heterojunctions have large band-edge staggered alignment, small interlayer bandgap, and good interlayer carrier recombination, which predict the direct Z-scheme charge transfer path formation. Meanwhile, the small bandgap of the 2D WSeTe/XS2 direct Z-scheme heterojunctions enables it to obtain a wide light absorption range. The built-in electric field from WSeTe to XS2 changes the charge transfer mode of the heterojunction and improves the separation efficiency of photo-generated carriers, and the vertical intrinsic electric field not only improves the hydrogen evolution reaction (HER) ability but also reduces the bandgap limitation of photocatalytic materials. In this paper, the 2D WSeTe/XS2 heterojunctions show significant advantages as photocatalytic materials, providing unique insights for researching and developing this kind of heterojunction.