WS₂/BSe van der Waals type-II heterostructure as a promising water splitting photocatalyst

The structure, electronic properties, charge transfer, band edge alignments and optical properties of WS₂/BSe heterostructures are investigated by using first-principle calculations. Results imply that WS₂/BSe heterostructures are semiconductor with an indirect energy gap (E_gap) of 1.73 eV. Additionally, it has a feature of type-II band alignment, which contributes to spatial separation of photo-generated electron-hole pairs in WS₂/BSe heterostructures. Charge transfer takes place from BSe to WS₂ monolayers, which extends lifetime of the separated photo-induced charge carriers. Most importantly, band edges of the heterostructure are found to meet hydrogen evolution reaction (HER) in acid solutions (0 < pH < 7). Moreover, compared with only one for WS₂ and BSe monolayers, the optical-absorption strength of the heterostructure is significantly enhanced and WS₂/BSe heterostructures larges the range of absorption to 717 nm in the visible light region, improving the potential photocatalytic efficiency. These results explain the underlying mechanism of the enhanced photocatalytic activity of WS₂/BSe heterostructures. Thus WS₂/BSe heterostructures can be applied to 2D heterostructured photocatalysts. (paper)