Construction of a Z-scheme heterojunction based on two-dimensional Janus materials XWSiN2 (X=S; Se; Te) for effective photocatalytic water splitting by DFT

Photocatalysts play an important role in solving energy problems, and Z-scheme heterojunctions have garnered significant interest due to their ability to efficiently separate photogenerated carriers and improve redox capacity. In this work, we construct a Z-scheme heterojunction by substituting Se and Te for S atoms in the SWSiN₂ bilayer. The findings demonstrate that they have high kinetic stability, and the construction of heterojunctions can narrow the bandgap, effectively improving light absorption. The existence of the built-in electric field can be explained by studying the charge density difference, which breaks through the band gap limitation in water photocatalytic splitting. Their photocatalytic characteristics with and without strain are described in depth, with the spectroscopic limited maximum efficiency (SLME) of TeWSiN₂/SWSiN₂ surpassing 30 % under no strain. With tensile strain, SeWSiN₂/SWSiN₂ energy bands rise, but TeWSiN₂/SWSiN₂ energy bands decrease. Meanwhile, the band edge arrangement of XWSiN₂/SWSiN₂ (X=Se; Te) becomes smaller with increasing strain. The spectral finite maximum efficiency of SeWSiN₂/SWSiN₂ increases from 12 % to 27 % and shows good light absorption (η_STH = 10.60 % for SeWSiN₂/SWSiN₂, η_STH = 14.17 % for TeWSiN₂/SWSiN₂) and carrier utilization.