WSi₂N₄/XSe and WSiGeN₄/XSe (X=Al, Ga, and In) heterostructures for photocatalytic water splitting: a DFT...

The research for an effective photocatalyst is ongoing, and this study considers the WSi₂N₄/XSe and WSiGeN₄/XSe (X = Al, Ga, and In) heterostructures for photocatalytic water splitting using Density Functional Theory. The heterostructures are constructed using a 7 × 7 × 1 supercell for the WSi₂N₄ and WSiGeN₄ monolayers and 2 × 2 × 1 supercell for the XSe monolayers. The structural optimizations reveal that the heterostructures with the InSe monolayers have positive binding energy, which reveals their structural instability. The WSi₂N₄/XSe and WSiGeN₄/XSe (X = Al and Ga) heterostructures have been further considered for their mechanical and thermodynamic stabilities, where all the heterostructures are structurally, mechanically, and thermodynamically stable. The electronic properties of WSi₂N₄/XSe and WSiGeN₄/XSe (X = Al and Ga) heterostructures are studied in detail using PBE and HSE methods. The WSi₂N₄/AlSe, WSi₂N₄/GaSe, and WSiGeN₄/AlSe heterostructures have band gaps as 1.83 eV, 1.66 eV and 1.69 eV, respectively, that satisfy the band gap requirement for photocatalytic water splitting. In addition, the valence band and conduction band levels are determined that must satisfy the redox potential. This analysis reveals that the WSi₂N₄/AlSe and WSi₂N₄/GaSe heterostructures have an S-scheme mechanism, while the WSiGeN₄/AlSe heterostructure has a type-II mechanism. Furthermore, the optical properties and solvent effect are investigated to reveal the performance of these heterostructures further. The present study determines the stability of WSi₂N₄/XSe and WSiGeN₄/XSe heterostructures and examines their photocatalytic water splitting potential in detail. It is therefore posited that the results presented in this study will serve as a guide to inform future studies and pave the way for new research in this field.