Janus SiS/SeWS heterostructure for efficient solar-driven water splitting

Optimal photocatalytic performance in solar water splitting systems requires meticulous regulation of both charge carrier separation dynamics and interfacial charge transfer kinetics, we computationally demonstrate that the Janus SiS/SeWS vdW heterostructure exhibits ideal characteristics for both processes. This structure aims to enhance photocatalytic performance through synergistic bandgap alignment and dipole electric field effects. The heterostructure exhibits exceptional stability (thermodynamic, dynamic, and mechanical) with a low lattice mismatch (2.8 %), ensuring experimental feasibility. The observed Type II band alignment features CBM/VBM localization on distinct material components (S p-orbitals/W d-orbitals), promoting charge separation. The structure is dominated by the dipole electric field generated by the Janus structure, achieving highly efficient electron-hole separation and an ultra-high electron mobility (3837.44 cm²/Vs). Its free energy calculations indicate the possibility of hydrogen evolution reaction (HER) under acidic photochemical conditions (ΔG ≈ 0.09 eV) and oxygen evolution reaction (OER) under neutral conditions, achieving a solar-to-hydrogen (STH) efficiency of 24.32 %. This performance significantly surpasses the 10 % feasibility benchmark adopted for practical economic applications. This work underscores the critical role of synergistic band engineering and dipole electric field in designing high-performance Janus heterostructures for solar energy conversion.