Improved efficiency of hydrogen production from water decomposition via dual electric field drive in WSe₂/SeSnS heterojunction structure

The rational design of Z-scheme heterojunctions combining broadband light absorption and effective charge separation remains challenged by interfacial carrier behavior. Herein, a Janus WSe₂/SeSnS van der Waals heterostructure is designed, utilizing structural asymmetry to establish a coupled built-in and dipole field (0.319 eV potential) that guides carrier flow and reduces recombination. The heterojunction features a narrow bandgap (0.54 eV) for infrared harvesting, high electron mobility (3536 cm²s⁻¹ V⁻¹), and suitable band edges for water splitting, achieving 12.05 % solar-to‑hydrogen efficiency. It demonstrates thermal, dynamical, and mechanical stability, together with minimal lattice mismatch (1.27 %), providing a scalable route to efficient solar fuel production.