A Highly Efficient BiOSe/BiWO S-Scheme Heterojunction Photocatalyst for Solar Water Splitting: A First-Principles Study.

Two-dimensional (2D) S-scheme heterojunctions have garnered significant interest, owing to their remarkable redox capability and excellent potential in solar energy harvesting. In the work, a 2D/2D S-scheme heterojunction consisting of monolayer BiOSe and BiWO was designed, and its performance in photocatalytic water splitting was comprehensively investigated using first-principles calculations. The results reveal that the BiOSe/BiWO heterojunction features well-aligned electronic band structures and generates an intrinsic built-in electric field directed from BiOSe toward BiWO. The internal electric field promotes effective charge separation via the S-scheme mechanism, significantly reducing carrier recombination and improving the dissociation of photogenerated electron-hole pairs. Furthermore, Gibbs free energy calculations indicate that solar energy can drive spontaneous water splitting of the BiOSe/BiWO heterojunction. Owing to its efficient S-scheme charge migration and strong light-harvesting capability across a wide spectral range, the BiOSe/BiWO heterojunction exhibits an impressive solar-to-hydrogen (STH) conversion efficiency that reaches 23.48%. These findings demonstrate that the BiOSe/BiWO S-scheme heterojunction is a highly promising and stable photocatalyst for efficient solar-driven hydrogen production.