A Highly Efficient Bi₂O₂Se/Bi₂WO₆ 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 Bi₂O₂Se and Bi₂WO₆ was designed, and its performance in photocatalytic water splitting was comprehensively investigated using first-principles calculations. The results reveal that the Bi₂O₂Se/Bi₂WO₆ heterojunction features well-aligned electronic band structures and generates an intrinsic built-in electric field directed from Bi₂O₂Se toward Bi₂WO₆. 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 Bi₂O₂Se/Bi₂WO₆ heterojunction. Owing to its efficient S-scheme charge migration and strong light-harvesting capability across a wide spectral range, the Bi₂O₂Se/Bi₂WO₆ heterojunction exhibits an impressive solar-to-hydrogen (STH) conversion efficiency that reaches 23.48%. These findings demonstrate that the Bi₂O₂Se/Bi₂WO₆ S-scheme heterojunction is a highly promising and stable photocatalyst for efficient solar-driven hydrogen production.