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.