Direct Z-Scheme SiP/SnS2 van der Waals Heterostructure for Photocatalytic Overall Water Splitting

Abstract Photocatalytic water splitting is an effective approach for converting solar energy into hydrogen toward clean and sustainable energy utilization. In this work, a two-dimensional SiP/SnS2 van der Waals heterostructure is designed, and its efficacy as a photocatalyst for water splitting is comprehensively examined using density functional theory calculations. The results demonstrate that the SiP/SnS2 heterostructure exhibits enhanced broad-spectrum light absorption compared with the individual monolayers, because the constituent monolayers exhibit obvious band gap narrowing after heterostructure construction. Due to the establishment of a direct Z-scheme carrier-transfer route, the heterostructure realizes effective charge separation while preserving a robust redox capacity. The favorable alignment of band edges provides adequate thermodynamic driving force for both the hydrogen evolution reaction and the oxygen evolution reaction, thus allowing spontaneous overall water splitting. These findings identify the SiP/SnS2 heterostructure as a promising direct Z-scheme photocatalyst for overall water splitting and provide valuable theoretical guidance for the rational design of high-performance two-dimensional photocatalytic materials.