Abstract:

Designing efficient S-scheme photocatalysts for simultaneous H₂ evolution and organic oxidation is highly desirable for sustainable energy conversion. Herein, a novel SnS₂/CdS S-scheme heterojunction loaded with transition metal single atoms (TM = Pt, Pd, Au) was constructed. Systematic density functional theory (DFT) calculations are performed to investigate the geometric structure, electronic properties, and the mechanisms of surface H adsorption and lactic acid (LA) oxidation reactions. The results reveal that in the heterojunction, electrons transfer from CdS to SnS₂ through interfacial Cd–S bonds, forming a stable composite structure, while the TM single atoms are stabilized by forming TM–S bonds with surface S atoms. The incorporation of TM atoms enhances the interfacial electron transfer. Notably, the TM atoms anchored on the CdS surface effectively modulate the p-band center of neighboring S atoms, thereby weakening the S–H bond and optimizing the H adsorption-desorption equilibrium. Concurrently, those on the SnS₂ surface enhance the adsorption energy of LA and reduce the energy barrier of the rate-determining step in the dehydrogenation oxidation process. This work demonstrates that the strategic placement of single atoms on different components of an S-scheme heterojunction can synergistically enhance both the reduction and oxidation half-reactions, offering profound insights for the rational design of high-performance single-atom-loaded S-scheme photocatalytic systems for cooperative H₂ production and value-added chemical synthesis.

Key words: S-scheme heterojunctions, Metal single atoms, Electron transfer, Hydrogen adsorption, Lactic acid oxidation