Improving Charge Carrier Separation through S-Scheme-Based 2D–2D WS2/Sulfur-Doped g-C3N4 Heterojunctions for a Superior Photocatalytic O2 Reduction Reaction

Hydrogen peroxide (H₂O₂) generation via a photocatalytic O₂ reduction reaction has been considered an economically efficient and environmentally friendly synthesis method. However, the productivity of H₂O₂ production is restricted because of sluggish reaction kinetics and fast recombination of photoinduced excitons. Therefore, a superior two-dimensional (2D)–2D WS₂/sulfur-doped g-C₃N₄ (WSCN) hybrid material was successfully fabricated to address the associated limitations through a combination of wet impregnation and calcination techniques for H₂O₂ production. The effective anchoring of WS₂ nanoplates onto sulfur-doped g-C₃N₄ (SCN) nanosheets facilitates effective separation of photoinduced excitons with sturdy redox properties, which is attributable to the establishment of S-scheme heterojunctions between WS₂ and SCN through W–S bonding as substantiated by X-ray photoelectron spectroscopy (XPS) analysis. The W–S bond at the interface acts as a bridge for effective charge segregation pathways. Among all, 2.5 WSCN displays an exceptional H₂O₂ production of 817 μmol, which was 7.9- and 2.68-fold higher than those of pristine WS₂ and SCN, respectively. The solar-to-chemical conversion efficiency was found to be 0.24%, whereas the apparent quantum yield was estimated to be 3.19% at 420 nm irradiation. The improved photocatalytic activity was figured out by a higher cathodic photocurrent of −1.51 mA cm^–2 and delayed recombination of excitons, as supported by photoluminescence and electrochemical impedance spectroscopy measurements. The S-scheme charge-transfer pathway was well validated by a radical scavenging experiment and work function, which was evaluated from VB-XPS analysis and in situ XPS measurement. This research offers a paradigmatic idea for constructing an S-scheme photocatalyst for H₂O₂ generation.