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.