An interfacial C-S bond bridged S-scheme ZnS/C3N5 for photocatalytic H2 evolution: Opposite internal-electric-field of ZnS/C3N4, increased field strength, and accelerated surface reaction

An interfacial C-S bond bridged ZnS/C3N5 S-scheme heterojunction was constructed for photocatalytic H2 evolution. Benefiting from the interfacial covalent bond, enhanced internal-electric-field strength, and accelerated surface photocatalytic reaction, the photocatalytic H2 production of ZnS/C3N5 was 3.2 and 2.5 times higher than those of ZnS/C3N4 and ZnS/C3N5-300 without C-S bond. [Display omitted] •C-S bond is susceptive to preparation temperatures, and it is broken above 300 °C.•C-S bond promotes e− separation and improves H2O adsorption and activation behaviors.•IEF strength of ZnS/C3N5 with opposite direction is 2.6 times than that of ZnS/C3N4.•e− transfer respectively follow S-scheme and type-II pathway in ZnS/C3N5 and ZnS/C3N4.•H2 yield of ZnS/C3N5 is 3.2 and 2.5 times than ZnS/C3N4 and ZnS/C3N5-300 without C-S. An interfacial C-S bond bridged ZnS/C3N5 heterojunction was constructed for photocatalytic H2 evolution. Different from traditional type-II ZnS/C3N4 heterojunction, the electron transfer followed S-scheme pathway, due to opposite internal-electric-field (IEF) directions in these two heterojunctions. The C-S bond formation was carefully investigated, and they were susceptive to the preparation temperatures. In photocatalytic reaction, C-S bond was functioned as the “high-speed channel” for electron separation and transfer, and the IEF strength in ZnS/C3N5 was 1.86 × 108 V/m, 2.6 times higher than that in ZnS/C3N4. Moreover, the C-S bond also altered the surface molecular structure of ZnS/C3N5, and hence the surface reaction was accelerated via improving H2O adsorption and activation behaviors. Benefiting from the S-scheme pathway, enhanced IEF strength, and accelerated surface reaction, the photocatalytic H2 production over ZnS/C3N5 reached up to 20.18 mmol/g/h, 3.2 and 2.5 times higher than those of ZnS/C3N4 and ZnS/C3N5-300 without C-S bond.