Tailoring of efficient electron-extracting system: S-scheme g-C3N4/CoTiO3 heterojunction modified with Co3O4 quantum dots for photocatalytic hydrogen evolution

• g-C 3 N 4 /CoTiO 3 S-scheme heterojunction was successfully designed and prepared. • Co 3 O 4 quantum dots were uniformly and tightly attached to the surface of the heterojunction. • The integration of S-scheme/promoter realized an efficient electronic-extracting system. • The hydrogen evolution performance of the ternary nanoreactor exceeds the binary system. Enhancing the utilization rate of photogenerated electrons has been considered as one of the bottlenecks in obtaining efficient photocatalytic hydrogen production system. This work deals with Co 3 O 4 quantum dots (CDs) modified S-scheme g-C 3 N 4 /CoTiO 3 (CN/CTO) heterojunction as a photocatalyst for water splitting. The S-scheme heterojunction retains a good carrier separation, and the built-in electric field also endows vigorous driving force for charge transport. CDs can be used as the electron acceptor, providing more active sites and achieving rapid capture of photogenerated electrons. The synergistic utilization of S-scheme structure and promoter considerably optimizes the electron transfer path, with enhanced spatial charge separation leading to more useful electrons with higher reducing capacity to participate in hydrogen evolution reaction. Using triethanolamine solution as sacrificial agent and eosin-Y as photosensitizer, the average H 2 evolution rate of optimized CN/CTO/CDs within 5 h of visible light irradiation was 1971.7 μmol g -1 h −1 , which was 102.7, 2.5 and 2.3 times higher than that of pure CN, CN/CTO and CN/CDs, respectively, with a corresponding apparent quantum efficiency was 3.39 %. Additionally, the charge transfer mechanism of S-scheme and the co-catalytic properties of CDs were further verified by the results of photoluminescence and photoelectrochemistry. This research contributes a valuable opinion for the integration of multicomponent photocatalytic systems.