Boosted photocatalytic H2 production over p-n S-scheme heterojunction of 0D Ni3V2O8 quantum dots decorated on ultra-thin 2D g-C3N4 nanosheets

Novel 0D Ni3V2O8 quantum dots (QDs) were decorated on the ultra-thin 2D g-C3N4 nanosheet (UCN) using a hydrothermal approach. The embedded Ni3V2O8 QDs play a dual role by trapping charge carriers, promoting electron-hole separation, and forming a p-n S-scheme heterojunction, improving the redox potential of the electrons and holes for surface reactions. HR-TEM analysis confirmed that Ni3V2O8 QDs with a size varying between 3 to 5 nm have intimate contact with the UCN surface. XPS and ESR spin-trapping agents experiment confirmed the formation of S-scheme heterojunctions between Ni3V2O8 QDs and UCN. Photocurrent and PL spectra indicated the synthesized heterostructures have high charge carrier transportation and lower recombination rates. The optimum Ni3V2O8 QDs/UCN heterostructure showed the highest photocatalytic hydrogen evolution activity, about 14 times higher than that of pristine UCN. This remarkable improvement in activity can be ascribed to the synergy effect of the S-scheme charge pathway mechanism and the improved light absorption facilitated by the Ni3V2O8 quantum dots. As a result, these factors effectively accelerate the migration and transportation of photoinduced charge carriers, offering increased active sites for the H2 generation process. This study emphasizes the importance of a well-designed interfacial heterojunction to achieve enhanced photocatalytic performance.