High temperature hydrothermal etching of g-C3N4 for synthesis of N doped carbon quantum dots-supported CdS photocatalyst to enhance visible light driven hydrogen generation

Herein, we proposed a facile method to synthesize N doped carbon quantum dots (NCQDs) using g-C3N4 as carbon-nitrogen source, and the NCQDs-modified CdS nanocomposite catalysts for photocatalytic water splitting were synthesized by one-step hydrothermal method. The results showed that the NCQDs with a size of 3.2 nm obtained by hydrothermal etching were adsorbed on the surface of CdS particles with a size of 80 nm and induced the regulation of the surface morphology of CdS particles. There was strong interaction between NCQDs and CdS through C-S bond. The introduction of NCQDs in composite catalysts not only increased the photo-absorption performance but also suppressed the recombination of photo-generated carriers, which enabled the photo-generated electrons to transfer to NCQDs effectively and quickly and improved the photocatalytic performance of hydrogen production from water splitting. The composite photocatalysts showed good response to visible light in UV-Vis DRS and the photocatalytic water splitting experiment showed that the photocatalytic hydrogen production activity of composite catalysts was significantly improved under visible light (λ > 400 nm). And the maximum hydrogen production rate reached 2306.1 μmol/g/h, which was about 7 times the amount of unsupported NCQDs sample.