Platinum nanodots modified Nitrogen-vacancies g-C3N4 Schottky junction for enhancing photocatalytic hydrogen evolution

[Display omitted] •Highly dispersed Pt nanodots and N vacancies co-modified g-C3N4 was fabricated.•Changing KOH dosage in melamine condensation to regulate N defects concentration.•Nitrogen vacancies narrowed bandgap and promoted photogenerated charges separation.•Introducing nitrogen vacancies into g-C3N4 caused a lower work function.•NVCN@Pt Schottky junction constructed further enhanced charges’ separation. Photocatalytic hydrogen evolution has attracted enormous attention owing to its possibility in solving environmental and energy-shortage issues. Herein, Pt nanodots and nitrogen-vacancies co-modified g-C3N4 (NVCN@Pt) Schottky junction photocatalyst was synthesized by the KOH-assisted thermopolymerization of melamine and photoreduction deposition method. The characterization and calculation results demonstrated the formation of nitrogen vacancies enhanced light absorption, narrowed bandgap, promoted charges separation, and reduced work function. Besides, nitrogen vacancies led to tightly contacted and uniformly anchored small Pt nanodots on g-C3N4, which and highly dispersed Pt nanodots would further accelerate the transfer and separation of photogenerated charges via Schottky junction, and provided an abundance of active sites for H2 generation. The optimized 0.15-NVCN@Pt composite exhibited the 3.71 times photocatalytic H2 evolution performance (99.4 μmol/h) than pristine bulk g-C3N4 with Pt nanodots modification (BCN@Pt, 26.8 μmol/h). The apparent quantum efficiency at 420 nm of 0.15-NVCN@Pt reached 8.6%. These results demonstrated nitrogen-vacancies introducing Pt nanodots modified g-C3N4 was an effective method to boost photocatalytic H2 evolution. Our work was expected to provide insights on the interaction between support and metal for constructing highly active semiconductor-based photocatalysts.