Hydroxyl decorated g-C3N4 nanoparticles with narrowed bandgap for high efficient photocatalyst design.

Graphical abstract Highlights • Hydroxyl decorated 0D g-C 3 N 4 NPs were synthesized via a simple hydrothermal method. • The NPs possess narrowed bandgap, increased surface area and better hydrophily than bulk g-C 3 N 4. • ZnS-g-C 3 N 4 photocatalysts present a high photocatalytic activity of 112 μmol h−1. • Theoretical calculations are carried out to explain the high photocatalytic activity. • A systematic investigation of photocatalytic mechanism is proposed. Abstract Zero-dimensional graphitic carbon nitride nanoparticles (0D g-C 3 N 4 NPs) possess the advantages of non-toxicity, metal-free, and rich surface catalytic active sites. However, the complex preparation process, wide bandgap structure, easily particle aggregation and rapid carriers' recombination still limit their development in photocatalysis. Herein, these issues are addressed by synthesizing a novel hydroxyl (-OH) modified g-C 3 N 4 NPs with a simple hydrothermal method without using any etching agents. Besides the high hydrophily and small particle size, the OH decorated 0D g-C 3 N 4 NPs possess obvious narrowed bandgap and high reduction potential. To further improve their dispersity and carriers' separation rate, 0D/3D g-C 3 N 4 NPs/ZnS type II heterojunction is fabricated, which simultaneously improves the hydrophily, passivates the surface defects and extends the sunlight absorption range of ZnS. As a result, a high and cyclable photocatalytic activity of 112 μmol h−1 (5.6 mmol h−1 g−1) is achieved under visible light irradiation without any co-catalysts, which is 140 times higher than that of pure ZnS and much better than the pure 0D g-C 3 N 4 NPs. A systematic study of photocatalytic mechanism is proposed by combining the theoretical calculations and experimental results. This work offers a new sight for the design of 0D g-C 3 N 4 NPs based photocatalysts for H 2 production. [ABSTRACT FROM AUTHOR]