van der Waals type II carbon nitride homojunctions for visible light photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution reaction (PC-HER) provides a solution to energy crisis and environmental pollution. Herein, different graphitic carbon nitride (g-C₃N₄)-based van der Waals (vdW) type II homojunctions have been fabricated and g-C₃N₄/K-doped g-C₃N₄ nanosheets have an outstanding PC-HER rate of 1,243 μmol·h⁻¹·g⁻¹ under visible light, higher than that of bulk g-C₃N₄, doped g-C₃N₄ nanosheets, and mixed nanosheets. The enhanced PC-HER performance can be ascribed to the cooperative effects of the shortened bandgap, enlarged specific surface area, matched type II energy band structure, “face to face” vdW charge interaction, and peculiarly partite positions of the conduction and valence bands in different layers. Besides, the type II junctions were found superior to binary type II junction. This study highlights the synergistic effect of different strategies in improving the PC-HER capacities of g-C₃N₄, especially the application of particular vdW junctions, and provides new insights to the structures and mechanism.