Metal-free π-conjugated hybrid g-C₃N₄ with tunable band structure for enhanced visible-light photocatalytic H₂ production

Development of low-cost and efficient photocatalytic materials with visible-light response is of urgent need for solving energy and environmental problems. Here, a metal-free two-dimensional (2D) π-conjugated hybrid g-C₃N₄ photocatalyst with tunable band structure was prepared by a novel one-pot bottom-up method based on a supersaturated precipitation process of urea and triethanolamine (TEOA) solution. The microstructure of the hybrid g-C₃N₄ is revealed to be a compound of periodic tri-s-triazine units grafted with N-doped graphene (GR) fragments. From experimental evidence and theoretical calculations, the two different π-conjugated fragments in the hybrid g-C₃N₄ material are proved to construct a 2D in-plane junction structure, thereby expanding the light absorption range and accelerating the interface charge transfer. The π-conjugated electron coupling in the 2D photocatalyst eliminates the grain boundary effect, and the coupled highest occupied molecular orbital (HOMO) effectively promotes the separation of photo-induced charge carriers. Compared with the g-C₃N₄ prepared by the conventional method, the visible-light H₂ production activity of the optimized sample is enhanced by 253 %. This work provides a new strategy of constructing metal-free g-C₃N₄ hybrids for efficient photocatalytic water splitting.