Self-Coupled g-C₃N₄ van der Waals Heterojunctions for Enhanced Photocatalytic Hydrogen Production

Constructing junctions can efficiently improve the photocatalytic performance by suppressing the recombination of photogenerated electron–hole pairs and prolonging the lifetime of carriers. In this work, we exploited a facile method to fabricate g-C3N4 nanosheet (g-CNNS)/g-C3N4 nanofiber (g-CNNF) heterojunctional composites. The valence and conductive band offsets between g-CNNS and g-CNNF cause band bending, and van der Waals (vdW) heterojunctions are constructed at the interface of g-CNNS and g-CNNF. Because of the shorter diffusion distance of charge carriers and spontaneous electron motion, g-CNNS/g-CNNF vdW heterojunctions with intimate contact can effectively suppress the recombination of the photoexcited electron and hole and thus increase the carrier lifetime and further enhance the photocatalytic performance. Under the visible-light irradiation, these heterojunctions exhibit a 3 times higher photocatalytic hydrogen evolution rate of 1375.9 μmol g–1 h–1 compared with pristine g-CNNS. This work demonstrates that the fabricated vdW heterojunctions can effectively prolong the carrier lifetime through separating the photogenerated electron–hole pairs and provide a new perspective to design and develop the 2D photocatalysts with high charge-transfer efficiency.