Regulating the exciton dissociation and charge carrier behavior of graphitic carbon nitride <i>via</i> 3,9-perylenedicarboxylic acid for efficient photocatalytic hydrogen evolution

Graphitic carbon nitride (GCN) is known as a promising photocatalyst due to its suitable energy level, low cost and high stability. However, its deficient light-absorption capacity and charge transfer driving force hinder its further application. In this work, 3,9-perylenedicarboxylic acid (PA) was introduced into GCN during thermal polymerization to form a new photocatalyst, which was then applied in photocatalytic hydrogen evolution. By doping 0.1 wt% PA, the optimized photocatalyst affords a hydrogen evolution rate of up to 1.47 mmol g^-1 h^-1. The apparent quantum efficiency of the optimized catalyst reaches 1.36% at 420 nm. Photophysical characterizations indicate that the prepared PA_<i>x</i>-GCN photocatalyst enhances the light response in the visible region and promotes charge transfer. According to DFT calculation results, spatially separated LUMO and HOMO were obtained by grafting PA onto GCN, which provides proof of intramolecular charge transfer and an explanation for the improved charge separation. Moreover, the modified photocatalyst exhibits good operational stability without obvious decay over five cycles.