Engineering the High Concentration of N_3C Nitrogen Vacancies Toward Strong Solar Light-Driven Photocatalyst-Based g-C₃N₄

Graphitic carbon nitride (g-C3N4) has emerged as promising metal-free semiconductor-based photocatalysts for solar energy conversion. However, the photocatalytic performance of g-C3N4 is still moderate, due to the lack of the architecture design, which enables solar light harvesting, excited electron–hole separation as well as extending their availability for redox reactions, and far from practical application. Herein, we engineer the structure of g-C3N4 through a polyethylenimine (PEI)/alkaline coassisted technique. The resulting materials show the high concentration of both N3C nitrogen vacancies and hydroxyl groups on the g-C3N4 surface. These features significantly contribute to enhancing electron–hole generation and separation and harvest solar light absorption, which boosts the photocatalytic hydrogen production compared to bare g-C3N4 under solar irradiation.