Hydrogen-Induced Defective Crystalline Carbon Nitride with Enhanced Bidirectional Charge Migration for Persulfate Photoactivation

A feasible way to overcome the moderate photoactivity of carbon nitride is by decreasing the carrier diffusion distance and increasing the intralayer active sites by synthesizing defective crystalline carbon nitride. However, the additive-free synthesis of this type of structure remains a great challenge, due to the trade-off between crystallinity control and defect modulation. Herein, we demonstrate the hydrogen-assisted synthesis of ultrathin carbon nitride nanosheets with efficient exciton dissociation and fast electron transfer. Experimental and theoretical investigations indicate that hydrogen not only facilitates intermolecular cross-linking for crystallization but also generates abundant nitrogen vacancies among non-hydrogen-bonded tri-s-triazine units for charge transportation. The simultaneous modulation of interlayer and intralayer interactions contributes to the efficient bidirectional charge transfer during photocatalytic reactions. The synergy of defective crystalline carbon nitride and persulfate oxidants results in a striking performance for contaminant degradation, with 9.2- and 18.4-times higher activity than separate photocatalysis and persulfate photoactivated by bulk g-C3N4, respectively. This work not only provides a facile approach to synthesizing defective crystalline carbon nitride without employing any extrinsic additives but also opens up a new avenue to improve the efficiency of metal-free photocatalysts by bidirectional charge modulation.