Precisely Tailoring Nitrogen Defects in Carbon Nitride for Efficient Photocatalytic Overall Water Splitting

Precisely tailoring the nitrogen defects has been verified to be a promising approach for promoting the photocatalytic efficiency of C3N4. Herein, two-coordinated-N vacancies are selectively introduced into the C3N4 framework by a facile Cl– modification method, whereas its concentration can be facilely tuned by varying Cl– usage in the process of thermal polymerization. Impressively, the optimal defective C3N4 (20 mg) exhibited superior hydrogen and oxygen evolution rates of 48.2 and 21.8 μmol h–1, respectively, in photocatalytic overall water splitting and an apparent quantum efficiency of 6.9% at 420 nm, the highest of reported single-component C3N4 photocatalysts for overall water splitting. Systematic studies including XPS, DFT simulations, and NEXAFS reveal that Cl– modification preferentially facilitates the introduction of two-coordinated-N vacancies through tuning the formation energy and promotes charge carrier separation efficiency, thereby greatly enhancing the photocatalytic efficiency. This work allows for a viable approach to rationally designing defective C3N4 for efficient photocatalysis.