Progress in preparation, identification and photocatalytic application of defective g-C3N4

Graphitized carbon nitride (g-C3N4) has gained increasing prominence as a metal-free photocatalyst with a suitable bandgap. The limited absorption range of visible light and the fast complexation rate of photoexcited carriers of g-C3N4 hinder its photocatalytic activity. Fortunately, defect engineering of g-C3N4 can effectively enhance photogenerated electron migration. Therefore, optimizing the electronic structure and bandgap width by introducing vacancies can significantly improve the photocatalytic performance of g-C3N4. While the significance of defect engineering for enhancing the photocatalytic efficiency of g-C3N4 cannot be neglected, to date, there is a lack of comprehensive review articles including the applications of defective g-C3N4 in photocatalysis. In this review, we review the state of latest study on the preparation of defective g-C3N4 and systematically conclude the preparation strategies before, during, and after polymerization. Simultaneously, defective g-C3N4 photocatalysts were applied in denitrification, wastewater remediation, hydrogen production, CO2 conversion, disinfection, tumor treatment, and H2O2 generation are comprehensively discussed. Finally, we present the challenges associated with the specification of g-C3N4 photocatalysts based on vacancy defects and elemental doping, as well as the prospects for future developments in this particular field. This review has the potential to serve as a comprehensive theoretical framework and practicable guide to synthesize defective g-C3N4 photocatalysts.