Vacancy-modified g-C3N4 and its photocatalytic applications

Abstract

As an emerging semiconductor-based catalyst, g-C₃N₄ has attracted significant attention for visible light-driven photocatalytic energy conversion, synthesis of chemicals, and environmental remediation. However, pristine g-C₃N₄ exhibits a weak response to visible light, low surface area, and rapid photogenerated carrier recombination. Thus, the introduction of structural vacancies can deeply modify the morphology and band structure of g-C₃N₄ to overcome these issues. This work provides a critical overview and perspective on the recent development of g-C₃N₄ photocatalysts modified by carbon (C_v) and nitrogen vacancies (N_v), or both, and their implementation in various photocatalytic applications. Initially, the methods for the identification of C_v and N_v in g-C₃N₄ and their critical role in altering the morphological and structural properties of g-C₃N₄ are presented. Then, the strategies for manipulating the microstructure and properties of g-C₃N₄ are critically discussed, including modification with N_v, C_v, and functional groups or their combination, porous architecture engineering, heteroatom doping, texture and surface area mediation, and their combinations. Based on vacancy modification and other positive structural tuning aspects, the corresponding photocatalytic performance of g-C₃N₄ is analyzed for the applications currently attracting significant research attention, including water splitting, CO₂ reduction, N₂ fixation, NO removal, pollutant degradation, selective oxidation, and H₂O₂ production. Finally, the current challenges and future research suggestions regarding the vacancy modification of g-C₃N₄ are presented.