Graphitic Carbon Nitride-Based Heterojunction Photoactive Nanocomposites: Applications and Mechanism Insight

The design of heterojunction with superior performance of light absorption and appropriate conduction band and valence band potentials is a promising approach for the applications in efficient environmental remediation and the solar energy storage. In recent years, many studies have been devoted to the applications of graphitic carbon nitride (g-C₃N₄)-based heterojunction photoactive nanomaterials under visible light irradiation due to its excellent physical, optical, and electrical properties, which inspired us to compile this review. Although many reviews demonstrated about the syntheses and applications of g-C₃N₄ composites, a targeted review on the systematic application and photocatalytic mechanisms of g-C₃N₄-based heterojunction, in which components are in intimate linkage with each other rather than a physical mixture, is still absent. In this review, the applications of g-C₃N₄-based heterojunction photoactive nanomaterials in environmental remediation and solar energy storage, such as photocatalytic treatment of persistent organic pollutants, heavy-metal-ion redox, oxidative decomposition of pathogens, water splitting for H₂ evolution, and CO₂ reduction, are systematically discussed. In addition, some emerging applications, such as solar cells and biosensors, are also introduced. Meanwhile, a comprehensive assessment on the basis of first-principles calculations and the thermodynamics and kinetics of surface catalytic reaction for the electronic structure and photocatalytic properties of g-C₃N₄-based heterojunction are valued by this review. In the end, a brief summary and perspectives in designing practical heterojunction photoactive nanomaterials also showed the bright future of g-C₃N₄-based heterojunction. Altogether, this review systematically complements the information that previous reviews have frequently ignored and points out the future development trends of g-C₃N₄-based heterojunction, which expected to provide important references and right directions for the development and practical applications of g-C₃N₄-based heterojunction photoactive nanomaterials.