A review on graphitic carbon nitride (g-C3N4) based nanocomposites: Synthesis, categories, and their application in photocatalysis

In recent years, heterogeneous photocatalysis using semiconductor and solar energy has gained a lot of attention owing to its potential applications in many fields such as the generation of renewable and sustainable hydrogen fuel, degradation of organic pollutants, and CO2 photoreduction. Due to its photochemical stability, fascinating electronic band structures, and effective light harvesting accompanied by suitable bandgap energy of 2.7 eV, graphitic carbon nitride (g-C3N4) has been considered as a promising metal-free photocatalyst for solving the energy crisis and environmental problems. Nevertheless, due to the low-charge carrier mobility, and low surface area, its photocatalytic efficiency is limited. Because of its unique band structure, coupling it with a large bandgap semiconductor to produce a heterojunction composite offers a promising way to improve the charge separation, expand the surface area, and boost light absorption. For that, g-C3N4 as a robust photocatalyst together with numerous synthesis methods has been highlighted. Three primary systems of g-C3N4-based nanocomposites have been classified and summarized: namely metal oxides, sulfides, and ferrites. We have summarized the latest applications of g-C3N4/nanocomposites in solar energy conversion and environmental remediation. This review ends with an overview and several insights on the problems and future avenues in investigating advanced nanomaterials based on g-C3N4.