Recent advances on graphitic carbon nitride-based S-scheme photocatalysts: Synthesis, environmental applications, and challenges

With the advent of modern industry and increasing economic activity, energy scarcity and pollution are the two most pressing issues facing humanity and the environment today. Moreover, these issues are considered crucial scientific problems that need to be solved. One technology that shows promise in solving the current environmental problem is photocatalysts. Among all photocatalysts, graphite carbon nitride (g-C3N4) is widely used because it is inexpensive, stable, easy to synthesize, and absorbs visible light well. However, the rapid recombination of light-generated charge carriers results in limited photoactivity of pure g-C3N4. The g-C3N4-based S-scheme is a better solution to this problem because they have identical band configurations but a different method of producing charge carriers generated by light. In this review, the mechanism of S-scheme heterojunctions, and various preparation techniques for S-scheme heterojunctions based on g-C3N4 were summarized. Also presented is a recent study on S-scheme heterojunctions based on g-C3N4 for environmental applications, including pollutant removal, carbon dioxide (CO2) reduction, hydrogen production, and bacterial disinfection. This review concludes with an outlook on potential future challenges for S-scheme heterojunctions based on g-C3N4.