Review on g-C3N4-based S-scheme heterojunction photocatalysts

• Review of recent advances in g-C 3 N 4 -based S-scheme heterojunction photocatalysts. • The basic theory and preparation strategy of g-C 3 N 4 -based S-scheme heterojunctions are discussed. • The potential applications of g-C 3 N 4 S-scheme heterojunctions are reviewed. • The possible tendency of g-C 3 N 4 -based S-scheme heterojunctions is proposed. With the rapid development of economy and modern industry, serious environmental pollution and energy shortage have become major urgent challenges to the human society. Photocatalysis is a promising technology to provide green energy. As a typical metal-free polymer photocatalyst, g-C 3 N 4 has attracted more and more attention due to its excellent performance. Unfortunately, the fast recombination of photo-induced charges, limited light response range as well as weak oxidation ability are still the key drawback that restrict the photocatalytic performance of g-C 3 N 4 . These problems can be effectively addressed by constructing g-C 3 N 4 -based heterojunctions with two or more semiconductor materials, during which the respective advantages can be integrated. Up to now, the various oxidation semiconductor photocatalysts have been tried to construct the novel S-scheme heterojunction photocatalysts with g-C 3 N 4 . Thus, this review provides a comprehensive introduction of g-C 3 N 4 -based S-scheme heterojunctions, including the main characteristics of the S-scheme heterojunction, photocatalytic mechanisms, design rules and preparation methods of g-C 3 N 4 -based S-scheme heterojunction photocatalysts. Moreover, this review summarizes recently reported works on the potential applications of g-C 3 N 4 -based S-scheme photocatalysts in various important photocatalytic reactions, including photocatalytic hydrogen production, photocatalytic degradation of contaminants, photo-reduction of CO 2 into fuels, and photocatalytic sterilization. Finally, based on the current research progress, we propose some shortages in the preparation methods and applications of g-C 3 N 4 -based S-scheme heterojunctions, which are to be further investigated and resolved in this promising and creative research field.