Recent progress on S-scheme heterojunction strategy enabling polymer carbon nitrides C3N4 and C3N5 enhanced photocatalysis in energy conversion and environmental remediation

Polymer carbon nitrides, such as C₃N₄ and C₃N₅, have considerable promise in photocatalysis because of their unusual thermostability, nontoxicity, and high solar energy usage efficiency. The S-scheme charge transfer mechanism can strengthen the whole photoactivity of a heterojunction by facilitating effective charge separation and maximizing redox capabilities. We outline the evolution from classic C₃N₄ to current C₃N₅, as well as the advanced S-scheme heterojunction technique for further photocatalysis advancement in energy conversion and environmental remediation. Furthermore, an outlook on future challenges and prospects for C₃N₄- and C₃N₅-based S-scheme heterojunction photocatalysts is presented.