Applications of graphitic carbon nitride-based S-scheme heterojunctions for environmental remediation and energy conversion

The contemporary era's top environmental problems include the lack of energy, recycling of waste resources, and water pollution. Due to the speedy growth of modern industrialization, the utilization of non-renewable sources has increased rapidly, which has caused many serious environmental and energy issues. In photocatalysis, as a proficient candidate, g-C3N4 (metal-free polymeric photocatalyst) has gained much attention due to its auspicious properties and excellent photocatalytic performance. But, regrettably, the quick recombination of photoinduced charge carriers, feeble redox ability, and inadequate visible light absorption are some major drawbacks of g-C3N4 that hamper its photocatalytic ability. Henceforth, these significant limitations can be solved by incorporating modification strategies. Among all modification techniques, the amalgamation of g-C3N4 with two or more photocatalytic semiconducting materials via heterojunction formation is more advantageous. In this review, we have discussed various modification strategies, including conventional, Z-scheme and S-scheme heterojunctions. S-scheme heterojunction is consideredan efficient and profitable charge transferal pathway due to the excellent departure and transferal of photoexcited charge carriers with outstanding redox ability. Consequently, the current review is focused on various photocatalytic applications of S-scheme-based g-C3N4 photocatalysts in pollutant degradation, H2 production, and CO2 reduction.