A novel all-organic S-scheme heterojunction with rapid interfacial charges migration for efficient photocatalytic H2 production

Poly (triazine imide), as a kind of highly crystalline g-C3N4, exhibits a promising potential for photocatalytic hydrogen production, however, some drawbacks still limit its photocatalytic performance. The strategy of constructing S-scheme heterojunction with different semiconductor photocatalysts enables the effective separation of photogenerated electrons and holes, and the strong oxidative and reductive properties of the original photocatalysts could be retained, which will significantly improve the photocatalytic activity. In this work, we synthesized the organic-organic S-scheme heterojunction between PTI and organic small molecule poly (barbituric acid) (PBA) by hydrogen bond self-assembly method, which results in a significant enhancement of photocatalytic H2 production activity. The H2 production rate of the optimum PBA/PTI-2 sample under visible light irradiation is about 0.92 mmol g–1, which is 5.5 times higher than that of PTI and 14.4 times higher than that of PBA. This excellent photocatalytic performance is attributed to the successful construction of S-scheme heterojunction between PTI and PBA, which effectively accelerates carrier transport and spatial segregation by the formation of a built-in electric field and band bending at the interface. In addition, the S-scheme heterojunction could also reserve the maximum redox capability and enhance the light absorption of the prepared photocatalytic system. This work provides a new strategy and understanding for the design and development of organic-organic S-scheme heterojunction photocatalysts.