Fabrication of an Organic/Inorganic Hybrid TpPa-1-COF/ZnIn2S4 S-Scheme Heterojunction for Boosted Photocatalytic Hydrogen Production

Covalent organic frameworks (COFs) exhibit significant prospects in photocatalytic H2 evolution because of their periodic pore structure, large surface area, and outstanding chemical stability. Nevertheless, a bare COF always suffers from poor photogenerated charge separation efficiency. Hence, it is crucial to design highly effective COF-based heterojunction photocatalysts. In this work, we have successfully prepared an organic/inorganic hybrid TpPa-1-COF/ZnIn2S4 (ZIS) heterojunc-tion with well-matched S-scheme interfacial charge-transfer channels. The results demonstrate that COF/ZIS-20% has an optimal photocatalytic H2 evolution rate, which can reach 853 smol g-1 h-1 in the absence of any cocatalyst, 6.2 times that of the bare TpPa-1-COF when exposed to visible light. Moreover, the apparent quantum efficiency (AQE) of COF/ZIS-20% at 420 nm is up to 2.08%. Density functional theory (DFT) calculations have demonstrated the presence of interfacial charge transfers from TpPa-1-COF to the surface of ZnIn2S4 spontaneously and the formation of an electric field at the area of the COF/ZIS heterojunction under the ground-state condition. Furthermore, the creation of a tuned built-in electric field drives the directional S-scheme charge transfer, while the photogenerated electron has a high reduction, thus synergistically promoting photocatalytic H2 evolution, which has been demonstrated by experiments and theoretical calculation results. This work provides an advanced method for the preparation of S-scheme high-efficiency heterojunction photocatalysts based on COF by matching the band structures.

Automated summary

This study successfully prepared an organic-inorganic hybrid TpPa-1-COF/ZnIn2S4 heterojunction with well-matched S-scheme interfacial charge-transfer channels. The optimized COF/ZIS-20% exhibited a photocatalytic H2 evolution rate of up to 853 smol g-1 h-1, 6.2 times higher than that of bare TpPa-1-COF under visible light. The presence of interfacial charge transfers and the creation of a tuned built-in electric field were demonstrated through experiments and theoretical calculations, promoting directional S-scheme charge transfer and enhancing photocatalytic H2 evolution.