Photocatalytic Properties and Reaction Mechanism of PDI/ZnIn₂S₄ S-Scheme Heterojunction

The construction of step scheme (S-scheme) heterojunction with a great redox ability and a high charge transfer efficiency is an effective strategy to enhance the photocatalytic activity. ZnIn₂S₄ nanosheets were grown in-situ on the surface of perylenimide (PDI) rods via a solvothermal method. A PDI/ZnIn₂S₄ heterojunction exhibits an excellent photocatalytic performance due to its tight interfacial contact and matched band structures. Moreover, the 5% PDI/ZnIn₂S₄ affords high H₂/benzaldehyde production rates of 21.66 mmol/(g·h) and 1.02 mmol/(g·h), respectively, which is 2.12 and 3.00 folds of pristine ZnIn₂S₄, respectively when coupling the photocatalytic H₂ evolution and the benzyl alcohol oxidation in the reaction system. Based on the results by X-ray photoelectron spectroscopy, transient photoluminescence spectroscopy and electron paramagnetic resonance analysis, the formation of the built-in electric field at the interface of PDI/ZnIn₂S₄ and the S-scheme electron transfer path was confirmed. The enhanced photocatalytic performance and stability can be attributed to the close contact and rich active sites of PDI/ZnIn₂S₄, and the charge carrier migration and increased photoredox properties were improved by a S-scheme charge-transfer route. This organic–inorganic PDI/ZnIn₂S₄ S-scheme heterojunction photocatalyst can be used as a novel bifunctional photocatalyst in converting solar light into clean fuel and chemicals.