Enhanced Visible-Light-Driven Photocatalytic Hydrogen Production by Internal Electric Fields Generated by the Rational Design and Synthesis of ZIF-Derived Co₃O₄/ZnIn₂S₄ with Z-Scheme Heterojunctions

The construction of Z-scheme heterojunctions in photocatalysts presents significant potential for enhancing photocatalytic water splitting by improving visible-light absorption, redox capability, and the separation and transfer of charge carriers. In this study, a novel ZIF-derived Co3O4/ZnIn2S4 photocatalyst with a Z-scheme heterojunction was designed and synthesized to achieve high photoactivity under visible light, maximizing solar energy utilization. Experimental evidence confirmed the successful formation of a Z-scheme heterojunction in the composite materials. It was also found that the modified ZIF-67-derived Co3O4 exhibited a narrow band gap, leading to improved visible-light absorption, and the unique Z-scheme heterojunction generated an internal electric field (IEF) within the composite that enhanced the spatial migration of the photogenerated charge carriers, promoting their separation and transfer while boosting redox capabilities. The ZIF-derived Co3O4/ZnIn2S4 photocatalyst showed an outstanding photocatalytic hydrogen generation of 23.99 mmol g–1 h–1, approximately 17 times higher than that of the original ZnIn2S4 with an apparent quantum efficiency of 10.49% at 420 nm for hydrogen production. The presence of a heterojunction was further confirmed by density functional theory calculations. This study demonstrates a promising strategy for the development of visible-light-responsive photocatalysts with enhanced photocatalytic activity by introducing Z-scheme heterojunctions to create an IEF within the catalyst.