Enhanced Visible-Light-Driven\nPhotocatalytic Hydrogen\nProduction by Internal Electric Fields Generated by the Rational Design\nand Synthesis of ZIF-Derived Co<sub>3</sub>O<sub>4</sub>/ZnIn<sub>2</sub>S<sub>

The construction of Z-scheme heterojunctions in photocatalysts\npresents significant potential for enhancing photocatalytic water\nsplitting by improving visible-light absorption, redox capability,\nand the separation and transfer of charge carriers. In this study,\na novel ZIF-derived Co<sub>3</sub>O<sub>4</sub>/ZnIn<sub>2</sub>S<sub>4</sub> photocatalyst with a Z-scheme heterojunction was designed\nand synthesized to achieve high photoactivity under visible light,\nmaximizing solar energy utilization. Experimental evidence confirmed\nthe successful formation of a Z-scheme heterojunction in the composite\nmaterials. It was also found that the modified ZIF-67-derived Co<sub>3</sub>O<sub>4</sub> exhibited a narrow band gap, leading to improved\nvisible-light absorption, and the unique Z-scheme heterojunction generated\nan internal electric field (IEF) within the composite that enhanced\nthe spatial migration of the photogenerated charge carriers, promoting\ntheir separation and transfer while boosting redox capabilities. The\nZIF-derived Co<sub>3</sub>O<sub>4</sub>/ZnIn<sub>2</sub>S<sub>4</sub> photocatalyst showed an outstanding photocatalytic hydrogen generation\nof 23.99 mmol g<sup>–1</sup> h<sup>–1</sup>, approximately\n17 times higher than that of the original ZnIn<sub>2</sub>S<sub>4</sub> with an apparent quantum efficiency of 10.49% at 420 nm for hydrogen\nproduction. The presence of a heterojunction was further confirmed\nby density functional theory calculations. This study demonstrates\na promising strategy for the development of visible-light-responsive\nphotocatalysts with enhanced photocatalytic activity by introducing\nZ-scheme heterojunctions to create an IEF within the catalyst.