In Situ Growth Facilitated Photocharge Dynamics in ZIF-8- and NiS-Decorated ZnO Nanorods for Enhanced H₂ Production

Efficient charge separation at the photocatalyst interface is critical for maximizing solar-to-hydrogen conversion. The effectiveness of this separation is heavily influenced by the interfacial contact area between photocatalysts, which, in turn, depends on the surface morphology of the materials. In this report, rod-shaped ZnO, integrated via in situ growth of ZIF-8, exhibits strong light absorption capacity and enhanced photocatalytic hydrogen production activity, utilizing NiS as a cocatalyst. This synthesis strategy improves the interaction between photoinduced electrons and holes, boosting overall photocatalytic efficiency. The heterostructure ZnO-ZIF-8-NiS (ZZ8-NiS) is synthesized via a facile hydrothermal method with the optimized loading of NiS 0.035 mmol, where the porous ZIF-8 serves as an electron mediator, transferring photogenerated electrons to NiS acting as a cocatalyst, NiS efficiently accepts these electrons and facilitates proton reduction, resulting in the production of hydrogen. X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electrochemical measurements confirm that the photoinduced charge transfer between the ZnO NR and ZIF-8 provides an efficient pathway for carrier transfer while also preserving more active electrons and holes to participate in the hydrogen evolution reaction. The hybrid nanocomposite ZZ8-NiS demonstrates an exceptional hydrogen production rate of 3.25 mmol g–1 h–1 under simulated light irradiation. This performance significantly surpasses those of pure ZnO (0.68 mmol g–1 h–1), ZZ8 (0.80 mmol g–1 h–1), and ZnO@NiS (2.20 mmol g–1 h–1). Density functional theory calculations are performed to clarify the charge transfer mechanism in the ZIF-8-NiS heterostructure. The ZZ8-NiS photocatalyst composite achieves a remarkable hydrogen generation rate of 3.25 mmol g–1 h–1 (AQY: 11.7%), which is significantly higher than that of pure ZnO (0.68 mmol g–1 h–1, AQY: 2.5%), ZZ8 (0.80 mmol g–1 h–1, AQY: 2.9%), and ZnO-NiS (2.20 mmol g–1 h–1, AQY: 8.0%), with improvements of 1, 1.3, and 3.6 times, respectively. This enhancement is attributed to the strong electronic interaction between ZnO-ZIF-8 and NiS, which facilitates electron transport at the interface and significantly boosts the photocatalytic activity of ZnO, supporting the experimental results observed in the ZZ8-NiS composite.