Ni(OH)₂/CoWO₄ S-Scheme Heterojunction for Enhanced Photocatalytic Hydrogen Evolution

The primary focus has traditionally been noble-metal-free photocatalytic hydrogen evolution (PHE) research. Transition metal-layered hydroxides usually exhibit excellent redox performance. Herein, we synthesized flower-like Ni(OH)2 with layered structure via a simple hydrothermal method and loaded CoWO4 nanoparticles on it. The Ni(OH)2/CoWO4 photocatalyst with an S-scheme heterojunction was successfully constructed. During the 4 h photocatalytic evaluation test, the hydrogen generation rate of Ni(OH)2/CoWO4-15 reached 3329.83 μmol g–1 h–1, which was significantly higher compared to pure Ni(OH)2 (584.13 μmol g–1 h–1) and CoWO4 (1358.33 μmol g–1 h–1), exhibiting a respective increase of 5.70 and 2.45 times. The charge transfer mechanism of the S-scheme heterojunction was confirmed through in situ X-ray photoelectron spectroscopy. By achieving a high redox potential and efficiently accelerating the separation of photogenerated electron–hole pairs, the S-scheme heterojunction enhances photocatalytic performance. This work provides insights into the rational design of nickel-based photocatalysts.