NiS‐Decorated ZnO/ZnS Nanorod Heterostructures for Enhanced Photocatalytic Hydrogen Production: Insight into the Role of NiS

Loading cocatalysts can effectively enhance the surface hydrogen reduction in photocatalytic water splitting by introducing a positive Schottky barrier. NiS is regarded as a promising cocatalyst to replace the noble metals due to its low cost and equivalent or even better performance. However, there is a huge controversy over whether the NiS cocatalyst is used to trap electrons or holes in the photocatalytic process. Herein, a new type of NiS‐decorated ZnO/ZnS (ZnOS) nanorod heterostructure photocatalysts is first designed from the corresponding bimetallic organic frameworks (ZnNi–MOFs). The Zn species in the bimetallic–MOFs can spatially separate the Ni species to restrain their aggregation, which is beneficial for the formation of NiS with a small enough size. The optimal heterostructure photocatalysts exhibit an excellent hydrogen production rate of 27 mmol g −1 h −1 , which is about seven times higher than that of the ZnOS heterostructure. X‐ray photoelectron spectroscopy and open‐circuit potential characterizations disclose that NiS can effectively facilitate the migration of the electrons. Density functional theory calculations, including differential charge density, Mulliken population analyses, and d‐band center, intuitively reveal that the real role of NiS in the photocatalytic process is to capture the electrons rather than the holes.