Interfacial Vacancy Engineering in CdS–CeO 2 S‐Scheme Heterojunctions for Efficient Photocatalytic Hydrogen Evolution and Wastewater Remediation

A hydrothermal–calcination route combined with an in situ oil‐bath deposition process was designed to construct CdS nanoparticle‐decorated CeO 2 nanorod heterostructures. The intimate interfacial contact between the two components, along with the presence of sulfur vacancies in the CdS lattice, was corroborated by x‐ray diffraction, Raman spectroscopy, high‐resolution transmission electron microscopy, and electron paramagnetic resonance spectroscopy. The resulting heterostructure, with an optimal composition, shows substantially improved photocatalytic performance in visible‐light‐driven H 2 generation and the decomposition of various organic contaminants, including dyes, antibiotics, and phenolic derivatives. A suite of characterization techniques—including photoluminescence spectroscopy, transient photocurrent measurements, electrochemical impedance spectroscopy, and radical quenching assays—was employed to probe the charge dynamics. The results reveal that the S scheme charge transfer mechanism, working in concert with vacancy engineering, facilitates charge‐carrier separation and migration while retaining the robust redox capacity inherent to both semiconductors. Collectively, these findings establish defect engineered CdS/CeO 2 heterojunctions as a versatile and promising candidate for simultaneous solar‐to‐chemical energy conversion and water purification.