Interfacial Vacancy Engineering in CdS-CeO₂ 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 CeO₂ 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 H₂ 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/CeO₂ heterojunctions as a versatile and promising candidate for simultaneous solar-to-chemical energy conversion and water purification.