Nanostructured ZnO/CdS Electrodes for Visible-Light-Driven Photoelectrochemical Oxidation Processes

The evaluation of photoelectrochemical (PEC) oxidation capabilities of materials, particularly nanostructured metal oxides, is a rapidly advancing area with significant implications for energy production, environmental remediation, and chemical conversion. In this study, ZnO nanorod photoanodes were fabricated using both one-step and two-step electrodeposition methods to assess their PEC performance. To enhance visible light absorption, the photoanode surfaces were further modified with CdS. Comprehensive characterization of the materials was carried out using SEM/EDS, XPS, XRD, Raman, and UV–vis DRS to investigate their morphological, structural, and optical properties. The PEC activity of both ZnO and ZnO/CdS photoanodes was tested in water-splitting and methanol oxidation experiments. The results demonstrated successful heterojunction formation, which improved light absorption and increased charge carrier concentration under illumination, leading to enhanced PEC responses. Both ZnO and ZnO/CdS photoanodes exhibited significantly higher PEC oxidation activity than the bare FTO substrate, generating formaldehyde amounts of ∼6 and ∼9 μmol with the 74% and 92% Faradaic efficiency, respectively. These findings confirm enhanced photoelectrooxidation performance of ZnO/CdS compared to ZnO, highlighting its potential for PEC water-splitting and alcohol oxidation applications.