Photoelectrochemical Detection of Phenol using ZnO-Modified Reduced Graphene Oxide-Cocoa Shell Electrode

The investigation focused on the photoelectrochemical detection of phenol using a ZnO-modified reduced graphene oxide (rGO) electrode. The cocoa shell waste was oxidized to produce graphene, which was subsequently used to obtain rGO. The resulting electrode material was analyzed using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy and subjected to photoelectrochemical examinations. The study employed three distinct electrochemical techniques: cyclic voltammetry, linear sweep voltammetry, and multi-pulse amperometry. The synergistic interaction between light variation and photocurrent response revealed that pristine rGO was active under ultraviolet light, generating a photocurrent (I_pa) of 0.99 µA. In contrast, the rGO/ZnO electrode exhibited higher performance under visible light, achieving an I_pa of 4.02 µA. Compared to pristine rGO, the rGO/ZnO composites demonstrated significantly enhanced absorption within the visible light spectrum. The developed rGO/ZnO photoelectrochemical electrode demonstrated excellent phenol-sensing capabilities, featuring a broad linear detection range from 0.01 to 10 ppm and a low detection limit of 0.085 ppm. Moreover, the prepared electrodes showed good repeatability and long-term stability, making them suitable for practical applications in environmental monitoring and sensing.