Photocatalytic and Photoelectrocatalytic Performance of (1-x)CePO₄/xZnO Composite for Rhodamine B Degradation

CePO₄ and ZnO were synthesized via co-precipitation to explore their synergistic effect on the degradation of the organic pollutant Rhodamine B (RhB). XRD analysis confirmed that both semiconductors crystallize in the hexagonal system, while morphological analysis revealed that CePO₄ consists of agglomerated fine, elongated particles (1–6 µm), whereas ZnO exhibits uniform, rounded particles (140–190 nm). UV-vis DRS measurements indicated that both materials absorb in the UV region, with bandgap energies of 3.6 eV for CePO₄ and 3.21 eV for ZnO. Mott-Schottky analysis determined the flat-band potentials and band positions, confirming the formation of an n-n heterojunction in the composite. Photocatalytic tests demonstrated that the 0.2CePO₄/0.8ZnO composite exhibited the highest activity, achieving 95% RhB degradation within 180 minutes. Trapping experiments identified ^●O₂⁻, h⁺ and ^●OH as the main reactive species responsible for the degradation, and cycling tests confirmed the photocatalyst’s stability over four consecutive runs. Based on these findings, a Z-scheme charge transfer mechanism was proposed. To further enhance degradation efficiency, photoelectrocatalytic tests were performed on all electrodes, with 0.2CePO₄/0.8ZnO@FTO achieving complete RhB degradation (100%) in just 6 minutes. Electrochemical analyses, including EIS and LSV, further confirmed the improved charge separation and enhanced degradation performance under applied bias.