CuO/Cu2O/ZnO ternary oxide heterojunctions: Composition-dependent photocatalytic degradation of organic pollutants

CuO/Cu 2 O/ZnO ternary photocatalysts with different CuO:Cu 2 O:ZnO ratios were synthesized via a facile wet-chemical precipitation method and investigated for the degradation of organic pollutants under xenon-lamp irradiation. The effects of phase composition on structural, morphological, optical, and photocatalytic properties were systematically evaluated by XRD, Williamsons - Hall analysis, FESEM, EDS, Raman, FTIR, and UV-Vis spectroscopy. XRD and Raman results confirmed the coexistence and successful strructural integration of ZnO, Cu 2 O, and CuO phases, while UV-Vis analysis revealed the combined optical contribution of wide-band-gap ZnO and visible-light-responsive copper oxide phases. Control experiments verified that the self-photolysis of the target pollutants was negligible. Among the investigated compositions, the 1:1:2 (CuO/Cu 2 O/ZnO) photocatalyst exhibited the highest activity, achieving nearly complete Rhodamine B degradation within 60 min with an apparent rate constant of 0.0822 min -1 . The optimized sample also showed high ciprofloxacin removal efficiency of approximately 90-95% after 60 min, demonstrating its applicability toward both dye and antibiotic pollutants. In addition, the photocatalyst retained high activity after five consecutive cycles, with degradation efficiencies of 99.2%, 97.8%, 96.2%, 95.8% and 93.2%, and maintained its crystalline structure after reuse. The enhanced photocatalytic performance is attributed to the synergistic effect of composition-engineered CuO/Cu 2 O/ZnO heterojunctions, improved light absorption, and efficient interfacial charge separation, which was further supported by radical scavenging experiments identifying superoxide and hydroxyl radicals as the predominant active species. These results indicate that Zn-rich CuO/Cu 2 O/ZnO ternary heterostructures are promising photocatalysts for aqueous pollutant degradation.