NiCd/ZnO nanocomposites: novel materials for photocatalytic degradation of Allura Red dye

Pristine ZnO, binary CdZnO, and ternary NiCdZnO nanocomposites were synthesized via simple co-precipitation method and systematically characterized by XRD, SEM, TEM/HRTEM, EDX mapping, Raman spectroscopy, PL, DRS, UV-VIS, and BET analyses. The results confirmed well-crystalline hexagonal wurtzite structures with controlled morphology, mesoporosity, and band-gap tuning (3.2 eV for ZnO, 3.0 eV for CdZnO, and 2.45 eV for NiCdZnO). Photoluminescence analysis revealed reduced electron-hole recombination in the Cd- and Ni-modified nanocomposites. Under UV-VIS irradiation, NiCdZnO achieved 95% degradation of Allura Red (AR) dye within 50 min, compared with 80% for CdZnO and 50% for ZnO, following pseudo-first-order kinetics. COD analysis further confirmed strong mineralization, with NiCdZnO showing 95-100% reduction at 10 ppm, outperforming CdZnO (80%) and ZnO (65%). Radical scavenging experiments indicated the involvement of reactive oxygen species, while recyclability tests demonstrated stable performance. These results indicate that Cd and Ni incorporation into ZnO can generate a synergistic enhancement in photocatalytic activity, and the present study provides a detailed evaluation of this co-modified system for the degradation of AR dye, a target pollutant that has not been widely explored with such nanocomposites.