Abstract

The persistent pollution of textile wastewater by toxic azo dyes necessitates the development of efficient photocatalysts for solar-driven environmental remediation. In this study, cerium oxide (CeO₂) nanohybrids were individually doped with nickel (Ni) and cobalt (Co) via a facile sol-gel method to overcome the inherent UV-light dependency of the pristine material. Ni- and Co-doped CeO₂ nanoparticles were synthesized using precursor molar ratios of 1:150 and 1:50, respectively. Comprehensive characterization confirmed the successful incorporation of Ni and Co into the CeO₂ fluorite cubic lattice without the formation of secondary phases. Structural analysis revealed a uniform, spherical morphology with an average particle size of approximately 15nm. Crucially, the introduction of dopants enhanced the absorption of visible light. The photocatalytic efficiency of the nanohybrids was evaluated for the degradation of methylene blue under simulated solar irradiation, where both doped catalysts significantly outperformed their undoped counterpart. The Co‑doped CeO₂ (1:50) achieved 96% degradation within 10 minutes, exhibiting a rate constant approximately 4.3 times higher than pristine CeO₂ under identical conditions. This enhanced activity is attributed to the dopant’s role in creating abundant oxygen vacancies, which act as charge separation centres to suppress the recombination of photogenerated electron-hole pairs effectively. This work highlights that strategic doping of CeO₂ with transition metals is a powerful approach for engineering robust nanomaterials for solar-powered water purification.

Keywords:Cerium dioxide; Doping; Dye degradation; Sol-gel; Photocatalytic degradation