Production and characterization of transition metal-doped cerium oxide nanoparticles (Ce1-xMxO2) for application in the degradation of organic dyes.

Abstract

In this study, pure and gadolinium-doped cerium oxide (CeO2 and Ce0,9Gd0,1O2-y) nanoparticles were successfully synthesized via a hydro-alcoholic co-precipitation method to evaluate their performance in the photodegradation of Rhodamine 6G (Rh6G) dye under ultraviolet irradiation. X-ray diffraction (XRD) analysis confirmed a single-phase cubic fluorite-type structure (Fm3̅m) for both samples, showing a reduction in average crystallite size from 6.2 nm (CeO₂) to 5.1 nm (Ce0,9Gd0,1O2-y) due to doping. UV-Vis spectroscopy and Tauc plot extrapolation revealed an optical bandgap energy of approximately 2.7 eV for both nanomaterials. Raman spectra exhibited a distinct band at approximately 550 cm⁻¹ in the Gd-doped sample, directly associated with extrinsic oxygen vacancies created for charge compensation. Photocatalytic assays, monitored via integrated UV-Vis absorption areas, demonstrated that 10 mol% Gd doping significantly enhanced dye removal, achieving 40.2% degradation after 180 min, compared to 23.2% for pure CeO₂ and 7.0% for direct photolysis. The kinetic model followed a pseudo-first-order law, with Ce0,9Gd0,1O2-y exhibiting an apparent rate constant (kapp = 2.644 × 10^-3 min^-1) approximately 2.0 times higher than that of pure CeO₂ and 5.9 times higher than that of photolysis. These findings highlight the fundamental role of Gd-induced defect engineering in improving electron-hole pair dynamics and surface reactivity for Advanced Oxidation Processes (AOPs).

Keywords: Photocatalysis; Rhodamine; Doping