Study of obtaining thin films of CeO₂ doped with 2 and 4 mol% of europium, terbium and thulium by spin coating: photocatalytic properties

Estudo da obtenção de filmes finos de CeO ₂ dopados com 2 e 4 %mol de európio, térbio e túlio por spin coating: propriedades fotocatalíticas

Abstract

In this study, thin films of Eu³⁺, Tb³⁺ and Tm³⁺ doped CeO₂ in the proportions of 2 and 4 mol% were obtained by spin coating and calcined at 700 °C. The films were characterized by XRD, SEM, AFM and UV-vis techniques. The photocatalytic activity of the thin films was measured by the degradation of the methylene blue (MB) dye. The thin films were submitted to 4 photocatalytic cycles to analyze the capacity to be reused. XRD patterns showed no secondary phase formation, where all characteristic peaks were related to CeO₂. SEM micrographs indicated that doping at 4 mol% promoted the reduction in the thickness and surface porosity of the thin films. AFM images indicated the increase in surface roughness with rare earths doping. Doping with Eu³⁺, Tb³⁺ and Tm³⁺ increased the degradation of the methylene blue dye by at least 15% for thin films doped at 4 mol%. The reuse tests indicated that the photocatalytic activity remained practically constant even with the application of four consecutive cycles.

Keywords:
Eu³⁺; Tb³⁺ and Tm³⁺ doped CeO₂; thin films; spin coating; photocatalytic reuse