Effect of temperature on the photocatalytic properties of TiO₂-CeO₂ multilayer thin films obtained by spin coating method

Efeito da temperatura nas propriedades fotocatalíticas de filmes finos multicamadas de TiO ₂ -CeO ₂ obtidos por spin coating

Abstract

TiO₂-CeO₂ multilayer thin films were deposited by the spin coating method and calcined at 500 and 700 °C. Thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and diffuse reflectance spectroscopy. Photocatalytic properties were estimated by varying the concentration of the methylene blue dye (MB) when illuminated by UV radiation. The XRD patterns showed that the temperatures of 500 and 700 °C were effective to obtain TiO₂ and CeO₂ phases. The difference in the homogeneity of TiO₂ and CeO₂ films was evident in the AFM images, where the films showed an average roughness of 2.0 and 5.3 nm, respectively. The CeO₂-TiO₂ thin film obtained at 700 °C showed the best photocatalytic activity, reducing the concentration of MB by approximately 80%, while the CeO₂ and TiO₂ films obtained at 700 °C reduced only 20% and 29%, respectively. The reuse test showed that the thin films maintained their photocatalytic activity after 4 cycles, and there was no need for thermal treatment, indicating that it is an immobilized photocatalyst with high efficiency in the degradation of organic dyes.

Keywords: spin coating; multilayer thin films; CeO₂-TiO₂; photocatalytic reuse