CeO ₂ –Nb ₂ O ₅ photocatalysts for degradation of organic pollutants in water

Abstract

Abstract The photocatalytic properties of CeO 2 –Nb 2 O 5 photocatalysts in heterogeneous photocatalysis (under ultraviolet and visible radiation) and in Fenton‐like process were reported. Methylene blue dye (MB) and phenol (Ph) were used as models of pollutant molecules for these reactions, and the photocatalysts were characterized by X‐ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX) and thermally stimulated luminescence (TL). The results indicated that the addition of CeO 2 (0.3 wt%, 1.0 wt% and 2.0 wt%) to Nb 2 O 5 sensitized the resultant materials, increasing light absorption in the visible region. However, there is a suitable formulation of CeO 2 –Nb 2 O 5 photocatalysts to improve each photocatalytic process. In heterogeneous photocatalysis, the addition of small CeO 2 quantities to Nb 2 O 5 was enough to improve the photocatalytic activity of CeO 2 –Nb 2 O 5 photocatalysts (The best composition reported was CeO 2 0.3 wt%.). The effectiveness of the catalyst was explained by the decrease in the number of trapping and luminescence centers in the conduction band of the material after the addition of CeO 2 to Nb 2 O 5 , but a large amount of CeO 2 decreased the number of trapping, luminescent and active centers to a large extent. Contrarily, in a Fenton‐like process, the addition of CeO 2 to Nb 2 O 5 was favorable in all the proportions studied. (The best composition was 2.0 wt% CeO 2 .) In this case, the effectiveness was explained by the influence of the adsorption process (adsorption‐triggered process), and the interactions between H 2 O 2 and Ce 3+ of the CeO 2 in each photocatalyst thus formed surface peroxide species O 2 2− , which induced the removal of the organic molecules under visible light.