Ta/TiO2 -and Nb/TiO2 -mixed oxides as efficient solar photocatalysts: Preparation, characterization, and photocatalytic activity

Abstract

Ta/TiO2- and Nb/TiO2-mixed oxides photocatalysts were prepared by simple impregnation method at different TiO2:Nb or Ta mass ratios of 1:0.1, 1:0.5, and 1:1, followed by calcination at 500()C. The prepared powders have been characterized by XRD, XPS, UV-Vis spectra, and SEM. The photocatalytic activity was evaluated under natural solar light for decolorization and mineralization of azo dye Orange II solution. The results showed that Nb/TiO2- and Ta/TiO2-mixed oxides have higher activity than the untreated TiO2 under natural solar light. The maximum activity was observed for Nb/TiO2 sample (at mass ratio of 1:0.1), which is characterized by the smallest crystalline size (17.79nm). Comparing with the untreated TiO2, the solar decolorization and mineralization rates improved by about 140 and 237, respectively, and the band gap reduced to 2.80eV. The results suggest that the crystal lattices of TiO 2 powder are locally distorted by incorporating Nb5+ species into TiO2, forming a new band energy structure, which is responsible for the absorption in the visible region. Unlike Ta/TiO2, the Nb/TiO2-mixed oxides can prevent the grain size growth of the treated TiO2, which is important to achieve high solar photoactivity. © 2012 Hussein Znad et al.