The layered double hydroxide route to Bi-Zn co-doped TiO2 with high photocatalytic activity under visible light

In this work, a co-doped Bi-Zn-TiO2 photocatalist is synthesized by an original synthesis route of layered double hydroxide followed by heat treatment at 670 degrees C. After characterization the photocatalyst efficiency is estimated by the photo-discoloration of an anionic dye (indigo carmine) under visible light and compare to TiO2-P25 as reference material. In this new photocatalyst, anatase and ZnO wurtzite are the only identified crystalline phase, rutile and Bi2O3 being undetected. Moreover, the binding energy of Bi determined (XPS analysis) is different from the one of Bi in Bi2O3. Compared to TiO2-P25, the absorption is red shifted (UV-vis DRS) and the Bi-Zn-TiO2 photocatalyst showed sorption capacity toward indigo carmine higher than that TiO2-P25. The kinetics of the photo-discoloration is faster with Bi-Zn-TiO2 than with TiO2-P25. Indeed, a complete discoloration is obtained after 70 min and 120 min in the presence of Bi-Zn-TiO2 and TiO2-P25 respectively. The identification of the responsible species on photo-discoloration was carried out in the presence of different scavengers. The study showed that the first responsible is h(+) specie with a moderate contribution of superoxide anion radical and a minor contribution of the hydroxyl radical. The material showed high stability after five uses with the same rate of photo-discoloration. (C) 2015 Elsevier B.V. All rights reserved.