Preparation, characterization and photocatalytic studies of N, Sn-doped defect pyrochlore oxide KTi0.5W1.5O6

Abstract

Quaternary oxides containing transition metal and tungsten with the general formula AMWO6 (A=K, Rb, Cs; M=Sb, Nb, Ti) have been studied as photocatalysts for decomposition of organic dyes. In this paper, defect pyrochlore of composition KTi0.5W1.5O6 was prepared via facile sol–gel method. Its nitrogen and tin doped analogues were prepared by solid state and ion exchange methods respectively. All compounds were characterized by powder X-ray diffraction, Thermogravimetric analysis, FT-IR, Raman, Scanning electron microscopy and UV–Vis diffuse reflectance spectra. X-ray photoelectron spectroscopy and energy dispersive spectroscopy were also used to characterize the incorporation of doped ions into the defect pyrochlore lattice. The photocatalytic activity of all compounds was studied by degradation of methylene blue and Rhodamine B. The tin doped KTi0.5W1.5O6 shows higher photocatalytic activity against both the dyes. The experimental results show that the higher photocatalytic activity of tin doped KTi0.5W1.5O6 is due to more absorption of light energy in the visible region attributable to the lowering of bandgap energy. Further, the role of reactive intermediate species in the photocatalytic degradation of dyes was studied using their appropriate scavengers and the obtained results show that OH radicals produced in the photocatalytic reaction play dominant role.