Mesocrystalline Cr and Sb-codoped anatase visible-light-driven photocatalyst

We report on the synthesis, characterization and visible-light-driven photocatalytic activity of mesocrystalline Cr- and Sb-codoped anatase nanoparticles. Discrete and morphologically well-defined assemblies of anatase nanoparticles sized below 100 nm x 50 nm were prepared by hydrothermal aging of aqueous solutions containing titanium alkoxide, chromium acetylacetonate, antimony acetate and triethanolamine (TEOA) as stabilizer. The as-prepared and TEOA-free doped nanoparticles showed similar crystallographic parameters and spectroscopic features. The incorporation of Cr- and Sb dopant cations into the anatase nanoparticles was evaluated by Rietveld refinement of X-ray diffraction patterns and several spectroscopic characterization techniques. Interestingly, the morphology of the final particles was strongly dependent on the dopant amount. On increasing the nominal dopant load the spheroidal cross section changed to ellipsoidal (elongated) and the nanoparticles exhibited large pore volume and high surface area values. Transmission and scanning electron microscopies, TEM and SEM, respectively also revealed that the hydrothermally prepared nanoparticles were built of smaller primary nanoparticles sized around 4 nm. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) revealed the mesocrystalline nature of the synthesized nanoparticles. UV-Vis diffuse reflectance (DR) and X-ray photoelectron (XPS) spectra indicated that the oxidation numbers of antimony and chromium codoped into TiO2 are 5+ and 3+, respectively. The results on the photocatalytic activity of the prepared photocatalyst nanoparticles built of discrete assemblies of very small nanoparticles of Cr- and Sb-codoped TiO2 anatase proved their high efficiency in the degradation of MO (methyl orange) dye under visible light irradiation.