Effect of Nb doping on structural, optical and photocatalytic properties of flame-made TiO2 nanopowder

TiO2:Nb nanopowders within a dopant concentration in the range of 0.1-15 at.% were prepared by one-step flame spray synthesis. Effect of niobium doping on structural, optical and photocatalytic properties of titanium dioxide nanopowders was studied. Morphology and structure were investigated by means of Brunauer-Emmett-Teller isotherm, X-ray diffraction and transmission electron microscopy. Diffuse reflectance and the resulting band gap energy were determined by diffuse reflectance spectroscopy. Photocatalytic activity of the investigated nanopowders was revised for the photodecomposition of methylene blue (MB), methyl orange (MO) and 4-chlorophenol under UVA and VIS light irradiation. Commercial TiO2-P25 nanopowder was used as a reference. The specific surface area of the powders was ranging from 42.9 m(2)/g for TiO2:0.1 at.% Nb to 90.0 m(2)/g for TiO2:15 at.% Nb. TiO2:Nb particles were nanosized, spherically shaped and polycrystalline. Anatase was the predominant phase in all samples. The anatase-related transition was at 3.31 eV and rutile-related one at 3.14 eV. TiO2:Nb nanopowders exhibited additional absorption in the visible range. In comparison to TiO2-P25, improved photocatalytic activity of TiO2:Nb was observed for the degradation of MB and MO under both UVA and VIS irradiation, where low doping level (Nb < 1 at.%) was the most effective. Niobium doping affected structural, optical and photocatalytic properties of TiO2. Low dopant level enhanced photocatalytic performance under UVA and VIS irradiation. Therefore, TiO2:Nb (Nb < 1 at.%) can be proposed as an efficient selective solar light photocatalyst.