Effect of Cationic or Anionic Dopants on Optical and Photocatalytic Properties of TiO 2 Nanopowders made by Flame Spray
- PDF / 790,170 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 40 Downloads / 206 Views
1171-S02-05
Effect of cationic or anionic dopants on optical and photocatalytic properties of TiO2 nanopowders made by flame spray synthesis (FSS). Katarzyna A. Michalow1,2, Andre Heel2, Thomas Graule2, Mieczyslaw Rekas1 1 Faculty of Material Science and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland 2 Laboratory for High Performance Ceramics, EMPA Swiss Federal Laboratories for Materials Testing and Research, Ueberlandstrasse 129, 8600 Duebendorf, Switzerland ABSTRACT TiO2, TiO2-1at.% W and TiO2-1at.% Cr were produced from metal-organic precursors by flame spray synthesis (FSS). TiO2-0.5at.% N was obtained by ammonolysis of FSS made TiO2 nanopowder in a rotating tube furnace under NH3 atmosphere. According to the X-ray diffraction (XRD) analysis, anatase is the predominant phase in all samples. Diffusive reflectance and the resulting band gap energy (Eg) were determined by diffusive reflection spectroscopy (DRS). Additional impurity bands at 2.43 and 2.57 eV for N- and Cr-doped TiO2, respectively have been observed. The impurity band formed in the band gap resulted in increase of the light absorption in the visible range. The photocatalytic performance of the nanopowders under ultraviolet (UV, 290-410 nm) and visible light irradiation (Vis, 400-500 nm) was studied by the degradation of methylene blue (MB) in aqueous suspensions. It was found that all types of dopants influence the structure, interaction with the visible light as well as photocatalytic activity. Among all nanopowders, TiO2-W exhibited the best photoactivity, much higher than the commercial TiO2-P25 nanopowder. The optimum of the photodecolourization was obtained for 0.7 and 1 at.% W. INTRODUCTION Bare TiO2 is the most common photocatalyst, due to its high corrosion resistivity and the non-toxicity. However, TiO2 shows poor photocatalytic efficiency under solar light irradiation, due to its wide band gap and recombination losses of the photo charge pairs [1, 2]. There are several ways to overcome these drawbacks like doping of cationic sublattice of TiO2 with either donor-type ions such as W6+, Mo6+ and Nb5+ [3-5] or acceptor-type ions such as Cr3+, Fe3+ [6, 7]. This type of modification by metal doping is particularly interesting to increase the electrical conductivity, resulting in a decrease of the recombination losses, as well as to modify the photocatalyst’s surface properties leading to an improvement of the optical properties and relating electronic structure. Recently non-metal doping attracted considerable attention due to its enhanced photocatalytic activity in the visible light [8, 9]. An anionic doping by nitrogen seems to be the most interesting due to the noticeable red-shift of light absorption. New physical and chemical properties emerge when the size of the material becomes smaller and goes down to the nanometre scale. Well crystalline anatase particles with a size of about 11-21 nm are most suitable for a photocatalytic application [9-11]. The present study reports on the effect of: W6
Data Loading...
