Comparative study on the photocatalytic decomposition of nitrogen oxides using TiO2 coatings prepared by conventional plasma spraying and suspension plasma spraying

Titanium dioxide is one of the most important photocatalysts that allows the environmental purification of various toxic organic compounds in water and removal of harmful air pollutants. In this paper, two techniques of plasma spraying – plasma spraying from an agglomerated nanopowder and liquid suspension plasma spraying – were used to produce thin deposits. The microstructure of coatings was characterized using scanning electron microscopy and X-ray diffraction. The photocatalytic properties of the coatings were evaluated by the decomposition test of nitrogen oxides and compared with the efficiency of the initial agglomerated nanopowder and that of the Degussa P25 powder. Noticeable different behaviours in the photocatalytic tests were observed for coatings performed either from conventional or liquid plasma spraying. The TiO2 deposits realized by spraying of the liquid suspension exhibited higher photocatalytic efficiency. It is found that the plasma spraying of a slurry is an effective method to retain the original anatase phase and prevent the increase of the crystallite size. This new method of modified spraying is proved to be a promising technique to elaborate photocatalytic coatings for the removal of nitrogen oxide pollutants.

[1]  J. Gang,et al.  Nanostructures in thermal spray coatings , 2003 .

[2]  R. McPherson,et al.  The relationship between the mechanism of formation, microstructure and properties of plasma-sprayed coatings , 1981 .

[3]  P. Fauchais,et al.  Plasma spraying using Ar-He-H2 gas mixtures , 1999 .

[4]  M. Matsumura,et al.  Synergism between rutile and anatase TiO2 particles in photocatalytic oxidation of naphthalene , 2003 .

[5]  A. Fujishima,et al.  Electrochemical Photolysis of Water at a Semiconductor Electrode , 1972, Nature.

[6]  Changhee Lee,et al.  Photocatalytic properties of nano-structured TiO2 plasma sprayed coating , 2003 .

[7]  T. Ibusuki,et al.  The surface structure of titanium dioxide thin film photocatalyst , 1997 .

[8]  M. Kuhn,et al.  Chemistry of NO2 on Mo(110): decomposition reactions and formation of MoO2 , 2000 .

[9]  J. Yates,et al.  Adsorption of NO on the TiO2(110) Surface: An Experimental and Theoretical Study , 2000 .

[10]  A. Maiti,et al.  Chemistry of NO2 on oxide surfaces: formation of NO3 on TiO2(110) and NO2<-->O vacancy interactions. , 2001, Journal of the American Chemical Society.

[11]  Hiroyuki Hatano,et al.  Ultrafine particle fluidization and its application to photocatalytic NOx treatment , 2001 .

[12]  C. Coddet,et al.  Microstructure of plasma-sprayed titania coatings deposited from spray-dried powder , 2003 .

[13]  Kimberly A. Gray,et al.  Explaining the Enhanced Photocatalytic Activity of Degussa P25 Mixed-Phase TiO2 Using EPR , 2003 .

[14]  C. Berndt,et al.  Preparation of nanophase materials by thermal spray processing of liquid precursors , 1997 .

[15]  C. Coddet,et al.  Photocatalytic removal of nitrogen oxides via titanium dioxide , 2004 .

[16]  A. Maiti,et al.  Interaction of NO and NO2 with MgO(1 0 0): photoemission and density-functional studies , 2000 .

[17]  C. Moreau,et al.  Thermal Spray 2003: Advancing the Science And Applying the Technology , 2003 .

[18]  B. Cullity,et al.  Elements of X-ray diffraction , 1957 .

[19]  Xinqing Ma,et al.  Deposition mechanisms of thermal barrier coatings in the solution precursor plasma spray process , 2004 .

[20]  J. Yates,et al.  Photochemistry of NO Chemisorbed on TiO2(110) and TiO2 Powders , 2000 .

[21]  S. Chaturvedi,et al.  Chemistry of SO2 and NO2 on ZnO(0001)-Zn and ZnO powders: changes in reactivity with surface structure and composition , 2001 .

[22]  A. Ohmori,et al.  The photocatalytic activity and photo-absorption of plasma sprayed TiO2–Fe3O4 binary oxide coatings , 2002 .

[23]  E. Jordan,et al.  Highly durable thermal barrier coatings made by the solution precursor plasma spray process , 2004 .