Mesostructured WO3 as a sensing material for NO2 detection
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0915-R06-09
Mesostructured WO3 as a sensing material for NO2 detection E. Rossinyol1, A. Prim1, E. Pellicer1, J. Arbiol1, F. Peiró1, A. Cornet1, J. R. Morante1, L. A. Solovyov2, B. Tian3, T. Bo3, and D. Zhao3 1 Electronics, University of Barcelona, Martí i Franquès, 1, Barcelona, Catalonia, 08028, Spain 2 Institute of Chemistry and Chemical Technology, K. Marx av., 42, Krasnoyarsk, 660049, Russian Federation 3 Molecular Catalysis and Innovative Materials Laboratory, Department of Chemistry, Fudan University, Shanghai, 200433, China, People's Republic of
ABSTRACT Nanostructured tungsten oxide synthesized from SiO2 templates (SBA-15 and KIT-6) has been used for NO2 gas sensing. Chromium has been added as catalytic additive to WO3 in order to enhance sensor response. Several techniques have been used for identifying both additive location in the tungsten oxide matrix and its oxidation state. Raman spectroscopy confirmed the presence of terminal chromium-oxygen bonds at the material surface. Besides, X-ray photoelectron spectroscopy showed chromium peaks attributable to Cr(III) species. Electrical behavior of pure WO3 has found to be highly dependent on the nanostructure type, i. e. 2D SBA15 and 3D KIT-6 replicas. Chromium addition diminishes response time and improves sensor response at low NO2 concentrations. Electrical differences due to WO3 nanostructure disappears as a result of additive introduction in the material.
INTRODUCTION Solid state semiconductor sensors have been extensively investigated during the last tenyear period because they offer many advantages for gas sensing applications in comparison to other sensor devices [1-3]. Low cost, good reliability and easy implementation are the main traits of solid state gas sensors. With the aim of improving sensor response, many efforts have been done towards increasing the active surface area of the semiconductor material [4, 5]. Given that adsorption is a surface phenomenon, the preparation of nanostructured mesoporous materials has become an important issue as these materials have a large surface/volume ratio with a controllable pore size. Different synthetic routes have been reported concerning the preparation of these nanostructures [6]. Here we report the preparation and characterization of both pure and chromium-catalyzed tungsten oxide. The so-called hard template route has been used for synthesizing the material from SBA-15 and KIT-6 silica templates. The former present a twodimensional hexagonal structure (space group p6mm) and the latter have a three-dimensional cubic structure (space group la-3d). The templates are impregnated with an appropriate WO3 precursor, which is subsequently mineralized to obtain the oxide. Further removal of the solid template allows releasing the mesoporous oxide. WO3 is known as a good material for NO2 detection [7, 8]. A comparison on the gas sensing properties showed by pure and chromiumcatalyzed WO3 will be carried out to assess the additive effect.
EXPERIMENT Synthesis SBA-15 and KIT-6 mesoporous silica templates wer
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