Theoretical calculations, using the density functional theory with the X3LYP and B3LYP hybrid functionals have been applied to study the NOX (x=1,2) adsorption on the (WO3)n (n=2-6) nano-clusters. The adsorption of NO and NO2 molecules on the cluster models was investigated to evaluate the reactivity of the nano-clusters. In this research different orientations of NO and NO2 on the nano-clusters were analyzed. It was found that the best orientation for NO is the N-head and for NO2 is accordance to model d (O atom of the NO2 molecule closes to W atom(, respectively. Electronic structure of WO3 is substantially affected by the NOX adsorption. Natural bond orbital and the electronic density of states calculations were also confirm the charge transfer and Fermi level shifting during the adsorption. NO and NO2 orientation and their charge transfer manner in the metal oxide cluster are different. Finally, although the chemical behavior of the clusters in the presence of NOx molecules are not surprising, but Fermi level behavior confirms that tungsten oxide cyclic clusters can be used as NOx sensor.

Keywords