Photodecomposition of NOx on Ag/TiO2 composite catalysts in a gas phase reactor

With NO as model gas component, photocatalytic NOx decomposition under UV and visible light irradiation has been investigated in a gas phase photocatalytic reactor over anatase TiO2 and Ag/TiO2, respectively. TiO2 and AgiTiO(2) were prepared by a solvothermal method and characterized by X-ray diffraction (XRD), BET, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) etc. The activity of the photocatalysts was evaluated by decomposition rate of NO and yield of N-2, respectively. It was found that although photodecomposition of NO over pure TiO2 is very quick, NO has not been converted into N-2 and O-2. It means that some by-products have formed. N-2 formation is a relatively slower process. It was found that the selectivity for photodecomposition of NOx into N-2 can be significantly improved by introducing appropriate amount of Ag into TiO2. The 1 wt% Ag loaded on TiO2 showed the highest activity for both NO decomposition and N-2 production. The possible mechanism for the enhancement of photocatalytic activity of anatase AgiTiO(2) was attributed to the coexistence of Ag and Ag+ on the surface of TiO2, with a Ag+/Ag ratio of ca. 0.86, which played different roles in the photo catalytic process. Our study could be valuable for the development of efficient photocatalyst for NOx photodecomposition with a high selectivity. (C) 2016 Elsevier B.V. All rights reserved.