NO x Photooxidation over Different Noble Metals Modified TiO 2.

We compared the activity enhancement effect of noble metal deposited on TiO₂ in photocatalytic nitrogen oxides oxidation. Titanium dioxide was decorated with Ag, Au, Pt or Pd in the sol-gel process. Synthesized catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller measurement (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). All catalysts together with pure TiO₂ obtained by sol-gel (SG) technique were tested for their photocatalytic activity towards nitrogen oxide oxidation (high concentrations of 50, 150 and 250 ppm). FTIR spectrometry was used to determine the gas phase composition and identify TiO₂ surface species. The Ag0.1 sample turned out to be deactivated within 60 min of UV/Vis irradiation. Photocatalytic oxidation rate towards NO₂ turned to be the highest over SG (photocatalyst without metal deposition). NO₂ formation was also observed for Au0.1, Au0.5, Pt0.1, Pt0.5 and Pd0.1. The best NO_x removal, i.e., conversion to final product HNO₃ was obtained with the Au0.5 photocatalyst. [ABSTRACT FROM AUTHOR]