Simultaneous Elimination of Formaldehyde and Ozone Byproduct Using Noble Metal Modified TiO_2 Films in the Gaseous VUV Photocatalysis

摘要

Simultaneous removal of low concentration formaldehyde (HCHO) and ozone byproduct was investigated in the gaseous VUV (vacuum ultraviolet) photocatalysis by using noble metal modified TiO_2 films. Noble metal (Pt, Au, or Pd) nanoparticles were deposited on TiO_2 films with ultrafine particle size and uniform distribution. Under 35 h VUV irradiation, the HCHO gas (ca. 420 ppbv) was dynamically degraded to a level of 10～45 ppbv without catalyst deactivation, and over 50% O_3 byproduct was in situ decomposed in the reactor. However, under the same conditions, the outlet HCHO concentration remained at 125～178 ppbv in the O_3 + UV_(254nm) photocatalysis process and 190～260 ppbv in the UV_(254nm) photocatalysis process. And the catalyst deactivation also appeared under UV_(254 nm) irradiation. Metallic Pt or Au could simultaneously increase the elimination of HCHO and ozone, but the PdO oxide seemed to inhibit the HCHO oxidation in the UV_(254nm) photocatalysis. Deposition of metallic Pt or Au reduces the recombination of h~+/e~- pairs and thus increases the HCHO oxidation and O_3 reduction reactions. In addition, adsorbed O_3 may be partly decomposed by photogenerated electrons trapped on metallic Pt or Au nanoparticles under UV irradiation.