Simultaneous Elimination of Formaldehyde and Ozone Byproduct Using Noble Metal Modified TiO2Films in the Gaseous VUV Photocatalysis

Abstract

Simultaneous removal of low concentration formaldehyde (HCHO) and ozone byproduct was investigated in the gaseous VUV (vacuum ultraviolet) photocatalysis by using noble metal modified TiO2films. Noble metal (Pt, Au, or Pd) nanoparticles were deposited on TiO2films 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% O3byproduct wasin situdecomposed in the reactor. However, under the same conditions, the outlet HCHO concentration remained at 125~178 ppbv in the O3+ UV254 nmphotocatalysis process and 190~260 ppbv in the UV254 nmphotocatalysis process. And the catalyst deactivation also appeared under UV254 nmirradiation. 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 UV254 nmphotocatalysis. Deposition of metallic Pt or Au reduces the recombination of h+/e−pairs and thus increases the HCHO oxidation and O3reduction reactions. In addition, adsorbed O3may be partly decomposed by photogenerated electrons trapped on metallic Pt or Au nanoparticles under UV irradiation.