Photocatalytic degradation of gaseous acetaldehyde on TiO2 with photodeposited metals and metal oxides

The photocatalytic degradation of acetaldehyde by metal-photodeposited TiO2 was analyzed at room temperature and elevated temperatures. In the humid condition, the acetaldehyde degradation rate of Pt–TiO2 was larger than that of pure TiO2, however, the degradation rate of Pd or Ag–TiO2 was smaller. The degradation rate of metal-deposited TiO2 depended on the oxidation state of metal, which also influenced the signal intensities of O2− and Ti3+ in electron spin resonance (ESR) spectrum recorded at 77 K. By elevating temperature from 40 to 130 °C, the acetaldehyde degradation rate and the CO2 production rate of Pt–TiO2 were increased by the aid of metal Pt. Acetaldehyde is also thermocatalytically degraded by photodeposited Pt on TiO2 at 70–190 °C without UV irradiation, however the UV irradiation is necessary for complete mineralization of acetaldehyde. The mineralization of acetaldehyde is considered to be enhanced by the partial oxidation of acetaldehyde by Pt thermocatalyst and the oxidation of intermediates into CO2 by TiO2 photocatalyst.