Effect of trichloroethylene on the photocatalytic oxidation of methanol onTiO2

During photocatalytic oxidation (PCO), methanol reacts to formaldehyde, som e of which desorbs from TiO2 at room temperature. Formaldehyde that remains on the surface oxidizes to adsorbed formate, which dehydrogenates to CO2 i n a single step without forming any long-lived intermediates. Adding trichl oroethylene (TCE) during PCO of methanol increases the rates of methanol do uble right arrow formaldehyde and formic acid double right arrow CO2. Trich loroethylene decreases the rate that formaldehyde oxidizes to formate, howe ver. Adding TCE during PCO of methanol, formaldehyde, and formic acid does not produce any new surface species or reaction pathways. Chlorine radicals that are produced during PCO of TCE may be responsible for the increases i n dehydrogenation rates of methanol and formic acid. (C) 2001 Academic Pres s.