Direct observation of ozone formation on SiO2 surfaces in O2 discharges

Ozone production is studied in a pulsed O2 discharge at pressures in the range 1.3–6.7 mbar. Time-resolved absolute concentrations of O3 and O are measured in the post-discharge using UV absorption spectroscopy and two-photon absorption laser-induced fluorescence. In a bare silica discharge tube ozone is formed mainly by three-body gas-phase recombination. When the tube surface is covered by a high specific surface silica catalyst heterogeneous formation becomes the main source of ozone. The efficiency of this surface process increases with O2 pressure and is favoured by the presence of OH groups and adsorbed H2O on the surface. At p = 6.7 mbar ozone production accounts for up to 25% of the atomic oxygen losses on the surface. (Some figures may appear in colour only in the online journal) Ozone is a strong oxidizing agent which is widely used for treatment of water and decontamination of various surfaces. Ozone formation from surface recombination of atomic oxygen with oxygen molecules