ELECTROCHEMICAL INVESTIGATION OF PHOTOCATALYTIC OXIDATION OF NO2- AT TIO2 (ANATASE) IN THE PRESENCE OF O-2

Photocatalytic oxidation of NO2− was studied in connection with nitric acid formation in the environmental air. The oxidation of NO2− by O2 proceeds in zero order reaction with.respect to NO2− in aqueous TiO2 (anatase) suspension under illumination. Electrochemical measurements with TiO2 particle-coated electrode revealed that the NO2− is oxidized in an electrochemical mechanism. The faradaic efficiencies of NO2− oxidation at catalyst-coated electrode were less than 50%, reaching saturation at high concentrations under constant current conditions. H202 did not promote oxidation of NO2− with and without Ti02-coated electrode. The mechanism is discussed in terms of oxidation of NO2− by OH radical intermediately formed in anodic oxidation of H20 at the catalyst surface under illumination. © 1990, The Electrochemical Society, Inc. All rights reserved.