ELECTROCATALYSIS OF ANODIC OXYGEN-TRANSFER REACTIONS - EVOLUTION OF OZONE

Current efficiencies are compared for the generation of O3 simultaneou sly with O2 during anodic discharge of H2O at pure and iron(III)-doped beta-lead dioxide film electrodes in phosphate buffer (pH 7.5, 10-deg rees-C) containing 2.5 mM KF. Also examined is the effect of applied c urrent density. A current efficiency of 14.6% was obtained for the Fe( III)-doped PbO2 film electrode deposited on an internally cooled (10-d egrees-C) tubular titanium substrate at a current density of 200 mA cm -2 as compared to only 6.1% at the undoped PbO2 electrode under the sa me conditions. This result is tentatively explained on the basis of a mechanism involving the transfer of oxygen from hydroxyl radicals adso rbed on Pb(IV) sites adjacent to Fe(III) sites to O2 adsorbed at the F e(III) sites in the surface of the Fe(III)-doped PbO2 electrodes.