CORROSION OF TIN OXIDE AT ANODIC POTENTIALS

Tin dioxide electrodes are used as anodes for the electrochemical dest ruction of organic pollutants in wastewater: The lifetime of such elec trodes is limited because of corrosion phenomena which are shown to ta ke place under anodic polarization. These corrosion processes are stud ied by quartz microbalance experiments, impedance measurements, transm ission electron microscopy and scanning electron microscopy observatio ns, carried out on sprayed SnO2 layers. Localized corrosion phenomena are observed and related to the reaction of radical species with the o xide surface. The extent and the morphology of the attack is shown to depend on the doping (F, Sb) of the SnO2 electrodes, the solution pH, and the concentration of chloride ions. It is also shown that because of corrosion the conduction band energy level is shifted toward much m ore positive potentials, allowing the SnO2 electrode to be activated f or oxygen evolution.