Ozone prodn. in 5M H2SO4 with Ti/IrO2/SnO2 - Sb2O5 electrodes was studied. Electrodes were prepd. at 550 Deg by spray pyrolysis of a soln. of precursors contg. tin and antimony chlorides. The aim of this work was to elucidate the mechanism of activation and deactivation of Ti/IrO2/SnO2-Sb2O5 electrodes for ozone prodn. Under galvanostatic conditions the anodic potential and O3 prodn. increases firstly reaching a max. then suddenly decrease. The authors explain this observation by considering that the SnO2 layer prepd. by spray pyrolysis is under stoichiometric for oxygen. During the activation SnO2 becomes stoichiometric. This condition is necessary for ozone prodn. XRD anal. showed no modification of the structure of the bulk during ozone prodn. Nevertheless XRF anal. revealed an inhomogeneity of the at. Sb/Sn ratio on the surface of the electrode leading to pitting corrosion which is responsible of the deactivation of the electrode. [on SciFinder (R)]