INFLUENCE OF THE ELECTRODE HISTORY AND EFFECTS OF THE ELECTROLYTE COMPOSITION AND TEMPERATURE ON O2 EVOLUTION AT BETA-PbO2 ANODES IN ACID MEDIA

An investigation is reported on O2 electrogeneration at b-PbO2 electrodes in HClO4, H2SO4 and CF3SO3H (TFMSA) using steady-state and impedance measurements. It is established that desorption of reaction intermediates is rate limiting in all the cases examined, and it is proposed that elementary reactions leading to oxygen evolution take place at a surface consisting of crystal line (PbO2) and hydrous zones. ...Different important factors are found to affect the electrochemical process: (i) pre-treatment of the electrode....; (ii) the temperature at which electrodeposition of PbO2 is carried out....; (iii) electrolite anions are adsorbed and inhibit desorption of reaction intermediates....; (iv) fluoride added to the electrolyte is strognly adsorbed and suppresses or modifies the structure of the hydrous layer .....; (v) a low electrolite temperature also inhibits O2 evolution ....