PLATINUM OXIDE-GROWTH KINETICS FOR CYCLIC VOLTAMMETRY

The oxide growth law dsigma(ox)/dt = a(o) exp(cE) exp(- bsigma(ox)), previously derived on theoretical grounds and shown to explain constant potential growth data for the anodic oxide on Pt, is used to predict the current-potential relationship for cyclic voltammetry. The current is predicted to rise to a plateau current whose value is proportional to the sweep rate, as observed experimentally. Experimental data from constant-potential experiments are used to find values of the parameters a(o), b and c. These parameters are then used in the cyclic voltammetry equations and shown to explain correctly the experimental data. The results of sweep-hold-sweep experiments, in which the final oxide coverage is nearly independent of the hold time, are also shown to be consistent with the same rate law.