A study of the cathodic reduction of ozone at the rotating disc electrode in acid electrolyte

The cathodic reduction of ozone according to O₃+2H⁺+2e^?→H₂O+O₂ was studied at a rotating disc electrode consisting of bright platinum in 1 M HClO₄ at 20°C. The current-potential curves obtained potentiostatically are determined by slow charge transfer in the range of low polarization (Tafel region) and diffusion as rate controlling step at high overvoltage. From the exchange current densities (i₀), obtained by extrapolation of Tafel lines to the reversible potentials, the heterogeneous rate constant k was evaluated giving an average value of 2.5×10^?7 cm s^?1. Likewise the diffusion coefficient (D_O3=1.7×10^?5 cm² s^?1) was calculated from the limiting currents measured at various partial pressures of ozone and different values of rotation rate. An equation for the total current-polarization curve was developed. The computed curves are in good agreement with the data which were obtained experimentally.