Voltammetric determination of the heterogeneous charge transfer rate constant for superoxide formation at a glassy carbon electrode in aprotic medium

A detailed investigation on the electrochemical reduction of oxygen was carried out using cyclic voltammetry at a glassy carbon electrode in dimethylsulphoxide (DMSO) containing 0.1 M tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. A diffusion-limited, quasi-reversible one-electron peak corresponding to the oxygen-superoxide anion couple is seen. The quasi-reversibility was supported by the ΔEp and Ip behavior with the square root of the scan rate, which is typical for a quasi-reversible process. We have used the theory developed by Nicholson for a study of the electrode reaction kinetics in order to measure a precise and reproducible value for the standard rate constant, k0, of the quasi-reversible reduction of oxygen to superoxide anion. The k0 mean value obtained was 9.3×10−2 with a standard deviation of ±0.4×10−2 cm s−1, and a coefficient of variation of 4.6%. The k0 value obtained was compared with both a previous value found in the literature and with simulated curves.