Electrolytic reduction of oxygen at solid electrodes in aprotic solvents-the superoxide ion

Cyclic voltammetric behavior of oxygen reduction to superoxide ion in DMF and CH 3 CN in presence of tetrabutyl ammonium hexafluorophosphate as supporting electrolyte at glassy carbon, rhodium, palladium, lead and tungsten electrodes was investigated. The first reduction step to superoxide ion was found to approach reversibility with an average rate constant of 2.2 × 10 −2 cms −1 at the glassy carbon electrode whereas at rhodium and palladium, the behavior was irreversible exhibiting high cathodic currents on the anodic scans which presumably is caused due to surface disproportion of superoxide ion at these electrodes. At lead and tungsten electrodes one irreversible reduction step was observed in both aprotic solvents.