Oxidation of hydroxide to oxygen at an electrode modified with a film containing palladium and iridium oxides

Hydroxide is oxidized to oxygen at 0.7 V versus a saturated calomel electrode in a pH 11 solution at a glassy carbon electrode modified with a film containing palladium and iridium oxide. Although this converts to a value that is among the lowest of the reported overpotentials for this reaction, the utility for large-scale electrolyses is limited by the need to periodically reactivate the surface with an acid treatment. The reaction, however, has considerable promise for electroanalytical chemistry. Voltammetric working curves in the millimolar range are linear at slow scan rates; at 40 mV/s, the sensitivity is 241 mA/mol. The current is mass transport limited at a rotating disk electrode. A general mechanism, proposed in part on the basis of a Tafel plot, is presented.