A new indicator electrode for oxygen sensors

The electrochemical reduction of O 2 was studied at Ni‐Cu alloy electrodes in aqueous alkaline solution (0.1–6.0 M KOH) and in unbuffered neutral solution (0.1–2.0 M KCl) using the rotating disk electrode technique. Voltammetric measurements showed that the overall O 2 reduction process at the electrodes containing 70–90% Cu is transport‐limited at cathodic potentials, and that they can be used as indicator electrodes for galvanic‐type oxygen sensors. An industrially produced Ni‐Cu alloy “melhior”, which contains ∼ 30% Ni, was also studied, and this alloy proved to be an excellent O 2 reduction catalyst. Melhior electrodes were utilized as indicator electrodes for oxygen sensors, and showed high output current stability and a long lifetime (exceeding one year).