Surface redox catalysis and reduction kinetics of oxygen on copper–nickel alloys

The reduction of oxygen on single phase Cu90Ni10 and Cu70Ni30 alloys in contact with 0.1 M borax at pH 9.2 has been investigated. The rate constant measured is independent of alloy composition for steady-state measurements. When the currents are measured in sweep experiments the current densities are larger for the alloy richer in nickel, indicating slow surface equilibrium processes. The value of n is 3.5±0.2 for pre-reduced electrodes in a wide potential range, from −1.5 to −0.8 V versus the Hg ∣ Hg2SO4 ∣ K2SO4 (sat) electrode. The proposed reduction mechanism involves a bifurcation between a direct and a sequential mechanism involving O2 chemisorbed on Cu(0).