Potential and temperature dependence of hydrogen peroxide oxidation at nickel electrodes

The electrochemical oxidation of H2O2 at a nickel rotating disc electrode was studied in 100 mM phosphate buffer at pH 7.26 over the temperature range 5-35 degreesC, [H2O2] range 0 to 130 mM, rotation rates 630 to 10 000 rpm and anodic potential +364 to +1068 mV vs. Ag/AgCl using staircase voltammetry. These results were compared with those previously reported for platinum electrodes (S. B. Hall, E. A. Khudaish and A. L. Hart, Electrochim, Acta., 1998, 43, 579; ibid., 1998, 43, 2015; ibid., 1999, 44, 2455; ibid., 1999, 44, 4573; ibid., 2000, 45, 3573). The rate of oxidation of H2O2 on nickel is 15-20 times slower than on platinum. Modifications were made to the binding-site mechanism established for the reaction at platinum (S. B. Hall, E. A. Khudaish and A. L. Hart, Electrochim. Acta, 1999, 44, 2455) to account for the kinetics at nickel. These included removing the consideration of proton inhibition and constraining the rate of regeneration of the binding site to potential-invariance. Thermodynamic and kinetic parameters together with the pseudo-activation energy for the formation of the reduced binding site were evaluated.