Electrochemical study of spinel oxide systems with nominal compositions Ni 1− x Cu x Co 2 O 4 and NiCo 2− y Cu y O 4

Studies on the electrochemical behaviour of Ni1− x Cu x Co2O4 (x ≤ 0.75) and NiCo2− y Cu y O4 (y ≤ 0.30) electrodes in 5 mol dm−3 KOH aqueous solutions are presented. The oxide layers have been prepared by thermal decomposition of aqueous nitrate solutions on nickel supports at 623 K. Powder samples were also prepared by thermal decomposition under the same conditions. The powder samples and the oxide layers were characterised by X-ray powder diffraction. The influence of the copper content on the voltammetric response of the electrodes and activity towards oxygen evolution reaction is analysed and correlated with the surface composition of the electrodes by means of X-ray photoelectron spectroscopy data. The analysis of the results reveals that the presence of Cu affects the electrode behaviour and its influence depends on which cation has been replaced.