Effect of FeOx on the electrocatalytic properties of NiCo2O4 for O-2 evolution from alkaline solutions

Mixtures of NiCo 2O 4 and FeO x were obtained by thermal decomposition of the nitrates of Ni, Co, and Fe in appropriate proportions. Two series of electrodes were prepared: (1) at constant composition (20 mol% FeO x ) and various calcination temperatures in the range 200 to 480 °C and (2) at constant calcination temperature (300 °C) and various compositions in the whole composition range 0 to 100 mol% FeO x . The oxide layers were characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and cyclic voltammetry. Experimental data showed that the layers consist of a mixture of phases in which Fe oxide is present as Fe 2O 3. The electrocatalytic properties were assessed by means of quasi-stationary potentiostatic current-potential curves for the O 2 evolution reaction from alkaline solution. Results have shown that the mechanism of O 2 evolution depends on composition moderately. The electrocatalytic activity appears to depend on composition only slightly.