Electrocatalytic Properties of Sol-Gel Derived Spinel CoxFe3-xO4 (0 ≤ x ≤ 1.5) Electrodes for Oxygen Evolution in Alkaline Solution

Abstract

The spinel-type oxide electrodes of CoxFe3-xO4 (0 ≤ x ≤ 1.5) have been studied for their electrocatalytic properties with regards to oxygen evolution reaction in 1M KOH solution at 25 0C. These oxides were prepared by ammonium hydroxide sol-gel auto-combustion method and reproduced in the form of film on nickel support by an oxide-slurry painting technique. Oxides, so synthesized, were characterized physicochemically by using scanning electron microscopy (SEM), infrared (IR) spectroscopy. Cyclic voltammetry and Tafel polarization techniques were used for electrochemical characterization. The study showed that substitution of cobalt in the base oxide greatly influences the electrocatalytic properties. Among synthesized oxides, the Co1.5Fe1.5O4 electrode was found to be the most active electrode for oxygen evolution reaction. The Tafel slope values of the oxide electrodes were ranged between 44 – 56 mVdecade-1. The order for the OER with respect to OH- concentration was found to be ~ 2 with each oxide electrocatalyst. The catalytic activities of the electrodes are correlated with their surface roughness. The thermodynamic parameters for oxygen evolution reaction (OER) such as, standard electrochemical enthalpy of activation (ΔH0#el), standard enthalpy of activation (ΔH0#) and standard entropy of activation (ΔS0#) have also been calculated.