Electrocatalytic Oxygen Evolution on Glassy Carbon Electrode Modified with Optimized GC/CuxFe3 – xO4 (0 ≤ x ≤ 1.0) Nanocomposite in 1 M KOH Solution

Abstract

Copper substituted ferrites (Cu_xFe_3 – xO₄; (0 ≤ x ≤ 1.0) were prepared by the egg white auto-combustion method at 550°C and investigated their physicochemical properties via the thermogravimetric analysis, infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and electrochemical ones via cyclic voltammenry and Tafel polarization. The formation of copper ferrites with a spinel phase was confirmed by the Fourier-transform infrared spectra having characteristic vibration peaks and by the X-ray diffraction spectra with reflection planes. The electrochemical performance of the oxygen evolution reaction of copper ferrites on glassy carbon electrodes was investigated in 1 M KOH. No redox couple was observed in cyclic voltammograms of the glassy carbon/oxide electrode in the selected oxygen overpotential regions. The iR-free Tafel polarization curves having higher Tafel slopes (b = 72–125 mV dec^–1) and a lower current density (i = 0.29–4.7 mA cm^–2 at 0.85 V) exhibited a sluggish nature of the fabricated oxide electrodes from the electrocatalytic point of view. The substitution of Fe by Cu in the oxide lattice considerably increased the electrocatalytic activity for the oxygen evolution reaction. Based on the current density for the oxygen evolution reaction, the 0.75 mol Cu-substituted oxide electrode was found to be the most active electrode among the prepared oxides. The order of the reaction related to the [OH^–] concentration was a unity for almost all of the electrodes except when 0.25 mol Cu-substitution followed the second-order kinetics.