Electrocatalytic activity of Ni_xFe_3-xO₄ (0 ≤ x ≤ 1.5) film electrode for oxygen evolution in KOH solutions

Abstract

Spinel-type pure and Ni-substituted ferrites have been synthesised by novel ammonium hydroxide precipitation method at <em>p</em>H 11.5 and their electrocatalytic properties have been studied with regards to oxygen evolution reaction (OER) in alkaline solutions. Physicochemical and electrochemical techniques used to characterize the materials are X-ray diffraction (XRD), scanning electron microscope (SEM), infrared (IR), cyclic voltammetry (CV) and anodic polarization (Tafel plot). Results of IR and XRD studies show the formation of spinel phase of the material along with some small impurity. All the electrochemical studies are carried out in a three electrode single compartment glass cell. For the purpose, materials have been transformed in the oxide film electrode by oxide slurry painting technique. The cyclic voltammetric curve of each oxide electrode exhibit redox peaks (anodic: 519 ± 33mV and cathodic: 362 ± 2 mV) prior to the oxygen evolution reaction (OER). The electrocatalytic activity of the material has been determined by recording the anodic polarization curve in 1 M KOH at 25°C. Data show that the Ni-substitution in the base oxide enhance the electrocatalytic activity of the material and value is found to be greatest with 0.5 mol Ni. This material produced overpotential 583 mV at 100 mA cm^-2 current density. Tafel slope values are ranged between 64-81 mV decade^-1 with fractional order of reaction. The activation energy and other thermodynamic parameters are also estimated by recording the anodic polarization curve in 1M KOH at different temperatures.