Electrocatalytic Activity of Sr-Doped Lanthanum Cobaltate for Oxygen Evolution Reaction in Alkaline Medium

Abstract

La_{1 – x}Sr_xCoO₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by the alginic acid sol–gel route and characterized by thermo gravimetric analysis (TGA), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. The electrocatalytic activity of fabricated oxide electrodes (Ni/oxide) was studied for oxygen evolution reaction (OER) in an alkaline medium. The cyclic voltammetry of oxide electrodes shows a pair of redox couple at anodic peak potential (E_pa) = 400 ± 6 mV and cathodic peak potential (E_pc) = 296 ± 8 mV. The observed values of electrode kinetic parameters such as the Tafel slope (b) lie between 91 and 126 mV dec^–1 and current density (j) lie between 17.0–73.1 mA cm^–2 at 0.85 V. The Sr-substitution in lanthanum cobaltate matrix improve electrocatalytic activity for OER in an alkaline medium and maximum improvement was observed in the case of 0.4 mol Sr-substituted oxide. The order of reaction (p) with respect to the concentration of [OH^–] is found unity and the highly negative value of entropy of the reaction indicated the oxygen evolution follows the same mechanism and involves the adsorption of the reaction intermediate.