Tailoring spinel with perovskite: Sr substitution in the perovskite phase of CoFe2O4-LaCoO3 nanocomposite for Oxygen evolution and Methanol oxidation in Alkaline medium

Abstract

CoFe2O4–La1−xSrxCoO3 (x = 0.2, 0.6, 0.8) composites have been synthesized using a two-step, low-temperature wet chemical approach that combines coprecipitation and sol–gel techniques. The composite materials have been physicochemically analyzed using Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. The electrocatalytic properties of the composite materials have been assessed in terms of their performance in oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. Cyclic voltammetry has been used for analyzing the redox behavior of the materials in 1 M KOH solution. The electrocatalytic activity of the materials has been assessed using anodic polarization curves on Ni substrate and the CoFe2O4–La0.2Sr0.8CoO3 film electrode demonstrates excellent activity, with current densities of 11.1 mA cm−2 for OER and 47.4 mA cm−2 for MOR at 650 mV. Also, the CoFe2O4–La0.2Sr0.8CoO3 film electrode has the maximum specific activity of 1.1 × 103 mA cm−2 g−1 at 650 mV toward OER. The electrodes’ stability has been assessed through chronoamperometric experiments and additional insight into the enhancement of electrocatalytic activity gained through the electrochemical surface area estimations using electrochemical impedance spectroscopy. From chronoamperometric experiment, it has been observed that the CoFe2O4–La0.2Sr0.8CoO3 film electrode attains stability within 114 s with a current density of 108.7 mA cm−2. Furthermore, the thermodynamic parameters, including the standard enthalpy of activation (ΔH°#), standard entropy of activation (ΔS°#), and standard electrochemical energy of activation (ΔHel#), have been estimated by anodic polarization curve recorded in KOH as well as KOH with CH3OH solutions at various temperatures.