Synthesis and Electrocatalytic Properties of Ni-substituted Co3O4 for Oxygen Evolution in Alkaline Medium

Cobalt based Ni-substituted spinel-type oxides were synthesized by carbonate co-precipitation method using Na2CO3 as precipitant and studied their electrocatalytic properties towards oxygen evolution reaction (OER) in alkaline medium. Materials were synthesized by using nitrates of nickel and cobalt. For electrochemical studies, oxide powder was transformed in the form of oxide film electrode on nickel substrate. Techniques used were cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and anodic Tafel polarization. Results obtained show that the Ni-substitution in Co3O4 matrix increase the oxide roughness factor considerably but did not significantly contribute in electrocatalytic properties for oxygen evolution reaction (OER). Tafel slope and order of reacton with respect to [OH-] concentration at low overpotential were found to be similar to 2.303RT/nF and similar to 1, respectively. The effect of temperature on the electrochemical behaviopur has also been investigated for oxide electrode. Thermodynamic parameters such as, standard electrochemical enthalpy of activation (Delta H-el(0#)), standard enthalpy of activation (Delta H-0#) and standard entropy of activation (Delta S-0#) were estimated by recording the Tafel polarization curves at different temperatures. X-ray diffraction (XRD), infrared (IR) spectroscopy and scanning electron microscope (SEM) techniques have been used to characterize the materials physicochemically.