Abstract
To study the effect of partial Co substitution by Fe in the B-site of MnCo2O4 spinel on its physicochemical and electrochemical properties, a series of MnCo2-xFexO4 powders (x = 0.125; 0.250; 0.500; 0.750; 1.000) were synthesized by means of the sol-gel method. The produced powders were characterized by powder X-ray diffraction (pXRD), scanning and transmission electron microscopy (SEM & TEM) coupled with energy dispersive spectroscopy (EDS), X-ray photoelectron and absorption spectroscopy (XPS & XAS), Fourier transformed infrared spectroscopy (FTIR), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity towards oxygen evolution reaction (OER) was evaluated in an alkaline environment (0.1 M KOH). From our findings, the activity increased with the addition of Fe up to x = 0.5, characterized by a decrease of overpotential at 10 mA cm−2GEO from 406 mV for MnCo2O4 to 376 mV for MnCo1·5Fe0·5O4, with a corresponding 44 mV dec−1 Tafel slope. It was identified that the OER-specific activity exhibits a volcano-type shape as a function of the eg occupancy at octahedral sites tuned by Co substitution with Fe.
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