Synthesis and Characterisation of Cobalt Ferrite Coatings for Oxygen Evolution Reaction

Abstract

In this paper, two novel procedures based on powder sedimentation, thermal treatment, and galvanostatic deposition were proposed for the preparation of porous cobalt ferrite (CoFe2O4) coatings with a metallic and organic binder for use as catalysts in the oxygen evolution reaction (OER). The electrochemical properties of the obtained electrode materials were determined as well, using both dc and ac methods. It was found that cobalt ferrite coatings show excellent electrocatalytic properties towards the oxygen evolution reaction (OER) with overpotential measured at a current density of 10 mAcm−2 from 287 to 295 mV and a Tafel slope of 35–45 mVdec−1. It was shown that the increase in the apparent activity of the CoFe2O4 coatings with an organic binder results mainly from a large electrochemically active area. Incorporation of the nickel binder between the CoFe2O4 particles causes an increase in both the conductivity and the electrochemically active area. The Tafel slopes indicate that the same rate-determining step controls the OER for all obtained coatings. Furthermore, it was shown that the CoFe2O4 electrodes exhibit no significant activity decrease after 28 h of oxygen evolution. The proposed coating preparation procedures open a new path to develop high-performance OER electrocatalysts.