Electrocatalytic activity of electrodeposited CoO thin film on low-carbon unalloyed steel substrate toward electrochemical oxygen evolution reaction (OER).

In this study, we report elaboration of a thin film of CoO on a low carbon unalloyed steel substrate by electrochemical route and the study of its electrocatalytic performances with respect to the evolution reaction of oxygen (OER) in NaOH medium. The elaborated deposits were well-characterized using X-ray diffraction. Kinetic and thermodynamic parameters such as exchange current density, Tafel slope, reaction order with respect to OH- ions and apparent activation energy were studied. The CoO displays satisfactory OER performance in an alkaline medium, with a low overvoltage of 362 mV at 10 mA/cm and a Tafel slope of 81 mV/dec at 293 K. The apparent kinetic activation energy (= 29.79 kJ/mol) was similar to those obtained for the reported catalytic electrode materials. The O gas obtained on the cobalt oxide electrode was 2.865 mmol/s.cm, which is 28 times higher than that obtained for the platinum electrode (0.102 mmol/s.cm). Chronoamperometry demonstrates a better electrochemical stability under a polarization potential of 2 V in 1 M NaOH for nearly 25 h. The low cost, the high OER performance, as well as the good stability of the CoOx electrode make it a promising candidate for the industrial-scale water electrolysis.