Cobalt oxide nanoparticle-modified carbon nanotubes as an electrocatalysts for electrocatalytic evolution of oxygen gas

A simple procedure was developed to prepare cobalt oxide nanoparticles (nano-CoOx) on multiwall carbon nanotube-modified glassy carbon electrode (MWNT/GCE). Scanning electron microscopy revealed the electrodeposition of nano-CoOx with an average particle size of 25 nm onto MWNT/GCE. Also, the presence of nano-CoOx was revealed by energy dispersive X-ray spectra. The electrocatalytic activity of nano-CoOx and MWNT composite-modified GCE (CoOx–MWNT/GCE) has been examined towards the oxygen evolution reaction (OER) by linear sweep voltammetry. The OER is significantly enhanced at CoOx–MWNT/GCE, as demonstrated by a negative shift in the polarization curves at the CoOx–MWNT/GCE compared with that obtained at the CoOx–GCE and GCE. Optimization of the operating experimental conditions (i.e., solution pH and loading level of nano-CoOx) has been achieved to maximize the electrocatalytic activity of CoOx–MWNT/GCE. The maximum electrocatalytic activity towards the OER was obtained in alkaline media (pH = 13). The electrocatalytic activity of CoOx–MWNT/GCE increased with the number of potential cycles employed for the CoOx deposition till a certain loading (20 cycles) beyond which an adverse effect is observed. The fabricated CoOx–MWNT/GCE exhibited a good stability and durability. The value of energy saving per gram of oxygen gas at a current density of 10 mA cm−2 is 19 .3 kWh kg−1.