Facile and simple deposition of cobalt oxide onto oxidized multiwall carbon nanotubes for electrocatalytic oxygen reduction

Cobalt oxide (CoOx) nanoparticles were synthesized onto oxygenated carbon nanotubes (FCNTs) using a simple cyclic voltammetry technique, and used as an electrocatalyst for oxygen reduction reaction (ORR) in alkaline media. The electrodeposition process was optimized by controlling the deposition cycles to achieve the highest catalytic activity. The electrocatalytic activity of the prepared electrocatalyst towards ORR has been studied in 0.1 M KOH. The results showed that coupling of CoOx with FCNTs enhanced the catalytic activity of the obtained catalyst (CoOx/FCNTs) towards ORR in terms of the onset potential (E-onset), the half-wave potential (E-1/2) and the kinetic current (I-K). Moreover, based on RDE measurements, the catalyst CoOx/FCNTs was able to catalyze the ORR through a 4-electron reduction pathway. The higher activity of CoOx/FCNTs has been explained by the formation of an active interface upon coupling of CoOx with FCNTs leading to creation of more active sites for oxygen reduction and reduction of the reaction intermediates (peroxide). In term of stability, the CoOx/FCNTs catalyst demonstrated a higher stability under ORR condition for a long time (6 h) than the commercial Pt/C catalyst. These findings indicated that CoOx/FCNTs catalyst is a promising non-precious catalyst for ORR electrode in alkaline fuel cells.