Electroreduction of oxygen on nitrogen-doped carbon nanotube modified glassy carbon electrodes in acid and alkaline solutions

The electrochemical reduction of oxygen was studied on vertically aligned N-doped carbon nanotube (NCNT) modified glassy carbon (GC) electrodes in 0.5 M H2SO4 and in 0.1 M KOH solutions using the rotating disk electrode (RDE) method. For comparison purposes, the oxygen reduction behaviour of undoped carbon nanotube material has been also investigated. Both catalysts were prepared by chemical vapour deposition (CVD). Acetonitrile was used as the precursor in the synthesis of the NCNT material. The surface morphology and chemical composition of the NCNT catalysts were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The NCNT/GC electrodes showed a significant enhancement of the kinetics of oxygen reduction in both solutions. In acid media the half-wave potential of O2 reduction on NCNT-modified electrodes shifted by 250 mV to more positive potentials as compared to that of vertically aligned undoped CNT materials. The factors that determine the high electrocatalytic activity of nitrogen-doped carbon nanotubes towards oxygen reduction are discussed.