On the Origin of Oxygen Reduction Reaction at Nitrogen-Doped Carbon Nanotubes: A Computational Study

It has been shown experimentally that nitrogen doped carbon nanotube network is an excellent material for the oxygen reduction reaction in fuel cells. The specific origin of this catalytic action has however remained unclear. Based on density functional theory calculations we propose the atomic origin of the observed high catalytic activity. The formation energy of defects and the binding energy of oxygen to them is found to be dependent on the radius of the nanotube. According to our results, the catalytic activity occurs only when the radius of the nitrogen doped carbon nanotube is large enough. Formation and binding energy considerations suggest a N4V2H2 defect as the atom-level origin for the oxygen reduction reaction.