Oxidized carbon nanotubes as an efficient metal-free electrocatalyst for the oxygen reduction reaction

An acid treatment can efficiently incorporate a large number of oxygen containing functional groups including -OH, -COOH, C=O onto the surface of a carbon nanotube. These oxidized carbon nanotubes significantly improve the electrocatalytic activity towards the oxygen reduction reaction due to a more hydrophilic surface, more defect sites and the doping effect.