Cobalt based non-precious metal catalysts were prepared by supporting cobalt-ethylene diamine complex on carbon followed by a heat treatment at elevated temperatures (800 degrees C). Surface oxygen groups on carbon were introduced with HNO3 oxidation. Co catalysts supported on oxidized carbon showed improved activity and selectivity towards four-electron reduction of molecular oxygen. Quinone groups introduced by nitric acid treatment, in addition to increasing the dispersion of the chelate complexes, play a role in forming the active site for oxygen reduction. (c) 2005 Elsevier B.V All rights reserved.