Composite electrocatalysts based on the transition metal cobalt are synthesized for the oxygen reduction reaction (ORR) by mechanically mixing three basic precursors containing carbon black, cobalt acetate and tetramethoxy-phenylporphyrin (TMPP). The influence of various mixing processes, solvents, pyrolysis temperature and precursor ratios on the ORR activity of the electrocatalysts is investigated by means of their electrochemical characteristics. Levich-Koutecky plots show that the number of transferred electrons during ORR on these catalysts varies between 2 and 4. A pyrolyzed mixture synthesized by ultrasonication exhibits better activity for ORR than that prepared by ball milling. The solvent is found to have a significant effect on the performance of the catalysts in acidic media. The catalyst synthesized in water, a poor solvent of TMPR has better activity than that synthesized in a good solvent of TMPP. such as N,N-dimethylformamide and acetic acid. The optimum pyrolysis temperature is 600 degrees C. Various mole ratios and Co/carbon weight ratios are examined. Maximum activity is found at a 1: 1 TMPP/Co mole ratio and a 5% Co/carbon weight ratio. (C) 2008 Elsevier B.V. All rights reserved.