Temperature dependence of oxygen reduction catalyzed by cobalt fluoro-phthalocyanine adsorbed on a graphite electrode

The graphite electrode surface onto which cobalt(II) 1,2,3,4,8,9, 10,1 1,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (abbreviated as (CoHFPC)-H-II) is adsorbed displays a strong electrocatalytic activity toward O2 reduction. The electrochemical response of surface adsorbed (CoHFPC)-H-II is investigated at different pHs and temperatures by cyclic voltammetry. The kinetics of the catalyzed O2 reduction at different temperatures, measured by cyclic voltammetric and rotating disk electrode methods, is analyzed and a corresponding reaction mechanism is proposed. A two-electron/two-proton process is found to be the dominating pathway for (CoHFPC)-H-II catalyzed O-2 reduction. The increase in temperature, from 20 to 70 degrees C, enhances the reduction rate significantly. The presence of methanol has no effect on its catalytic activity towards O-2 reduction. The implications of using this non-noble electrocatalyst for the cathode reaction in low temperature fuel cells, including direct organic, metal-air fuel cells, etc., are discussed in this paper.