OXYGEN REDUCTION IN AN ACID-MEDIUM - ELECTROCATALYSIS BY CONPC(1,2) IMPREGNATED ON A CARBON-BLACK SUPPORT - EFFECT OF LOADING AND HEAT-TREATMENT

O2 reduction in an acid medium has been investigated on a transition m etal macrocycle, CoNPc(1,2), impregnated on a carbon black support wit h a high dibutylphthalate adsorption value, using a rotating disk elec trode and voltammetry techniques described previously, combined with X -ray photoelectron spectroscopy measurements. Optimal activity was fou nd for a bilayer coverage (n = 2) at 17%-18% w/w loading. Heat treatme nt seems to be beneficial for n less-than-or-equal-to 3: it increases the overall number N of exchanged electrons and improves the electrode wetting. For the most active samples, mixed Co(II)/Co(III) valencies were displayed.