The Effect of Heat Treatment Atmospheres on the Electrocatalytic Activity of Cobalt Tetraazaannulenes: Preliminary Results

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Ambient heat treatment atmospheres have been found to have significant effect on the oxygen reduction catalytic activity of Co tetraazaannulene and its dibromo derivative. Two macrocyclic chelates were absorbed on acetylene black carbon from DMF (dimethyl formamide) solutions, then heat treated in each of the following environments: N2, Ar, vacuum and nitrogen passed over heated copper turnings. Electrodes were prepared by pasting the catalyst mixed with a Teflon slurry onto a carbon cloth. The catalytic activity was evaluated from steady state current vs voltage measurements for the electrochemical reduction of oxygen in 4 N H2SO4. The results indicate that the activity of the two chelates is influenced by the ambient atmospheres of heat treatment. ESCA examination of the adsorbed Co tetraazaannulene dibromide on the acetylene black carbon heat treated in N2 and vacuum indicated evidence of bonding with the carbon surface for the former and possible polymerization of the catalyst on the surface for the latter.

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