| Cobalt(II)tetrakis(3,4-dimethoxyphenyl)porphyrin (Co(II)TDMPP), adsorbed on an edge-plane pyrolytic graphite (EPG) electrode, exhibits electrochemical oxidative demethylation to convert a portion of the 3,4-dimethoxyphenyl groups to redox-active o-quinones. Following the partial oxidative demethylation, the adsorbed cobalt(II) porphyrin is an improved electrocatalyst for O2 reduction in 0.5 M HClO4 solution. In this thesis further aspects of the oxidative demethylation/polymerization reaction are explored with a series of cobalt(II) porphyrins containing one to four meso-3,4-dimethoxyphenyl groups. These cobalt(II) porphyrins exhibit enhanced activity for O2 reduction following oxidative demethylation demonstrating that even one quinone group attached to the porphyrin ring can facilitate O2 electrocatalysis.; When Co(II)TDMPP is diluted by an inert porphyrin on the electrode surface, the amount of quinone/catechol generated by oxidative demethylation is proportional to the amount of Co(II)TDMPP at low concentration but polymerization and perhaps degradation processes lower the quinone/catechol yield at higher concentrations. The lower reduction potential and slow rate observed for H2O 2 reduction catalyzed by the conditioned Co(II)TDMPP suggest that the enhanced O2 reduction is not the result of a 2e−+2e − reduction via hydrogen peroxide but is more likely a 4e − process. |
