Electrochemical catalytic reduction of molecular oxygen by phthalocyanine modified electrode

Abstract

The electroreduction of molecular oxygen to hydrogen peroxide was catalyzed when various cobalt phthalocyanines were adsorbed on the surface of graphite electrodes. Their catalytic activity was studied with respect to factors such as phthalocyanine ligand structures, redox properties, etc. Ligand substitution of phthalocyanine shifted redox potential of metal center to negative a few tens of mV. This is because of the presence of electron donating group. Bulky alkyl chain reduced catalytic activity of catalysts, but linear chain has no effect on the catalytic activity. Cyclic and Rotating disk voltammetry was used to examine the kinetics of the catalyzed reactions. It shows that there is rate determining chemical step that precedes electron transfer step, and the magnitude of overpotential changed rate determining step. The possible electrode reaction mechanism was considered to account for the observed kinetics.