The electrochemical behavior of iron phthalocyanine films, supported on gold and other metal substrates, was studied in solution using cyclic voltammetry and rotating disk (with ring) electrode techniques. Reduction of oxygen on the electrodes was observed to be accompanied by the production of hydrogen peroxide. Previously reported “deactivation” of films with repeated cycling was found to be associated with the adsorption of peroxide intermediates. Multiple redox waves on in the region of −0.05 to −1.0V vs. have been assigned as due to hydrogen adsorbed on different surface sites.