Cathodic reduction of oxygen and hydrogen peroxide at cobalt and iron crowned phthalocyanines adsorbed on highly oriented pyrolytic graphite electrodes

Article abstract of DOI:10.1021/ic00051a006

The surface electrochemistry of iron and cobalt crowned phthalocyanine (Fe^IICRPc(-2) and Co^IICRPc(-2)) adsorbed on a highly oriented pyrolytic graphite (HOPG) electrode has been explored under an argon atmosphere. The redox processes of surface bound Co^IICRPc(-2)/[Co^ICRPc(-2)]-, [Fe^IIICRPc(-2)]⁺/Fe^IICRPc(-2), and Fe^II-CRPc(-2)/[Fe^ICRPc(-2)]- couples were identified and their pH dependence reported in the range 1-13. Under an oxygen atmosphere at the Co^IICRPc(-2)/HOPG electrode, two reduction processes, oxygen to hydrogen peroxide and hydrogen peroxide to water, were clearly delineated and their pH dependences explored. Surface bound Fe^II-CRPc(-2) catalyzes the four-electron reduction of oxygen in alkaline medium. The Co^IICRPc(-2)/HOPG electrode is very stable both in the presence and absence of oxygen, but the Fe^IICRPc(-2)/HOPG electrode is much less stable when electrocatalytic oxygen reduction takes place on its surface.