Electrochemical behaviour of hemin and PEO-hemin in ion-conductive polymer matrices

Abstract

Both iron(III) protoporphyrin IX (hemin) and polyethylene oxide (PEO)-modified hemin (PEO-hemin) were incorporated into liquid or solid state ion-conductive polymer matrices. Their electrochemical behaviour was examined by cyclic voltammetry. Under nitrogen, PEO-hemin (like hemin) shows two redox processes in PEO oligomer. However, in the PEO solution of hemin, only one electrocatalytic reduction wave of dioxygen was observed at −0.50 V (vs. Ag). PEO-hemin also catalysed the electrochemical reduction of dioxygen in solution, and two waves appeared at −0.50 and −0.65 V (vs. Ag). Hemin cannot be dispersed well in solid polymer electrolytes because of the affinity problem. On the contrary, PEO-hemin can be dispersed into them at the molecular level. Similar redox behaviour of PEO-hemin was detected in solid polymer electrolytes. In the solid state, the redox potential of PEO-hemin is always higher than that in solution.