Electronic Modulation of Iron Phthalocyanine Molecular Catalysts via Cyano-Substitution for Oxygen Reduction Reaction Activity

Abstract

High-performance oxygen reduction reaction (ORR) catalysts are crucial as cathode catalysts for fuel cells and metal-air batteries. We have previously reported that iron azaphthalocyanine molecularly supported on Ketjenblack exhibits higher ORR activity than both iron phthalocyanine and Pt/C, while being free of precious metals. This enhancement is attributed to the modulation of the electronic state at the active center through the introduction of electron-withdrawing groups into the peripheral positions. In this study, we theoretically and experimentally investigate how the introduction of more strongly electron-withdrawing cyano groups influences ORR activity. Furthermore, we discuss the relationship between the ionization potential and the catalytic activity.