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.