Exploring the Synergistic Effects of Chlorine Coordination in Iron Phthalocyanine for Efficient Oxygen Reduction Catalysis.

Abstract

Chlorine-coordinated iron phthalocyanine is designed and synthesized for 4 e^- pathway oxygen reduction reaction (ORR). Iron phthalocyanine (FePc) is a promising nonprecious catalyst for the ORR. Unfortunately, FePc with plane-symmetric Fe-N4 site usually exhibits an unsatisfactory ORR activity due to its poor O₂ adsorption and activation. In this work, Chlorine-coordinated iron phthalocyanine (Cl-FePc) has been studied as a catalyst for the electrochemical ORR. Coordination of iron phthalocyanine with chlorine introduces additional active sites for ORR, improving its catalytic activity. The chlorine atoms enhance the electron transfer process and facilitate the ORR validated by in situ Raman spectroscopy. The obtained catalyst exhibits fast kinetics for O₂ adsorption and activation with an ultralow Tafel slope of 30 mV dec^-1 and a remarkable half-wave potential of 0.80 V. This work offers a new strategy to regulate catalytic sites for better performance ORR.