Iron and Nitrogen containing Carbon Catalysts with Enhanced Activity for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

Abstract

Iron and nitrogen containing carbon catalysts were prepared by the pyrolysis of iron(III)tetramethoxy- phenylporphyrin complex adsorbed on as-received as well as nitric acid treated carbon black and employed them as oxygen reduction electrodes for hydrogen-oxygen PEM fuel cells. The influence of carbon surface functional groups on the dispersion of active species and electrocatalytic performance is investigated using electron microscopic and electrochemical techniques. The existence of quinone functional groups on the ni- tric acid treated carbon was evident from X-ray photoelectron spectroscopy and cyclic voltammetry. Rotat- ing disk electrode voltammetry results affirmed the good electrocatalytic activity and stability of pyrolyzed macrocyclic complex adsorbed on nitric acid treated carbon compared to that of as-received carbon. This is ascribed to the greater number of Fe/N active species as well as good dispersion of metal clusters over nitric acid treated carbon support. Fuel cell tests depicted the comparable performance of pyrolyzed complex ad- sorbed on nitric acid treated carbon with commercial Pt/C at 353 K. Durability measurements performed un- der fuel cell operating conditions for 120 h indicate the good stability of the catalysts.