X-ray absorption analysis of nitrogen contribution to oxygen reduction reaction in carbon alloy cathode catalysts for polymer electrolyte fuel cells

The electronic Structure of nitrogen introduced into various carbon-based cathode catalysts for the polymer electrolyte fuel cell (PEFC) is investigated using X-ray absorption spectroscopy (XAS). The profile of pi* peaks at the pre-edge of N 1s XAS spectra is used to determine the chemical state of nitrogen, which can be an indicator of oxygen reduction reaction (ORR) activity. It is found that catalysts with a relatively larger amount of graphite-like nitrogen exhibit a higher ORR activity than those with a relatively larger amount of pyridine-like nitrogen. We propose that effective doping with graphite-like nitrogen is a practical guideline for the synthesis of active carbon alloy catalysts. (c) 2008 Elsevier B.V. All rights reserved.