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Electronic Structures of Non-Pt Carbon Alloy Catalysts for Polymer Electrolyte Membrane Fuel Cells Revealed by Synchrotron Radiation Analyses

Published online by Cambridge University Press:  02 March 2011

Masaharu Oshima
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Synchrotron Radiation Research Organization, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-8656, Japan
Hideharu Niwa
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Makoto Saito
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Masaki. Kobayashi
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Synchrotron Radiation Research Organization, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-8656, Japan
Koji Horiba
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Synchrotron Radiation Research Organization, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-8656, Japan
Yoshihisa Harada
Affiliation:
School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Synchrotron Radiation Research Organization, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-8656, Japan
Kiyoyuki Terakura
Affiliation:
Research Center for Integrated Science, Japan Advanced Institute of Science Technology (JAIST), 1-1 Asahidai, Nomi Ishikawa 923-1292, Japan
Takashi Ikeda
Affiliation:
Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
Jun-ichi Ozaki
Affiliation:
Department of Chemical & Environmental Engineering, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515, Japan
Yuta Nabae
Affiliation:
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
Seizo Miyata
Affiliation:
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
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Abstract

The oxygen reduction reaction (ORR) mechanism of non-Pt catalysts was elucidated by investigating electronic structures of carbon alloy catalysts (CACs) for polymer electrolyte membrane fuel cells (PEMFC). For metal phthalocyanine-based carbon alloy catalysts with 1-2% of nitrogen and less than 0.1% of Co or Fe, photoelectron spectroscopy, X-ray absorption spectroscopy (XAS), and X-ray Absorption Fine Structure (XAFS) have revealed that Co or Fe metal sites are not the ORR active site, whereas the carbon atoms adjacent to graphitic nitrogens at a zigzag edge of graphite may act as the ORR active site, which is in good agreement with first principles calculations. These studies have also revealed that the zigzag edges, detected as a XAS shoulder component, are well evolved for catalysts pyrolyzed at 600°C, which show the maximum ORR activity. Based on these analyses, we have realized significantly improved carbon alloy based ORR performance, up to about 70 % of that with Pt catalysts. Further, to analyze the electronic structure of CACs during operation, we constructed a new in situ soft X-ray emission spectroscopy system with very high energy resolution (ΔE) of 120 meV at 640 eV at the University of Tokyo beamline BL07LSU in SPring-8.

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Articles
Copyright
Copyright © Materials Research Society 2011

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