The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium

Journal article


Publication Details

Author(s): Choi CH, Lim HK, Chung MW, Chon G, Sahraie NR, Altin A, Sougrati MT, Stievano L, Oh HS, Park ES, Luo F, Strasser P, Drazic G, Mayrhofer K, Kim H, Jaouen F
Journal: Energy and Environmental Science
Publisher: ROYAL SOC CHEMISTRY
Publication year: 2018
Volume: 11
Journal issue: 11
Pages range: 3176-3182
ISSN: 1754-5692


Abstract

For catalysing dioxygen reduction, iron-nitrogen-carbon (Fe-N-C) materials are today the best candidates to replace platinum in proton-exchange membrane fuel cell (PEMFC) cathodes. Despite tremendous progress in their activity and site-structure understanding, improved durability is critically needed but challenged by insufficient understanding of their degradation mechanisms during operation. Here, we show that FeNxCy moieties in a representative Fe-N-C catalyst are structurally stable but electrochemically unstable when exposed in an acidic medium to H2O2, the main oxygen reduction reaction (ORR) byproduct. We reveal that exposure to H2O2 leaves iron-based catalytic sites untouched but decreases their turnover frequency (TOF) via oxidation of the carbon surface, leading to weakened O-2-binding on iron-based sites. Their TOF is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Our results reveal for the first time a hitherto unsuspected key deactivation mechanism during the ORR in an acidic medium. This study identifies the N-doped carbon surface as the Achilles' heel during ORR catalysis in PEMFCs. Observed in acidic but not in alkaline electrolytes, these insights suggest that durable Fe-N-C catalysts are within reach for PEMFCs if rational strategies minimizing the amount of H2O2 or reactive oxygen species (ROS) produced during the ORR are developed.


FAU Authors / FAU Editors

Mayrhofer, Karl Prof. Dr.
Lehrstuhl für Elektrokatalyse (HIERN)


External institutions with authors

Gwangju Institute of Science and Technology (GIST) / 광주과학기술원
Korea Advanced Institute of Science and Technology (KAIST)
Max-Planck-Institut für Eisenforschung GmbH (MPIE) / Max Planck Institute for Iron Research
National Institute of Chemistry / Kemijski inštitut
Seoul National University (SNU) / 서울대학교
Technische Universität Berlin
University of Montpellier / Université Montpellier


How to cite

APA:
Choi, C.H., Lim, H.-K., Chung, M.W., Chon, G., Sahraie, N.R., Altin, A.,... Jaouen, F. (2018). The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium. Energy and Environmental Science, 11(11), 3176-3182. https://dx.doi.org/10.1039/c8ee01855c

MLA:
Choi, Chang Hyuck, et al. "The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium." Energy and Environmental Science 11.11 (2018): 3176-3182.

BibTeX: 

Last updated on 2019-14-08 at 13:08