title: Stability of Fe-N-C Catalysts in Acidic Medium Studied by Operando Spectroscopy.
abstract: Fundamental understanding of non-precious metal catalysts for the oxygen reduction reaction (ORR) is the nub for the successful replacement of noble Pt in fuel cells and, therefore, of central importance for a technological breakthrough. Herein, the degradation mechanisms of a model high-performance Fe-N-C catalyst have been studied with online inductively coupled plasma mass spectrometry (ICP-MS) and differential electrochemical mass spectroscopy (DEMS) coupled to a modified scanning flow cell (SFC) system. We demonstrate that Fe leaching from iron particles occurs at low potential (<0.7 V) without a direct adverse effect on the ORR activity, while carbon oxidation occurs at high potential (>0.9 V) with a destruction of active sites such as FeNx Cy species. Operando techniques combined with identical location-scanning transmission electron spectroscopy (IL-STEM) identify that the latter mechanism leads to a major ORR activity decay, depending on the upper potential limit and electrolyte temperature. Stable operando potential windows and operational strategies are suggested for avoiding degradation of Fe-N-C catalysts in acidic medium.
authors: Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany). c.h.choi@mpie.de.
authors: Chang Hyuck
authors: CH
authors: Choi
authors: Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany).
authors: Claudio
authors: C
authors: Baldizzone
authors: Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany).
authors: Jan-Philipp
authors: JP
authors: Grote
authors: Université de Montpellier, Institut Charles Gerhardt Montpellier, 2 place Eugène Bataillon, 34095, Montpellier (France).
authors: Anna K
authors: AK
authors: Schuppert
authors: Université de Montpellier, Institut Charles Gerhardt Montpellier, 2 place Eugène Bataillon, 34095, Montpellier (France). frederic.jaouen@univ-montp2.fr.
authors: Frédéric
authors: F
authors: Jaouen
authors: Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany). mayrhofer@mpie.de.
authors: Karl J J
authors: KJ
authors: Mayrhofer
keywords: corrosion; degradation mechanisms; demetalation; electrochemistry; fuel cells