Degradation by Hydrogen Peroxide of Metal-Nitrogen-Carbon Catalysts for Oxygen Reduction

Vincent Goellner (1) , Vanessa Armel (1) , Andrea Zitolo (2) , Emiliano Fonda (2) , Frédéric Jaouen (1)

1 ICGM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier
2 SSOLEIL - Synchrotron SOLEIL

7 8 Fe-N-C and CoN -C materials are promising catalysts for reducing oxygen in fuel cells. The degradation of such catalysts induced by H 2 O 2 was investigated by contacting them ex situ with various amounts of H 2 O 2. The degradation increased with increasing amounts of H 2 O 2. The effect was most severe for Cr-N-C followed by Fe-N-C and last by CoN -C. Treatment with H 2 O 2 leads to diminished oxygen reduction activity at high potential and/or reduced transport properties at high current density in fuel cell. From spectroscopic characterisation, it was found that 66 and 80% of the CoN x C y and FeN x C y moieties present in pristine catalysts survived the extensive H 2 O 2 treatment, respectively. In parallel, the activity for oxygen reduction was divided by ca 6–10 for Fe-N-C and by ca 3 for CoN -C. The results suggest that the main degradation mechanism in fuel cell for such catalysts is due to a chemical reaction with H 2 O 2 that is generated during operation. The super-proportional decrease of the oxygen reduction activity with loss of FeN x C y and CoN x C y moieties suggests either that only a small fraction of such moieties are initially located on the top surface, or that their turnover frequency for oxygen reduction was drastically reduced due to surface oxidation by H 2 O 2 .

Domaines: Catalyse

Vincent Goellner, Vanessa Armel, Andrea Zitolo, Emiliano Fonda, Frédéric Jaouen. Degradation by Hydrogen Peroxide of Metal-Nitrogen-Carbon Catalysts for Oxygen Reduction. Journal of The Electrochemical Society, 2015, 162 (6), pp.H403-H404. ⟨10.1149/2.1091506jes⟩. ⟨hal-01174287⟩