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Influence of sulfur in the precursor mixture on the structural composition of Fe-N-C catalysts

Janßen, A. and Martinaiou, I. and Wagner, S. and Weidler, N. and Shahraei, A. and Kramm, U. I. (2018):
Influence of sulfur in the precursor mixture on the structural composition of Fe-N-C catalysts.
In: Hyperfine Interactions, Springer International Publishing AG, part of Springer Nature, p. 7, 239, (1), ISSN 0304-3843, DOI: 10.1007/s10751-017-1481-z, [Online-Edition: https://doi.org/10.1007/s10751-017-1481-z],
[Article]

Abstract

Fe-N-C catalysts were prepared by a new synthesis protocol at 800 ∘C with subsequent acid leaching. The effect of sulfur was investigated by a systematic study in which the molar S/Fe ratio in the precursor was varied from 0.0 to 2.45. The obtained catalysts were evaluated for their ORR activity in 0.1 M H2 SO 4. In addition, the specific BET surface area was determined from N2 sorption measurements and structural characterization was made by Mößbauer spectroscopy. Catalysts contain FeN4 moieties and inorganic iron species. Structure activity correlation indicate a dominance of the ferrous low-spin FeN4 site for the ORR activity. This is in agreement with previous findings. In addition, the optimum in terms of ORR activity is in the same S/Me range as found for porphyrin-based catalysts. However, in contrast to previous conclusions of an avoidance of iron carbide formation by sulfur addition, a very high S/Fe ratio is required to obtain a catalyst free of iron carbide. Further work is required to identify the parameter that indeed enables inhibition of iron carbide formation.

Item Type: Article
Erschienen: 2018
Creators: Janßen, A. and Martinaiou, I. and Wagner, S. and Weidler, N. and Shahraei, A. and Kramm, U. I.
Title: Influence of sulfur in the precursor mixture on the structural composition of Fe-N-C catalysts
Language: English
Abstract:

Fe-N-C catalysts were prepared by a new synthesis protocol at 800 ∘C with subsequent acid leaching. The effect of sulfur was investigated by a systematic study in which the molar S/Fe ratio in the precursor was varied from 0.0 to 2.45. The obtained catalysts were evaluated for their ORR activity in 0.1 M H2 SO 4. In addition, the specific BET surface area was determined from N2 sorption measurements and structural characterization was made by Mößbauer spectroscopy. Catalysts contain FeN4 moieties and inorganic iron species. Structure activity correlation indicate a dominance of the ferrous low-spin FeN4 site for the ORR activity. This is in agreement with previous findings. In addition, the optimum in terms of ORR activity is in the same S/Me range as found for porphyrin-based catalysts. However, in contrast to previous conclusions of an avoidance of iron carbide formation by sulfur addition, a very high S/Fe ratio is required to obtain a catalyst free of iron carbide. Further work is required to identify the parameter that indeed enables inhibition of iron carbide formation.

Journal or Publication Title: Hyperfine Interactions
Volume: 239
Number: 1
Publisher: Springer International Publishing AG, part of Springer Nature
Uncontrolled Keywords: Fe-N-C catalysts, Electrocatalysis, Mößbauer spectroscopy, Oxygen reduction reaction (ORR)
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Catalysts and Electrocatalysts
07 Department of Chemistry
Date Deposited: 06 Jul 2018 12:13
DOI: 10.1007/s10751-017-1481-z
Official URL: https://doi.org/10.1007/s10751-017-1481-z
Funders: Financial support by the German Research Foundation (DFG) for the Graduate School of Excellence Energy Science and Engineering (GSC1070), the Federal Ministry of Education and Research (BMBF) via the projects NUKFER (05K16RD1) and StRedO (03XP0092), is gratefully acknowledged.
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