Issue 10, 2024

Operando X-ray absorption spectroscopy of Fe–N–C catalysts based on carbon black and biomass-derived support materials for the ORR

Abstract

Iron nitrogen carbon (Fe–N–C) catalysts are among the most promising non-platinum group metal catalysts for the oxygen reduction reaction (ORR). Their activity and stability are considerably influenced by the structure of the C-support. New biochar materials offer native heteroatom doping, making them a promising precursor for Fe–N–C catalysts. In this study, we apply operando X-ray absorption spectroscopy at the Fe K-edge to characterize the atomic Fe-based active sites of a commercial Fe–N–C catalyst, a carbon black-based catalyst as well as a novel biomass-based Fe–N–C catalyst. We compare the density and the potential-dependent nature of the FeNx-type active sites during operation. Our results demonstrate that the novel biomass-based catalyst exhibits a higher active-site density compared to commercial and carbon black-based Fe–N–C catalysts. Moreover, dynamic detection of the Fe K-edge intensity during potential cycling reveals that their reversible iron redox potential is lower compared to that of conventional catalysts. Evaluation of the Fe K-edge shift as well as of the extended X-ray absorption fine structure (EXAFS) suggests hetero-atom doping and iron under-coordination as potential causes for the observed differences. These insights open the pathway to develop new optimization strategies for Fe–N–C catalysts based on biomass support materials.

Graphical abstract: Operando X-ray absorption spectroscopy of Fe–N–C catalysts based on carbon black and biomass-derived support materials for the ORR

Supplementary files

Article information

Article type
Paper
Submitted
11 Mac 2024
Accepted
12 Apr 2024
First published
15 Apr 2024
This article is Open Access
Creative Commons BY license

Sustainable Energy Fuels, 2024,8, 2309-2320

Operando X-ray absorption spectroscopy of Fe–N–C catalysts based on carbon black and biomass-derived support materials for the ORR

G. Wartner, J. Müller-Hülstede, H. Trzesniowski, M. Wark, P. Wagner and R. Seidel, Sustainable Energy Fuels, 2024, 8, 2309 DOI: 10.1039/D4SE00342J

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