Determination of Iron
Active Sites in Pyrolyzed Iron-Based
Catalysts for the Oxygen Reduction Reaction
- Publication date
- Publisher
Abstract
Fe-based oxygen reduction reaction (ORR) catalyst materials
are
considered promising nonprecious alternatives to traditional platinum-based
catalysts. These catalyst materials are generally produced by high-temperature
pyrolysis treatments of readily available carbon, nitrogen, and iron
sources. Adequate control of the structure and active site formation
during pyrolysis methods is nearly impossible. Thus, the chemical
nature, structure, and ORR mechanism of catalytically active sites
in these materials is a subject of significant debate. We have proposed
a method, utilizing CN<sup>–</sup> ions as ORR inhibitors on
Fe-based catalysts, to provide insight into the exact nature and chemistry
of the catalytically active sites. Moreover, we propose two possible
catalytically active site formation mechanisms occurring during high-temperature
pyrolysis treatments, dependent on the specific type of precursor
and synthesis methods utilized. We have further provided direct evidence
of our proposed active site formations using ToF-SIMS negative and
positive ion imaging. This knowledge will be beneficial to future
work directed at the development of Fe-based catalysts with improved
ORR activity and operational stabilities for fuel cell and battery
applications