Rait Kanarbik oral presentation (SN3-Wed2-2-6)
Estimation of Nitrogen concentration on synthesized Fe-N/C catalysts based on silicon carbide derived carbon using SEM WDS, XPS,
1 Institute of Chemistry / University of Tartu - Institute of Chemistry / University of Tartu, Ravila 14a, 50411 Tartu, Estonia
2 Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz, 14109 Berlin, Germany
3 Institute of Physics, University of Tartu, 1. W.Ostwald Str., 50411 Tartu, Estonia
4 Institute of Solid State Physics, University of Latvia - Kengar, Kengaraga 8, 1063 Riga, Latvia
Different Fe-N/C based catalysts for fuel cells on have been synthesized from highly porous carbide derived carbon (CDC) precursor material. For the proper optimization of the catalyst proper physical characterization techniques must be developed. Since only the surface of the material is catalytically active, the most often analysis methods as SEM EDS and WDS may not provide proper comparison between different synthesis batches because of high interaction depth and high porosity of the material. Usually with these methods mostly bulk concentration values are received. As addition to SEM-EDS/WDS methods, XPS, Raman and SIMS methods have been used for characterization of the catalysts. ICP-MS method has been used for the complete bulk concentration values.
The fastest method for getting approximate concentration data is SEM-EDS, however, one of the most significant parameters to be mapped for these catalysts are the concentration of nitrogen and since SEM-EDS method lacks the resolution to properly separate carbon from nitrogen, SEM-WDS data has also been collected. Both methods are highly surface insensitive which brought the need to use XPS and SIMS methods as addition. The concentration data received using different methods differ highly from each other, which is presumed to be a consequence of most catalyst material being on surface. Peaks m/z 18+(NH3+ and 26-(CN-)were observed as the total nitrogen in the SIMS which more less correlate to XPS data. WDS data collected gave contradictory results which may very well be explained by the difference of the analysis depth.
It was found that the SIMS instrument is a useful and compared to XPS a rather fast analysis tool for comparing the catalyst surface concentrations of different species between different synthesis batches and optimization steps.