Modified carbon aerogels as Fe-N-C catalysts

Abstract

Carbon aerogels have a great potential to be used in applications like adsorption, catalysis, supercapacitors, fuel cells or batteries based on their unique properties such as well-controlled pore size distribution, high porosity, large specific surface area, high electrical conductivity and low envelope density.[1] They have a three-dimensional, open porous structure and are produced via carbonization of organic aerogels based on e.g. resorcinol-formaldehyde polymers. Polymer electrolyte membrane fuel cells are a very promising technique for converting hydrogen into electrical energy. But until now, one major problem for large-scale application are the high platinum catalyst costs. A suitable alternative to the critical raw materials are iron-nitrogen (Fe-Nx) complexes embedded in a porous, carbonaceous structure. For the application as a catalyst, the carbon matrix has to be modified in order to incorporate the active Fe-Nx sites into the carbon structure. Therefore, the carbon is treated with different synthesis steps to introduce nitrogen and iron into the carbon structure.[2] Prior nitrogen doping of the carbon aerogel, oxygen doping was identified as a crucial step. To introduce nitrogen and iron, the oxidized carbon aerogel is mixed with nitrogen and iron precursors and thermally treated to obtain Fe-N-C materials. The presentation will focus on our recent studies showing different synthesis techniques and the results of physicochemical and electrochemical characterization of the doped carbon aerogels using physisorption measurements, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, electrical conductivity measurements and rotating ring-disk electrode measurements.[3] [1] Pekala, R. W. and C. T. Alviso (1992). Carbon Aerogels and Xerogels. MRS Online Proceedings Library. [2] Müller-Hülstede, J., et al., Journal of Power Sources 2022, doi: 10.1016/j.jpowsour.2022.231529 [3] Zierdt, T., et al., ChemSusChem 2024, doi: 10.1002/cssc.202401843