Developing a New Synthesis Strategy for Fe-N-C Catalysts for the Oxygen Reduction Reaction in Proton-Exchange-Membrane Fuel Cells

Within this work, a new synthesis method for a Fe-N-C catalyst is developed. Fe-N-C catalysts are considered promising materials for the replacement of expensive Pt and catalyze the oxygen reduction reaction (ORR) on the cathode inside proton-exchange-membrane fuel cells (PEMFCs). This work briefly summarizes the standpoint of current PEMFC technology and provides a detailed overview on the to this day reported synthesis methods and applied precursors for Fe-N-C catalysts. One major concern with the synthesis of Fe-N-C catalysts is that for a high performance often complex precursors like porphyrins or zeolitic imidazolate frameworks (ZIFs) are used. These precursors are expensive or not well suited for a scale-up [1-3]. Here, a new method is presented which is based on a cheap and simple polypyrrole precursor which at the same time yields catalysts with a high fuel cell performance. Important parameters for the new preparation method are systematically investigated and useful insights, for instance on the influence of the iron salt precursor, a bimetallic iron and manganese approach, the heat-treatment temperature, or the effectiveness of the acid leaching, are presented. The final catalyst of this work is compared to the best-off performing Fe-N-C catalysts reported in literature. Further, the overall preparation method is briefly discussed with respect to its scale-up practicability by comparing the individual synthesis steps to the to this day commercially most advanced Fe-N-C catalysts