Elucidating the Structural Composition of an Fe–N–C Catalyst by Nuclear‐ and Electron‐Resonance Techniques. Issue 31 (1st July 2019) - Wagner, Stephan
Abstract: Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands. Abstract : An Fe–N–C catalyst is analyzed using nuclear‐ and electron‐resonance techniques. The results show that even after mild pyrolysis and acid leaching, it contains considerable fractions of α‐iron and iron oxide. This raises the question how many FeN4 sites, which are active centers in the oxygen reduction reaction, can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above.