Carbon-Supported Fe–Nx Catalysts Synthesized by Pyrolysis of the Fe(II)–2,3,5,6-Tetra(2-pyridyl)pyrazine Complex: Structure, Electrochemical Properties, and Oxygen Reduction Reaction Activity

• DOI: 10.1021/jp2020897
• Publication Date: 2011-06-17T18:59:11Z
• Authors: Amado Velázquez-P...; Lei Zhang; Liucheng Wang; Pere Lluís Cabot; Enric Brillas; Ken Tsay; Jiujun Zhang
• Keywords: Selected area diffraction; Carbon fibers; Pyrazine

Carbon-supported Fe–Nx/C catalysts were synthesized at several pyrolysis temperatures such as 600, 700, 800, and 900 °C in the effort to investigate temperature effect on catalyst structures. The Fe contents found be about 1 wt % more than that Fe–TPPZ/C precursor complex (5 %), indicating both carbon support ligand might decomposed during pyrolysis. X-ray diffraction (XRD) analysis revealed samples 600–800 had no iron species segregation, while formed showed formation of Fe3C Fe3O4, confirmed by transmission electron microscopy (TEM), selected-area (SAED), energy dispersive (EDX) measurements. TEM images clearly large sizes Fe3O4 with a diameter 500 nm wrapped up thin layer. For states, photoelectron spectroscopy (XPS) data Fe3+ was dominant sample. Several nitrogen-containing pyridinic N, Fe–N(pyr) bond, quaternary N,N-oxides, well graphitic nitrogen identified XPS samples. Electrochemical characterization reversible Fe(III)–Nx/Fe(II)–Nx redox wave 0.63 V vs RHE, which is believed active sites for oxygen reduction reaction (ORR). density this site dependent temperature, high densities obtained range 700–800 °C. In addition, morphology also analyzed using change double-layer charge potential scan rate. Furthermore, have strong catalytic activity toward an overall transfer number 3.6.