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Thermally Controlled Construction of Fe–N x Active Sites on the Edge of a Graphene Nanoribbon for an Electrocatalytic Oxygen Reduction Reaction

Abstract : Pyrolytically prepared iron and nitrogen codoped carbon (Fe/N/C) catalysts are promising nonprecious metal electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell applications. Fabrication of the Fe/N/C catalysts with Fe–Nx active sites having precise structures is now required. We developed a strategy for thermally controlled construction of the Fe–Nx structure in Fe/N/C catalysts by applying a bottom-up synthetic methodology based on a N-doped graphene nanoribbon (N-GNR). The preorganized aromatic rings within the precursors assist graphitization during generation of the N-GNR structure with iron-coordinating sites. The Fe/N/C catalyst prepared from the N-GNR precursor, iron ion, and the carbon support Vulcan XC-72R provides a high onset potential of 0.88 V (vs reversible hydrogen electrode (RHE)) and promotes efficient four-electron ORR. X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) studies reveal that the N-GNR precursor induces the formation of iron-coordinating nitrogen species during pyrolysis. The details of the graphitization process of the precursor were further investigated by analyzing the precursors pyrolyzed at various temperatures using MgO particles as a sacrificial template, with the results indicating that the graphitized structure was obtained at 700 °C. The preorganized N-GNR precursors and its pyrolysis conditions for graphitization are found to be important factors for generation of the Fe–Nx active sites along with the N-GNR structure in high-performance Fe/N/C catalysts for the ORR.
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https://hal-cea.archives-ouvertes.fr/cea-03175432
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Submitted on : Saturday, March 20, 2021 - 9:50:33 AM
Last modification on : Thursday, July 1, 2021 - 4:43:42 PM

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Koki Matsumoto, Akira Onoda, Tomoyuki Kitano, Takao Sakata, Hidehiro Yasuda, et al.. Thermally Controlled Construction of Fe–N x Active Sites on the Edge of a Graphene Nanoribbon for an Electrocatalytic Oxygen Reduction Reaction. ACS Applied Materials & Interfaces, Washington, D.C. : American Chemical Society, In press, 13 (13), pp.15101-15112. ⟨10.1021/acsami.0c21321⟩. ⟨cea-03175432⟩

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