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Fe-N-C electrocatalysts in the oxygen and nitrogen cycles in alkaline media: the role of iron carbide.

Tomer Y BurshteinDenial AiasJin WangMatan SananisEliyahu M FarberOz M GazitIlya GrinbergDavid Eisenberg
Published in: Physical chemistry chemical physics : PCCP (2021)
Fe-N-C electrocatalysts hold a great promise for Pt-free energy conversion, driving the electrocatalysis of oxygen reduction and evolution, oxidation of nitrogen fuels, and reduction of N2, CO2, and NOx. Nevertheless, the catalytic role of iron carbide, a component of nearly every pyrolytic Fe-N-C material, is at the focus of a heated controversy. We now resolve the debate by examining a broad range of Fe3C sites, spanning across many typical size distributions and carbon environments. Removing Fe3C selectively by a non-oxidizing acid reveals its inactivity towards two representative reactions in alkaline media, oxygen reduction and hydrazine oxidation. The activity is assigned to other pre-existing sites, most probably Fe-Nx. DFT calculations prove that the Fe3C surface binds O and N intermediates too strongly to be catalytic. By settling the argument on the catalytic role of Fe3C in alkaline electrocatalysis, we hope to spur innovation in this critical field.
Keyphrases
  • metal organic framework
  • visible light
  • machine learning
  • crystal structure
  • reactive oxygen species