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Study of the evolution of FeNxCy and Fe3C species in Fe/N/C catalysts during the oxygen reduction reaction in acid and alkaline electrolyte

DOI: 10.1016/j.jpowsour.2021.229487 DOI Help

Authors: Álvaro García (Instituto de Catálisis y Petroleoquímica, CSIC) , Laura Pascual (Instituto de Catálisis y Petroleoquímica, CSIC) , Pilar Ferrer (Diamond Light Source) , Diego Gianolio (Diamond Light Source) , Georg Held (Diamond Light Source) , David C. Grinter (Diamond Light Source) , Miguel A. Peña (Instituto de Catálisis y Petroleoquímica, CSIC) , Maria Retuerto (Instituto de Catálisis y Petroleoquímica, CSIC) , Sergio Rojas (Instituto de Catálisis y Petroleoquímica, CSIC)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Power Sources , VOL 490

State: Published (Approved)
Published: April 2021
Diamond Proposal Number(s): 26554

Open Access Open Access

Abstract: The nature and evolution of FeNxCy moieties in Fe/C/N catalysts has been studied by analysing Fe and N environments. TEM and Fe-XAS reveal the presence of FeNx moieties and Fe3C particles in the fresh catalyst. NEXAFS reveals the presence of two groups of (Fe)NxCy ensembles, namely (Fe)Nx-pyridinic and (Fe)Nx-pyrrolic. The architecture of the FeNxCy ensembles and their evolution during the ORR has been analysed by XAS, NEXAFS, and identical locations TEM. NxCy, FeNxCy and Fe3C species are partially removed during the ORR, resulting in the formation of Fe2O3 and Fe3O4 particles with different morphologies. The process is more severe in acid electrolyte than in alkaline one. (Fe)Nx-pyrrolic moieties are the main ones in the fresh catalysts, but (Fe)Nx-pyridinic groups are more stable after the ORR. The correlation between the evolution of the ORR activity and that of the FeNxCy ensembles indicates that FeNx-pyridinic ensembles are responsible for the ORR activity.

Journal Keywords: Fe/N/C; ORR; Fe–N-pyridinic; Fe–N-pyrrolic; NEXAFS; Surface sites

Diamond Keywords: Fuel Cells

Subject Areas: Chemistry, Energy

Instruments: B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS , B18-Core EXAFS


Discipline Tags:

Catalysis Energy Energy Storage Sustainable Energy Systems Chemistry

Technical Tags:

Spectroscopy Energy Dispersive X-ray Spectroscopy (EDX) X-ray Absorption Spectroscopy (XAS) Near Edge X-ray Absorption Fine Structures (NEXAFS)