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Title: Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis

Abstract

Pyrolysis is indispensable for synthesizing highly active Fe–N–C catalysts for the oxygen reduction reaction (ORR) in acid, but how Fe, N, and C precursors transform to ORR-active sites during pyrolysis remains unclear. This knowledge gap obscures the connections between the input precursors and the output products, clouding the pathway toward Fe–N–C catalyst improvement. Here, we unravel the evolution pathway of precursors to ORR-active catalyst comprised exclusively of single-atom Fe1(II)–N4 sites via in-temperature X-ray absorption spectroscopy. The Fe precursor transforms to Fe oxides below 300 °C and then to tetrahedral Fe1(II)–O4 via a crystal-to-melt-like transformation below 600 °C. The Fe1(II)–O4 releases a single Fe atom that diffuses into the N-doped carbon defect forming Fe1(II)–N4 above 600 °C. This vapor-phase single Fe atom transport mechanism is verified by synthesizing Fe1(II)–N4 sites via “noncontact pyrolysis” wherein the Fe precursor is not in physical contact with the N and C precursors during pyrolysis.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [2]; ORCiD logo [2]; ORCiD logo [4]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [5]; ORCiD logo [5];  [6];  [6];  [6];  [3]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [2]
  1. Univ. Montpellier (France)
  2. Northeastern Univ., Boston, MA (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Synchrotron SOLEIL, Gif-sur-Yvette (France)
  5. Univ. of California, Los Angeles, CA (United States)
  6. Giner, Inc., Newton, MA (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
OSTI Identifier:
1598180
Grant/Contract Number:  
AC02-06CH11357; EE0008416; EE0008075
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 142; Journal Issue: 3; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; redox reactions; oxides; precursors; catalysts; pyrolysis

Citation Formats

Li, Jingkun, Jiao, Li, Wegener, Evan, Richard, Lynne Larochelle, Liu, Ershuai, Zitolo, Andrea, Sougrati, Moulay Tahar, Mukerjee, Sanjeev, Zhao, Zipeng, Huang, Yu, Yang, Fan, Zhong, Sichen, Xu, Hui, Kropf, A. Jeremy, Jaouen, Frédéric, Myers, Deborah J., and Jia, Qingying. Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis. United States: N. p., 2019. Web. https://doi.org/10.1021/jacs.9b11197.
Li, Jingkun, Jiao, Li, Wegener, Evan, Richard, Lynne Larochelle, Liu, Ershuai, Zitolo, Andrea, Sougrati, Moulay Tahar, Mukerjee, Sanjeev, Zhao, Zipeng, Huang, Yu, Yang, Fan, Zhong, Sichen, Xu, Hui, Kropf, A. Jeremy, Jaouen, Frédéric, Myers, Deborah J., & Jia, Qingying. Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis. United States. https://doi.org/10.1021/jacs.9b11197
Li, Jingkun, Jiao, Li, Wegener, Evan, Richard, Lynne Larochelle, Liu, Ershuai, Zitolo, Andrea, Sougrati, Moulay Tahar, Mukerjee, Sanjeev, Zhao, Zipeng, Huang, Yu, Yang, Fan, Zhong, Sichen, Xu, Hui, Kropf, A. Jeremy, Jaouen, Frédéric, Myers, Deborah J., and Jia, Qingying. Fri . "Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis". United States. https://doi.org/10.1021/jacs.9b11197. https://www.osti.gov/servlets/purl/1598180.
@article{osti_1598180,
title = {Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis},
author = {Li, Jingkun and Jiao, Li and Wegener, Evan and Richard, Lynne Larochelle and Liu, Ershuai and Zitolo, Andrea and Sougrati, Moulay Tahar and Mukerjee, Sanjeev and Zhao, Zipeng and Huang, Yu and Yang, Fan and Zhong, Sichen and Xu, Hui and Kropf, A. Jeremy and Jaouen, Frédéric and Myers, Deborah J. and Jia, Qingying},
abstractNote = {Pyrolysis is indispensable for synthesizing highly active Fe–N–C catalysts for the oxygen reduction reaction (ORR) in acid, but how Fe, N, and C precursors transform to ORR-active sites during pyrolysis remains unclear. This knowledge gap obscures the connections between the input precursors and the output products, clouding the pathway toward Fe–N–C catalyst improvement. Here, we unravel the evolution pathway of precursors to ORR-active catalyst comprised exclusively of single-atom Fe1(II)–N4 sites via in-temperature X-ray absorption spectroscopy. The Fe precursor transforms to Fe oxides below 300 °C and then to tetrahedral Fe1(II)–O4 via a crystal-to-melt-like transformation below 600 °C. The Fe1(II)–O4 releases a single Fe atom that diffuses into the N-doped carbon defect forming Fe1(II)–N4 above 600 °C. This vapor-phase single Fe atom transport mechanism is verified by synthesizing Fe1(II)–N4 sites via “noncontact pyrolysis” wherein the Fe precursor is not in physical contact with the N and C precursors during pyrolysis.},
doi = {10.1021/jacs.9b11197},
journal = {Journal of the American Chemical Society},
number = 3,
volume = 142,
place = {United States},
year = {2019},
month = {12}
}

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