Evolution Pathway from Iron Compunds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis
[1];
[2];
[2];
[4];
[1];
[2];
[5];
[5];
[1];
[3];
[2]
- Univ. Montpellier (France)
- Northeastern Univ., Boston, MA (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Synchrotron SOLEIL, Gif-sur-Yvette (France)
- Univ. of California, Los Angeles, CA (United States)
- Giner, Inc., Newton, MA (United States)
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.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
- Grant/Contract Number:
- AC02-06CH11357; EE0008075; EE0008416
- OSTI ID:
- 1598180
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 3 Vol. 142; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Spectroscopic insights into the nature of active sites in iron–nitrogen–carbon electrocatalysts for oxygen reduction in acid
Single-Iron Site Catalysts with Self-Assembled Dual-size Architecture and Hierarchical Porosity for Proton-Exchange Membrane Fuel Cells