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

Jingkun Li; Li Jiao; Evan Wegener; Lynne Larochelle Richard; Ershuai Liu; Andrea Zitolo; Moulay Tahar Sougrati; Sanjeev Mukerjee; Zipeng Zhao; Yu Huang; Fan Yang; Sichen Zhong; Hui Xu; A. Jeremy Kropf; Frédéric Jaouen; Deborah J. Myers; Qingying Jia

doi:10.1021/jacs.9b11197

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

Jingkun Li, Li Jiao, Evan Wegener, Lynne Larochelle Richard, Ershuai Liu, Andrea Zitolo, Moulay Tahar Sougrati, Sanjeev Mukerjee, Zipeng Zhao, Yu Huang, Fan Yang, Sichen Zhong, Hui Xu, A. Jeremy Kropf, Frédéric Jaouen, Deborah J. Myers^*, Qingying Jia

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

212 Citations (Scopus)

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. Herein, 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.

Original language	English
Pages (from-to)	1417-1423
Number of pages	7
Journal	Journal of the American Chemical Society
Volume	142
Issue number	3
DOIs	https://doi.org/10.1021/jacs.9b11197
Publication status	Published - 22 Jan 2020
Externally published	Yes

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Li, J., Jiao, L., Wegener, E., Richard, L. L., Liu, E., Zitolo, A., Sougrati, M. T., Mukerjee, S., Zhao, Z., Huang, Y., Yang, F., Zhong, S., Xu, H., Kropf, A. J., Jaouen, F., Myers, D. J., & Jia, Q. (2020). Evolution Pathway from Iron Compounds to Fe₁(II)-N₄ Sites through Gas-Phase Iron during Pyrolysis. Journal of the American Chemical Society, 142(3), 1417-1423. https://doi.org/10.1021/jacs.9b11197

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title = "Evolution Pathway from Iron Compounds 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. Herein, 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.",

author = "Jingkun Li and Li Jiao and Evan Wegener and Richard, {Lynne Larochelle} and Ershuai Liu and Andrea Zitolo and Sougrati, {Moulay Tahar} and Sanjeev Mukerjee and Zipeng Zhao and Yu Huang and Fan Yang and Sichen Zhong and Hui Xu and Kropf, {A. Jeremy} and Fr{\'e}d{\'e}ric Jaouen and Myers, {Deborah J.} and Qingying Jia",

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year = "2020",

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doi = "10.1021/jacs.9b11197",

language = "English",

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Li, J, Jiao, L, Wegener, E, Richard, LL, Liu, E, Zitolo, A, Sougrati, MT, Mukerjee, S, Zhao, Z, Huang, Y, Yang, F, Zhong, S, Xu, H, Kropf, AJ, Jaouen, F, Myers, DJ & Jia, Q 2020, 'Evolution Pathway from Iron Compounds to Fe₁(II)-N₄ Sites through Gas-Phase Iron during Pyrolysis', Journal of the American Chemical Society, vol. 142, no. 3, pp. 1417-1423. https://doi.org/10.1021/jacs.9b11197

TY - JOUR

T1 - Evolution Pathway from Iron Compounds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis

AU - Li, Jingkun

AU - Jiao, Li

AU - Wegener, Evan

AU - Richard, Lynne Larochelle

AU - Liu, Ershuai

AU - Zitolo, Andrea

AU - Sougrati, Moulay Tahar

AU - Mukerjee, Sanjeev

AU - Zhao, Zipeng

AU - Huang, Yu

AU - Yang, Fan

AU - Zhong, Sichen

AU - Xu, Hui

AU - Kropf, A. Jeremy

AU - Jaouen, Frédéric

AU - Myers, Deborah J.

AU - Jia, Qingying

PY - 2020/1/22

Y1 - 2020/1/22

N2 - 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. Herein, 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.

AB - 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. Herein, 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.

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DO - 10.1021/jacs.9b11197

M3 - Article

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AN - SCOPUS:85078335253

SN - 0002-7863

VL - 142

SP - 1417

EP - 1423

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 3

ER -

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

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