Cooperative Atomically Dispersed Fe-N4 and Sn-Nx Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells

Fan Xia; Bomin Li; Bowen An; Michael J. Zachman; Xiaohong Xie; Yiqi Liu; Shicheng Xu; Sulay Saha; Qin Wu; Siyuan Gao; Iddrisu B. Abdul Razak; Dennis E. Brown; Vijay Ramani; Rongyue Wang; Tobin J. Marks; Yuyan Shao; Yingwen Cheng

doi:10.1021/jacs.4c11121

Cooperative Atomically Dispersed Fe-N₄ and Sn-N_x Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells

Fan Xia, Bomin Li, Bowen An, Michael J. Zachman, Xiaohong Xie, Yiqi Liu, Shicheng Xu, Sulay Saha, Qin Wu, Siyuan Gao, Iddrisu B. Abdul Razak, Dennis E. Brown, Vijay Ramani, Rongyue Wang, Tobin J. Marks, Yuyan Shao, Yingwen Cheng

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

Abstract

One grand challenge for deploying porous carbons with embedded metal-nitrogen-carbon (M-N-C) moieties as platinum group metal (PGM)-free electrocatalysts in proton-exchange membrane fuel cells is their fast degradation and inferior activity. Here, we report the modulation of the local environment at Fe-N₄ sites via the application of atomic Sn-N_x sites for simultaneously improved durability and activity. We discovered that Sn-N_x sites not only promote the formation of the more stable D2 FeN₄C₁₀ sites but also invoke a unique D3 SnN_x-Fe^IIN₄ site that is characterized by having atomically dispersed bridged Sn-N_x and Fe-N₄. This new D3 site exhibits significantly improved stability against demetalation and several times higher turnover frequency for the oxygen reduction reaction (ORR) due to the shift of the reaction pathway from a single-site associative mechanism to a dual-site dissociative mechanism with the adjacent Sn site facilitating a lower overpotential cleavage of the O-O bond. This mechanism bypasses the formation of the otherwise inevitable intermediate that is responsible for demetalation, where two hydroxyl intermediates bind to one Fe site. As a result, a mesoporous Fe/Sn-PNC catalyst exhibits a positively shifted ORR half-wave potential and more than 50% lower peroxide formation. This, in combination with the stable D3 site and enriched D2 Fe sites, significantly enhanced the catalyst’s durability as demonstrated in membrane electrode assemblies using complementary accelerated durability testing protocols.

Original language	English
Journal	Journal of the American Chemical Society
DOIs	https://doi.org/10.1021/jacs.4c11121
State	Accepted/In press - 2024

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under award DE-SC0023266. Y.S. acknowledges support from the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technology Office (DOE-EERE-HFTO) through the Electrocatalysis Consortium (ElectroCat). The computational work was done at the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under contract no. DE-SC0012704. Y.L. and T.J.M. acknowledge support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award DE-SC0024448. This work made use of the Keck-II facility of Northwestern University\u2019s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern\u2019s MRSEC program (NSF DMR-1720139). The STEM, EELS, and EDS mapping portions of this research were supported by the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-SC0012704.

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10.1021/jacs.4c11121

Cite this

Xia, F., Li, B., An, B., Zachman, M. J., Xie, X., Liu, Y., Xu, S., Saha, S., Wu, Q., Gao, S., Abdul Razak, I. B., Brown, D. E., Ramani, V., Wang, R., Marks, T. J., Shao, Y., & Cheng, Y. (Accepted/In press). Cooperative Atomically Dispersed Fe-N₄ and Sn-N_x Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells. Journal of the American Chemical Society. https://doi.org/10.1021/jacs.4c11121

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title = "Cooperative Atomically Dispersed Fe-N4 and Sn-Nx Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells",

abstract = "One grand challenge for deploying porous carbons with embedded metal-nitrogen-carbon (M-N-C) moieties as platinum group metal (PGM)-free electrocatalysts in proton-exchange membrane fuel cells is their fast degradation and inferior activity. Here, we report the modulation of the local environment at Fe-N4 sites via the application of atomic Sn-Nx sites for simultaneously improved durability and activity. We discovered that Sn-Nx sites not only promote the formation of the more stable D2 FeN4C10 sites but also invoke a unique D3 SnNx-FeIIN4 site that is characterized by having atomically dispersed bridged Sn-Nx and Fe-N4. This new D3 site exhibits significantly improved stability against demetalation and several times higher turnover frequency for the oxygen reduction reaction (ORR) due to the shift of the reaction pathway from a single-site associative mechanism to a dual-site dissociative mechanism with the adjacent Sn site facilitating a lower overpotential cleavage of the O-O bond. This mechanism bypasses the formation of the otherwise inevitable intermediate that is responsible for demetalation, where two hydroxyl intermediates bind to one Fe site. As a result, a mesoporous Fe/Sn-PNC catalyst exhibits a positively shifted ORR half-wave potential and more than 50% lower peroxide formation. This, in combination with the stable D3 site and enriched D2 Fe sites, significantly enhanced the catalyst{\textquoteright}s durability as demonstrated in membrane electrode assemblies using complementary accelerated durability testing protocols.",

author = "Fan Xia and Bomin Li and Bowen An and Zachman, {Michael J.} and Xiaohong Xie and Yiqi Liu and Shicheng Xu and Sulay Saha and Qin Wu and Siyuan Gao and {Abdul Razak}, {Iddrisu B.} and Brown, {Dennis E.} and Vijay Ramani and Rongyue Wang and Marks, {Tobin J.} and Yuyan Shao and Yingwen Cheng",

note = "Publisher Copyright: {\textcopyright} 2024 American Chemical Society.",

year = "2024",

doi = "10.1021/jacs.4c11121",

language = "English",

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Xia, F, Li, B, An, B, Zachman, MJ, Xie, X, Liu, Y, Xu, S, Saha, S, Wu, Q, Gao, S, Abdul Razak, IB, Brown, DE, Ramani, V, Wang, R, Marks, TJ, Shao, Y & Cheng, Y 2024, 'Cooperative Atomically Dispersed Fe-N₄ and Sn-N_x Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells', Journal of the American Chemical Society. https://doi.org/10.1021/jacs.4c11121

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T1 - Cooperative Atomically Dispersed Fe-N4 and Sn-Nx Moieties for Durable and More Active Oxygen Electroreduction in Fuel Cells

AU - Xia, Fan

AU - Li, Bomin

AU - An, Bowen

AU - Zachman, Michael J.

AU - Xie, Xiaohong

AU - Liu, Yiqi

AU - Xu, Shicheng

AU - Saha, Sulay

AU - Wu, Qin

AU - Gao, Siyuan

AU - Abdul Razak, Iddrisu B.

AU - Brown, Dennis E.

AU - Ramani, Vijay

AU - Wang, Rongyue

AU - Marks, Tobin J.

AU - Shao, Yuyan

AU - Cheng, Yingwen

PY - 2024

Y1 - 2024

N2 - One grand challenge for deploying porous carbons with embedded metal-nitrogen-carbon (M-N-C) moieties as platinum group metal (PGM)-free electrocatalysts in proton-exchange membrane fuel cells is their fast degradation and inferior activity. Here, we report the modulation of the local environment at Fe-N4 sites via the application of atomic Sn-Nx sites for simultaneously improved durability and activity. We discovered that Sn-Nx sites not only promote the formation of the more stable D2 FeN4C10 sites but also invoke a unique D3 SnNx-FeIIN4 site that is characterized by having atomically dispersed bridged Sn-Nx and Fe-N4. This new D3 site exhibits significantly improved stability against demetalation and several times higher turnover frequency for the oxygen reduction reaction (ORR) due to the shift of the reaction pathway from a single-site associative mechanism to a dual-site dissociative mechanism with the adjacent Sn site facilitating a lower overpotential cleavage of the O-O bond. This mechanism bypasses the formation of the otherwise inevitable intermediate that is responsible for demetalation, where two hydroxyl intermediates bind to one Fe site. As a result, a mesoporous Fe/Sn-PNC catalyst exhibits a positively shifted ORR half-wave potential and more than 50% lower peroxide formation. This, in combination with the stable D3 site and enriched D2 Fe sites, significantly enhanced the catalyst’s durability as demonstrated in membrane electrode assemblies using complementary accelerated durability testing protocols.

AB - One grand challenge for deploying porous carbons with embedded metal-nitrogen-carbon (M-N-C) moieties as platinum group metal (PGM)-free electrocatalysts in proton-exchange membrane fuel cells is their fast degradation and inferior activity. Here, we report the modulation of the local environment at Fe-N4 sites via the application of atomic Sn-Nx sites for simultaneously improved durability and activity. We discovered that Sn-Nx sites not only promote the formation of the more stable D2 FeN4C10 sites but also invoke a unique D3 SnNx-FeIIN4 site that is characterized by having atomically dispersed bridged Sn-Nx and Fe-N4. This new D3 site exhibits significantly improved stability against demetalation and several times higher turnover frequency for the oxygen reduction reaction (ORR) due to the shift of the reaction pathway from a single-site associative mechanism to a dual-site dissociative mechanism with the adjacent Sn site facilitating a lower overpotential cleavage of the O-O bond. This mechanism bypasses the formation of the otherwise inevitable intermediate that is responsible for demetalation, where two hydroxyl intermediates bind to one Fe site. As a result, a mesoporous Fe/Sn-PNC catalyst exhibits a positively shifted ORR half-wave potential and more than 50% lower peroxide formation. This, in combination with the stable D3 site and enriched D2 Fe sites, significantly enhanced the catalyst’s durability as demonstrated in membrane electrode assemblies using complementary accelerated durability testing protocols.

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