Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells

Yanghua He; Hui Guo; Sooyeon Hwang; Xiaoxuan Yang; Zizhou He; Jonathan Braaten; Stavros Karakalos; Weitao Shan; Maoyu Wang; Hua Zhou; Zhenxing Feng; Karren L. More; Guofeng Wang; Dong Su; David A. Cullen; Ling Fei; Shawn Litster; Gang Wu

doi:10.1002/adma.202003577

Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells

Yanghua He, Hui Guo, Sooyeon Hwang, Xiaoxuan Yang, Zizhou He, Jonathan Braaten, Stavros Karakalos, Weitao Shan, Maoyu Wang, Hua Zhou, Zhenxing Feng, Karren L. More, Guofeng Wang, Dong Su, David A. Cullen, Ling Fei, Shawn Litster, Gang Wu

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

303 Scopus citations

Abstract

Increasing catalytic activity and durability of atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable Co–N–C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN₄ moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm⁻² in a practical H₂/air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

Original language	English
Article number	2003577
Journal	Advanced Materials
Volume	32
Issue number	46
DOIs	https://doi.org/10.1002/adma.202003577
State	Published - Nov 19 2020

Funding

Y.H., H.G., S.H., and X.Y. contributed equally to this work. G.W., G.F.W., and S.L. acknowledge the support from U.S. DOE‐EERE Fuel Cell Technologies Office (DE‐EE0008076). G.W. is grateful for the financial support from the National Science Foundation (NSF) (CBET‐1604392, 1804326). L.F. acknowledges the financial support from NSF (No.1832963) and Chevron Corporation for providing Chevron Endowed Professorship in Chemical Engineering at UL Lafayette. Electron microscopy research was conducted at the Center for Functional Nanomaterials at Brookhaven National Laboratory (S.H. and D.S., under contract No. DE‐SC0012704) and the Center for Nanophase Materials Sciences of Oak Ridge National Laboratory (D.A.C. and K.L.M.), which both are DOE Office of Science User Facilities. Z.F. thanks for the startup funding from Oregon State University. X‐ray absorption analysis used the resources of the beamline 12‐BM of the Advanced Photon Source (APS), a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE‐AC02‐06CH11357. G.F.W. also gratefully acknowledges the computational resources provided by the University of Pittsburgh Center for Research Computing as well as the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF (ACI‐1053575). Y.H., H.G., S.H., and X.Y. contributed equally to this work. G.W., G.F.W., and S.L. acknowledge the support from U.S. DOE-EERE Fuel Cell Technologies Office (DE-EE0008076). G.W. is grateful for the financial support from the National Science Foundation (NSF) (CBET-1604392, 1804326). L.F. acknowledges the financial support from NSF (No.1832963) and Chevron Corporation for providing Chevron Endowed Professorship in Chemical Engineering at UL Lafayette. Electron microscopy research was conducted at the Center for Functional Nanomaterials at Brookhaven National Laboratory (S.H. and D.S., under contract No. DE-SC0012704) and the Center for Nanophase Materials Sciences of Oak Ridge National Laboratory (D.A.C. and K.L.M.), which both are DOE Office of Science User Facilities. Z.F. thanks for the startup funding from Oregon State University. X-ray absorption analysis used the resources of the beamline 12-BM of the Advanced Photon Source (APS), a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. G.F.W. also gratefully acknowledges the computational resources provided by the University of Pittsburgh Center for Research Computing as well as the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF (ACI-1053575).

Keywords

electrocatalysis
electrospinning
fuel cells
oxygen reduction
single Co sites

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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He, Y., Guo, H., Hwang, S., Yang, X., He, Z., Braaten, J., Karakalos, S., Shan, W., Wang, M., Zhou, H., Feng, Z., More, K. L., Wang, G., Su, D., Cullen, D. A., Fei, L., Litster, S., & Wu, G. (2020). Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells. Advanced Materials, 32(46), Article 2003577. https://doi.org/10.1002/adma.202003577

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title = "Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells",

abstract = "Increasing catalytic activity and durability of atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable Co–N–C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm−2 in a practical H2/air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.",

keywords = "electrocatalysis, electrospinning, fuel cells, oxygen reduction, single Co sites",

author = "Yanghua He and Hui Guo and Sooyeon Hwang and Xiaoxuan Yang and Zizhou He and Jonathan Braaten and Stavros Karakalos and Weitao Shan and Maoyu Wang and Hua Zhou and Zhenxing Feng and More, {Karren L.} and Guofeng Wang and Dong Su and Cullen, {David A.} and Ling Fei and Shawn Litster and Gang Wu",

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month = nov,

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doi = "10.1002/adma.202003577",

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He, Y, Guo, H, Hwang, S, Yang, X, He, Z, Braaten, J, Karakalos, S, Shan, W, Wang, M, Zhou, H, Feng, Z, More, KL, Wang, G, Su, D, Cullen, DA, Fei, L, Litster, S & Wu, G 2020, 'Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells', Advanced Materials, vol. 32, no. 46, 2003577. https://doi.org/10.1002/adma.202003577

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T1 - Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells

AU - He, Yanghua

AU - Guo, Hui

AU - Hwang, Sooyeon

AU - Yang, Xiaoxuan

AU - He, Zizhou

AU - Braaten, Jonathan

AU - Karakalos, Stavros

AU - Shan, Weitao

AU - Wang, Maoyu

AU - Zhou, Hua

AU - Feng, Zhenxing

AU - More, Karren L.

AU - Wang, Guofeng

AU - Su, Dong

AU - Cullen, David A.

AU - Fei, Ling

AU - Litster, Shawn

AU - Wu, Gang

PY - 2020/11/19

Y1 - 2020/11/19

N2 - Increasing catalytic activity and durability of atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable Co–N–C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm−2 in a practical H2/air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

AB - Increasing catalytic activity and durability of atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction (ORR) cathode in proton-exchange-membrane fuel cells remains a grand challenge. Here, a high-power and durable Co–N–C nanofiber catalyst synthesized through electrospinning cobalt-doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X-ray computed tomography verifies the well-distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm−2 in a practical H2/air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM-free electrodes with improved performance and durability.

KW - electrocatalysis

KW - electrospinning

KW - fuel cells

KW - oxygen reduction

KW - single Co sites

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U2 - 10.1002/adma.202003577

DO - 10.1002/adma.202003577

M3 - Article

C2 - 33058263

AN - SCOPUS:85092452614

SN - 0935-9648

VL - 32

JO - Advanced Materials

JF - Advanced Materials

IS - 46

M1 - 2003577

ER -

Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High-Power PGM-Free Cathodes in Fuel Cells

Abstract

Funding

Keywords

UN SDGs

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