Promoting Atomically Dispersed MnN4Sites via Sulfur Doping for Oxygen Reduction: Unveiling Intrinsic Activity and Degradation in Fuel Cells

Lin Guo; Sooyeon Hwang; Boyang Li; Fan Yang; Maoyu Wang; Mengjie Chen; Xiaoxuan Yang; Stavros G. Karakalos; David A. Cullen; Zhenxing Feng; Guofeng Wang; Gang Wu; Hui Xu

doi:10.1021/acsnano.0c10637

Promoting Atomically Dispersed MnN₄Sites via Sulfur Doping for Oxygen Reduction: Unveiling Intrinsic Activity and Degradation in Fuel Cells

Lin Guo, Sooyeon Hwang, Boyang Li, Fan Yang, Maoyu Wang, Mengjie Chen, Xiaoxuan Yang, Stavros G. Karakalos, David A. Cullen, Zhenxing Feng, Guofeng Wang, Gang Wu, Hui Xu

Materials MicroAnalysis

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

135 Scopus citations

Abstract

Carbon supported and nitrogen coordinated single Mn site (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (vs. Fe), earth abundances (vs. Co), and encouraging activity and stability. However, current Mn-N-C catalysts suffer from high overpotential due to low intrinsic activity and less dense MnN4 sites. Herein, we present a sulfur-doped Mn-N-C catalyst (Mn-N-C-S) synthesized through an effective adsorption-pyrolysis process. Using electron microscopy and X-ray absorption spectroscopy (XAS) techniques, we verify the uniform dispersion of MnN4 sites and confirm the effect of S doping on the Mn-N coordination. The Mn-N-C-S catalyst exhibits a favorable oxygen reduction reaction (ORR) activity in acidic media relative to the S-free Mn-N-C catalyst. The corresponding membrane electrode assembly (MEA) generates enhanced performance with a peak power density of 500 mW cm-2 under a realistic H2/air environment. The constant voltage tests of fuel cells confirm the much-enhanced stability of the Mn-N-C-S catalyst compared to the Fe-N-C and Fe-N-C-S catalysts. The electron microscopy and Fourier transform XAS analyses provide insights into catalyst degradation associated with Mn oxidation and agglomeration. The theoretical calculation elucidates that the promoted ORR activity is mainly attributed to the spatial effect stemmed from the repulsive interaction between the ORR intermediates and adjacent S dopants.

Original language	English
Pages (from-to)	6886-6899
Number of pages	14
Journal	ACS Nano
Volume	15
Issue number	4
DOIs	https://doi.org/10.1021/acsnano.0c10637
State	Published - Apr 27 2021

Funding

The authors are grateful for the financial support from U.S. Department of Energy, Fuel Cell Technologies Office (DE-EE0008075), and the ElectroCat Consortium. The XAS experiments were used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory. Part of XAS was done at 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 No. DE-AC02-06CH11357. Electron microscopy analysis were carried out at the Center for Functional Nanomaterials of the Brookhaven National Laboratory (under Contract No. DE-SC0012704) and at the Center for Nanophase Materials Sciences of the Oak Ridge National laboratory, which are DOE Office of Science User facilities. The DFT calculations used the computational resources provided by the University of Pittsburgh Center for Research Computing and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation grant number ACI-1053575. The authors are grateful for the financial support from U.S. Department of Energy, Fuel Cell Technologies Office (DE-EE0008075) and the ElectroCat Consortium. The XAS experiments were used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory. Part of XAS was done at 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 No. DE-AC02-06CH11357. Electron microscopy analysis were carried out at the Center for Functional Nanomaterials of the Brookhaven National Laboratory (under Contract No. DE-SC0012704) and at the Center for Nanophase Materials Sciences of the Oak Ridge National laboratory, which are DOE Office of Science User facilities. The DFT calculations used the computational resources provided by the University of Pittsburgh Center for Research Computing and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation grant number ACI-1053575.

Funders	Funder number
Center for Functional Nanomaterials Brookhaven National Laboratory	DE-SC0012704
ElectroCat Consortium
National Science Foundation	ACI-1053575
U.S. Department of Energy
Office of Science
Argonne National Laboratory	DE-AC02-06CH11357
Brookhaven National Laboratory
University of Pittsburgh
Hydrogen and Fuel Cell Technologies Office	DE-EE0008075

Keywords

electrocatalysis
fuel cells
oxygen reduction
single metal site
sulfur doping

UN SDGs

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

Access to Document

10.1021/acsnano.0c10637

Cite this

@article{bb3d6c59f7974fb2a8578fd233a35555,

title = "Promoting Atomically Dispersed MnN4Sites via Sulfur Doping for Oxygen Reduction: Unveiling Intrinsic Activity and Degradation in Fuel Cells",

abstract = "Carbon supported and nitrogen coordinated single Mn site (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (vs. Fe), earth abundances (vs. Co), and encouraging activity and stability. However, current Mn-N-C catalysts suffer from high overpotential due to low intrinsic activity and less dense MnN4 sites. Herein, we present a sulfur-doped Mn-N-C catalyst (Mn-N-C-S) synthesized through an effective adsorption-pyrolysis process. Using electron microscopy and X-ray absorption spectroscopy (XAS) techniques, we verify the uniform dispersion of MnN4 sites and confirm the effect of S doping on the Mn-N coordination. The Mn-N-C-S catalyst exhibits a favorable oxygen reduction reaction (ORR) activity in acidic media relative to the S-free Mn-N-C catalyst. The corresponding membrane electrode assembly (MEA) generates enhanced performance with a peak power density of 500 mW cm-2 under a realistic H2/air environment. The constant voltage tests of fuel cells confirm the much-enhanced stability of the Mn-N-C-S catalyst compared to the Fe-N-C and Fe-N-C-S catalysts. The electron microscopy and Fourier transform XAS analyses provide insights into catalyst degradation associated with Mn oxidation and agglomeration. The theoretical calculation elucidates that the promoted ORR activity is mainly attributed to the spatial effect stemmed from the repulsive interaction between the ORR intermediates and adjacent S dopants.",

keywords = "electrocatalysis, fuel cells, oxygen reduction, single metal site, sulfur doping",

author = "Lin Guo and Sooyeon Hwang and Boyang Li and Fan Yang and Maoyu Wang and Mengjie Chen and Xiaoxuan Yang and Karakalos, {Stavros G.} and Cullen, {David A.} and Zhenxing Feng and Guofeng Wang and Gang Wu and Hui Xu",

note = "Publisher Copyright: {\textcopyright} 2021 American Chemical Society.",

year = "2021",

month = apr,

day = "27",

doi = "10.1021/acsnano.0c10637",

language = "English",

volume = "15",

pages = "6886--6899",

journal = "ACS Nano",

issn = "1936-0851",

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TY - JOUR

T1 - Promoting Atomically Dispersed MnN4Sites via Sulfur Doping for Oxygen Reduction

T2 - Unveiling Intrinsic Activity and Degradation in Fuel Cells

AU - Guo, Lin

AU - Hwang, Sooyeon

AU - Li, Boyang

AU - Yang, Fan

AU - Wang, Maoyu

AU - Chen, Mengjie

AU - Yang, Xiaoxuan

AU - Karakalos, Stavros G.

AU - Cullen, David A.

AU - Feng, Zhenxing

AU - Wang, Guofeng

AU - Wu, Gang

AU - Xu, Hui

PY - 2021/4/27

Y1 - 2021/4/27

N2 - Carbon supported and nitrogen coordinated single Mn site (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (vs. Fe), earth abundances (vs. Co), and encouraging activity and stability. However, current Mn-N-C catalysts suffer from high overpotential due to low intrinsic activity and less dense MnN4 sites. Herein, we present a sulfur-doped Mn-N-C catalyst (Mn-N-C-S) synthesized through an effective adsorption-pyrolysis process. Using electron microscopy and X-ray absorption spectroscopy (XAS) techniques, we verify the uniform dispersion of MnN4 sites and confirm the effect of S doping on the Mn-N coordination. The Mn-N-C-S catalyst exhibits a favorable oxygen reduction reaction (ORR) activity in acidic media relative to the S-free Mn-N-C catalyst. The corresponding membrane electrode assembly (MEA) generates enhanced performance with a peak power density of 500 mW cm-2 under a realistic H2/air environment. The constant voltage tests of fuel cells confirm the much-enhanced stability of the Mn-N-C-S catalyst compared to the Fe-N-C and Fe-N-C-S catalysts. The electron microscopy and Fourier transform XAS analyses provide insights into catalyst degradation associated with Mn oxidation and agglomeration. The theoretical calculation elucidates that the promoted ORR activity is mainly attributed to the spatial effect stemmed from the repulsive interaction between the ORR intermediates and adjacent S dopants.

AB - Carbon supported and nitrogen coordinated single Mn site (Mn-N-C) catalysts are the most desirable platinum group metal (PGM)-free cathode catalysts for proton-exchange membrane fuel cells (PEMFCs) due to their insignificant Fenton reactions (vs. Fe), earth abundances (vs. Co), and encouraging activity and stability. However, current Mn-N-C catalysts suffer from high overpotential due to low intrinsic activity and less dense MnN4 sites. Herein, we present a sulfur-doped Mn-N-C catalyst (Mn-N-C-S) synthesized through an effective adsorption-pyrolysis process. Using electron microscopy and X-ray absorption spectroscopy (XAS) techniques, we verify the uniform dispersion of MnN4 sites and confirm the effect of S doping on the Mn-N coordination. The Mn-N-C-S catalyst exhibits a favorable oxygen reduction reaction (ORR) activity in acidic media relative to the S-free Mn-N-C catalyst. The corresponding membrane electrode assembly (MEA) generates enhanced performance with a peak power density of 500 mW cm-2 under a realistic H2/air environment. The constant voltage tests of fuel cells confirm the much-enhanced stability of the Mn-N-C-S catalyst compared to the Fe-N-C and Fe-N-C-S catalysts. The electron microscopy and Fourier transform XAS analyses provide insights into catalyst degradation associated with Mn oxidation and agglomeration. The theoretical calculation elucidates that the promoted ORR activity is mainly attributed to the spatial effect stemmed from the repulsive interaction between the ORR intermediates and adjacent S dopants.

KW - electrocatalysis

KW - fuel cells

KW - oxygen reduction

KW - single metal site

KW - sulfur doping

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DO - 10.1021/acsnano.0c10637

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AN - SCOPUS:85104914023

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VL - 15

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EP - 6899

JO - ACS Nano

JF - ACS Nano

IS - 4

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