Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC

Luigi Osmieri; Rajesh K. Ahluwalia; Xiaohua Wang; Hoon T. Chung; Xi Yin; A. Jeremy Kropf; Jaehyung Park; David A. Cullen; Karren L. More; Piotr Zelenay; Deborah J. Myers; K. C. Neyerlin

doi:10.1016/j.apcatb.2019.117929

Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC

Luigi Osmieri, Rajesh K. Ahluwalia, Xiaohua Wang, Hoon T. Chung, Xi Yin, A. Jeremy Kropf, Jaehyung Park, David A. Cullen, Karren L. More, Piotr Zelenay, Deborah J. Myers, K. C. Neyerlin

electron Microscopy and Microanalysis

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

72 Scopus citations

Abstract

In the past decade the notable effort placed on improving intrinsic electrochemical kinetics of platinum group metal (PGM)-free electrocatalysts for the oxygen reduction reaction (ORR) has led to a significant improvement in both performance and understanding of this class of electrocatalysts. However, a limited amount of this development and understanding has been undertaken using operando electrochemical diagnostics at the membrane electrode assembly (MEA) level. In this work, the operando ORR kinetics on an atomically dispersed iron-nitrogen-carbon ((AD)Fe-N-C) PGM-free electrocatalyst have been examined to extract the reaction order and the activation energy of the ORR. The experiments were carefully designed to ensure the stability/predictability of the electrocatalyst during the data collection process and thus validate the relevance of the values obtained for the aforementioned parameters. A kinetic model that considers a potential-dependent availability of active sites (θ) is proposed. Active site availability is shown to be a function of both the change in the oxidation state (n_R) and the redox potential at which the metal center transitions from a higher oxidation state to a lower one The resulting model fitting parameters for n_R and (0.71 and 0.788 V, respectively) obtained from the analysis of operando data correlate well with those from in situ X-ray absorption near edge structure measurements (n_R = 0.57) and in situ cyclic voltammetry measurements (0.75 V < < 0.8 V) in the MEA environment. The resulting model provides an excellent fit of MEA performance across the range of pressures, temperatures, and potentials under which the data were collected.

Original language	English
Article number	117929
Journal	Applied Catalysis B: Environmental
Volume	257
DOIs	https://doi.org/10.1016/j.apcatb.2019.117929
State	Published - Nov 15 2019

Funding

This work was authored in part by Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Research performed as part of the Electrocatalysis Consortium (ElectroCat), established as part of the Energy Materials Network, which is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office (FCTO). Microscopy performed as part of a user project at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, which is a U.S. Department of Energy, Office of Science User Facility. This research used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. The authors wish to thank Evan Wegener and Nancy Kariuki for their assistance setting up the X-ray absorption experiments as well as Dimitrios Papageorgopoulos and Simon Thompson in FCTO at DOE.

Keywords

Activation energy
Fe-N-C catalyst
Modeling
Polymer electrolyte fuel cell
Reaction order

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Osmieri, L., Ahluwalia, R. K., Wang, X., Chung, H. T., Yin, X., Kropf, A. J., Park, J., Cullen, D. A., More, K. L., Zelenay, P., Myers, D. J., & Neyerlin, K. C. (2019). Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC. Applied Catalysis B: Environmental, 257, Article 117929. https://doi.org/10.1016/j.apcatb.2019.117929

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title = "Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC",

abstract = "In the past decade the notable effort placed on improving intrinsic electrochemical kinetics of platinum group metal (PGM)-free electrocatalysts for the oxygen reduction reaction (ORR) has led to a significant improvement in both performance and understanding of this class of electrocatalysts. However, a limited amount of this development and understanding has been undertaken using operando electrochemical diagnostics at the membrane electrode assembly (MEA) level. In this work, the operando ORR kinetics on an atomically dispersed iron-nitrogen-carbon ((AD)Fe-N-C) PGM-free electrocatalyst have been examined to extract the reaction order and the activation energy of the ORR. The experiments were carefully designed to ensure the stability/predictability of the electrocatalyst during the data collection process and thus validate the relevance of the values obtained for the aforementioned parameters. A kinetic model that considers a potential-dependent availability of active sites (θ) is proposed. Active site availability is shown to be a function of both the change in the oxidation state (nR) and the redox potential at which the metal center transitions from a higher oxidation state to a lower one The resulting model fitting parameters for nR and (0.71 and 0.788 V, respectively) obtained from the analysis of operando data correlate well with those from in situ X-ray absorption near edge structure measurements (nR = 0.57) and in situ cyclic voltammetry measurements (0.75 V < < 0.8 V) in the MEA environment. The resulting model provides an excellent fit of MEA performance across the range of pressures, temperatures, and potentials under which the data were collected.",

keywords = "Activation energy, Fe-N-C catalyst, Modeling, Polymer electrolyte fuel cell, Reaction order",

author = "Luigi Osmieri and Ahluwalia, \{Rajesh K.\} and Xiaohua Wang and Chung, \{Hoon T.\} and Xi Yin and Kropf, \{A. Jeremy\} and Jaehyung Park and Cullen, \{David A.\} and More, \{Karren L.\} and Piotr Zelenay and Myers, \{Deborah J.\} and Neyerlin, \{K. C.\}",

note = "Publisher Copyright: {\textcopyright} 2019",

year = "2019",

month = nov,

day = "15",

doi = "10.1016/j.apcatb.2019.117929",

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Osmieri, L, Ahluwalia, RK, Wang, X, Chung, HT, Yin, X, Kropf, AJ, Park, J, Cullen, DA , More, KL, Zelenay, P, Myers, DJ & Neyerlin, KC 2019, 'Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC', Applied Catalysis B: Environmental, vol. 257, 117929. https://doi.org/10.1016/j.apcatb.2019.117929

TY - JOUR

T1 - Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC

AU - Osmieri, Luigi

AU - Ahluwalia, Rajesh K.

AU - Wang, Xiaohua

AU - Chung, Hoon T.

AU - Yin, Xi

AU - Kropf, A. Jeremy

AU - Park, Jaehyung

AU - Cullen, David A.

AU - More, Karren L.

AU - Zelenay, Piotr

AU - Myers, Deborah J.

AU - Neyerlin, K. C.

PY - 2019/11/15

Y1 - 2019/11/15

N2 - In the past decade the notable effort placed on improving intrinsic electrochemical kinetics of platinum group metal (PGM)-free electrocatalysts for the oxygen reduction reaction (ORR) has led to a significant improvement in both performance and understanding of this class of electrocatalysts. However, a limited amount of this development and understanding has been undertaken using operando electrochemical diagnostics at the membrane electrode assembly (MEA) level. In this work, the operando ORR kinetics on an atomically dispersed iron-nitrogen-carbon ((AD)Fe-N-C) PGM-free electrocatalyst have been examined to extract the reaction order and the activation energy of the ORR. The experiments were carefully designed to ensure the stability/predictability of the electrocatalyst during the data collection process and thus validate the relevance of the values obtained for the aforementioned parameters. A kinetic model that considers a potential-dependent availability of active sites (θ) is proposed. Active site availability is shown to be a function of both the change in the oxidation state (nR) and the redox potential at which the metal center transitions from a higher oxidation state to a lower one The resulting model fitting parameters for nR and (0.71 and 0.788 V, respectively) obtained from the analysis of operando data correlate well with those from in situ X-ray absorption near edge structure measurements (nR = 0.57) and in situ cyclic voltammetry measurements (0.75 V < < 0.8 V) in the MEA environment. The resulting model provides an excellent fit of MEA performance across the range of pressures, temperatures, and potentials under which the data were collected.

AB - In the past decade the notable effort placed on improving intrinsic electrochemical kinetics of platinum group metal (PGM)-free electrocatalysts for the oxygen reduction reaction (ORR) has led to a significant improvement in both performance and understanding of this class of electrocatalysts. However, a limited amount of this development and understanding has been undertaken using operando electrochemical diagnostics at the membrane electrode assembly (MEA) level. In this work, the operando ORR kinetics on an atomically dispersed iron-nitrogen-carbon ((AD)Fe-N-C) PGM-free electrocatalyst have been examined to extract the reaction order and the activation energy of the ORR. The experiments were carefully designed to ensure the stability/predictability of the electrocatalyst during the data collection process and thus validate the relevance of the values obtained for the aforementioned parameters. A kinetic model that considers a potential-dependent availability of active sites (θ) is proposed. Active site availability is shown to be a function of both the change in the oxidation state (nR) and the redox potential at which the metal center transitions from a higher oxidation state to a lower one The resulting model fitting parameters for nR and (0.71 and 0.788 V, respectively) obtained from the analysis of operando data correlate well with those from in situ X-ray absorption near edge structure measurements (nR = 0.57) and in situ cyclic voltammetry measurements (0.75 V < < 0.8 V) in the MEA environment. The resulting model provides an excellent fit of MEA performance across the range of pressures, temperatures, and potentials under which the data were collected.

KW - Activation energy

KW - Fe-N-C catalyst

KW - Modeling

KW - Polymer electrolyte fuel cell

KW - Reaction order

UR - https://www.scopus.com/pages/publications/85068939530

U2 - 10.1016/j.apcatb.2019.117929

DO - 10.1016/j.apcatb.2019.117929

M3 - Article

AN - SCOPUS:85068939530

SN - 0926-3373

VL - 257

JO - Applied Catalysis B: Environmental

JF - Applied Catalysis B: Environmental

M1 - 117929

ER -

Elucidation of Fe-N-C electrocatalyst active site functionality via in-situ X-ray absorption and operando determination of oxygen reduction reaction kinetics in a PEFC

Abstract

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Keywords

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