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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 (..theta..) 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 (ER). 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 thosemore » from in situ X-ray absorption near edge structure measurements (nR = 0.57) and in situ cyclic voltammetry measurements (0.75 V < ER < 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.« less

Authors:
; ; ; ; ORCiD logo; ; ; ; ; ; ; ORCiD logo
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
OSTI Identifier:
1561590
Alternate Identifier(s):
OSTI ID: 1545258
Report Number(s):
NREL/JA-5900-73102
Journal ID: ISSN 0926-3373
Grant/Contract Number:  
AC36-08GO28308; AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Applied Catalysis B: Environmental
Additional Journal Information:
Journal Volume: 257; Journal Issue: C; Journal ID: ISSN 0926-3373
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; Fe-N-C catalyst; polymer electrolyte fuel cell; reaction order; activation energy; modeling; 25 ENERGY STORAGE

Citation Formats

Osmieri, Luigi, Ahluwalia, Rajesh K., Wang, Xiaohua, Chung, Hoon T., Yin, Xi, Kropf, A. Jeremy, Park, Jaehyung, Cullen, David A., More, Karren L., Zelenay, Piotr, Myers, Deborah J., and Neyerlin, K. C. 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. United States: N. p., 2019. Web. doi:10.1016/j.apcatb.2019.117929.
Osmieri, Luigi, Ahluwalia, Rajesh K., Wang, Xiaohua, Chung, Hoon T., Yin, Xi, Kropf, A. Jeremy, Park, Jaehyung, Cullen, David A., More, Karren L., Zelenay, Piotr, Myers, Deborah J., & Neyerlin, K. C. 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. United States. doi:10.1016/j.apcatb.2019.117929.
Osmieri, Luigi, Ahluwalia, Rajesh K., Wang, Xiaohua, Chung, Hoon T., Yin, Xi, Kropf, A. Jeremy, Park, Jaehyung, Cullen, David A., More, Karren L., Zelenay, Piotr, Myers, Deborah J., and Neyerlin, K. C. Fri . "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". United States. doi:10.1016/j.apcatb.2019.117929.
@article{osti_1561590,
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},
author = {Osmieri, Luigi and Ahluwalia, Rajesh K. and Wang, Xiaohua and Chung, Hoon T. and Yin, Xi and Kropf, A. Jeremy and Park, Jaehyung and Cullen, David A. and More, Karren L. and Zelenay, Piotr and Myers, Deborah J. and Neyerlin, K. C.},
abstractNote = {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 (..theta..) 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 (ER). 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 < ER < 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.},
doi = {10.1016/j.apcatb.2019.117929},
journal = {Applied Catalysis B: Environmental},
number = C,
volume = 257,
place = {United States},
year = {2019},
month = {11}
}

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