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Title: Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus on chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting protonmore » transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [3] ; ORCiD logo [3] ;  [1] ; ORCiD logo [1]
  1. Univ. of New Mexico, Albuquerque, NM (United States)
  2. Univ. of New Mexico, Albuquerque, NM (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Report Number(s):
LA-UR-17-24807
Journal ID: ISSN 2574-0962
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 1; Journal ID: ISSN 2574-0962
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
National Science Foundation (NSF); USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; material science; catalyst−ionomer interactions; catalytic layer chemistry; PGM-free electrocatalyst; transition metal−nitrogen−carbon; XPS
OSTI Identifier:
1418766

Artyushkova, Kateryna, Workman, Michael J., Matanovic, Ivana, Dzara, Michael J., Ngo, Chilan, Pylypenko, Svitlana, Serov, Alexey, and Atanassov, Plamen. Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts. United States: N. p., Web. doi:10.1021/acsaem.7b00002.
Artyushkova, Kateryna, Workman, Michael J., Matanovic, Ivana, Dzara, Michael J., Ngo, Chilan, Pylypenko, Svitlana, Serov, Alexey, & Atanassov, Plamen. Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts. United States. doi:10.1021/acsaem.7b00002.
Artyushkova, Kateryna, Workman, Michael J., Matanovic, Ivana, Dzara, Michael J., Ngo, Chilan, Pylypenko, Svitlana, Serov, Alexey, and Atanassov, Plamen. 2017. "Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts". United States. doi:10.1021/acsaem.7b00002.
@article{osti_1418766,
title = {Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts},
author = {Artyushkova, Kateryna and Workman, Michael J. and Matanovic, Ivana and Dzara, Michael J. and Ngo, Chilan and Pylypenko, Svitlana and Serov, Alexey and Atanassov, Plamen},
abstractNote = {The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus on chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.},
doi = {10.1021/acsaem.7b00002},
journal = {ACS Applied Energy Materials},
number = 1,
volume = 1,
place = {United States},
year = {2017},
month = {12}
}