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Title: Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O 2 Transport Resistance

Abstract

The morphology and ionomer distribution in a polymer electrolyte membrane fuel cell (PEMFC) cathode electrode are quantified with nano-scale resolution X-ray computed tomography (nano-CT). Using the nano-CT data, different shapes, sizes and compositions of agglomerates are extracted. Statistical information from multiple techniques, including transmission electron microscopy (TEM), ultra-small angle X-ray scattering (USAXS), and Brunauer-Emmett-Teller (BET) gas adsorption porosimetry are combined to reconstruct the high surface-area porous carbon (HSC) support, exterior (on the surface of carbon) and interior (inside carbon pores) catalysts, ionomer, and primary pores in the extracted agglomerates. Application of capillary condensation theory to the reconstructed agglomerate structure is shown to accurately represent the experimentally-observed relative humidity (RH) dependence of the electrochemically-active surface area (ECA). Direct numerical simulations show that the high local O 2 transport resistance ( R O2) under dry conditions is mainly associated with the reduced ECA. We demonstrate that the agglomerate shape and size affect R O2 only if the primary pores are poorly accessible (i.e., capillary-condensed water filled primary pores). We also evaluate the effect of transport to the interior catalyst particles on R O2.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE) - Office of Fuel Cell Technologies (FCTO)
OSTI Identifier:
1570441
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 167; Journal Issue: 1; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English
Subject:
PEMFC catalyst layer; PEMFC electrode; RH dependence of ECA; agglomerate; agglomerate model; high surface area carbon morphology; local O2 transport resistance

Citation Formats

Cetinbas, Firat C., Ahluwalia, Rajesh K., Kariuki, Nancy N., De Andrade, Vincent, and Myers, Deborah J. Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O2 Transport Resistance. United States: N. p., 2019. Web. doi:10.1149/2.0082001JES.
Cetinbas, Firat C., Ahluwalia, Rajesh K., Kariuki, Nancy N., De Andrade, Vincent, & Myers, Deborah J. Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O2 Transport Resistance. United States. doi:10.1149/2.0082001JES.
Cetinbas, Firat C., Ahluwalia, Rajesh K., Kariuki, Nancy N., De Andrade, Vincent, and Myers, Deborah J. Mon . "Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O2 Transport Resistance". United States. doi:10.1149/2.0082001JES.
@article{osti_1570441,
title = {Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O2 Transport Resistance},
author = {Cetinbas, Firat C. and Ahluwalia, Rajesh K. and Kariuki, Nancy N. and De Andrade, Vincent and Myers, Deborah J.},
abstractNote = {The morphology and ionomer distribution in a polymer electrolyte membrane fuel cell (PEMFC) cathode electrode are quantified with nano-scale resolution X-ray computed tomography (nano-CT). Using the nano-CT data, different shapes, sizes and compositions of agglomerates are extracted. Statistical information from multiple techniques, including transmission electron microscopy (TEM), ultra-small angle X-ray scattering (USAXS), and Brunauer-Emmett-Teller (BET) gas adsorption porosimetry are combined to reconstruct the high surface-area porous carbon (HSC) support, exterior (on the surface of carbon) and interior (inside carbon pores) catalysts, ionomer, and primary pores in the extracted agglomerates. Application of capillary condensation theory to the reconstructed agglomerate structure is shown to accurately represent the experimentally-observed relative humidity (RH) dependence of the electrochemically-active surface area (ECA). Direct numerical simulations show that the high local O2 transport resistance (RO2) under dry conditions is mainly associated with the reduced ECA. We demonstrate that the agglomerate shape and size affect RO2 only if the primary pores are poorly accessible (i.e., capillary-condensed water filled primary pores). We also evaluate the effect of transport to the interior catalyst particles on RO2.},
doi = {10.1149/2.0082001JES},
journal = {Journal of the Electrochemical Society},
issn = {0013-4651},
number = 1,
volume = 167,
place = {United States},
year = {2019},
month = {9}
}