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Title: Effects of Porous Carbon Morphology, Agglomerate Structure and Relative Humidity on Local O2 Transport Resistance

Journal Article · · Journal of the Electrochemical Society
DOI:https://doi.org/10.1149/2.0082001JES· OSTI ID:1570441

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.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE) - Office of Fuel Cell Technologies (FCTO)
DOE Contract Number:
AC02-06CH11357
OSTI ID:
1570441
Journal Information:
Journal of the Electrochemical Society, Vol. 167, Issue 1; ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English

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