Accurate measurement of the through-plane water content of proton-exchange membranes using neutron radiography

TitleAccurate measurement of the through-plane water content of proton-exchange membranes using neutron radiography
Publication TypeJournal Article
Year of Publication2012
AuthorsHussey, Daniel S., Dusan Spernjak, Adam Z. Weber, Rangachary Mukundan, Joseph Fairweather, Eric L. Brosha, John Davey, Jacob S. Spendelow, David L. Jacobson, and Rodney L. Borup
JournalJournal of Applied Physics
Volume112
Issue10
Pagination104906
Date Published2012
ISSN00218979
Keywordselectrolyte fuel-cells, in-situ, liquid water, microchannel plate detectors, model, nafion, polymer electrolytes, schroeders-paradox, transportation, x-ray-scattering
Abstract

The water sorption of proton-exchange membranes (PEMs) was measured in situ using high-resolution neutron imaging in small-scale fuel cell test sections. A detailed characterization of the measurement uncertainties and corrections associated with the technique is presented. An image-processing procedure resolved a previously reported discrepancy between the measured and predicted membrane water content. With high-resolution neutron-imaging detectors, the water distributions across N1140 and N117 Nafion membranes are resolved in vapor-sorption experiments and during fuel cell and hydrogen-pump operation. The measured in situ water content of a restricted membrane at 80 degrees C is shown to agree with ex situ gravimetric measurements of free-swelling membranes over a water activity range of 0.5 to 1.0 including at liquid equilibration. Schroeder's paradox was verified by in situ water-content measurements which go from a high value at supersaturated or liquid conditions to a lower one with fully saturated vapor. At open circuit and during fuel cell operation, the measured water content indicates that the membrane is operating between the vapor-and liquid-equilibrated states.

DOI10.1063/1.4767118
Short TitleJ. Appl. Phys.
DOI10.1063/1.4767118