Transient observation of 2H labeled species in an operating PEFC using neutron radiography

High resolution neutron radiography was used to observe the time resolved distribution of 2H nuclei in the membrane of an operating polymer electrolyte fuel cell (PEFC) after changing the anode gas from 1H2 to 2H2. The rate of replacement and the distribution of 2H nuclei shortly after the change of the anode gas were found to be independent of the applied current density. This behavior can be explained by a high exchange current density of the hydrogen oxidation reaction (HOR), the uptake of 2H nuclei in the membrane being limited by diffusive transport. A simple calculation as well as qualitative analysis is given to support this explanation.