Local Structure and Proton Transport in HT-PEFCs Measured with Neutron Scattering
Small angle neutron scattering (SANS) provides insight into the fractal structure of the PA doped membrane on length scales of ~10-500 nm. We present results on the variation of the microscopic structure between different lots of the same material. Small angle X-ray scattering (SAXS) provided insight into the Pt distribution and structure of the electrode layers, a multicomponent system consisting of carbon support, PTFE and the Pt catalyst itself.
With quasielastic neutron scattering (QENS), proton diffusion can be measured on local length scales of about 0.1-10 nm (1). The length scale dependent energy transfer measured with QENS gives insight into local proton transport processes in the PBI membrane and in the adjacent electrode layers and allows to relate microscopic proton mobilities with macroscopic measurements, e.g. of the proton conductivity of the membrane (2).
Complementary techniques such as X-ray scattering, TEM or PFG-NMR round up the picture on a broad range of length scales. With this approach, the proton conducting membrane and the electrode layers of a HT-PEFC is studied and the results then linked to macroscopic properties of the membranes.
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