Small angle scattering with X-rays (SAXS) and neutrons (SANS) is used as a powerful tool to investigate different components of fuel cells or even groups such as membrane electrode assemblies (MEAs) (1,2). In particular, the structure of electrode layers and membrane electrode assemblies of High Temperature Polymer Electrolyte Fuel Cells (HT-PEFCs) is studied in this contribution with neutron and x-ray scattering (1). Electrode layers in different stages of preparation, pure and doped with different amounts of phosphoric acid have been studied with SAXS. Structural changes have been observed with the addition of phosphoric acid, which is used in this type of HT-PEFC as proton conducting electrolyte.

Details of the phosphoric acid distribution and possible void distribution in electrode layers have been obtained with contrast variation experiments in small angle neutron scattering, where the different parts of the sample can be highlighted by exchanging hydrogen with deuterium, here in the phosphoric acid.

An outlook will point at the strength of quasielastic neutron scattering experiments to shed light on the proton diffusion on different length scales in the range of 0.1-10 nm, as a microscopic equivalent to the macroscopic conductivity, and it will address the question of what can be retrieved from a multicomponent system such as the different parts of a fuel cell.

1. M. Khaneft, O. Holderer, O. Ivanova, W. Lüke, E. Kentzinger, M.S. Appavou, R. Zorn, W. Lehnert, Fuel Cells 16 (2016), 406 – 413
2. O. Holderer, O. Ivanova, B. Hopfenmüller, M. Zamponi, W. Maier, A. Majerus, W. Lehnert, M. Monkenbusch, R. Zorn, Int. J. Hydrogen Energy 39 (2014) 21657 – 21662