Combined Operando High Resolution SANS and Neutron Imaging Reveals In-situ Local Water Distribution in an Operating Fuel Cell

By producing electricity and heat from hydrogen with high yield and with only water as a byproduct, the Proton Exchange Membrane Fuel cell (PEMFC) is one of the most promising carbon-free alternative energy conversion system for transportation and stationary applications. Water management is a key issue in these systems as it drives performance, thus preventing their large scale implementation. Indeed, numerous studies have shown that a proper water balance should be achieved in operation, i.e. water must be present in large quantities in the proton conducting polymer - or ionomer - membrane, while other components must contain only moderate amounts of it. In this paper, we explore the in-situ water distribution of water in a working fuel cell using a dual Neutron Imaging and high resolution Small Angle Neutron Scattering approach, allowing to quantify both liquid water and polymer membrane swelling on a μm scale, i.e. at the rib-channel level. We observed that liquid water tends to accumulate sharply at ...