Evaluation of Imaging Techniques Applied to Water Management Research in PEMFCs

Water management in proton exchange membrane fuel cells (PEMFCs) is critical in efficient operation of fuel cells during normal operation as well as purge and start-up conditions. Insufficient membrane hydration impedes the flow of protons and an overabundance of water obstructs the flow of reactants in the gas diffusion layer (GDL) and in gas distribution channels. These two extremes of water content in PEMFCs significantly reduce performance and efficiency, causing material degradation and potential failure. Visualization and quantitative measurement of water content in PEMFCs lead to greater comprehension of water distribution and transport processes. A wide variety of imaging techniques have been employed in literature to reveal water distribution and transport processes on both macroscale and microscale. The presented techniques utilize visible, infrared, X-rays, fluorescence microscopy, nuclear magnetic resonance (NMR), and neutron radiography to visualize water, measure temperature distributions, and quantify water content. Each imaging technique has intrinsic advantages, disadvantages, and limitations for water detection and will be discussed. A critical evaluation of these techniques and their suitability for visualization of specific components of PEMFC are also discussed.