Investigation of water generation and accumulation in polymer electrolyte fuel cells using hydro electrochemical impedance Imaging

In depth understanding of water management is essential for the optimization of the performance and durability of polymer electrolyte fuel cells PEFCs . Neutron imaging of liquid water has proven to be a powerful diagnostic technique, but it cannot distinguish between legacy water that has accumulated in the system over time and nascent water recently generated by reaction. Here, a novel technique is introduced to investigate the spatially resolved water exchange characteristics inside PEFCs. Hydro electrochemical impedance imaging HECII involves making a small AC sinusoidal perturbation to a cell and measuring the consequential water generated, using neutron radiographs, associated with the stimulus frequency. Subsequently, a least squares estimation LSE analysis is applied to derive the spatial amplitude ratio and phase shift. This technique provides a complementary view to conventional neutron imaging and provides information on the source and history of water in the system. By selecting a suitable perturbation frequency, HECII can be used to achieve an alternative image contrast and identify different features involved in the water dynamics of operational fuel cell