Towards Monitoring Water Content in Membrane Electrode Assembly of Low Temperature Fuel Cells Using Ultrasound

Low temperature fuel cells (LTFCs) present promising technical solutions for enabling broad applications of green Hydrogen energy. However, the efficiencies and durability of LTFCs are limited by the dynamic water evolution and transport, especially when they are operated at high current densities. Developing water monitoring techniques therefore presents a crucial strategy for optimizing the designs and operating schemes of LTFCs, and eventually overcoming such water management issues. This work explores the possibilities of using ultrasonic techniques to investigate the water contents in the gas diffusion layers (GDL), as one of the key components of the membrane electrode assembly in LTFCs. For this purpose, we numerically and experimentally investigated the propagation of longitudinal mode ultrasonic waves in GDLs at different water saturation levels. The numerical simulations and experimental investigations both reveal the changes in the speed of sound and acoustic attenuation coefficient with respect to the water saturation level of the GDL. These physical effects open new horizons for developing simplified and cost-effective ultrasound based water monitoring systems towards applications in operating LTFCs.