Capillary Pressure Evolution in Operating Polymer Electrolyte Fuel Cells

Abstract

Capillary pressure driven transport of liquid water through the gas diffusion layer has been studied in various ex-situ, in-situ and operando setups. So far, insights into the actual capillary pressure has been limited to ex-situ experiments. Advanced image analysis tools like 3D interfacial curvature analysis, that have been developed to determine the capillary pressure in digital rock physics investigations [1], were recently applied to ex-situ X-ray tomographic microscopy (XTM) imaging experiments of the droplet release cycle in polymer electrolyte fuel cells [2]. Within this presentation, we will give insights into the water cluster formation using operando XTM imaging at a frequency of 1 Hz from liquid water emergence at the catalyst layer – gas diffusion layer interface until liquid water breakthrough and droplet formation in the gas channel of the flow field. With the help of interfacial curvature analysis as well as volume of fluid simulations [3], it was possible to obtain information about the capillary pressure evolution in the water phase [4]. We will explain the nuanced interactions of water volume and pressure evolution during the growth of the percolation network within the GDL and the droplet formation and comment on the observed distinct differences to ex-situ pressure evaluations.