Water Management in Low Temperature Fuel Cells through in-Operando X-Ray Computed Tomography

Abstract

For polymer-electrolyte fuel cells (PEFCs) and anion exchange membrane fuel cells (AEMFCs) optimal water management is essential. During start-up and at low operating temperatures, where water is present in a liquid form, it can block reactant delivery to electrocatalyst sites, resulting in significant mass-transport losses, flooding and low fuel cell power densities. Using synchrotron X-ray computed tomography (CT) we have previously shown how water transport properties depend on porous materials morphology and chemical composition, as well as cell compression.1-3 These ex- and in-situ studies isolate specific porous membrane / electrode assembly (MEA) component’s effect on water management (such as micro-porous (MPL) or gas-diffusion layer (GDL)). To understand water transport under operating conditions we use in-operandoX-ray CT studies, where water distribution is observed under various steady-state conditions. In-operando single serpentine channel (1x1 mm) fuel cell testing hardware for synchrotron X-ray CT is used with active area of 1 cm2. Steady-state water generation and removal is observed in PEFCs and AEMFCs for temperature of 30oC with chronoamperometric holds at current densities ranges of 20 – 100 mA/cm2. Furthermore, comparison of water distribution in PGM and PGM-free catalysts for both type of fuel-cells will be presented. In all of these systems water pooling is observed at the component interfaces, indicating the importance of interfaces design. Acknowledgment: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.