Operando Sub-Second Tomographic Imaging of Water in PEFC Gas Diffusion Layers

Abstract

The evolution of the liquid water distribution in the gas diffusion layers (GDL) of polymer electrolyte fuel cells (PEFC) during transient operation conditions was visualized by operando sub-second X-ray tomographic microscopy (XTM) at the TOMCAT beamline of the Swiss Light Source. The consequences of the reduced exposure time and lower number of angular steps on image quality are discussed and the temporal and spatial development of the water distribution in the channel and the GDL following a current density variation from 0.1 A/cm² to 1.0 A/cm² are presented. Special focus is put on channel vs. land variations, formation of liquid water percolation paths, their stability over time as well as the influence of the water saturation on diffusive gas transport.