Transient and Steady State Two-Phase Flow in Anodic Porous Transport Layer of Proton Exchange Membrane Water Electrolyzer

Abstract

Mass transport losses are one of the least understood contributors to the over potential in proton exchange membrane water electrolyzers. In order to explore the possible contribution of porous media two phase flow to these losses, we have used neutronimaging techniques and took a closer look at water and gas distribution profiles at various current densities, ranging from kinetic to mass transport-governed regions at ambient and elevated pressures. Gas volume and velocity have been computed through quantified neutron images and the two-phase flow regime has been identified. Using sub-second imaging, information on dynamics of gas pathway establishment and re-imbibition during startup and shutdown of electrolyzers has been acquired. Using X-ray tomography and simulated mercury intrusion porosimetry coupled with capillary pressure calculations, the hydrophilicity of the internal surfaces of the porous transport layer material has been determined.