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 neutron-imaging 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.

Observation of Preferential Pathways for Oxygen Removal through Porous Transport Layers of Polymer Electrolyte Water Electrolyzers

“…Zlobinski et al. ( Zlobinski et al., 2020 ) and Seweryn et al. ( Seweryn et al., 2016 ) were able to quantify water saturation in the PTL via neutron radiography.…”

“…Zlobinski et al. ( Zlobinski et al., 2020 ) suggest that the pore network inherent to a porous media – in their case it was sintered Ti PTL – could account for the gas traps. Gas traps are areas of either high hydrophobicity or hydrophilicity inherent to a porous media.…”

“…As an effort to better understand the two-phase transport behavior in the PTL, studies ( Abdin et al., 2015 ; Dedigama et al., 2014 ; García-Valverde et al., 2012 ; Han et al., 2016 ; Kadyk et al., 2016 ; Kang et al., 2018 ; 2017 ; Kim et al., 2020 ; Lee et al., 2020a ; Lee et al., 2017 ; Leonard et al., 2020 ; 2018 ; Lopata et al., 2020 ; Schuler et al., 2019 ; Seweryn et al., 2016 ; Suermann et al., 2017 ; Zlobinski et al., 2020 ) have focused on using imaging techniques to investigate the evolution and transport of oxygen in electrolyzers, including optical, neutron, or X-ray imaging, as well as computational studies. Optical microscopy was utilized by Dedigama et al.…”

“…Zlobinski et al. ( Zlobinski et al., 2020 ) have studied the effect of the two-phase flow behavior within the PTLs under steady state and dynamic load of the electrolyzer by using a neutron imaging with high spatial resolution (6 μm) and relatively high temporal resolution (1 s exposure time). They concluded that the two-phase flow in the PTLs is purely capillary driven for a wide range of operating conditions and that viscous forces are negligible.…”

An Analytical Model for Liquid and Gas Diffusion Layers in Electrolyzers and Fuel Cells

“…[29][30][31][32] Various researchers in the past have studied the two-phase flow in the diffusion layer of the electrochemical cells through numerical simulations. [13][14][15][16][17]19,[33][34][35] and experiments 9,[36][37][38][39] However, far fewer attempts have been made to establish analytical relations for limiting currents, effective diffusivity and saturation in a diffusion layer based on two-phase flow. 40,41 This work is an attempt to provide a new modeling perspective to the researchers in the electrochemical engineering community and provide explicit formulae that enable quick engineering estimates, can be used for analytical optimization, and in real-time energy management systems.…”