Effects of membrane electrode assembly properties on two-phase transport and performance in proton exchange membrane electrolyzer cells

Abstract

A mathematical model is developed to simulate the two-phase transport behaviors and the performance in a proton exchange membrane electrolyzer cell (PEMEC). The parameter effects of the liquid/gas diffusion layer (LGDL), including contact angle, porosity, and pore size, on the capillary flow and liquid water distribution are comprehensively studied.In addition, the effects of the LGDL pore size and membrane humidity on the performance and efficiency of PEMEC are also investigated. The results indicate thatLGDL properties have significant impacts on its capillary pressure and liquid water distribution, which consequently affects the two-phase transport and performance in the PEMEC. Increasing the porosity and/or pore size or decreasing the contact angle can enhance the liquid water saturation along the LGDL thickness direction, and consequently improve the performance and efficiency of PEMEC. The variation of PEM humidity contributes to a portion of the cell ohmic loss as well.

Thin liquid/gas diffusion layers for high-efficiency hydrogen production from water splitting

“…With optimal designs of thickness, porosity and pore size/shape, a better PEMEC performance can be achieved with thin structured LGDLs by taking advantage of well-tunable and straight-through micropores, while maintaining excellent properties for two phase flow in LGDLs. For conventionalLGDLs of titanium felts with interconnect pore structure at a thickness of 350 µm and a mean pore size of about 100 µm, liquid water needs large capillary pressure to get through the titanium felt LGDL and reach the interfaces of LGDL and the catalyst layer -the reaction sites , which has been demonstrated with two-phase modeling in our group[50]. In addition, the thickness reduction of the felt-based LGDLs has been limited by felt diameters, felt loading quantities, and required LGDL electrical/mechanical/interfacial properties, as addressed previously.…”

“…Those plane-surface contacts significantly reduce the CL/LGDL/BP interfacial resistances, which dominate the total ohmic resistances in a PEMEC [10,50]. This is the main reason that the total ohmic resistance with titanium thin LGDL is significantly lower compared to the titanium felt…”

“…Vthermal is about 1.4841V [49,50]. As shown in Figure 4, at a current density of 2 A/cm 2 , the PEMEC efficiency is increased from 79% with the titanium conventional felt LGDL to 88% with titanium thin/well tunable LGDL.…”

Mass transport in polymer electrolyte membrane water electrolyser liquid-gas diffusion layers: A combined neutron imaging and X-ray computed tomography study

“…The existence of a concentration (or mass transport) overpotential in polymer electrolyte membrane water electrolysers (PEMWEs) is a major cause of performance limitation when operating at high current densities [1]. However, detailed mechanistic elucidation and reliable quantification of this effect is limited and tend to be empirical in nature [2][3][4][5]. The concentration overpotential primarily occurs at the anode at high current densities, when the generation of oxygen gas via the consumption of water exceeds the rate at which water can be supplied through flow channels and liquid-gas diffusion layers (LGDLs).…”

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

“…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.…”