Utilization of 3-D Volume of Fluid Simulations to Understand Oxygen Evolution through Multilayer Porous Transport Layers for PEMWE Improvement

Abstract

In this work, direct numerical modeling techniques were applied to 3-D generated porous transport layers (PTL), with the addition of a microporous layer (MPL), to understand the effect pore structure has on oxygen evolution. Proton Exchange Membrane Water Electrolyzers rely on PTLs to remove oxygen from the catalyst layer. Traditionally, an MPL is added to the PTL surface in contact with the catalyst layer. This creates a bilayer PTL, which is believed to improve oxygen removal, while maintaining liquid saturation. Two questions arise when creating a PTL sample for PEMWE application. First, how thick should the MPL be to achieve adequate oxygen removal? Second, is a bilayer PTL sufficient, or does a multilayer PTL result in improved oxygen removal?The objectives of this work are to observe the influence that the MPL has on oxygen transport, the effect of the MPL on oxygen removal when compared to a single layer PTL, determine an ideal MPL to PTL ratio, and identify if multilayer PTLs aid in oxygen removal. Each sample is created through an improved image processing technique that eliminates the need for interface communication when meshing. This process allows for multilayer PTL structures to be created as one geometry. Due to the improved imaging technique, meshing of these complex structures is possible. The Finite Volume Method combined with a volume of fluid model was used to simulate two phase flow, liquid water and gaseous oxygen, through all PTL samples. Each PTL/MPL combination has three different MPL thickness, which corresponds to a PTL/MPL ratio of 90:10, 80:20, and 70:30. Bilayer, trilayer, and quadlayer PTL samples were also studied. Oxygen bubble evolution, growth, and surface interaction through all sample microstructures was observed. In-plane and through-plane permeability, liquid saturation, and liquid/gas interfacial area were calculated from simulation results. Findings from this work will provide insight into ideal MPL thickness and number of MPL layers for improved oxygen removal inside PEMWEs.