A Two-Dimensional Two-Phase Model of a PEM Fuel Cell

Abstract

A two-dimensional, two-phase, steady-state, isothermal model was developed for a fuel cell region consisting of the catalyst and gas diffusion layers bonded to a proton exchange membrane ͑PEM͒. This model extends the previously published one-dimensional model of the gas diffusion and catalyst layers to two dimensions in order to account for the effects of the shoulder of the gas distributor and the electronic conductivity of the solid phase. The new model was validated with experimental results and then used to investigate the effect of the relative dimensions of the shoulders and channels on the cell performance. The effects of the in-plane liquid water permeability and electronic conductivity of the gas diffusion layer on cell performance were also examined. It was found that more channels, smaller shoulder widths on the gas distributor, and higher in-plane water permeability of the gas diffusion layer can enhance the transport of liquid water and oxygen, leading to better cell performance. The in-plane electronic conductivity of the gas diffusion layer was found to have minimal effect on the cell performance. However, a highly nonuniform distribution of electronic current was formed within the gas diffusion and catalyst layers when the in-plane electronic conductivity was low.

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

“…159,311,312,336,337 For accounting for transport into and through the film, a two-stage process is used, comprised of transport through the film [114] and the slow oxygen dissolution process at the gas/ionomer interface, 266,338,339 …”

Water Management in A PEMFC: Water Transport Mechanism and Material Degradation in Gas Diffusion Layers

“…Different MPL mechanisms presented in the literature for performance improvement are summarized below: (i) The MPL increases the back diffusion of water and improves the humidification of the membrane at the anode side [6,9,45,46]; (ii) The MPL increases the hydraulic pressure differential across the membrane due to strong capillary pressure in the MPL, which enhances the water transport from the cathode to the anode [7]; (iii) The MPL reduces the liquid water saturation in the cathode and improves oxygen diffusion [8,10,14,47]; (iv) The MPL increases effective drainage of water from the CL/GDL interface by the capillary forces due to the presence of two different pore sizes [48]; (v) The MPL enhances the formation and transport of the water vapor in the CL and the MPL [49]; (vi) The MPL improves the electrical contact between the GDL and the CL [6]; (vii) The MPL on the cathode neither enhances back diffusion nor increases water removal from the cathode CL to the GDL [50,51]; (viii) The MPL plays a role in controlling the water configuration (or morphology) by limiting the liquid entry locations from the CL to the GDL and in reducing the water saturation in the GDL [52][53][54][55]. The experimental results [50,51] of the net water drag indicate that an MPL on the cathode GDL has a negligible effect on back diffusion and water removal from the cathode CL, despite the fact that an improvement in fuel cell performance was observed by adding an MPL to the cathode GDL.…”

Visualization of Fuel Cell Water Transport and Performance Characterization under Freezing Conditions

“…The critical role of MPL in reducing flooding is a result of the modification of the GDL pore structure (e.g., porosity, pore size distribution, hydrophobicity, and nonuniformity) has received wider acceptance in many recent studies [49][50][51][52]. Weber and Newmann [53] and Lin and Nguyen [54] explained the function of the MPL in reducing the cathode flooding as a capillary barrier, which prevents water from entering the cathode GDL and forces water to permeate from cathode to anode. However, recent experimental studies show that the MPL does not significantly influence the water back-diffusion rate [55,56].…”