Effects of Cathode GDL Gradient Porosity Distribution along the Flow Channel Direction on Gas–Liquid Transport and Performance of PEMFC

Abstract

The gas diffusion layer (GDL) is an important component of proton exchange membrane fuel cells (PEMFCs), and its porosity distribution has considerable effects on the transport properties and durability of PEMFCs. A 3-D two-phase flow computation fluid dynamics model was developed in this study, to numerically investigate the effects of three different porosity distributions in a cathode GDL: gradient-increasing (Case 1), gradient-decreasing (Case 3), and uniform constant (Case 2), on the gas–liquid transport and performance of PEMFCs; the novelty lies in the porosity gradient being along the channel direction, and the physical properties of the GDL related to porosity were modified accordingly. The results showed that at a high current density (2400 mA·cm−2), the GDL of Case 1 had a gas velocity of up to 0.5 cm·s−1 along the channel direction. The liquid water in the membrane electrode assembly could be easily removed because of the larger gas velocity and capillary pressure, resulting in a higher oxygen concentration in the GDL and the catalyst layer. Therefore, the cell performance increased. The voltage in Case 1 increased by 8% and 71% compared to Cases 2 and 3, respectively. In addition, this could ameliorate the distribution uniformity of the dissolved water and the current density in the membrane along the channel direction, which was beneficial for the durability of the PEMFC. The distribution of the GDL porosity at lower current densities had a less significant effect on the cell performance. The findings of this study may provide significant guidance for the design and optimization of the GDL in PEMFCs.

Study on Self-Humidification in PEMFC with Crossed Flow Channels and an Ultra-Thin Membrane

“…where k ele , k ion , ϕ ele , ϕ ion , S ele , S ion represent electron conductivity, proton conductivity, solid phase potential, membrane potential, electron source term, and proton source term, respectively. The description of the details of all the source terms can be referred to in [43,44].…”

Analytical analysis of the effects of the porosity distribution on liquid-water management in the cathode of a polymer electrolyte membrane fuel cell

“…They investigate the effects of wetting characteristics of the GDL, the current density, and the GDL porosity on the liquid water saturation and the performance of the PEM fuel cell. Many other experimental and numerical works [25][26][27][28][29][30][31] demonstrated that a gradient in the porosity of the GDL improves liquid water removal and gas reactant transport in the GDL of the PEMFC.…”

Carbon Fiber Papers Prepared by Wet-Laid Technique Using PVB/PF Composite Fibers as the Binders

“…Carbon fiber paper (CFP), with the properties of high porosity, good electrical conductivity, excellent mechanical strength, outstanding corrosion resistance, etc. [1], has become the ideal material as a gas diffusion layer (GDL) of proton exchange membrane fuel cells (PEMFCs) and provides reactant and product permeability, transport of electrons, and heat and support of membrane electrode assembly (MEA) [2][3][4].…”