Liquid Water Characteristics in the Compressed Gradient Porosity Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells Using the Lattice Boltzmann Method

Abstract

The mitigation of water flooding in the gas diffusion layer (GDL) at relatively high current densities is indispensable for enhancing the performance of proton exchange membrane fuel cells (PEMFCs). In this paper, a 2D multicomponent LBM model is developed to investigate the effects of porosity distribution and compression on the liquid water dynamic behaviors and distribution. The results suggest that adopting the gradient GDL structure with increasing porosity along the thickness direction significantly reduces the breakthrough time and steady–state total water saturation inside the GDL. Moreover, the positive gradient structure reaches the highest breakthrough time and water saturation at 10% compression ratio (CR) when the GDL is compressed, and the corresponding values decrease with further increase of the CR. Considering the breakthrough time, total water saturation and water distribution at the entrance of the GDL at the same time, the gradient structure with continuously increasing porosity can perform better water management capacity at 30% CR. This paper is useful for understanding the two–phase process in a gradient GDL structure and provides guidance for future design and manufacturing.

Experimental Investigation into the Performance of PEMFCs with Three Different Hydrogen Recirculation Schemes

“…The gas involved in the reaction reaches the proton exchange membrane through the diffusion layer on the electrode. On the anode side of the membrane, hydrogen is dissociated into hydrogen ions and electrons under the action of the catalyst, and hydrogen ions form hydronium ions in the carrier of water and reach the cathode through the PEM, thus completing the proton transfer process [7][8][9][10][11][12][13]. The anode reaction equation is as follows:…”

“…With the development of PEMFCs towards the high-power range, a massive amount of liquid water will inevitably be produced when PEMFCs work at high current densities. If the excessive water cannot be discharged in time, it will cause flooding, hindering the full diffusion of gas into the anode and cathode side, which causes local overheating, overpressure, or a lack of reaction medium inside the flow channel, thus resulting in 'hydrogen starvation' and 'oxygen starvation', leading to the formation of a reverse pole and the acceleration of the performance degradation of PEMFCs [10]. To solve this 'hydrogen starvation' problem, PEMFC hydrogen supply systems usually pass excessive hydrogen to carry the water produced by the anode channel out of the stack, meaning that the anode outlet mixture contains some unreacted hydrogen.…”

Numerical Simulation of Double Layered Wire Mesh Integration on the Cathode for a Proton Exchange Membrane Fuel Cell (PEMFC)

“…Optimal cell performance occurs with a dry ionomer volume fraction of 0.25 at 60% RH, supporting prior findings. Insights into mass diffusion, proton conductivity, and the oxygen reduction reaction are revealed [7,8]. The earlier-mentioned technique to improve the performance and cost is both affordable and efficient [9].…”

Structural and Transport Properties of Hydrophilic and Hydrophobic Modified Ionomers in Proton Exchange Membrane Fuel Cells

“…On the other hand, excessive water can lead to flooding, obstructing the diffusion pathways of reactant gases, particularly at high power densities and flow rates where water production is elevated, yet insufficient drainage exacerbates the problem. The accumulation of liquid water can impede gas diffusion and precipitate a decline in cell performance due to exacerbated concentration polarization at the reaction sites and a decrease in the oxygen reduction reaction (ORR) rate [ 7 ]. Modification of the hydrophilicity and hydrophobicity of the cathode catalyst layer is one of the important ways to ameliorate water distribution in PEMFCs.…”