Impact of Microporous Layer Roughness on Gas-Diffusion-Electrode-Based Polymer Electrolyte Membrane Fuel Cell Performance

Abstract

This study explores the role of the gas diffusion media microporous layer (MPL) surface structure on the electrochemical properties of gas-diffusion-electrode (GDE)-based membrane electrode assemblies (MEAs). It has been shown that a thin ionomer layer on top of the GDE and hot pressing is needed to create good contact between the catalyst layer and the membrane. In this study, gas diffusion media with different MPL surface roughness were applied to fabricate GDE-based MEAs to understand how MPL roughness impacts the amount of ionomer overlayer required for maximum performance. Electron microscopy was employed to investigate MPL/catalyst layer and catalyst layer/membrane interfaces. In-situ performance testing was used to assess the impact of MPL roughness and ionomer overlayer on catalyst utilization and air polarization performance. We find that a smoother MPL surface required a thinner ionomer overlayer than gas diffusion media (GDM) with a rougher MPL surface to achieve a performance comparable to direct-coated catalyst-coated-membrane MEAs.

Designing Tailored Gas Diffusion Layers with Pore Size Gradients via Electrospinning for Polymer Electrolyte Membrane Fuel Cells

“…Commercial GDL materials are highly porous and have a dual-component design composed of a hydrophobic carbon fiber substrate and a thin microporous layer (positioned next to the catalyst layer) made of dispersed carbon particles within a polymeric binding agent. , The microporous layer (MPL) (pore size ranges from 0.1 to 0.5 μm) provides a high capillary pressure barrier to facilitate membrane hydration, while the hydrophobic carbon fiber substrate (pore size ranges from 10 to 30 μm) provides pathways for excess water egress from the cell. In efforts to manage the transport of water within the PEM fuel cell, both the design of the fibrous substrate and the MPL have received significant attention in recent years. − Pore structure and wettability of the MPL have both been tailored to improve water management at various operating conditions. ,− For instance, Shrestha et al applied a custom hydrophilic MPL coating onto a commercial hydrophobic GDL for fuel cell operation without anode humidification. The hydrophilic MPL coating was found to be effective at retaining liquid water at the catalyst layer (CL)/MPL interface and led to improved membrane hydration and higher cell voltages.…”

Optimizing the Mass-Transfer Efficiency of a Microporous Layer for High-Performance Proton Exchange Membrane Fuel Cells

“…It is known that polarization loss of MEA is mainly dominated by contact resistance and charge-transfer resistance under dry condition. After loading–unloading cycles, the contact of components has been improved . As a result, the ohmic polarization loss of aged MEAs was relieved.…”

“…After loading−unloading cycles, the contact of components has been improved. 33 As a result, the ohmic polarization loss of aged MEAs was relieved. As shown in Table 2, the maximum power density of aged MEAs containing GDL-C is 0.796 W cm −2 , which is 5.4% higher than that of fresh MEA (0.755 W cm −2 ).…”

Microporous Layer Containing CeO2-Doped 3D Graphene Foam for Proton Exchange Membrane Fuel Cells at Varying Operating Conditions

“…Due to the mixture of hydrophobic PTFE in the MPL slurry, these MPL samples reveal high contact angles of 140.9, 145.2, 145.1, and 146.1°. It is known that the static contact angle is a strong function of the surface properties, such as surface roughness and surface energy. , Corresponding to the top-view SEM images, the protrusions on the surface of the modified MPLs (MPL-G, MPL-G-CeO 2 NR and MPL-G-CeO 2 NN) increase the surface roughness. As a result, the wetting angle of the modified MPL shifts toward a higher value.…”