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

Abstract

To facilitate mass transfer in proton exchange membrane fuel cells (PEMFCs), carbon-based gel was used to fabricate micron-scale ordered indentations on the surface of the microporous layer (MPL). The high viscosity of carbon-based gel prevented the intrusion of slurry into the pores of macroporous substrate (MPS), providing more space for rapid mass transfer in the gas diffusion layer (GDL). The direction of ordered indentations was perpendicular to the direction of gas channels, working as an additional flow field at the interface of the catalyst layer and MPL. Besides, the indentations reduced the distance for water removal, providing an excellent water management efficiency. From measurements, the maximum power density of membrane electrode assembly (MEA) containing homemade GDL was 8.5% higher than that of MEA containing commercial GDL. Cyclic compressive loading on MEAs was carried out to in situ evaluate the correlation between mechanical degradation and mass-transfer efficiency. After being compressed five times, the mass-transfer efficiency of MEA containing homemade GDL was stable, but the MEA containing commercial GDL degraded seriously. From the structure and composition analysis, it is that commercial GDL revealed deformation of structure and a serious loss of hydrophobic materials after cyclic compressive loading. In contrast, the homemade GDL revealed high mechanical stability. In summary, this structural design of GDL is a promising strategy to improve the property of MEA for high-performance PEMFCs.

High-Performance Proton Exchange Membrane Fuel Cells Enabled by Highly Hydrophobic Hierarchical Microporous Carbon Layers Grafted with Silane

“…As can be seen, the carbon particles change from large blocks to small fragments with increasing ZnO content, and cracks appear on the surface of the GDL when the ZnO content is greater than 3.0 g (i.e., HPC-GDL-4 and HPC-GDL-5). It must be mentioned that these cracks can accumulate water and are therefore not conducive to the efficient transport of water and gas . The contact angles for all HPC-GDLs vary from 147.6 to 150.1° and are higher than that of SL, super-hydrophobicity is thus achieved (Figure S7), which is imperative for the drainage of water during the operation of PEMFCs.…”

“…It must be mentioned that these cracks can accumulate water and are therefore not conducive to the efficient transport of water and gas. 30 The contact angles for all HPC-GDLs vary from 147.6 to 150.1°and are higher than that of SL, super-hydrophobicity is thus achieved (Figure S7), which is imperative for the drainage of water during the operation of PEMFCs.…”

Overcoming Low C2+Yield in Acidic CO2Electroreduction: Modulating Local Hydrophobicity for Enhanced Performance

“…Preparation of the MPL: The preparation of the MPL is adapted from th previous work. [54] In short, carbon paper was treated with 20 wt% polytetrafluoroethylene (DISP30, DuPont) emulsion solution first and heated in air at 350 °C for 2 h to remove the surfactant in the PTFE emulsion solution. Then, carbon black ink containing acetylene black and PTFE was painted onto the PTFE-pretreated carbon paper to form the MPL.…”

Hierarchical Carbon Nanotube Hybrid Films Modified Gas Diffusion Layer for High-Performance Proton-Exchange Membrane Fuel Cells

“…GDLs are composed of a gas diffusion substrate (GDS) and a microporous layer (MPL), which are the vital transport channels of water and gas. − The conventional MPLs are fabricated via mixing carbon powder and hydrophobic agents, which are not effective in preventing the dehydration of PEM at dry operation conditions. − Therefore, to improve the water retaining capacity, researchers have tried to optimize the MPL by introducing hydrophilic materials (e.g., TiO 2 , HfO 2 ) or hydrophilic coatings (PANI). − However, most of these materials both have high contact resistance, thus declining the cell performance, and suffer from water flooding in the high-current-density region due to the strong water absorption of hydrophilic materials, hindering the diffusion of the reaction gas.…”