Effect of polytetrafluoroethylene distribution in the gas diffusion layer on water flooding in proton exchange membrane fuel cells

Mechanism and Model for Optimizing Polytetrafluoroethylene Distribution to Improve the Electrical and Thermal Conductivity of Treated Carbon Fiber Paper in Fuel Cells

“…Moreover, some unique methods to make the distribution of PTFE more uniform can improve the electrical and thermal conductivity of CFP. The simulated results reported herein are consistent with some reported experimental results. , …”

“…Polymer electrolyte membrane fuel cells (PEMFC), a device that utilizes hydrogen’s electrochemical reaction to generate electrical energy, are at the dawn of full commercialization. , One of the main components that make up a PEMFC is the gas diffusion layer (GDL), which is made of a microporous layer and carbon fiber paper (CFP). − The electrochemical reaction that takes place in a PEMFC is remarkably influenced by the multiphase transport of gas, mass, heat, and electricity. − The signature function of the GDL is to optimize the uniformity of gas distribution so that reactants can be present in each area in the cell to support the reaction. The GDL also has to play the role of conducting electrons and heat. − On the cathode side of a cell, many generated liquids need to be brought out of the catalyst layer immediately, and the surface wettability of carbon fibers in CFP affects the transport of liquid water remarkably. ,, Generally, to improve the CFP’s hydrophobic properties, it is common to treat CFP with a hydrophobic polymer such as polytetrafluoroethylene (PTFE). ,, However, most polymers exhibit low electrical and thermal conductivity properties, and their presence in the CFP will severely reduce the electrical and thermal conductivity of CFP. , Hence, studying the mechanism and prediction model for both the electrical and thermal conductivity in CFP is essential. Nevertheless, there is currently a lack of a direct mechanism to explain the conduction behavior of CFP, and there are only fewer effective prediction methods for both the electrical and thermal conductivity.…”

“…In previous studies, researchers were mainly in the virtue of experimental methods, simulation methods, or a combination of the two means to study the conduction characteristics of CFP. In the studies of CFP through experiments, the pristine carbon paper is usually treated using a variety of methods, and then, the electrical and thermal conductivities or single-cell testing are used to characterize the properties of CFP. − These studies have been developed from simple to complex using simulation methods. − In the early research term, the electrical and thermal properties of CFP were regarded as a homogeneous phase for simulation . Then, researchers considered the gradient characteristics or the anisotropy of CFP, making the model more complicated. ,, It is recently assumed that CFP is a model of carbon fiber-layered stacked structure, and the characteristics of CFP are simulated. ,, It is a widely used method that a complex CFP structure is abstracted and reconstructed as a carbon fiber-layered physical model through reasonable assumptions.…”

Coating Distribution Analysis on Gas Diffusion Layers for Polymer Electrolyte Fuel Cells by Neutron and X-ray High-Resolution Tomography

“…These characteristics make it an interesting sample for studying the coating coverage of fibers since the FEP interacts directly with the fiber instead of the binder, but the material has a very high fiber density, which makes the coating more likely to accumulate in the multiple fiber intersections. In order to improve the homogeneity, we used a vacuum coating application, 28 and since the detectability limits of the technique were being tested, low coating loads were also employed.…”

Recent Progress on the Key Materials and Components for Proton Exchange Membrane Fuel Cells in Vehicle Applications

“…The PTFE loading are unevenly distributed in the pores or on the surface of carbon paper [149] due to the residual air in the pores. In order to improve the uniformity of the PTFE distribution and the hydrophobicity of the substrate material, the pretreatments were carried out under vacuum by Song et al [150] to remove the residual air in the pores so that the PTFE can be evenly distributed in the pores (resulting in improved hydrophobicity of the GDL). These results showed that the water contact angle decreased with the vacuum pretreated carbon paper as more PTFE was immersed in the micropores of the paper.…”