Effect of Binder and Compression on the Transport Parameters of a Multilayer Gas Diffusion Layer

Abstract

The effect of binder and compression on the transport parameters of the multilayer gas diffusion layer (GDL) is numerically studied by the lattice Boltzmann method. A stochastic algorithm is implemented to generate three multilayer GDLs with a porosity gradient and a uniform GDL, and then, the GDLs are compressed after the binder is added to obtain structures with various binder volume fractions and various compression ratios. The pore size distribution, through-plane (TP) permeability, in-plane (IP) permeability, tortuosity, and electric conductivity of the four structures of GDLs are analyzed. The pore size distributions of GDLs move toward smaller pores due to compression, and the GDL with a larger porosity gradient has a larger maximum pore size. The TP permeability decreases with the increase of compression ratio and binder volume fraction, and the TP permeability of the four GDLs decreases similarly due to compression, but the TP permeability of the multilayer GDL with a larger porosity gradient drops more due to the binder. IP permeability is slightly affected by the compression. Similar to TP permeability, the IP permeability of the multilayer GDL with a large porosity gradient decreases more due to the binder. Multilayer GDL with a small porosity gradient has a smaller tortuosity, more superior pore connectivity, and thus more outstanding gas permeability. The electric conductivity increases with the increase in compression ratio and binder volume fraction.

Transport-Parameter-Based Correlations for Gas Diffusion Layers Considering Compression and Binder: An Investigation Using the Lattice Boltzmann Method

“…To reconstruct a GDL sample stochastically, some initial parameters, such as the number of fiber layers (n), fiber diameter (d), bulk porosity (ϕ 0 ), and side length of the calculation domain (L), here, L = L x = L z , need to be determined first, and the GDL thickness (L y ) can be calculated by n and d. When the total porosity of GDL is within 1% of ϕ 0 , the GDL is considered to meet the requirements. In our previous research, 43 by analysis of the porosity and pore size distribution of different volumes of GDL, the computational domain of 100 × 155 × 100 μm 3 has been proven to be reasonable. Here, 1 lattice unit (lu) = 1 μm.…”

“…When the total porosity of GDL is within 1% of ϕ 0 , the GDL is considered to meet the requirements. In our previous research, by analysis of the porosity and pore size distribution of different volumes of GDL, the computational domain of 100 × 155 × 100 μm 3 has been proven to be reasonable. Here, 1 lattice unit (lu) = 1 μm.…”

Effects of Compression and Porosity Gradients on Two-Phase Behavior in Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

“…The separation between different phases is realized by the forces between the fluid components, and the wettability of the fluid on the solid surface is depicted by the forces between the fluid components and the solid wall. The evolving equations of the distribution function ( ) and the equilibrium distribution function ( ) are expressed as follows [ 48 ]: where Δ t denotes the time step, and τ k and ρ k represent the relaxation time and density of component k , respectively. c s is the lattice speed of sound.…”

“…Deformation of the GDL below the GC can be neglected based on experimental observations and simulation work on cross-sections of compressed GDL by Jeon et al [ 53 ]. Details of the methodology for compression can be found in our previous work [ 48 ].…”

Investigation of the Ice Melting Process in a Simplified Gas Diffusion Layer of Fuel Cell by the Lattice Boltzmann Method

“…The 3D structure of the GDL is generated by a stochastic reconstruction method, the details of which are described in previous works. − The planar structure that meets the porosity requirement is selected for the 2D melting calculation, and for in-plane it is also necessary to ensure that the fiber diameter meets the set value. To investigate the effect of fiber diameter on the anisotropic melting process, the porosity of the porous structure is chosen to be 0.7.…”