Investigation of Gas Transport Properties of PEMFC Catalyst Layers Using a Microfluidic Device

Abstract

The effective gas diffusivity, porous structure, and tortuosity factor of catalyst layers used in proton exchange membrane fuel cells were evaluated using a microfluidic device. Sufficient gas transport properties of the catalyst layers are a key factor for achieving high-performance catalyst layers and fuel cells. In the present study, catalyst layers with different thicknesses and different carbon supports were evaluated. Stand-alone carbon black and multi-walled carbon nanotubes were blended into the catalyst layers as the support. The all-carbon-black-based catalyst layer contained some volume of isolated pores and some amount of microcracks, which depended on its thickness. The tortuosity factor was evaluated considering the effects of the isolated pores and microcracks. However, the tortuosity factor of the all-carbon-black-based catalyst layer was larger than the well-known Bruggeman-correlated tortuosity factor. When carbon nanotubes were blended into the catalyst layer, the tortuosity factor was drastically decreased to less than one-half that of the carbon-black-based catalyst layers. A change in the number of straight pores formed by the fibrous support and variation of the ionomer distribution can affect the tortuosity factor.

Simultaneous in situ measurements and numerical analysis of mass transfer in polymer electrolyte fuel cell electrode slurries during drying

“…Pore size is a key factor affecting cell performance because it affects the transport of reactant gas and liquid water (Suzuki et al, 2016a). Blending multiwalled carbon nanotubes (CNTs) into the CLs affects the porosity and pore size distribution because the structure of supports in the CLs changes (Suzuki et al, 2015(Suzuki et al, , 2020a. Material distribution in the thickness direction of CLs is also an important factor for electron, proton, reactant gas, and water transfer in the electrode and the resultant cell performance (Xing et al, 2017).…”

A Numerical Simulation of Evolution Processes and Entropy Generation for Optimal Architecture of an Electrochemical Reaction-Diffusion System: Comparison of Two Optimization Strategies

“…However, the transport properties and effective utilization of the catalyst material strongly depend on the structural design of the porous electrode. 11,12 A better design solution might improve the transport phenomena and consequently lead to a more effective utilization of the catalyst material. Modifying the composition of an electrode is an approach used by previous researchers [13][14][15] to get an appropriate compromise between various processes.…”

Cathode Design for Proton Exchange Membrane Fuel Cells in Automotive Applications

“…The tortuosity factor of CLs is much larger than the generally well-known tortuosity factor of porous media, which is attributed to the existence of isolated pores and non-spherical dead-end pores. The existence of isolated pores substantially affects gas diffusion in the CL, while the formation of non-spherical dead-end pores can lead to a higher tortuosity factor [104].…”

“…The isolated pores and the dead-end pores were formed by ionomer deposition onto Pt/C agglomerates. And support materials would result in different tortuosity within the CL [104]. Within a CL with an ultralow catalyst loading, the influence of Knudsen diffusion becomes less important [102].…”