Development of Novel Gas Diffusion Layer for Fuel Cells with Micro/Nano Technology

A new fabrication technique is employed to convert a metallic foil into a porous structure with an array of micron size pores. The motivation stems from the need to develop a more efficient and controllable gas diffusion medium for fuel cell applications. The influence of mask shape, mask width and etching time was investigated experimentally. A correlation to predict trench width with etching time was derived; normalizing by mask width allows one to collapse the data. The improvements of such gas diffusion layer, including pore shape, porosity, and surface properties, are fully discussed. In addition to good thermal and electrical conductivity of the GDL, its pore size distribution must be optimized for improving the transport of both gas and liquid phases during fuel cell operation. The rapid development of MEMS/nano technology provides the advantages for improved thermal and electrical conductivity, precisely controllable mass transport, and permeability. In this work, a novel and low-cost gas diffusion material is developed based on masked etching to convert a copper foil into a porous structure with an array of micron size pores. Figure 1 shows a scanning electron microscope image of the typical copper GDL after 20 minutes of etching. The number inside the pore indicates the mask width in microns. The number density of mask widths of 20, 15, 10, 8 and 5 μm relative to the number density at 20 μm is 1, 1, 8, 54, and 64, respectively. The mean pore size after etching for 20 min is 35.65 μm, while the porosity of the copper GDM is about 21%. It should be noted here that the mean pore size and porosity could be changed by altering the mask width, varying the etching time, and changing the number density ratio of the pores. This novel material was examined in an element cell with an active area of 10 cm2 and the exciting performance was obtained. Its improvement by enhancing the inplane transport and increasing the reaction area of fuel cell was also demonstrated [1]. Figure 1: Typical SEM image of the copper GDM after 20 minutes of etching. Summary of Research: The performance and durability of fuel cells are significantly impacted by the characteristics of the gas diffusion layer (GDL) whose principal functions are to efficiently transport the reactants and products to and from the membrane, as well as to conduct heat and electric current. Current GDL materials, which include carbon cloth or paper, have shown limited success, motivating the development of new materials.