A metallic gas diffusion layer and porous media flow field for proton exchange membrane fuel cells

Abstract

Recently, metal foams have been intensively studied to be used as alternative flow fields to the conventional channel-rib flow field in proton exchange membrane fuel cells (PEMFC) to enhance the uniformity of gas distribution and reduce the weight of fuel cells. This work demonstrates a simple and compact design at the cathode side for achieving effective electrons and gas transport in PEMFCs, which includes a porous metal foam flow media coated with a microporous layer (MPL) on its top to form one single hierarchical porous component functioning as both the gas distributor and diffusion media. With this low-cost and light-weight design, the conventional gas diffusion layer (GDL) can be eliminated. A comparative analysis of PEM fuel cell performances for the conventional carbon paper-based GDL and three metallic GDL designs containing different MPLs is conducted under varied stoichiometric ratios and relative humidity (RH). At 100% RH, the optimum performance is achieved on the CB/CNT MPL-coated metal foam, with the maximum power density increased by 21% than that of the conventional design when the stoichiometric ratio of air is 1.5. Under dry conditions (40% RH), all the metallic GDL structured cells outperform the conventional one at a low airflow rate (stoichiometric ratio = 1.5).