Experimental and numerical study on catalyst layer of polymer electrolyte membrane fuel cell prepared with diverse drying methods

High manufacturing cost is a major challenge to commercialization of the polymer electrolyte membrane fuel cell (PEMFC) technology in high volume market. Catalyst layer (CL) of PEMFC should incorporate high effective porosity, electrochemically active surface-area, gas permeability, and favorable ionomer distribution. Drying of the CL is a very significant step of electrode fabrication, and determines most of the properties mentioned above, but is rarely a subject of investigation. From various possible drying processes of CL, freeze-drying shows some beneficial properties, such as higher porosity, better ionomer distribution, and reduces the mass transport resistance significantly by allowing more reactant gas into reactive interface. In this work, the influence of diverse drying techniques on the microstructure and performance is investigated. Complementarily, a transient 2D physical continuum-model is used to investigate the effect of the structural properties on cell performance of electrodes prepared with different drying methods. A sensitivity analysis has been also performed to determine the influence of individual parameters applied in the model. Both of the experimental and simulation results stress on the fact that the freeze-drying technique not only significantly enhances the oxygen transport properties through ionomer but also improves the porosity along with the tortuosity of the CL microstructure.