The effect of gas diffusion layer on electrochemical effective reaction area of catalyst layer and water discharge capability

A gas diffusion layer (GDL) is one of the main components of a proton exchange membrane fuel cell (PEMFC), which helps discharge the water generated by the electrochemical reaction and promotes the diffusion of reactant gases. The GDL typically consists of a microporous layer (MPL) and a substrate, and the MPL is mainly composed of carbon black and PTFE (polytetrafluoroethylene). In this study, to optimize the effective reaction area of the catalyst layer by increasing the specific surface area of the MPL and improve the water discharge capability of GDL by increasing the porosity of the MPL, the GDLs are manufactured by varying the manufacturing methods of the MPL. The MPL design parameters considered in this study are the particle size of carbon black, the addition of smaller carbon black particles to the MPL, and the number of cracks in the MPL. The performance tendencies are quantitatively identified through polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, electrochemical surface area, liquid water, water vapor, gas permeabilities, and capillary pressure gradient. The results showed that the MPL has a dominant effect on the electrochemical surface area (ECSA) of the catalyst layer and the mass transport resistance of the PEMFC.