Determination of Properties of Ionomer Binder Using a Porous Plug Model for Preparation of Electrodes of Membrane-Electrode Assemblies for Polymer Electrolyte Fuel Cells

Abstract

A new characterization method using a porous plug model was proposed to determine the degree of sul-fonation (DS) of ionomer binder with respect to the membrane used in membrane-electrode assemblies (MEAs) andto analyze the fraction of proton pathways through ionomer-catalyst combined electrodes in MEAs for polymer elec-trolyte fuel cells (PEFCs). Sulfonated poly(ether ether ketone) was prepared to use a polymeric electrolyte and lab-oratory-made SPEEK solution (5wt.%, DMAc based) was added of the SPEEK-based MEAs in this study, DS of ionomer binder for catalyst layers should be the same or higherthan that of the SPEEK membrane used in the MEAs. The porous plug model suggested that most of protons werevia the ionomer binder (~92.5%) bridging the catalyst surface to the polymeric electrolyte, compared with the path-ways through the alternative betwen the interstitial water on the surface of ionomer binder or catalyst and.the ion-omer binder (~7.3%) and through only the interstitial water on the surface of ionomer or catalyst (~0.2%) in theelectrode of the MEA comprising of the sulfonated poly(ether ether ketone) membrane and the 5wt.% SPEEK ion-rity of proton at both electrodeds moves through ionomerbinder until reaching to electrolyte membrane. The porous plug model of the electrodes of MEAs reemphasized theimportance of well-optimized structure of ionomer binder and catalyst for fuel cells.