Catalyst Layer Modifications for Enhanced Performance of Fluorine-Free Proton Exchange Membrane Fuel Cells

Abstract

The inclusion of insoluble, hyperbranched sulfonated phenylated poly(phenylene) terphenyl (HB-sPPT) particles in catalyst layers (CLs) is demonstrated to enhance the current-voltage characteristics of proton exchange membrane fuel cells based on Pemion ionomer and Pemion membranes. HB-sPPT ionomer particles are prepared in three different sizes: as-prepared (45 μm), hand-ground (33 μm), or ball-milled (20 μm). Incorporated into CLs, the ionomer particles affect the CL's electrochemically active surface area, porosity, and ionic conductivity. This results in a 30% increment in maximum power in fuel cells containing ionomer particles in the CL, with the effect being inversely correlated to the particle size.