The Influence of Membrane Thickness and Catalyst Loading on Performance of Proton Exchange Membrane Fuel Cells

This paper explores the influence of membrane thickness and catalyst loading on fuel cell performance of commercially relevant membrane electrode assemblies (MEAs). A systematic study was carried out with MEAs comprised of commercially available Pt/C electrocatalysts and reinforced PFSA membranes to better understand the practical limitations of incorporating low platinum loadings and ultra-thin membranes in commercially viable MEA designs. Three different MEA configurations were compared where membrane thickness was either 15 µm or 10 µm and cathode catalyst loading was either 0.4 mgPt cm-2 or 0.1 mgPt cm-2. Extensive in-situ electrochemical characterization was carried out to extract the relevant physical and electrochemical parameters of each MEA configuration. By changing only one variable at a time, i.e., either thickness or catalyst loading, it was possible to deconvolute the specific contributions of membrane thickness and catalyst loading on fuel cell performance. Interestingly, as membrane thickness was reduced below 15 µm, no significant changes in fuel cell performance were observed as membrane interfacial effects begin to dominate compared to bulk transport effects. Conversely, reducing catalyst layer loading from 0.4 to 0.1 mgPt cm-2 introduces significant polarization losses attributed to a combination of kinetic and mass transport effects.