(Invited) Catalyst Layers for Fluorine-Free Hydrocarbon PEMFCs

Abstract

Electrochemical energy conversion devices such as fuel cells are crucial for the development of renewable, sustainable alternative energy vectors. The implementation of fuel cell technology is of particular interest in portable, transportation, and stationary energy conversion sectors. There are challenges that still impede fuel cell commercialization at scale: cost, performance, and durability of the membrane-electrode-assemblies (MEA)s that comprise fuel cell stacks. MEAs typically consist of catalyst layers (CL) coated on either side of a proton-exchange membrane (PEM), and gas diffusion layers (GDL) which control water management and reactant gas mass transport. The CL provides a path for proton, electron, and gas transport to (and from) the Pt catalyst surface. Commonly, a perfluorosulfonic acid (PFSA) ionomer, e.g., Nafion® is employed as both the proton exchange membrane (PEM) and ionomer. However, perfluorinated materials are not without challenges as their manufacture utilizes controlled substances and potentially environmentally hazardous chemical feedstocks, which add to their relatively high cost. In contrast, fluorine-free hydrocarbon-based analogues may be prepared from ubiquitous, readily available chemical feedstocks, and afford much-reduced gas permeability. In this presentation, highly performing (power densities of >1 W cm-2), sulfo-phenylated poly(phenylene)PPB-H+ solid polymer electrolyte will be reported as a complete substitute for incumbent PFSA materials in PEMFCs, serving both as the electrode catalyst binder, and membrane.