Development and electrochemical studies of membrane electrode assemblies for polymer electrolyte alkaline fuel cells using FAA membrane and ionomer

This paper provides guidelines on the fabrication and operation of alkaline fuel cells using quaternary ammonium hydroxide anion exchange membrane (FAA-3-fumatech), and includes a discussion of the electrode kinetic parameters based on the composition of the catalytic layer. The best peak power density performance, 223 mW cm^-2 was obtained with an electrode formed from Pt/C, 0.8 mg_Pt cm^-2 and 25% of FAA-3 ionomer in the catalyst layer for both the cathode and the anode. We demonstrate that the platinum loading can be lowered to values close to 0.5 mg_Pt cm ^-2, without appreciably affecting the fuel cell performance characteristics. The experimental fuel cell data were analyzed using theoretical models of the electrode structure and its kinetics studied over the assembling parameters. We show that most of the electrode systems present limiting currents, with some showing diffusion limitations in the gas channels and/or in the ionomer film covering the catalyst nanoparticles. We also provide some general strategies using Tafel slopes on evaluating the ionomer interaction with the electrode kinetics for the oxygen reduction reaction.