title: Steady-state dc and impedance investigations of H2/O2 alkaline membrane fuel cells with commercial Pt/C, Ag/C, and Au/C cathodes.
abstract: The performances of H(2)/O(2) metal-cation-free alkaline anion-exchange membrane (AAEM) fuel cells operated with commercially available Au/C and Ag/C cathodes are reported for the first time. Of major significance, the power density obtained with 4 mg cm(-2) Ag/C (60% mass) cathodes was comparable to that obtained with 0.5 mg cm(-2) Pt/C (20% mass) electrodes, whereas the performance when using the same Ag/C cathode in a Nafion-based acidic membrane electrode assembly (MEA) was poor. These initial studies demonstrate that the oxygen reduction electrokinetics are improved when operating Pt/C cathodes at high pH in AAEM-based fuel cells as compared with operation at low pH (in Nafion-based proton-exchange membrane fuel cells). The results of in situ alternating current impedance spectroscopy were core to the assignment of the source of the limited performances of the AAEM-based fuel cells as being the limited supply of water molecules to the cathode reaction sites. Minimizing the thickness of the AAEM improved the performances by facilitating back-transport of water molecules from the anode (where they are generated) to the cathode. The urgent need for development of electrode architectures that are specifically designed for use in AAEM-based fuel cells is highlighted.
authors.affiliation: Department of Chemistry and Microstructural Studies Unit, MSSU, School of Engineering, The University of Surrey, Guildford GU2 7XH, United Kingdom. j.varcoe@surrey.ac.uk
authors.forename: John R
authors.initials: JR
authors.lastname: Varcoe
authors.forename: Robert C T
authors.initials: RC
authors.lastname: Slade
authors.forename: Graham L
authors.initials: GL
authors.lastname: Wright
authors.forename: Yanling
authors.initials: Y
authors.lastname: Chen