Structured multilayered electrodes of proton/electron conducting polymer for polymer electrolyte membrane fuel cells assembled by spray coating

Membrane electrode assemblies (MEAs) for fuel cell applications consist of electron conductive support materials, proton conductive ionomer, and precious metal nanoparticles to enhance the catalytic activity towards H-2 oxidation and O-2 reduction. An optimized connection of all three phases is required to obtain a high noble metal utilization, and accordingly a good performance. Using polyaniline (PANI) as an alternative support material, the generally used ionomer Nafion (R) could be replaced in the catalyst layer. PANI has the advantage to be electron and proton conductive at the same time, and can be used as a catalyst support as well. In this study, a new technique building up alternating layers of PANI supported catalyst and single-walled carbon nanotubes (SWCNT) supported catalyst is introduced. Multilayers of PANI and SWCNT catalysts are used on the cathode side, whereas the anode side is composed of commercial platinum/carbon black catalyst and Nafion (R), applied by an airbrush. No additional Nafion (R) ionomer is used for proton conductivity of the cathode. The so called spray coating method results in high power densities up to 160 mW cm(-2) with a Pt loading of 0.06 mg cm(-2) at the cathode, yielding a Pt utilization of 2663 mW mg(Pt)(-1). As well as PANI, supports of SWCNTs have the advantage to have a fibrous structure and additional, they provide high electron conductivity. The combination of the new technique and the fibrous 1-dimensional support materials leads to a porous 3-dimensional electrode network which could enhance the gas transport through the electrode as well as the Pt utilization. The spray coating method could be upgraded to an in-line process and is not restricted to batch production. (C) 2010 Elsevier B.V. All rights reserved.