Efficient anodes for direct methanol and formic acid fuel cells: The synergy between catalyst and three-dimensional support

The synergy between three-dimensional support (graphite felt uncompressed thickness 2 mm, GF) and Pt-Ru catalyst preparation method afforded a four times reduction of the catalyst load in direct methanol fuel cell (DMFC) anodes while improving the power density compared to both the catalyst-coated membrane (CCM) and catalyst-coated diffusion layer designs (CCDL). In DMFC experiments the Pt-Ru (10 g m(-2))/GF anode generated a maximum power density of 741 W m(-2) at 333 K compared to 703 and 278 W m(-2) obtained with CCM and CCDL, respectively, both with 40 g m(-2) Pt-Ru load. In direct formic acid fuel cell experiments at 333 K and 1 M HCOOH concentration, the maximum power density using the Pt-Ru (10 g m(-2))/GF anode reached 860 W m(-2), compared to 526 W m(-2) with CCM. A micellar solution composed of the nonionic surfactant Triton X-102 and an aqueous phase containing H2PtCl6 and (NH4)(2)RuCl6 was utilized for the galvanostatic electrodeposition of Pt-Ru nanoparticles (5-10 nm crystallite size), assuring excellent catalyst penetration throughout the GF thickness as demonstrated by surface analytical techniques. The type of micellar media employed for electrodeposition had an impact on the crystallographic features of the Pt-Ru catalyst and conversely on the electrocatalytic activity. The highest activity was observed for Pt-Ru with the largest fraction of Pt [1,1,1] and [3,1,1] crystal facets and bimetallic Pt-Ru surface structure as opposed to alloy. The present work opened up a venue for "designing" the catalytic surface and exploiting the catalyst/three-dimensional support interaction for direct liquid fuel cell anodes. (C) 2008 The Electrochemical Society.