Noble metal fuel cell catalysts with nano-network structures

Two noble metal-based catalysts, Pt and Pt-Ru, with three-dimensional (3D) nano-network structures have been successfully prepared using a new approach totally different from conventionally recognized particle nanocatalysts. Each catalyst was formed in the void spaces of a self-assembled, layered template of polystyrene (PS) nanospheres by chemical reduction deposition. Removing the template by thermal decomposition resulted in the formation of a nano-network catalyst with the sizes of the network frames and hollow holes around 10-200 nm. Physical and electrochemical characterizations demonstrated that such nanostructured catalysts have distinctive characteristics including robust structures, spacious hollows, connected flow channels, large surface areas, and high electrocatalytic activities. The prepared Pt and Pt-Ru nano-network catalysts were applied to a single-cell direct methanol fuel cell (DMFC) as a cathode and an anode catalyst, respectively, with a low catalyst loading of 0.2 mg cm(-2) for each. The test result indicated that a good cell performance is obtained with very high normalized power densities. The maximal normalized power density at 60 degrees C was about 3-4 times that of a comparison DMFC using conventional catalysts with a high catalyst loading at 4.0 mg cm(-2). However, substantial improvements are still required in both catalyst loading and electrode size for more practical applications. (c) 2007 Elsevier B.V. All rights reserved.