Pt-Ru Nanoparticles Supported on Carbon Nanotubes as Methanol Fuel Cell Catalysts
Liang Li and Yangchuan Xing. Dept. of Chemical & Biological Engineering, University of Missouri-Rolla, Rolla, MO 65409
Bimetallic Pt-Ru alloy catalysts have been demonstrated to be more effective than pure Pt catalysts in the electro-oxidation of methanol. A synthesis method for the Pt-Ru catalysts supported on sonochemically functionalized carbon nanotubes is presented. The catalysts were prepared by directly reducing the corresponding salts, K2PtCl4 and K2RuCl5, in an ethylene glycol solution containing dispersed carbon nanotubes. Three catalysts with the same metal loading, 20 wt %, but different Pt to Ru atomic ratios, were prepared. These catalysts were characterized by transmission electron microscopy (TEM), and X-ray diffraction (XRD). TEM images showed that highly dispersed Pt-Ru bimetallic alloy nanoparticles were synthesized with average nanoparticle sizes of less than 3.0 nm in diameter. The catalyst nanoparticles are uniform and cover only the outside of the carbon nanotubes. XRD patterns showed a face-centerd cubic (fcc) crystal structure. Linear sweep voltammetry (LSV) showed that the catalysts are electrocatalytically active in the electro-oxidation of methanol. Results of LSV and the electrochemical endurance test showed that all three Pt-Ru catalysts supported on carbon nanotubes display enchanced activities than a commercial catalyst (E-TEK) of Pt-Ru supported on carbon black.