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Thermal treatment of cis-(2,2‘-bipyridine)2OsCl2, (η6-cymene)2Os2Cl4, or [(bpy)2Os(μ-bpm)PtCl2][CF3SO3]2/Vulcan carbon powder composites under solely reductive conditions affords Os or Pt−Os/carbon nanocomposites consisting of metal nanoparticles highly dispersed on the carbon support. Nanocomposites containing ca. 35−50 wt % metal with metal nanocrystals of ca. 5−6 nm average diameter are formed. Evaluation of the performance of these nanocomposites as methanol electrooxidation catalysts in direct methanol fuel cells and in an electrochemical cell designed for combinatorial testing reveals that, although the Os/carbon nanocomposites and the Pt−Os alloy/carbon nanocomposite give open circuit potentials indicative of thermodynamically favorable methanol oxidation, the kinetics of these oxidations are too low to be of practical importance. Unfortunately, the Os-containing electrocatalysts prepared by this synthesis strategy did not exhibit high performance for methanol oxidations as predicted by theoretical computations.

Thermal treatment of [Ru(2,3-bis(2-pyridyl)quinoxaline) 3 (PtCl 2 ) 3 ](BF 4 ) 2 /Vulcan carbon powder composites under reactive conditions forms Pt-Ru/carbon nanocomposites containing 27-34 wt % metal alloy as highly dispersed nanoparticles of ca. Pt 75 Ru 25 stoichiometry. The metal nanoparticles have an average diameter of 6 nm (by TEM) and an fcc unit cell of lattice constant 3.907 (9) Å, as expected for Pt-rich Pt-Ru alloys. On-particle HR-EDS analysis indicates that gross phase separation of Pt and Ru does not occur on the nanoparticle scale. Evaluation of the performance of this nanocomposite as a methanol electrooxidation catalyst in a direct methanol fuel cell and in an electrochemical cell designed for combinatorial testing is reported.