Synthesis and activation of PtRu alloyed nanoparticles with controlled size and composition

FCC PtRu nanoparticles with narrow size distribution were prepared by polyalcohol reduction of platinum acetylacetonate and ruthenium acetylacetonate in diphenyl ether, using oleylamine as the capping agent. The particle size ranged from 3.5 to 6.5 nm and was controlled by varying the amount of capping agent added in the synthesis. Adjusting the stoichiometric ratio of introduced Pt and Ru precursors yielded particles with different compositions. A simple fractionation was employed to narrow the size distribution of particles and nearly monodispersed particles were obtained. To activate the catalytic activity of the particles, oleylamine bound to the particle surface was removed through repeated washing of the as-prepared particles with ethanol and tetramethylammonium hydroxide (TMAOH) aqueous solution. The washed particles could be well redispersed and electrostatically stabilized in TMAOH aqueous solution and uniformly loaded on a Vulcan XC-72 carbon support. A cyclic voltammetry (CV) study revealed that the carbon-supported, cleaned PtRu nanoparticles exhibit considerably higher electrocatalytic activity for methanol oxidation compared with the as-prepared particles that have oleylamine ligands.