The oblate morphology of supported PtRu5 on carbon black

We have examined supported PtRu5 nanoparticles by a variety of electron microscopy techniques, including high-resolution, analytical and a unique mass-spectroscopic electron microscopy technique. The absolute intensity from very high angle annular dark-field images in a dedicated scanning transmission electron microscope can be quantified to determine the number of atoms in a nanoparticle on a support material. Analytical electron microscopy results revealed that the relative Pt:Ru atomic concentration in a nanoparticle does not vary significantly from particle to particle. The average diameter of the nanoparticles was 1.56 nm, and the average number of atoms was measured to be 24 atoms per nanoparticle. The combination of these techniques indicates that the PtRu5 nanoparticles are oblate on the carbon black support.