Single high platinum dispersion

Because the adsorption properties of highly dispersed metals may differ significantly from those of single-crystal surfaces, especially if the metal particles are very small 397), CO adsorption on platinum nanoparticles supported on Si02 (particle diameter > 6nm) is contrasted in the following section with that on Pt(l 11), with particular emphasis on the SFG signal intensities 132). 

As discussed earlier, it is now possible to make and study deposits of monosized, highly dispersed, transition metal clusters.(S) In this section we summarize results from the first measurements of the valence and core level photoemission spectra of mass selected, monodispersed platinum clusters. The samples are prepared by depositing single size clusters either on amorphous carbon or upon the natural silica layer of a silicon wafer. We allow the deposition to proceed until about 10 per cent of the surface in a 0.25 cm2 area is covered. For samples consisting of the platinum atom through the six atom duster, we have measured the evolution of the individual valence band electronic structure and the Pt 4f... 

A possibility to consider polyciystalline platinum surface as some combination of low index surfaces or as some disordered single crystalline surface surely caimot be immediately concluded from the values of zero charge potentials exclusively. Experiments with some intermediate model systems more or less reduceable to simple additive combinations of several planes, or of terraces and steps, are of increasing interest. Microfacetted electrodes, various types of nanoparticles prepared by precise non-electrochemical techniques, non-coalesced electrodeposited particles, " and single platinum microspheres deposited on micro-electrodes, as well as highly ordered templated electrdeposits can be considered as most ordered real platinum materials helpful to discover stractural effects at atomic level. However they all are still too simple to compare with, to say, platinized platinum, and attempts to electrodeposit the dispersed metallic multilayers of more and more ordered type ° are also relevant. 

Huang J-E, Guo D-J, Yao Y-G, Li H-L. High dispersion and electrocatalytic properties of platinum nanoparticles on surface-oxidized single-walled carbon nanotubes. J Electroanal Chem 2005 577 93-7. 

The preparation of highly dispersed cobalt oxide on carbon is detailed in another paper (D Souza et al., 2007). A 10 wt% CoA ulcan XC72 sample is shown in Figure 4, before and after adsorption of PTA at a pH 11. The PtCo sample was reduced at 400°C. The mass ratio of the Pt to Co adsorbed is 1 to 1.5. The particles are somewhat larger, on the order of 2-6 nm. Single spot analysis of many dozens of particles has revealed the virtually complete contacting of platinum with cobalt. The appearance of the PdCo sample was similar, with a similar essentially complete contacting of the Pd with Co. 

---