Hydrogen and oxygen adsorption stoichiometries on silica supported ruthenium nanoparticles

Treatment under H2 at 300 °C of Ru(COD)(COT) dispersed on silica yields 2 nm ruthenium nanoparticles, [Rup/SiO2], according to EXAFS, HRTEM and XPS. H2 adsorption measurements on [Rup/SiO2] in the absence of O2 show that Ru particles adsorb up to ca. 2H per surface ruthenium atoms (2H/Rus) on various samples; this technique can therefore be used to measure the dispersion of Ru particles. In contrast, O2 adsorption on [Rup/SiO2] leads to a partial oxidation of the bulk at 25 °C, to RuO2 at 200 °C and to sintering upon further reduction under H2, showing that O2 adsorption cannot be used to measure the dispersion of Ru particles.