Enhancing the catalytic activity of Ru NPs deposited with carbon species in yolk-shell nanostructuresElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ta03576k

The synthesis of metal NPs with a well-defined size, shape and composition provides opportunities for tuning the catalytic performance of metal NPs. However, the presence of a stabilizer on the metal surface always blocks the active sites of metal NPs. Herein, we report an efficient method to remove the stabilizer on the metal surface via H 2 pyrolysis with Ru-poly(amindoamine) encapsulated in silica-based yolk-shell nanostructures as an example. The CO uptake amount of Ru NPs increases sharply after H 2 pyrolysis, indicating that the exposure degree of Ru NPs is increased. No aggregation of the colloidal Ru NPs occurs after H 2 pyrolysis, which could be mainly assigned to the protection effect of C and N species formed on Ru NPs. The overall activity of Ru NPs in the yolk-shell nanostructure after the pyrolysis could reach as high as 20 300 mmol per mmol Ru per h in the hydrogenation of toluene, which is much higher than that of most reported Ru-based solid catalysts. It was found that the yolk-shell nanostructure could efficiently prevent the leaching of Ru NPs during the catalytic process. Ru NPs in the yolk-shell nanostructure could also catalyze the hydrogenation of benzoic acid and Levulinic acid with high activity and selectivity. An efficient H 2 pyrolysis method was developed to remove stabilizers on metal surfaces with Ru-poly(amindoamine) as the model. Ru NPs after pyrolysis with the TOF as high as 20 300 h −1 are among the most active solid catalysts for toluene hydrogenation. The high catalytic activity could be mainly attributed to the high exposure degree and accelerating effect of C and N residues at the Ru surface.