Modulating the surface structure of nanodiamonds to enhance the electronic metal–support interaction of efficient ruthenium catalysts for levulinic acid hydrogenation

The electron cloud density of the ruthenium nanoparticles plays a key role in catalyzing the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). Herein, the effects of interactions between the carbon support and ruthenium nanoparticles (Ru NPs) were systematically investigated by tailoring the surface of nanodiamonds (NDs). The binding energy of the Ru NPs increases first then decreases along with the increasing of the annealing temperature during the preparation of the carbon supports. The nanodiamonds annealed at 900 °C transferred more electrons to Ru NPs, which increased the electron density of the Ru NPs in the Ru/ND-900 catalyst. The Ru/ND-900 catalyst with high electron density exhibits an efficient activity for the hydrogenation of levulinic acid. Moreover, the Ru/ND-900 catalyst also exhibits much more stability than the Ru/ND catalyst for the hydrogenation of LA in the aqueous phase.