Ru
has been found to be a highly efficient catalyst for producing
γ-valerolactone from the hydrogenation of levulinic acid. However,
the active species on Ru nanoparticles (NPs) are still unclear. Here,
we synthesized a series of Ru NPs with tunable chemical states obtained
by altering the interaction with carbon-nanotube-based supports, achieved
by the strategies of doping carbon nanotubes with N and S atoms, changing
the amount of dopants, and varying the loading of Ru. The surface
species of the supported Ru NPs, identified by X-ray photoelectron
spectroscopy, were linked to the catalytic activities instrinsically.
We found that the Ru NPs possessing Ru0 with lower binding
energy (Ru 3p) showed higher activity independent of the parameters
of synthesis. Theoretical calculations indicated that the electron-rich
Ru0 enhanced LA hydrogenation through facilitating R–COOH
breaking into R–CO and −OH, suggesting a powerful tool
modifying the catalytic activity of carbon-supported metals by manipulating
the electronic metal–support interaction.