Enhanced Chemoselective Hydrogenation through Tuning the Interaction between Pt Nanoparticles and Carbon Supports: Insights from Identical Location Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy

Ultrasmall-sized platinum nanoparticles (Pt NPs) (∼1 nm) supported on carbon nanotubes (CNTs) with nitrogen doping and oxygen functional groups were synthesized and applied in the catalytic hydrogenation of nitroarenes. The advanced identical location transmission electron microscopy (IL-TEM) method was applied to probe the structure evolution of the Pt/CNT catalysts in the reaction. The results indicate that Pt NPs supported on CNTs with a high amount of nitrogen doping (Pt/H-NCNTs) afford 2-fold activity to that of Pt NPs supported on CNTs with oxygen functional groups (Pt/oCNTs) and 4-fold to that of the commercial Pt NPs supported on active carbon (Pt/C) catalyst toward nitrobenzene. The catalytic performance of Pt/H-NCNTs remained constant during four cycles, whereas the activity of the Pt/oCNTs was halved at the second cycle. Compared with Pt/oCNTs, Pt/H-NCNTs exhibited a higher selectivity (>99%) in chemoselective hydrogenation of halonitrobenzenes to haloanilines due to the electron-rich chemical state of Pt NPs. The strong metal–support interaction along with the electron-donor capacity of nitrogen sites on H-NCNTs are capable of stabilizing the Pt NPs and achieving related catalytic recyclability as well as approximately 100% selectivity. The catalyst also delivers exclusively selective hydrogenation toward nitro groups for a wide scope of substituent nitroarenes into their corresponding anilines.