In situ preparation of graphene oxide supported Pd nanoparticles in an ionic liquid and the long-term catalytic stability for the Heck reaction

Abstract

Palladium (Pd) nanoparticles supported on reduced graphene oxide (Pd/RGO) were successfully prepared in situ in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) ionic liquid (Pd/RGO–IL) by the phase transfer method from water. The prepared Pd/RGO catalyst was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The in situ synthesised Pd nanoparticles were uniformly dispersed on the surface of RGO with an average size distribution of 2 nm. The as-prepared Pd/RGO–IL exhibits good catalytic activity and long-term catalytic stability for Heck reactions in the IL. Initially the product conversion is 95% and still remains at 91% after being cycled ten times. The TEM images of Pd/RGO after the tenth run show that Pd nanoparticles are stably suspended in the IL with an average size of about 2.0 nm and there is almost no agglomeration during the long-term reaction. This may be due to the double protection of the organic cation [BMIM]⁺ of the IL and the evenly dispersed RGO in the IL. Hence, Pd nanoparticles supported on reduced graphene oxide show remarkable long-term catalytic stability in the IL.