Microwave-assisted synthesis of palladium nanoparticles supported on graphene: A highly active and recyclable catalyst for carbon-carbon cross-coupling reactions

We have developed an efficient method to generate highly active Pd nanoparticles supported on graphene (Pd/G) by microwave-assisted chemical reduction of the corresponding aqueous mixture of a palladium salt and dispersed graphite oxide (GO) sheets. The Pd/G demonstrated excellent catalytic activity for the carbon-carbon cross-coupling reactions (Suzuki, and Heck) with a broad range of utility under ligand-free ambient conditions in an environmentally friendly solvent system. It also offers a remarkable turnover frequency (108,000 h(-1)) observed in the microwave-assisted Suzuki cross-coupling reactions with easy removal from the reaction mixture, recyclability with no loss of activity, and significantly better performance than the well-known commercial Pd/C catalyst. The catalyst was fully characterized by a variety of spectroscopic techniques including X-ray diffraction (XRD), Raman, TGA, electron microscopy (SEM, TEM), and X-ray photoelectron spectroscopy (XPS). The remarkable reactivity of the Pd/G catalyst toward Suzuki cross-coupling reactions is attributed to the high degree of the dispersion and concentration of Pd(0) nanoparticles supported on graphene sheets with small particle size of 7-9 nm due to an efficient microwave-assisted reduction method. (c) 2010 Elsevier Inc. All rights reserved.