Facile in-situ synthesis and deposition of monodisperse palladium nanoparticles on polydopamine-functionalized silica gel as a heterogeneous and recyclable nanocatalyst for aerobic oxidation of alcohols

This paper describes a facile in-situ synthesis of palladium nanoparticles (Pd NPs) on silica gel/polydopamine composite (SiO2/PDA) without any stabilizer or reducing agent. In this approach, palladium ions were adsorbed on SiO2/PDA surfaces by immersing the PDA-coated SiO2 particles in a palladium plating bath. Then, they were reduced in situ to Pd nanoclusters by the reducing ability of PDA's N-containing groups. The structure, morphology, and physicochemical properties of the synthesized nanocomposites were characterized by different analytical techniques such as high-resolution transmission electron microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, inductively coupled plasma and Fourier-transform infrared spectroscopy. The Pd NPs capped by the PDA groups had a strikingly small size (30-40 nm). SiO2/PDA/Pd NPs exhibited high catalytic activity as a recyclable nanocatalyst in the aerobic oxidation of alcohols. Furthermore, recovery and multiple reuse of the catalyst revealed no detectable activity loss. (C) 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.