Systematic analysis of palladium-graphene nanocomposites and their catalytic applications in Sonogashira reaction

Abstract

Graphene has been modified with palladium nanoparticles (Pd NPs) to develop high performance catalysts for the Sonogashira cross coupling reaction. In this research, graphite oxide (GO) sheets exfoliated from graphite were impregnated with Pd(OAc)(2) to prepare Pd2+/GO. Thermal treatments of the Pd2+/GO in H-2 flow at 100 degrees C produced Pd/graphene (Pd/G) nanocomposites. TEM images show that Pd NPs were distributed quite uniformly on the graphene sheet without obvious aggregation, and the mean size of Pd NPs was determined to be less than 2 nm in diameter. Morphological and chemical structures of the GO, Pd2+/GO, and Pd/G were investigated using FF-IR, XRD, XPS, and XAFS. The resulting Pd/G showed excellent catalytic efficiency in the Sonogashira reaction and offers significant advantages over inorganic supported catalysts such as simple recovery and recycling. Finally, deactivation process of the Pd/G in recycling was investigated. We believe that the remarkable reactivity of the Pd/G catalyst toward the Sonogashira reaction is attributed to the high degree of the Pd NP dispersion and thus the increased low coordination numbers of smaller Pd NPs. Crown Copyright (C) 2013 Published by Elsevier Inc. All rights reserved.