Fabrication Of Graphene-based Composite Materials And Their Excellent Catalytic And Absorbing Performance

Metal nanoparticles have long attracted considerable attention owing to theirunique physical and chemical properties, as well as their broad and importantapplications in photonics, catalysis, information storage, chemical and biologicalsensing, and surface enhance Raman scattering (SERS).Here, using graphene oxide (GO) as both a reducing agent and a support, atwo-step method was used to fabricate GO decorated with Au-Ag alloy nanoparticleswith a Au-rich shell (Au-Ag/GO(Ⅰ)). The material exhibited excellent catalytic activityfor the reduction of4-nitrophenol (4-NP) to4-aminophenol in water at roomtemperature and its activity was superior to the GO decorated with either Au or Agnanoparticles alone.In addition, a one-step method was also developed to fabricate Au-Agnanoparticles/graphene oxide nanocomposites (Au-Ag/GO(Ⅱ)) by using simultaneousredox reactions between AgNO3, HAuCl4and GO. Moreover, Au-Ag alloynanoparticles with different shapes including core-shell, dendrimer-like andflower-like were obtained by simply modifying the concentration of the reactants andthe reaction temperature. With no reducing or stabilizing agents added, theAu-Ag/GO(Ⅱ)nanocomposites show superior catalytic performances for the reductionof4-NP and for the aerobic homocoupling of phenylboronic acid.Moreover, a facile and environmentally friendly method for the reduction of GOis reported, which for the first time utilizes copper nanoparticles as the reducing agent.The reaction was finished in about10min. Unlike the reduction of GO by Zn or Fepowders, this approach does not involve the use of any toxic reagents or acids. Inaddition, a mechanism that describes the role of the metal nanoparticles in thereduction of GO and the formation of the Cu2O nanoparticles on the reduced GO(rGO)(Cu2O/rGO) is proposed. The prepared Cu2O/rGO exhibits a high catalyticability for the degradation of a model dye pollutant, methylene blue.Three-dimensional (3D) graphene macrostructures, such as hydrogels andaerogels, have been developed recently since they not only retain the large accessiblesurface areas of the graphene nanosheets but also have highly porous structures withpore sizes of several micrometers. Here, a simple one-step method for the fabricationof graphene-based hydrogels (GHs) with3D macrostructures is demonstrated. Duringthis process rGO was gradually formed by using Cu NPs as the reducing agent and the rGO simultaneously self-assembled to GH. At the same time, the Cu NPs wereoxidized to form Cu2O. Graphene-based aerogels (GAs) were then obtained byfreeze-drying the GHs. In addition, GHs with different compositions were obtained bysimply adjusting the initial amount of Cu NPs or the concentration of GO suspension.The obtained GAs not only had good catalytic performance for the reduction of4-NPand the photocatalytic degradation of methyl orange but also excellent absorptioncapacities for the removal of various oils and dyes from water.