(578f) Flame Synthesis of Crumpled Graphene Nanostructures Decorated with Multicomponent Metal Nanoparticles

Among carbonaceous materials, graphene has become attractive because of its unique properties such as high specific surface area, good electrical conductivity, flexibility, and high mechanical strength. One of the most common methods of producing graphene is based on graphite oxidation to graphene oxide (GO) followed by thermal or chemical reduction of GO to reduced graphene oxide (rGO). In thermal reduction methods, a small amount of GO is typically placed in a high temperature inert or reducing environment for a specific time. In addition, to improve certain properties or to add new features, rGO can be decorated with other compounds which usually requires additional synthesis steps. Here, we demonstrate the continuous single-step synthesis of three-dimensional crumpled graphene (CG) nanostructures decorated with multicomponent metal nanoparticles including CG-cobalt-nickel and CG-iron-cobalt-nickel using the High Temperature Reducing Jet (HTRJ) process. In this process, combustion products of a fuel-rich hydrogen flame pass through a converging-diverging nozzle. An aqueous solution or dispersion of precursors injected at the throat section of the nozzle is atomized by the hot high-velocity gas stream. The resulting droplets evaporate in a reducing environment containing excess H₂. After the reaction zone, products are cooled immediately and collected on a filter. The key advantage of the HTRJ system over common flame-based aerosol synthesis methods is the separation of flame and product formation zones, which allows synthesis of non-oxide nanomaterials that can be reduced by H₂ in the presence of H₂O. We have utilized the capabilities of this system to synthesize CG nanostructures using an aqueous dispersion of GO as the precursor. Moreover, by adding nickel, cobalt, and ferric nitrate salts to the GO precursor solution, we decorated CG nanostructures with iron-cobalt-nickel nanoparticles of less than 10 nm average diameter. The HTRJ process is a potentially scalable, continuous synthesis method of CG and CG-metal nanostructures. The nanostructures made by this process can be used in electrocatalysts for fuel cells, electrodes in batteries and supercapacitors, conductive inks for printed electronics, wastewater treatment, and many other applications where a graphitized carbon-metal nanomaterial is needed.