Greener Synthesis of Reduced Graphene Oxide-Nickel Nanocomposite: Rapid and Sustainable Catalyst for the Reduction of Nitroaromatics

An efficient one-pot method for the preparation of reduced graphene oxide-nickel nanocomposite (RGO-Ni) has been developed using L-ascorbic acid as a greener reducing agent, which simultaneously reduces both graphene oxide and Ni-II. The nanocomposite was characterized using various analytical techniques such as Fourier Transform Infrared Spectroscopy (FT-IR), Powder X-Ray Diffraction analysis(PXRD), Raman, Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Energy Dispersive X-ray Spectroscopy (EDS), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS) and surface area measurements. ICP-OES confirms the presence of 19.7% nickel loading and TEM shows the average size of the particles to be 10nm. Subsequently, RGO-Ni nanocomposite was used as a sustainable catalyst for the reduction of nitroaromatics to the corresponding amines using NaBH4 in an aqueous methanol medium. A series of aromatic and aliphatic nitro compounds are chemoselectively reduced to amines over other reducible functionalities. RGO-Ni nanocomposite is highly stable, and can be recovered by magnetic separation and recycled for at least five consecutive cycles. The present catalytic system has achieved the dual requirements for reactivity and selectivity in a nitro reduction in short reaction time with minimum nickel load in greener media.