Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100–300 F g⁻¹. We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.

The ternary roles of polyethyleneimine (PEI) as a reducing agent, a surface modifier and a polymer host have been presented to fabricate reduced graphene oxide (RGO) based composite films with improved gas barrier property. The PEI functionalized RGO dispersion is prepared and filtered to fabricate thin films with a brick and mortar structure. The simultaneous reduction and functionalization of graphene oxide (GO) by PEI are confirmed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy analysis. The good dispersion of graphene sheets in the PEI matrix and the layered structure is confirmed by X-ray diffraction and field emission scanning electron microscopy analyses. Thermogravimetric analysis also confirms the removal of oxygen functionalities from GO and the attachment of PEI chains to the RGO sheets. The electrical conductivity of the RGO film is found to be 492 S m⁻¹ at low content of PEI (PEI : GO = 0.02 : 1), and increasing the PEI content leads to a decrease in the electrical conductivity of the films. In contrast, the water dispersibility and gas barrier properties increase with increasing PEI content in the composite film.

Ceria (CeO₂) nanoparticles were grown on reduced graphene oxide (RGO) via the in situ reduction of graphene oxide (GO) in the presence of cerium nitrate and CTAB, followed by a one step hydrothermal treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy (RS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the samples. The characterization suggests that the ammonia-assisted hydrothermal method is a facile and advantageous route to synthesize CeO₂–RGO nanocomposites compared to the widely used method utilising hydrazine hydrate as the reducing reagent. TEM investigations revealed that the CeO₂ nanoparticles with an average size of ∼14 nm were dispersed on the layers of RGO. The catalytic activity of the CeO₂–RGO nanocomposites towards the electrooxidation of hydrazine was further investigated by cyclic voltammetry measurements. The results obtained suggest that compared to bare CeO₂ nanoparticles, the CeO₂–RGO nanocomposite exhibits remarkably enhanced electrocatalytic activity, due to the synergistic effects between the CeO₂ nanoparticles and RGO.