Author(s)

Syed Nasimul Alam, Nidhi Sharma, Lailesh Kumar

Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Rourkela, India.

Over the span of years, improvements over various synthesis methods of graphene are constantly pursued to provide safer and more effective alternatives. Though the extraction of graphene through Hummers method is one of the oldest techniques yet it is one of the most suitable methods for the formation of bulk graphene. Graphene can be obtained in the form of reduced Graphite oxide, sometimes also referred as Graphene oxide. The effectiveness of this oxidation process can be evaluated by the magnitude of carbon/oxygen ratio of the obtained graphene. Here, graphene oxide (GO) was prepared by oxidizing the purified natural flake graphite (NFG) by a modified Hummers method. The attempts have been made to synthesize GO having few layers by using a modified Hummers method where the amount of NaNO₃ has been decreased, and the amount of KMnO₄ is increased. The reaction has been performed in a 9:1 (by volume) mixture of H₂SO₄/H₃PO₄. This modification is successful in increasing the reaction yield and reducing the toxic gas evolution while using a varied proportion of KMnO₄ and H₂SO₄ as those required by Hummers method. A new component of K₂S₂O₈ has been introduced to the reaction system to maintain the pH value. Reduced graphene oxide (rGO) was thereafter extracted by thermal modification of GO. Here, GO has been used as a precursor for graphene synthesis by thermal reduction processes. The results of FTIR and Raman spectroscopy analysis show that the NFG when oxidized by strong oxidants like KMnO₄ and NaNO₃, introduced oxygen atoms into the graphite layers and formed bonds like C=O, C-H, COOH and C-O-C with the carbon atoms in the graphite layers. The structure and morphology of both GO and rGO were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Graphene Oxide (GO), Reduced Graphene Oxide (rGO), Exfoliated Graphite Nanoplatelets (xGnP)

Alam, S. , Sharma, N. and Kumar, L. (2017) Synthesis of Graphene Oxide (GO) by Modified Hummers Method and Its Thermal Reduction to Obtain Reduced Graphene Oxide (rGO)*. Graphene, 6, 1-18. doi: 10.4236/graphene.2017.61001.