Electrochemical synthesis and characterization of thermally reduced graphene oxide: Influence of thermal annealing on microstructural features

Abstract

Controlling the overall microstructure of graphene oxide (GO), which influences its properties (grain size, structural disorder, degree of oxygen functions, thermal stability, and so on), is a major challenge in material research. Moreover, electrochemically generated GO is riddled with flaws and structural disorder. Thermal annealing was utilized to control the microstructural characteristics that affect the properties of the GO. There has been much discussion on whether annealing graphene at a high temperature cleans it or causes additional flaws and structural disorder. In this study, the effect of annealing on the microstructural characteristics of the thermally reduced graphene oxide (TrGO) has been investigated. To get a high yield, GO has been synthesized by using high potential (~80 V DC power) in an aqueous solution of 1 M sulfuric acid (H2SO4) and 3% hydrogen peroxide (H2O2). In order to have a high yield of GO, the electrolyte temperature is significantly essential. The synthesized GO was thermally reduced at 850, 900, 950, and 1000 °C followed by furnace cooling. The results of the XRD and the Raman spectral analysis show that the thermal annealing process has a substantial effect on the diffraction peak, the inter-planar distance, the crystallite size, and the structural disorder of the TrGO. The FE-SEM, TEM, and AFM analysis demonstrates that thermal annealing seemed to have a significant impact on the microstructural characteristics and surface topography of the TrGO. Thermal annealing has little impact on the thermal stability and oxygen-containing functional groups, according to FT-IR and TGA analysis.