Reduced graphene oxides by microwave-assisted ionothermal treatment

Abstract

Given their potential applications in electronic and optoelectronic devices and circuits, reduced graphene oxides (RGOs) have attracted considerable interest. However, more facile and environmentally friendly reduction methods, whether thermal or chemical reduction methods, still need to be further exploited. In this paper, a facile and environmentally friendly method was developed to reduce the graphene oxides (GOs) homogeneously exfoliated in ionic liquids by microwave-assisted ionothermal treatment under relative low temperature (200 °C) and atmospheric pressure. UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction pattern, atomic force microscopy, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis and electrical conductivity measurement were used to confirm the formation of RGOs with a high reduction degree. The large enhancement of C/O atomic ratio (from 1.32 to 7.65) and at least four orders of electrical conductivity rise of RGOs compared with GOs revealed the high deoxygenation and graphitization efficiency of this method. In addition, the conductive RGOs could be successfully exfoliated to a single layer in some organic solvents, which is paramount for their scalable applications. In consideration of the involatile and recyclable nature of ionic liquids, this novel method can be considered as an economical and green thermal reduction route.