Few-layer graphene prepared via microwave irradiation of black sesame for supercapacitor applications

Abstract

Traditional heating often generates amorphous carbon or very small graphite clusters, leading to poor electron transport capabilities and limiting the application of material in supercapacitors. Nevertheless, the superiority of microwave heating, a molecular-level heating that is different from traditional heating, has been seldom exploited to date. Herein, under microwave irradiation, we built biomass-based (black sesame) few-layer porous graphene using molysite (MPG). The MPG, with an IG/ID value of 2.37, an IG/I2D of about 1.05, possessed a thickness of 1.192 nm verified the few-layer structure. The proportion of sp2 hybridized carbon obtained 41.99% corresponding to graphitic carbon. Compared with traditionally heated sample (TGPC), it can be found that hyperthermic point provided by microwave can supply energy for the rearrangement from amorphous to ordered. The molysite created catalysis-wave absorption dual sites simultaneously, realizing high-density “hot spots”, allowing targeted, precise heating, and promoting the exfoliation of graphite layers was demonstrated through tracking the microwave reaction. The MPG formed by microwave technology not only possessed excellent specific surface area (2092.8 m2 g−1) but also formed natural nitrogen/oxygen self-doping. The electrochemical test demonstrated that MPG had an outstanding specific capacitance of 333.3F g−1 and a small charge transfer resistance (Rct) of 0.047 Ω. The energy density of 3.32 W h kg−1, relaxation time constant of 1.645 s and cyclability of 97.6% could be maintained at 20 mg cm−2. Our work demonstrated the potential of using microwave for preparing graphene and provides a new idea for high-energy and power supply in lightweight supercapacitors.