Abstract
Energy storage systems such as electrical double-layer capacitors (a.k.a. supercapacitors) are essential components of the renewable energy paradigm. Today, the widespread use of carbon materials as electrodes of supercapacitors is justified, for instance, by their remarkable electronic conductivity, chemical stability and wide range of operating temperatures. Still, current technology has not yet approached the maximum theoretical capacitance for pure carbon-based electrode materials (550 F/g). While recent literature has repeatedly investigated the use of chemically exfoliated graphene for supercapacitors, a systematic study on how different synthesis strategies affect the structure and chemistry of reduced graphene oxide (rGO) was missing. Likewise, steps such as the drying methodology had been mostly overlooked.
In this presentation, I will describe our strategy to rationally approach the synthesis of rGO materials4, 5 and how this enabled considerable improvements in electrochemical capacitance. Accordingly, besides a judicious selection of the oxidation–reduction route for the graphite, we observed that it is critical to control the final drying step. In these circumstances, it is possible to significantly increase the specific surface area of the rGO powder and preserve its porous network (Figure 1), thereby maximising the supercapacitance performance. While previous studies on hydrothermally reduced GO invariably reported low surface area (~100 m2/g) and (<300 F/g) capacitance, we achieved an unprecedented value of specific surface area of 364 m2/g and a remarkable supercapacitance of 441 F/g.