Capacitance of aggregated functionalized graphene in supercapacitors

Abstract

Functionalized graphene sheets are a promising material for electric double-layer capacitors due to their high specific surface area, conductivity, and intrinsic capacitance. However, it is difficult to maintain this high specific surface area because functionalized graphene sheets tend to aggregate when assembled in a bulk form. Previous publications have shown that vacuum filtration may be a promising process for overcoming the issue of aggregation and re-stacking of graphene sheets during electrode assembly. Using vacuum filtration, other research groups have produced high performing supercapacitors using chemically-reduced graphene sheets. This work investigated vacuum filtration as a viable method for constructing supercapacitor electrodes using thermally-reduced graphene, a material with higher intrinsic capacitance than chemically-reduced graphene and other forms of graphene. It was determined that the combination of vacuum filtration and thermally-reduced functionalized graphene does not produce supercapacitors with very high specific capacitance. This work also looked into the importance of the drying step prior to solvent infiltration of electrodes during the assembly process. The amount of drying time prior to solvent infiltration plays a role in maintaining ion-accessible surface area and sufficient pore size, both of which are important factors in the performance of electrodes in supercapacitors. This work demonstrated the unsuccessful application of vacuum filtration of thermally-reduced graphene to produce electrodes and laid groundwork for further study into solvent infiltration of supercapacitor electrodes.