Controlled porous structures of graphene aerogels and their effect on supercapacitor performance†
The design and optimization of 3D graphene nanostructures are critically important since the properties of electrochemical energy storages such as supercapacitors can be dramatically enhanced by tunable porous channels. In this work, we have developed porous graphene aerogels from graphene suspensions obtained via electrochemical exfoliation and explored their application as supercapacitor electrodes. By adjusting the content of the electrolyte in the exfoliation process, the aspect ratio of graphene sheets and the porosity of the graphene network can be optimized. Furthermore, the freezing temperature in the freeze drying step is also found to play a critical role in the resulting pore size distributions of the porous networks. The optimized conditions lead to meso- and macroporous graphene aerogels with a high specific surface area, extremely low densities and superior electrical properties. As a result, the graphene aerogel supercapacitors exhibit a specific capacitance of 325 F g−1 at 1 A g−1 and an energy density of 45 Wh kg−1 in a 0.5 M H2SO4 aqueous electrolyte with high electrochemical stability and electrode uniformity required for practical usage. This research provides a practical method for lightweight, high-performance and low-cost materials in the effective use of energy storage systems.