A Simple Approach towards Highly Dense Solvated Graphene Films for Supercapacitors

Highly dense porous solvated free‐standing graphene films were prepared by pressing graphene hydrogels obtained by a hydrothermal approach, which entails the generation of hematite nanoparticles that act as separators and endotemplate agents to generate pores. The as‐prepared solvated graphene films have characteristics that make them suitable for use in supercapacitors, that is, a free‐standing nature, a thickness of around 110 μm, a high packing density (1.1 g cm −3 ) and a large areal mass loading (12 mg cm −2 ). When used as supercapacitor electrodes, the graphene films show a high cell capacitance of ≈43 F g −1 (47 F cm −3 ) at 0.1 A g −1 in aqueous electrolyte (H 2 SO 4 ) and retain 50 % of their low rate capacitance even at a high current density of 40 A g −1 . Such porous yet highly dense materials could be used to fabricate lighter and more compact supercapacitor devices than those currently based on activated carbon.