Electric double layer capacitors (or supercapacitors) store charges through the physisorption of electrolyte ions onto porous carbon electrodes. The control over structure and morphology of carbon electrode materials is therefore an effective strategy to render them high surface area and efficient paths for ion diffusion. Here we demonstrate the fabrication of highly porous graphene-derived carbons with hierarchical pore structures in which mesopores are integrated into macroporous scaffolds. The macropores were introduced by assembling graphene-based hollow spheres, and the mesopores were derived from the chemical activation with potassium hydroxide. The unique three-dimensional pore structures in the produced graphene-derived carbons give rise to a Brunauer-Emmett-Teller surface area value of up to 3290 m(2) g(-1) and provide an efficient pathway for electrolyte ions to diffuse into the interior surfaces of bulk electrode particles. These carbons exhibit both high gravimetric (174 F g(-1)) and volumetric (~100 F cm(-3)) specific capacitance in an ionic liquid electrolyte in acetonitrile. The energy density and power density of the cell assembled with this carbon electrode are also high, with gravimetric values of 74 Wh kg(-1) and 338 kW kg(-1) and volumetric values of 44 Wh L(-1) and 199 kW L(-1), respectively. The supercapacitor performance achieved with these graphene-derived carbons is attributed to their unique pore structure and makes them potentially promising for diverse energy storage devices.

We report a high-performance supercapacitor incorporating a poly(ionic liquid)-modified reduced graphene oxide (PIL:RG-O) electrode and an ionic liquid (IL) electrolyte (specifically, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide or EMIM-NTf(2)). PIL:RG-O provides enhanced compatibility with the IL electrolyte, thereby increasing the effective electrode surface area accessible to electrolyte ions. The supercapacitor assembled with PIL:RG-O electrode and EMIM-NTf(2) electrolyte showed a stable electrochemical response up to 3.5 V operating voltage and was capable of yielding a maximum energy density of 6.5 W·h/kg with a power density of 2.4 kW/kg. These results demonstrate the potential of the PIL:RG-O material as an electrode in high-performance supercapacitors.

The fabrication and design principles for using silver‐nanowire (AgNW) networks as transparent electrodes for flexible film heaters are described. For best practice, AgNWs are synthesized with a small diameter and network structures of the AgNW films are optimized, demonstrating a favorably low surface resistivity in transparent layouts with a high figure‐of‐merit value. To explore their potential in transparent electrodes, a transparent film heater is constructed based on uniformly interconnected AgNW networks, which yields an effective and rapid heating of the film at low input voltages. In addition, the AgNW‐based film heater is capable of accommodating a large amount of compressive or tensile strains in a completely reversible fashion, thereby yielding an excellent mechanical flexibility. The AgNW networks demonstrated here possess attractive features for both conventional and emerging applications of transparent flexible electrodes.

A practical route to the production of solution phase transferable graphene sheets using ionic liquid polymers (PIL) as a transferring medium is developed. Chemically converted graphene sheets decorated with PIL were found to be stable against the chemical reduction and well dispersed in the aqueous phase without any agglomeration. Upon the anion exchange of the PIL on graphene sheets, these PIL-modified graphene sheets in aqueous phase are readily transferred into the organic phase by changing their properties from hydrophilic to hydrophobic.

Large-scale integration of vanadium dioxide (VO2) on mechanically flexible substrates is critical to the realization of flexible smart window films that can respond to environmental temperatures to modulate light transmittance. Until now, the formation of highly crystalline and stoichiometric VO2 on flexible substrate has not been demonstrated due to the high-temperature condition for VO2 growth. Here, we demonstrate a VO2-based thermochromic film with unprecedented mechanical flexibility by employing graphene as a versatile platform for VO2. The graphene effectively functions as an atomically thin, flexible, yet robust support which enables the formation of stoichiometric VO2 crystals with temperature-driven phase transition characteristics. The graphene-supported VO2 was capable of being transferred to a plastic substrate, forming a new type of flexible thermochromic film. The flexible VO2 films were then integrated into the mock-up house, exhibiting its efficient operation to reduce the in-house temperature under infrared irradiation. These results provide important progress for the fabrication of flexible thermochromic films for energy-saving windows.