Abstract
Carbon foams were produced from composites of macroporous poly(divinylbenzene) (poly(DVB) and reduced graphene oxide (rGO). Poly(DVB) was synthesized by polymerizing the continuous phase of water-in-oil high internal phase emulsions (HIPEs) stabilized at the interface by amphiphilic rGO, employed as a particulate emulsifier. The use of rGO as an emulsifier allows for the synthesis of stable macroporous composites of poly(DVB)HIPEs with a percolating network of rGO at the surface of the material. Both permeable and non-permeable carbon foams, or ‘carboHIPEs’, could be prepared by carbonization of these macroporous composites at 800 °C. The resulting carboHIPEs gave yields as high as 26 wt.% of the original material. Furthermore, carboHIPEs retain the pore structure of their macroporous precursor, while also producing a newly-formed microporous structure, leading to hierarchical porosity and huge increases in surface area upon carbonization. Surface areas of up to 1800 m2/g and excellent electrical conductivities of up to 270 S/m are achievable, among the highest reported within the fields of both polyHIPEs and carboHIPEs. Using an rGO emulsifier when creating these structures allows for the production of true ‘all-carbon’ foams upon carbonization. These polyHIPE composites do not require modification, such as additional crosslinking, prior to carbonization, due to the inherently crosslinked structure of poly(DVB). It is demonstrated that the rGO derived carboHIPEs are good candidates as electrodes in supercapacitor applications such as electrical double-layer capacitor (EDLC) devices, where carboHIPEs derived from more conventional silica-stabilized HIPEs perform poorly. The use of a pourable, aqueous emulsion-template enables simple moulding, minimizes waste and avoids the strong acid treatments used to remove many conventional solid-templates. The capability of producing monolithic, porous carbon foams allows for the production of binderless devices, potentially simplifying the production process of supercapacitors. Devices demonstrated maximum specific electrode capacitance to the tune of 26 F g-1 at 10 mV s-1, 5.2 Wh kg-1 of energy density, 280 W kg-1 of power density and coulombic efficiency of up to 99.6 %. In short, the carbonization of rGO-poly(DVB)HIPE composites enables the production of hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.