Graphene-based materials are extensively studied as promising candidates for supercapacitors (SCs) owing to the high surface area, electrical conductivity, and mechanical flexibility of graphene. Reduced graphene oxide (RGO), a close graphene-like material studied for SCs, offers limited specific capacitances (100 F·g^–1) as the reduced graphene sheets partially restack through π–π interactions. This paper presents pillared graphene materials designed to minimize such graphitic restacking by cross-linking the graphene sheets with a bifunctional pillar molecule. Solid-state NMR, X-ray diffraction, and electrochemical analyses reveal that the synthesized materials possess covalently cross-linked graphene galleries that offer additional sites for ion sorption in SCs. Indeed, high specific capacitances in SCs are observed for the graphene materials synthesized with an optimized number of pillars. Specifically, the straightforward synthesis of a graphene hydrogel containing pillared structures and an interconnected porous network delivered a material with gravimetric capacitances two times greater than that of RGO (200 F·g^–1vs 107 F·g^–1) and volumetric capacitances that are nearly four times larger (210 F·cm^–3vs 54 F·cm^–3). Additionally, despite the presence of pillars inside the graphene galleries, the optimized materials show efficient ion transport characteristics. This work therefore brings perspectives for the next generation of high-performance SCs.

Core double–shell cobalt/graphene//polystyrene nanocomposites (Co/C//PS) were synthesized by an in situ sonochemical polymerization technique. Commercial Co/C nanoparticles are used and successfully lead to gram-scale production of processable nanocomposite. Synthesized Co/C//PS nanocomposites result in homogeneous and dense dispersion of particles with or without additional polymeric matrix. They showed improved thermal properties such as higher initial degradation temperatures and a significant increase of glass transition temperature (i.e. 10 to 12 °C) in contrast to neat PS. These results suggest that covalent bonding occurs between PS and the graphene shell, and may be promoted by two surface reactions: “grafting from” when the monomer is pre-immobilized on graphene and grows to polymer, and “grafting to” when pre-synthesized polymer is immobilized on graphene. Both mechanisms are compared and explained. HR-TEM observations revealed polymer shells of 4 to 5 nm covering Co/C nanoparticles or at least small aggregates. However, the number of layers of the graphene shell which consists of 6 to 8 regular layers on raw particles decreases to 3, this layer reduction can be explained by a partial amorphization of graphene occurring during the polymerization. Nevertheless, Co particles are still efficiently protected from oxidation as final Co/C//PS nanocomposites are able to sustain high mass-magnetization (i.e. ∼49 emu g⁻¹ for 94% wt Co/C). First indications of satisfying mechanical cohesion are also shown by the formation of two relevant nanocomposite shapes (film and disk). In conclusion, in situ polymerization is a powerful synthesis method to produce processable high-magnetization nanocomposites.