Graphene is a new and exciting material that has attracted much attention in the last decade and is being extensively explored because of its properties, which have been described with so many superlatives. Production of graphene for large scale application is still a major challenge. Top-down graphene exfoliation methods from graphite, such as liquid-phase exfoliation which is promising because of low cost and high scalability potential will be briefly discussed. We also analyze the challenges and possibilities of using graphene as a nanofiller in polymer composites which has resulted in enhanced electrical, mechanical and thermal properties. In this review, we take a panoramic approach to give insight on the different aspects of graphene such as properties, graphite-based production methods and also examples of graphene application in polymer composites and will be beneficial to both novice and experts.

In this study, we present willow wood as a new low-cost, renewable, and sustainable biomass source for the production of a highly porous activated carbon for application in energy storage devices. The obtained activated carbon showed favorable features required for excellent electrochemical performance such as high surface area (∼2 800 m2 g–1) and pore volume (1.45 cm3 g–1), with coexistence of micropores and mesopores. This carbon material was tested as an electrode for supercapacitor application and showed a high specific capacitance of 394 F g–1 at a current density of 1 A g–1 and good cycling stability, retaining ∼94% capacitance after 5 000 cycles (at a current density of 5 A g–1) in 6 M KOH electrolyte. The prepared carbon material also showed an excellent rate performance in a symmetrical two-electrode full cell configuration using 1 M Na2SO4 electrolyte, in a high working voltage of 1.8 V. The maximum energy density and power density of the fabricated symmetric cell reach 23 W h kg–1 and 10 000 W kg–1, respectively. These results demonstrate that willow wood can serve as a low-cost carbon feedstock for production of high-performance electrode material for supercapacitors.

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To exploit the remarkable properties of graphene fully, an efficient large-scale production method is required. Sonication assisted liquid phase exfoliation of graphite, for example, has been extensively used for the production of few-layer graphene sheets, but suffers from low efficiency and high energy consumption, and thus is not viable for large scale production. Here we demonstrate a method that is more efficient and has higher scalability potential than sonication. We show that a few-layer graphene at high concentration of up to 1.1 mg ml-1 can be achieved in aqueous based medium by highly efficient shear exfoliation of graphite in a processing time of just 2 h. The exfoliation process was carried out in a commercially available high shear colloidal mixer fixed with a three stage rotor-stator shear generator for optimum exfoliation with a continuous circulation system. The high efficiency and significant improvement over sonication adopting our method was demonstrated by the fact that the conversion to few-layer graphene sheets produced after just 30 min by shear exfoliation required, in contrast, hundreds of hours by sonication. High concentration defect-free few-layer graphene in aqueous medium, produced at short shearing time, demonstrates that this method has high potential for large-scale production. The produced graphene films exhibit additionally a high electrical conductivity of about 29 000 S m-1 .

Few-layer graphene has been produced by mechanical delamination of exfoliated and naturally obtained graphite in aqueous suspension using the dispersion and suspension properties of nanofibrillated cellulose [NFC]. Various degrees of graphene platelet integrity were obtained depending upon the processing conditions and the optional adoption of surfactant to aid dispersion of the hydrophobic agglomerates of nanometre-thin carbon material. The presence of NFC in the suspension acts similarly to the presence of surfactant, increasing the hydrodynamic coupling between the particles and water as a function of processing time, regardless of the graphene-comprising source. In the light of extensive dynamic and viscoelastic rheological analysis, it was found that by fitting the stress growth region in the stress-shear rate relation to a concatenated series of single exponential functions of shear rate, the power law exponent and suspension consistency parameters [n and k] within a shear rate-localised Herschel-Bulkley [HB] expression provide a straightforward characteristic for monitoring the desired coupling response, and hence desired product constancy.