The applications for graphene appear boundless until its hydrophobic nature is considered. The material cannot be dissolved in water, which would facilitate spraying or coating various substrates with aqueous graphene dispersions. A remedy devised at Umeå University, Sweden, uses hydrophilic graphene oxide to prepare stable Schematic representation of the aqueous reduced and activated graphene oxide dispersion design for supercapacitor electrodes. The pie chart areas represent the weight content of each component in the dispersion. Source: Vasyl Skrypnychuk et al.water-based dispersions.

Efforts to synthesize graphene dispersions require use of toxic organic solvents or time-intensive sonication processes. By combining graphene oxide with particles of other hydrophobic carbons, such as graphene, activated graphene, and porous and activated carbons, the researchers formulated stable graphene dispersions without the need for other chemical agents or mechanical treatment. The dispersions were also demonstrated to be compatible with conventional methods of electrode deposition such as brush/blade deposition, spray coating and inkjet printing.

Carbon nanotubes were then added to form a dispersion suitable for the preparation of supercapacitor electrodes. The dispersion was applied to metallic foil, dried and heated at 200^o C. The result was a thin film of conductive electrode material with high surface area, good conductivity, energy density of 35.6 Wh/kg and a power density of 42.2 kW/kg.

The dispersions described in the Journal of Physical Chemistry Letters might be of value in other applications, such as inks for printing, protective coating and conductive paints.