Sweden researchers have found a surprisingly simple way to disperse the Graphene in water.
Graphene, graphite, activated carbons are quite different forms of carbon but what is common for them is their hydrophobic properties. It is impossible to dissolve or disperse these materials in water directly. On the other hand, using dispersions or solutions for many applications is a big advantage. Ideally, one can spray or paint graphene dispersion on metal foil and prepare e.g. electrode material by simply drying.
Scientists have been searching for good methods to prepare dispersions using graphene-related materials for many years. The most common method available so far is to use organic solvents and very strong mechanical treatment, e.g. sonication for long time. However, organic solvents are often toxic while mechanical treatment is not only time and energy consuming but also introduces many defects, which adversely affect conductivity of the graphene sheets.
Researchers from Umeå University in Sweden have found a simple and environmentally friendly solution to the problem: oxidized form of graphene, graphene oxide, is hydrophilic and easy to disperse in water.
What they have discovered is that stable water dispersions can be prepared by adding certain amount of graphene oxide to various hydrophobic carbons.
The research team tested the method using high surface area carbons like graphene, activated graphene, porous or activated carbons. The dispersions were stable and did not precipitate even after days of shelf storage. When they added some carbon nanotubes into the dispersion, it appeared to be rather good for preparation of supercapacitor electrodes. The dispersion was applied to metallic foil, dried and heated at 200o Celsius. All these steps could easily be scalable into industrial production.
What they get in the end is a thin film of conductive electrode material with rather high surface area, good conductivity and excellent performance in storage of electricity in supercapacitors. The high surface area is provided by the micrometer-sized particles of e.g. activated graphene, while nanotubes and thermally reduced graphene oxide provide good electrical contact between the particles.
The dispersions can be useful also in many other applications like inks for printing, protective coatings, and conductive paints.
The authors have applied for patent for the method to prepare dispersions.
News Source: Umeå University
