Although graphene is a simple material made up of a two-dimensional sheet of carbon atoms that are arranged in a hexagonal pattern, it has an unbelievably wide range of useful properties. It is thin and flexible, lightweight but still strong, and an excellent conductor of heat and electricity. These features have led it to appear in many different items, such as flexible electronics, hair dye, clothing, shoes, a face mask to protect against disease, smart bandages, water filters, air purifiers, flooring, bionic mushrooms for energy harvesting, and more.
Graphene is suitable for almost anything. However, there is one thing it can’t do well: be dispersed in water. This is quite unfortunate as that would open so many doors of possibility in utility and ease of use. Imagine just being able to spray or paint graphene (a conductive coating) onto a surface and turn it into a supercapacitor electrode.
Well, thanks to a team of researchers at Umeå University, that may soon be possible as they’ve found a way to essentially make graphene paint. The challenge was to find a way to overcome the fact that graphene is hydrophobic (it repels water). There are ways. However, they involve harsh organic solvents that are toxic or mechanical treatments that can introduce defects.
The solution? The researchers used oxidized graphene (graphene oxide), a different form of the material, which is hydrophilic (it dissolves in water). They were able to get graphene, active graphene, and other hydrophobic carbons (porous and activated) to disperse in water by mixing it with graphene oxide. Even after sitting on the shelf for days, the material didn’t settle at the bottom – it remained well mixed.
They then tested the dispersion by applying it to metallic foil, drying it, and then heating it to 200 °C (392 °F). The idea was to make a supercapacitor electrode film.
Alexandr Talyzin, a corresponding author of the study, said:
“What we get in the end is a thin film of conductive electrode material with a rather high surface area, good conductivity, and excellent performance in the storage of electricity in supercapacitors. The high surface area is provided by the micrometer-sized particles of (for example) activated graphene, while nanotubes and thermally reduced graphene oxide provide good electrical contact between the particles.”
It worked so well that the team swiftly applied for a patent for the technique. Talyzin said:
“It went surprisingly smooth and rapid once I contacted Innovation Office at Umeå University. We got an enormous amount of help in a short time thanks to experts like Daniel Hoffman and his colleagues. While the scientific paper was under review, we were able to complete the application for a patent.”
The team’s graphene dispersions can easily be scaled up for industrial production. It has value in various applications, such as conductive paints, inks for printing, and protective coatings.
