Researches from Vanderbilt University developed a new graphene-coated silicon based supercapacitor. This is an attractive design not just because of its excellent properties, but because it can be integrated into silicon chips.
Silicon isn't normally used for supercapacitors due to the extreme reactivity of silicon with electrolytes. But doped Silicon has very attractive features such as a low mass density, excellent conductivity, a controllably etched nanoporous structure. In addition silicon is abundant and used in many processes which makes it easier to integrate.
The researchers chose to start with porous silicon that has a controllable and well-defined nanostructure made by electrochemically etching the surface of a silicon wafer. This can be used to make a surface with optimal nanostructures for supercapacitor electrodes. By coating this silicon with graphene, the researchers managed to chemically stabilize it. The graphene coating improved energy densities by over two orders of magnitude compared to those made from uncoated porous silicon - and significantly better than commercial supercapacitors.
The researchers grew the graphene coating using a furnace at rather low temperatures 600 to 700 degrees Celsius. Usually graphene dot not grow at that temperature but on the porous silicon it did.