Carbon is a truly amazing element when examined in its many forms or allotropes, so it is not very surprising that researchers have been trying to combine these allotropes. Those at Rice University have successfully grown carbon nanotubes, up to 120 microns long, on a sheet of graphene. This new hybrid material though does not sacrifice the conductive properties of its parts, which is very important for potential uses.
To do this the researchers modified a method to grow nanotubes that has been developed over the past decade. This method grows the nanotubes on a carbon substrate using iron catalysts and an aluminum oxide buffer on top. What the researchers did for this new work was make a sheet of graphene the carbon substrate, while the original copper substrate it was grown on remained. It is important to note though that the nanotubes are not just like columns placed on the graphene surface but trees that have roots dug into the ground. In this case the roots are covalent bonds; a very strong molecular bond.
Potentially this hybrid material could be used for carbon-based supercapacitors thanks to its very high surface area. A single gram of the material can have a surface area exceeding 2,000 square meters, and it is on the surface that charge is built up in a capacitor. This is why it is already matching the best carbon-based supercapacitors previously produced.