Graphene/Nanotube Hybrid Makes Single-Surface Material for Energy Storage, Electronics
ScienceDaily (Nov. 27, 2012) — A seamless graphene/nanotube hybrid created at Rice University may be the best electrode interface material possible for many energy storage and electronics applications.
Seven-atom rings (in red) at the transition from graphene to nanotube make a new hybrid material from Rice University a seamless conductor. The hybrid may be the best electrode interface material possible for many energy storage and electronics applications. (Credit: Tour Group/Rice University)
Led by Rice chemist James Tour, researchers have successfully grown forests of carbon nanotubes that rise quickly from sheets of graphene to astounding lengths of up to 120 microns, according to a paper published November 27 by Nature Communications. A house on an average plot with the same aspect ratio would rise into space.
That translates into a massive amount of surface area, the key factor in making things like energy-storing supercapacitors.
The Rice hybrid combines two-dimensional graphene, which is a sheet of carbon one atom thick, and nanotubes into a seamless three-dimensional structure. The bonds between them are covalent, which means adjacent carbon atoms share electrons in a highly stable configuration. The nanotubes aren't merely sitting on the graphene sheet; they become a part of it.
"Many people have tried to attach nanotubes to a metal electrode and it's never gone very well because they get a little electronic barrier right at the interface," Tour said. "By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it's all one seamless material.
"This gives us, effectively, a very high surface area of more than 2,000 square meters per gram of material. It's a huge number," said Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science and a co-author with former postdoctoral researcher and lead author Yu Zhu, now an assistant professor at the University of Akron.