‘Broken’ Nanotubes are Better at Storing Electricity
University of San Diego researchers have discovered that carbon nanotubes don’t have to be perfect to do a better job. Prabhakar Bandaru, a professor in the UCSD Department of Mechanical and Aerospace Engineering have discovered that artificially introducing defects in carbon nanotubes would increase their energy storage capacity.
In most of the cases, the recently-discovered carbon nanotubes have been used for their excellent electricity-conducting properties, considered as one of the “wonder materials” of this century. CNTs have a cylindrical structure, with a diameter of 1 to 100 nm, and are atomically perfect – in theory.
Practically, though, carbon nanotubes are far from being perfect, and that has caught the attention of Jeff Nichols, an engineering graduate student. The effect rests in the creation of just the right amount of defects – enough to create additional charge sites on the nanotube, but not enough to break down its electrical conductivity.
The phenomena was then studied by Mark Hoefer: “We first realized that defective CNTs could be used for energy storage when we were investigating their use as electrodes for chemical sensors,” Hoefer said. “During our initial tests we noticed that we were able to create charged defects that could be used to increase CNT charge storage capabilities.”
Of course, all of this has a limit, because raising the defect rate for the nanotube above a certain threshold would alter its electrical conductivity properties, and make it worse. The scientists have also tried certain methods that could decrease the charge associated with the defects by bombarding the CNTs with argon or hydrogen.
We would all like our cellphones or laptops, or maybe electric cars in the future, to hold their charge for a long time, and to charge fast. Supercapacitors made with defective structured nanotubes could accomplish this dream.
Hoefer is very enthusiastic about the discovery: “It is remarkable how current tools and devices are becoming increasing more efficient and yet smaller due to discoveries made at the nanoscale,” he said. “My time spent investigating CNTs and their potential uses at the Jacobs School will prepare me for my career, since future research will continue the trend of miniaturization while increasing efficiency.”
image above is of carbon nanotubes taken using a field emission gun scanning electron microscope