Defect Ridden Nanotubes May Improve Fuel Cells and Batteries
Different materials behave differently, from nonconductive neon to highly conductive copper, and it is this variety of properties which enables a variety of technologies. Unfortunately it also limits many technologies when only one material has the required properties. Platinum is an excellent catalyst and is used in many devices, from fuel cells to catalytic converters. It is also quite rare, making it so expensive that some technologies cannot see widespread use. For this reason researchers are constantly looking for a new, cheaper catalyst, and researchers at Stanford University may have discovered one.
Carbon nanotubes are already well respected for their high conductivity, but normally are not useful as a catalyst. Placing imperfections in a nanotube's wall can make it a better catalyst, but this impairs its conductivity. The Stanford researchers got around this issue of mutual exclusivity by using two single-walled nanotubes, one inside the other.
With the appropriate chemicals, the researchers were able to cause the out nanotube to unzip and have nitrogen atoms attach to them, without disturbing the inner nanotube. The nitrogen atoms, along with iron atoms left over from the seed crystals that grew the nanotubes, makes the outer wall an effective catalyst, while the inner nanotube conducts electricity as needed to keep the catalyst working. If this design operates nearly as well as platinum we may see several devices drop in price, and some new technologies brought to market. For example, lithium-air batteries which can achieve an energy density 10 times greater than modern lithium ion batteries require a very efficient and cheap catalyst.