The discovery that nitrogen-doped, metal-free carbon nanotubes make better electrodes than do platinum nanoparticles may open the way for inexpensive nanotech fuel cells. From New Scientist, written by Stephen Battersby “Carbon catalyst could herald cut-price fuel cells“:
Fuel cells have been hailed as saviours of the environment, because they can cleanly and efficiently turn hydrogen and other fuels into electricity. But so far this technology has been hobbled by the high cost of the platinum catalysts needed to make it work.
Now a new type of fuel cell based on carbon nanotubes promises to be much cheaper, as well as more compact and more efficient.
A team led by Liming Dai of the University of Dayton, Ohio, has discovered that a bundle of nanotubes doped with nitrogen can act as the catalyst, helping oxygen to react inside the fuel cell.—
Carbon nanotubes had previously been shown to catalyse the fuel-cell reaction, but they were much less effective than platinum nanoparticles.
It had been thought that their slight catalytic properties were caused by traces of iron left over from the manufacturing process, but Dai’s group have discovered that the iron actually hinders catalysis.
They grew nanotubes doped with a trace of nitrogen using a process called chemical vapour deposition, in which nanotubes grow up from a base of iron nanoparticles. Then they removed the iron.
The original aim was to use these purified nanotubes in biosensors, but Dai also tried them out as catalysts — and found to his surprise that they worked very well.
“They are even better than platinum, long regarded as the best catalyst,” says Dai. The team’s device produces four times as much electric current as it would using platinum. And, while platinum nanoparticles can lose their effectiveness when they cluster together or become tainted by carbon monoxide, the nanotubes are immune to these degradations.
The crucial role of nitrogen doping is to create electron-accepting atoms in the CNT to facilitate the flow of electrons from the anode to the cathode. These doped CNTs may remove a major cost barrier by replacing platinum catalysts in fuel cells, but they first need to be tested under actual operating conditions. The research was published in Science (abstract). (Credit: KurzweilAI.net)