Researchers at SSRL and Stanford have taken a step closer to hydrogen-run cars by adding hydrogen to tiny cylinders made entirely out of carbon. Recent experiments at SSRL and the Advanced Light Source in Berkeley have shown that carbon nanotubes, 50,000 times narrower than a human hair, are a promising material for storing hydrogen safely, efficiently and compactly. To attempt to store hydrogen, the researchers bombarded a film of carbon nanotubes with a hydrogen beam. Then they studied the film with different x-ray spectroscopy techniques to see if any hydrogen atoms had formed chemical bonds with the carbon.

They found that about 65 percent of the carbon atoms had bonded to hydrogen atoms. In carbon nanotubes, the carbon atoms have double bonds between each other. The incoming hydrogens break the double bonds, allowing a hydrogen atom to attach to a carbon atom while the carbon atoms renew their attachment to each other with single bonds. The carbon nanotubes offer safe storage because the hydrogen atoms are bonded to other atoms, rather than freely floating as a gas, which is potentially explosive. The researchers estimated that five percent of the total weight of the hydrogenated nanotubes came from the hydrogen atoms, and they are already working to boost that number. For its FreedomCAR program, the Department of Energy has set the goal of developing a material that can hold six percent of the total weight in hydrogen by the year 2010.

A. Nikitin, H. Ogasawara, D. Mann, R. Denecke, Z. Zhang, H. Dai, K. Cho, and A. Nilsson, Phys. Rev. Lett. 95, 225507 (2005)