http://wired.com/news/planet/0,2782,67512,00.html?tw=wn_tophead_5
"perhaps the toughest challenge in fuel-cell research: designing a safe, lightweight and compact hydrogen fuel tank.
Two recent papers [] find the most promising hydrogen storage medium is in something called carbon nanostructures."

"the hydrogen revolution could be realized with the help of tiny balls or tubes of carbon decorated with periodic defects in their structure. Those defects are metallic elements that attract hydrogen to the nanostructures like Velcro."

"the tank would then soak up the hydrogen, incorporating the fuel into the structure of the tank itself."

"The upside is that the tank would theoretically hold enough hydrogen to power the car for as much as 300 miles of driving."