More Solid than Solid: A Potential Hydrogen-Storage Compound
Date: Wednesday, April 02, 2008 @ 22:04:21 UTC
Topic: Science
 MOF-74 resembles a series of tightly packed straws comprised mostly of
carbon atoms (white balls) with columns of zinc ions (blue balls)
running down the walls. Heavy hydrogen molecules (green balls) adsorbed
in MOF-74 pack into the tubes more densely than they would in solid
form. Credit: NIST
One of the key engineering challenges to building a clean, efficient,
hydrogen-powered car is how to design the fuel tank. Storing enough raw
hydrogen for a reasonable driving range would require either
impractically high pressures for gaseous hydrogen or extremely low
temperatures for liquid hydrogen. In a new paper researchers at the
National Institute of Standards and Technology’s Center for Neutron
Research have demonstrated that a novel class of materials could enable
a practical hydrogen fuel tank.
A research team from NIST, the University of
Maryland and the California Institute of Technology studied
metal-organic frameworks (MOFs). One of several classes of materials
that can bind and release hydrogen under the right conditions, they
have some distinct advantages over competitors. In principle they could
be engineered so that refueling is as easy as pumping gas at a service
station is today, and MOFs don’t require the high temperatures (110 to
500 C) some other materials need to release hydrogen.
In particular, the team examined MOF-74, a porous crystalline
powder developed at the University of California at Los Angeles. MOF-74
resembles a series of tightly packed straws comprised of mostly carbon
atoms with columns of zinc ions running down the inside walls. A gram
of the stuff has about the same surface area as two basketball courts.
The researchers used neutron scattering and gas adsorption
techniques to determine that at 77 K (-196 C), MOF-74 can adsorb more
hydrogen than any unpressurized framework structure studied to
date—packing the molecules in more densely than they would be if frozen
in a block...
More: http://www.physorg.com/news126355316.html
Source: National Institute of Standards and Technology
|
|