Researchers Assess Fullerene Nanocage Capacity for Hydrogen Storage
21 March 2008
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| Computed structures of all-carbon cages of fullerenes filled with hydrogen. Click to enlarge. |
Researchers at Rice University have modelled fullerene nanocages filled with hydrogen to assess their capacity to store the gas. Among their conclusions are that some buckyballs (a C60 cage) can hold about 8 wt% of hydrogen at room temperature, and that the hydrogen pressure inside the fullerene nanocage could reach values only a few times smaller than the pressure of hydrogen metallization—100 GPa (1 Mbar).
Earlier experiments have shown that it’s possible to store small volumes of hydrogen inside buckyballs. The new research by Boris Yakobson, professor of mechanical engineering and materials science at Rice, and former postdoctoral researchers Olga Pupysheva and Amir Farajian, offers the first method of precisely calculating how much hydrogen a buckyball can hold before breaking. The research is featured on the cover of the March 2008 edition of the journal Nano Letters.
Buckyballs, which were discovered at Rice more than 20 years ago, are part of a family of carbon molecules called fullerenes. The family includes carbon nanotubes, the typical 60-atom buckyball and larger buckyballs composed of 2,000 or more atoms.
Bonds between carbon atoms are among the strongest chemical bonds in nature. These bonds are what make diamond the hardest known substance, and our research showed that it takes an enormous amount of internal pressure to deform and break the carbon-carbon bonds in a fullerene.
Based on our calculations, it appears that some buckyballs are capable of holding volumes of hydrogen so dense as to be almost metallic.
—Boris Yakobson
Using density functional theory, Yakobson’s research team assessed the strength of each atomic bond in a buckyball and simulated what happened to the bonds as more hydrogen atoms were packed inside. The team showed that for large numbers of encapsulated hydrogen atoms, some of them become chemisorbed on the inner surface of the cage. A maximum of 58 hydrogen atoms inside a C60 cage was found to still remain a metastable structure.
If a feasible way to produce hydrogen-filled buckyballs is developed, Yakobson said, it might be possible to store them as a powder.
They will likely assemble into weak molecular crystals or form a thin powder. They might find use in their whole form or be punctured under certain conditions to release pure hydrogen for fuel cells or other types of engines.
—Boris Yakobson
The research was supported by the Office of Naval Research and the Department of Energy.
Resources
Olga V. Pupysheva, Amir A. Farajian, and Boris I. Yakobson, Fullerene Nanocage Capacity for Hydrogen Storage, Nano Lett., 2008, 8, (3), pp 767–774. DOI: 10.1021/nl071436g
W. J. Nellis, Metallization of Hydrogen and Other Small Molecules at 100 GPa Pressures, Lawrence Livermore National Laboratory, 2002
Amazing achievement.
Can't think of an application unless they can use deuterium and zap it with a laser to make micro-fusion.
Posted by: Alex, Tunbridge Wells | 21 March 2008 at 07:47 AM
This is interesting, put purely theoretical. No-one has come up with a way to actually stuff a lot of hydrogen atoms inside those cages, partly because hydrogen *molecules* are orders of magnitude larger.
Posted by: Rafael Seidl | 21 March 2008 at 02:47 PM
hydrogen atoms inside those cages, partly because hydrogen *molecules* are orders of magnitude larger.
Hydrogen molecules are not orders of magnitude larger than hydrogen atoms -- not even one order of magnitude larger.
Posted by: Paul F. Dietz | 23 March 2008 at 04:19 PM
This is potentially much more interesting for applications other than fuel cells; for example:
- does it provide a route to creating metallic hydrogen, which is expected to be a stable room-temperature electrical superconductor?
- is it possible to prepare and stably store a *single* hydrogen atom inside a buckyball? If so it could be an excellent rocket fuel.
If the LANL artificial gasoline and kerosene process works then hydrogen fueled vehicles have no future. See http://www.greencarcongress.com/2008/02/los-alamos-deve.html#more
Posted by: richard schumacher | 26 March 2008 at 07:23 AM
I prefer carbon nanospheres. Just one can bind 33% of its weight in hydrogen at room temperature.
It's also called a carbon atom. The hydrogen 'carrier' is also called methane, for which we already have an extant infrastructure.
The return carrier for the carbon is called CO2. The whole process to bind hydrogen is 80% efficient and wastes less water:
CO2 + 4H2 -> CH4 + 2H2O
Posted by: Jim | 26 March 2008 at 07:49 AM
I myself have been looking around this is some good information
Posted by: electrolysis hydrogen | 17 December 2008 at 07:00 AM