The buckyball, seen here, consists of 60 carbon atoms. It can store many atoms inside this sphere, including hydrogen. (Source: Psyclops.com)
The solution to storing hydrogen efficiently may be as simple as little ball-shaped carbon molecules
It seems these days that carbon nanotubes and carbon nanowires are getting all the attention. However, people should not neglect another very promising and unique carbon molecule-- the buckyball. Buckyballs, named after Buckminster Fuller, contain 60 carbon atoms. It is the smallest member of a class of carbon ball-shaped molecules known as fullerenes, which can contain as many as 2,000 atoms.
Now new research from Rice University indicates that carbon buckyballs can be used to store hydrogen at densities that rival those of the center of Jupiter. Hydrogen storage is a major challenge to the alternative energy industry. While hydrogen fuel cells and hydrogen combustion research are oft lauded as a possible key to independence from fossil fuel reliance, difficulties in hydrogen storage have held these technologies back from achieving economic feasibility. While hydrogen is incredibly light, in order for it to be economically competitive with gasoline in automobiles in terms of range per fill-up, it would need to be stored at densities greater than that of liquid hydrogen, a lofty challenge.
The new research, which will be published in the March 2008 cover of the American Chemical Society's journal Nano Letters, was funded in part by over a billion dollars in grant money the U.S. Department of Energy has put aside for hydrogen storage research, as well as the office of Naval research. Lead researcher Boris Yakobson, professor of mechanical engineering and materials science at Rice, is thrilled with the results. He states, "Based on our calculations, it appears that some buckyballs are capable
of holding volumes of hydrogen so dense as to be almost metallic. It appears they can hold about 8 percent of their weight in hydrogen at
room temperature, which is considerably better than the federal target
of 6 percent."
Yakobson admits that the idea of storing hydrogen inside a molecular container is not a new one. Indeed, it was known in the past, he commented, that buckyballs could contain hydrogen. However, Yakobsen and former postdoctoral researchers Olga Pupysheva and Amir Farajian's new research has offered the first method of calculating precisely how much hydrogen the little balls could store beforing breaking.
It is rather appropriate that the research should occur at Rice as the buckyball was first discovered at Rice over 20 years ago. Yakobson explains how the little balls can store so much hydrogen, stating, "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."
The new method for storage determination utilizes an advanced computer model. The model measures the strength of the bonds between the carbon atoms in the buckyball as hydrogen atoms are added. The model is especially optimal as it can be scaled to fullerenes of any size. It not only shows how much hydrogen can be stored, but also simulates how the buckyballs break when their maximum storage capacity is exceeded.
Yakobson says hydrogen-filled buckyballs could theoretically be stored as a powder. He states, "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."
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