Until recently, scientists thought that molecular hydrogen (H2) was too small to be contained in clathrate hydrates - crystalline solids where a framework of water molecules enclose molecules of gas. Now, researchers at the Carnegie Institution of Washington's Geophysical Laboratory, University of Chicago, and Los Alamos National Laboratory, have been able to trap the gas inside water-ice structures forming hydrogen hydrate.
According to team member Ho-kwang (Dave) Mao, "This result could be a first step toward an alternative way of storing environmentally friendly hydrogen gas. It also points to the possibility that hydrogen might exist in icy bodies in our solar system that we thought were incapable of retaining it." The scientists report their findings in the September 27, 2002, issue of Science. Hydrogen is the most abundant gas in the universe and the race has been on to find a cost-efficient, practical way to store it for fuel use. Using a diamond-anvil cell, the researchers subjected a mixture of hydrogen and water to a pressure equivalent to about 2,000 times the atmospheric pressure at sea level (220 megapascals) at room temperature (300 K or 80°F). Two regions formed --an H2 bubble and liquid water. When the mixture was cooled to minus 11°F (249 K) the two regions reacted and formed one solid compound.
Unlike most clathrate hydrates, where only one molecule of a gas can be trapped in each of the H2O cages, multiple hydrogen molecules were entrapped in this material--two molecules in small cages and four in larger ones. The synthesized material "showed remarkable stability," persisting when warmed to about 45°F (280K). Upon cooling to liquid nitrogen temperature (77 K, -321°F) and releasing pressure completely, the clathrate remained.
"Many microorganisms that appear to be ancient 'breathe' hydrogen," says Wesley Huntress, director of Carnegie's Geophysical Lab and former NASA Associate Administrator for Space Science. "The ability of water to trap hydrogen may also be significant for biology on the early Earth, providing a potential mechanism to supply this gas to the atmosphere at a time when life was just beginning on this planet. "
###Researchers on this project include the following: Wendy Mao, Univ. of Chicago and Carnegie Institution of Washington; Ho-kwang Mao, Alexander Goncharov, Viktor Struzhkin, Quanzhong Guo, Jingzhu Hu, Jinfu Shu, and Russell Hemley, Carnegie Institution of Washington; Maddury Somayazulu, HPCAT Advanced Photon Source, Argonne Nat'l Lab; Yusheng Zhao, Los Alamos Nat'l Lab.
The Carnegie Institution of Washington (http://www.CarnegieInstitution.org) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments in the U.S.: Plant Biology, Global Ecology, The Observatories, Embryology, the Department of Terrestrial Magnetism, and the Geophysical Laboratory.
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