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Loading up metals with H2 for fuel cells Metal hydrides are being explored as potential substrates in future hydrogen storage systems for fuel cells. So far, MHn species with up to nine hydrogen atoms have been made, such as ReH92-. Laura Gagliardi of the University of Palermo, in Italy, and Pekka Pyykkö of the University of Helsinki, in Finland, have now completed molecular-level calculations to show that MHn species with up to 12 hydrogen atoms are possible [J. Am. Chem. Soc., 126, 15014 (2004)]. They started by examining the analogy between hydride ions and gold anions, calculating that the hydrogen analog of the recently observed WAu12 would be stable. Gagliardi and Pyykkö then extended their calculations to MH12 species containing chromium, molybdenum, and other metals. They predict that H2 should bind side-on, M(h-H2), to the metal center for chromium and as a mixture of M(h-H2) and M–H bonds for molybdenum and tungsten. A design target of 6.5 weight % hydrogen has been set for fuel-cell storage, the researchers note. The CrH12 and MoH12 compounds, as well as salts containing TiH122–, VH12–, and MnH12+, weigh in at more than 10 wt % hydrogen |
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