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CHEMISTRY
Graphene nanostructures as tunable storage media for molecular hydrogen

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Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, ON, Canada K1A 0R6; and
Institut für Physikalische Chemie und Elektrochemie, Technische Universität Dresden, D-01062 Dresden, Germany
Edited by James L. Dye, Michigan State University, East Lansing, MI and approved June 2, 2005 (received for review February 9, 2005)
Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, the twin U.S. Department of Energy goals of 6.5% mass ratio and 62 kg/m3 volume density has not been achieved either experimentally or via theoretical simulations on reversible model systems. Carbon-based materials, such as carbon nanotubes, have always been regarded as the most attractive physisorption substrates for the storage of hydrogen. Theoretical studies on various model graphitic systems, however, failed to reach the elusive goal. Here, we show that insufficiently accurate carbonH2 interaction potentials, together with the neglect and incomplete treatment of the quantum effects in previous theoretical investigations, led to misleading conclusions for the absorption capacity. A proper account of the contribution of quantum effects to the free energy and the equilibrium constant for hydrogen adsorption suggest that the U.S. Department of Energy specification can be approached in a graphite-based physisorption system. The theoretical prediction can be realized by optimizing the structures of nano-graphite platelets (graphene), which are light-weight, cheap, chemically inert, and environmentally benign.
equilibrium constants | hydrogen storage | quantum effects
Abbreviations: DOE, U.S. Department of Energy; DOS, density-of-states; LJ, LennardJones; MP2, second-order MøllerPlessett; PAH, polycyclic aromatic hydrocarbon; PES, potential energy surface.
To whom correspondence should be addressed. E-mail: tse{at}ned.sims.nrc.ca.
© 2005 by The National Academy of Sciences of the USA
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