Graphene nanostructures as tunable storage media for molecular hydrogen

doi:10.1073/pnas.0501030102

Graphene nanostructures as tunable storage media for molecular hydrogen

^†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 (received for review February 9, 2005)

Abstract

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 carbon–H₂ 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.

Footnotes

↵ ‡ To whom correspondence should be addressed. E-mail: tse{at}ned.sims.nrc.ca.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: DOE, U.S. Department of Energy; DOS, density-of-states; LJ, Lennard–Jones; MP2, second-order Møller–Plessett; PAH, polycyclic aromatic hydrocarbon; PES, potential energy surface.