Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 7, Pages 2801-2806Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0905571107
Keywords
energetics; kinetics; nanomaterials; polarization; reversibility
Categories
Funding
- National Natural Science Foundation of China [10874007, 20973010, 10725418, 10990100]
- Foundation of National Laboratory for Infrared Physics
- National Grand Fundamental Research 973 Program of China [2010CB631301]
- US National Science Foundatio
- US Department of Energy
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Using density functional theory, we show that an applied electric field can substantially improve the hydrogen storage properties of polarizable substrates. This new concept is demonstrated by adsorbing a layer of hydrogen molecules on a number of nanomaterials. When one layer of H-2 molecules is adsorbed on a BN sheet, the binding energy per H-2 molecule increases from 0.03 eV/H-2 in the field-free case to 0.14 eV/H-2 in the presence of an electric field of 0.045 a.u. The corresponding gravimetric density of 7.5 wt% is consistent with the 6 wt% system target set by Department of Energy for 2010. The strength of the electric field can be reduced if the substrate is more polarizable. For example, a hydrogen adsorption energy of 0.14 eV/H-2 can be achieved by applying an electric field of 0.03 a.u. on an AlN substrate, 0.006 a.u. on a silsesquioxane molecule, and 0.007 a.u. on a silsesquioxane sheet. Thus, application of an electric field to a polarizable substrate provides a novel way to store hydrogen; once the applied electric field is removed, the stored H-2 molecules can be easily released, thus making storage reversible with fast kinetics. In addition, we show that materials with rich low-coordinated nonmetal anions are highly polarizable and can serve as a guide in the design of new hydrogen storage materials.
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