Environmental Engineering Reference
In-Depth Information
27
Hydrogen nanoreservoirs Made
of Boron nitride
Levan Chkhartishvili
Department of Engineering Physics, Georgian Technical University, Tbilisi, Georgia
Laboratory for Boron and Powdered Composite Materials, F. Tavadze Institute of Metallurgy and Materials Science, Tbilisi, Georgia
Hydrogen nanoreservoirs are nanotech tools that are useful for green energy production. Hydrogen exhibits the highest
heating value per mass of all chemical fuels. Furthermore, it is regenerative and environmental-friendly. As is known,
reducing the world's dependence on fossil fuels is one of the global research priorities. One strategy calls for powering vehi-
cles with fuel cells that use hydrogen extracted from a carrier-material to generate electricity. But usually the extraction
requires high temperatures, and that limits efficiency. Fortunately, these limits may be loosened by using catalysts to drasti-
cally lower the temperature to that required to liberate hydrogen. Attractive energy carriers are rich in hydrogen and do not
produce greenhouse gases upon oxidation. In addition, they remain liquid or solid over a wide temperature range, allowing
it to be handled. According to a recent reference topic [1] on energy change, two principal questions related to utilizing
hydrogen fuel need to be answered: “Is the hydrogen economy around the corner?” and “Is hydrogen an alternative to fossil
energy carriers?”
Current interest in the use of hydrogen as a transportation fuel has driven extensive research into novel gas storage
materials. The current materials lack the ability to store the necessary amounts of hydrogen under technologically useful
conditions. Hence, there is a need for new materials to solve the hydrogen storage problem. Many recent efforts have been
focused on boron-containing hydrogenous materials primarily with regard to the light constitutional elements and the
resulting high hydrogen storage capacities. In particular,
Handbook of Nanophysics
[2] discusses important possibilities in
the use of boron clusters (with proper addition of metal atoms) for efficient hydrogen storage. According to a review [3]
on the utilization of boron and its compounds, boron is a promising element for hydrogen storage with its hydrides and
nanostructural forms.
The hydrogen storage capacity of boron-rich nanostructured materials was estimated in a lecture [4]. Physisorption of
hydrogen needs lower energy, but produces lower capacities. As for chemisorption (usually in the form of metal hydrides,
CH
4
, etc.), this corresponds to higher hydrogen capacities, but requires higher energy as well. Between these limits, there
exists a window of 0.2-0.6 eV/H
2
necessary for efficient reversible storage at room temperature and moderate pressure for
onboard automotive applications. Materials needed for effective hydrogen storage should be able to bind hydrogen mole-
cules chemically, without nondissociation. The collective monograph [5] also illustrates the practical versatility of boron,
including the application of boron chemistry (e.g., designing large molecules containing icosahedral boron clusters) for
hydrogen storage.
Analytical geometric models suggested for boron nitride [6] and all-boron [7] nanosystems seem to be helpful in calculating
the available volumes of corresponding nanoreservoirs for hydrogen storage.
