| Hydrogen is
considered to be one of the promising power sources in the future. But
hydrogen has to be obtained, stored, transported. Various devices – hydrogen
accumulators - are used now for hydrogen storage. Their design is being
constantly improved, but so far devices have not been created that would
contain hydrogen sufficient for wide commercial application. In the accumulators
used nowadays, the hydrogen content does not exceed five to six percent
of the weight. In the industry, hydrogen is now stored in the compressed
gaseous state, in liquefied state, in the form of hydrides or metal-hydride
systems, and in zeolites.
As nanotechnologies developed, the
researchers proceeded to investigations of carbonic nanoelements – nanotubes,
nanofibers, nanocones, which possess unique properties to absorb various
gases. The hydrogen quantity in such systems depends on adsorptive properties
of nanostructures, pressure and environmental temperature. Their main advantage
is the ability to store hydrogen at low pressure. Although this did to
come to application yet, the researchers are carrying out theoretical study.
In general, they came to studying nanotubes’ properties. It has turned
out that they are theoretically capable to accumulate five to ten percent
of hydrogen at the temperature of 77 Kelvin degrees - the boiling temperature
of nitrogen.
The researchers from the Institute
of Applied Mechanics, Ural Branch of Russian Academy of Sciences, believe
that absorbing properties of fullerenes and other nanostructures that include
fullerenes have not been fully investigated. Therefore, they set a problem:
to study the influence of thermodynamic parameters – pressure and temperature
– on the process of molecular hydrogen absorption by such nanosystems.
With the help of molecular dynamics methods, they performed numerical analysis
of processes of hydrogen absorption by the C20, C60, C80, C180, C240, C540
fullerenes and the C46, C167, C505 carbonic clusters at various pressures
and temperatures. The researchers managed not only to determine the influence
of these thermodynamic parameters on the fullerenes’ hydrogen absorption
ability but also to discover the parameters at which hydrogen can be stably
stored in these nanoobjects.
“The quantity of hydrogen absorbed
at the temperature of 60 Kelvin degrees and the pressure of ten megapascals
achieves the 13.61 percent, and at the temperature of liquid nitrogen boiling
- 77 Kelvin degrees - and the pressure of tten megapascals it reaches 6.6
percent”, say the authors of the research. Utilization of carbonic clusters
the resemble fullerenes in shape is highly promising, the researchers state,
as clusters’ internal surface opens for absorption, which is not the case
with fullerenes.
|