Is graphene the key to solving hydrogen storage issue?
There
has been plenty of talk about hydrogen as future energy source No.1 primarily
because hydrogen is by far the most abundant element in universe. Hydrogen is environmentally
friendly source of energy because when hydrogen burns in air it produces only
water vapor. Still, in order for hydrogen to become one of the top energy
sources several important issues need to be resolved, and one of the most
important issues is definitely a hydrogen storage issue.
There
have been many interesting theories about hydrogen storage methods and one of the
most interesting proposals comes from the researchers at the National Institute
of Standards and Technology (NIST) and the University of Pennsylvania.
They believe that the solution for hydrogen storage issue can be found in form
of the layered graphene sheets. Can these graphene sheets really solve this
issue?
Graphene,
an allotrope of carbon, is recently attracting plenty of scientific research,
primarily because of its excellent conductive, optical, and thermal properties,
all of which make graphene very favorable choice for use in sensors and
semiconductor devices.
The
graphene in its original form cannot lead to successful hydrogen storage
solution because original graphene form means largely reduced hydrogen storage
ability. To bypass this, oxidized graphene sheets are stacked atop one another,
and connected by molecules that both link the layers to one another and
maintain space between them. The resulting layered graphene sheet can store
hydrogen in large quantities.
The
scientists have found out that layered graphene sheets can hold at least a
hundred times more hydrogen molecules than ordinary graphene oxide does. The benefits
of using this hydrogen storage method include easy synthesis, relatively low
costs and the fact that graphene is non toxic material.
Another
discovery that could be of great significance for solving hydrogen storage
issue was also a rather unusual relationship that layered graphene sheets
exhibit between temperature and hydrogen absorption.
In
most storage materials, the lower temperature normally means the bigger uptake
of hydrogen. The layered graphene sheets act differently than that, and
although they can absorb hydrogen, they do not uptake the significant amounts
at below 50 Kelvin (-223 degrees Celsius). Even more importantly, it does not
release any hydrogen below this temperature meaning that, with further
research, layered graphene sheets might be used to not only store hydrogen but
also to release it when it is needed, which can be of vital importance in fuel
cell applications.
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