Hydrogen,
a clean energy source, requires a highly reliable and safe storage system,
which is currently lacking. Layered hydrogen silicane (L-HSi) is a promising,
safe, lightweight, and energy-efficient solid-state hydrogen carrier with
potential for practical utility. This material releases hydrogen when
irradiated with low-intensity visible-light sources like sunlight or LEDs.
L-HSi represents a new direction for hydrogen carrier system research.
Hydrogen is a promising fuel that can
replace conventional fossil fuels as it emits no carbon dioxide during
combustion or oxidation and can be produced from a wide range of sources.
However, a hydrogen-based economy requires not only clean production but also
safe and efficient hydrogen storage and transportation.
Current systems pose several drawbacks: compressed hydrogen tanks have low hydrogen densities and pose explosion
risks, while liquid hydrogen tanks require extremely low temperatures and
considerable energy.
Ammonia is a well-known liquid hydrogen carrier with a high hydrogen density, but its
dehydrogenation requires extensive energy and comes with issues such as
corrosiveness and toxicity.
To solve these issues, researchers have
turned towards solid-state hydrogen carrier materials. Unfortunately, most solid-state alloys consist of heavy metals and have limited
gravimetric hydrogen capacities.
In a breakthrough, a research team
consisting of Mr. Hirona Ito and Professor Masahiro Miyauchi from Institute of
Science Tokyo (Science Tokyo), Ms. Mio Nakai and Professor Hideyuki Nakano from
Kindai University, and Professor Takahiro Kondo from the University of Tsukuba,
Japan, discovered a new solid-state hydrogen carrier called layered hydrogen
silicane (L-HSi).
Hydrogen can be released from L-HSi by
visible light irradiation under ambient temperature and pressure. Their
findings were published online in the journal Advanced Optical
Materials.
L-HSi consists of silicon and hydrogen
in a 1:1 ratio and exhibits a high gravimetric hydrogen capacity of 3.44 wt.%.
Unlike conventional hydrogen storage systems, it is a stable, solid-state
hydrogen carrier that can release hydrogen simply by exposure to low-intensity
light sources like sunlight or LEDs.
The researchers synthesized L-HSi via
decalcification of CaSi2 in
a reaction with HCl and tested its hydrogen release properties. They placed
L-HSi powder under an argon atmosphere in a gas-flow-type reactor and
irradiated it with a xenon lamp at ambient temperature and pressure.
The optical bandgap of L-HSi is 2.13 eV,
corresponding to a wavelength of 600 nm, which absorbs visible light. The light
was turned on 10 minutes after the experiment began and turned off at the
60-minute mark. During irradiation, the researchers clearly observed gaseous
hydrogen formation.
Further heating tests under a dark
environment and detailed spectroscopic analysis confirmed that hydrogen release
was not due to a photothermal process, but instead, driven by bandgap
excitation of L-HSi. Specifically, hydrogen was released when irradiated with
wavelengths below 600 nm. The material showed a maximum quantum efficiency of
7.3% at 550 nm.
The researchers also conducted long-term
irradiation tests, where L-HSi was dispersed in an organic medium inside the
dispersed reactor. Under extended visible-light exposure, about 46.7% of the
bonded hydrogen atoms were released. The team also confirmed that hydrogen
could be effectively produced using low-intensity, economical light sources,
including sunlight and LEDs.
L-HSi is a promising solid-state hydrogen carrier that can open new possibilities for safe, lightweight, and energy-efficient hydrogen storage. Looking forward, their research will focus on improving its reversibility and scalability for practical applications.
Source: Solid-state material can store and release hydrogen using sunlight or LEDs
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