Hydrogen is recognized as a clean energy source, but its widespread adoption faces challenges related to safe and efficient storage. Current methods, such as compressed gas and liquid hydrogen tanks, have drawbacks including low density, explosion risks, high energy requirements, and extreme temperatures. Ammonia, another carrier, requires significant energy for dehydrogenation and presents toxicity and corrosiveness issues. Solid-state carriers, while promising, have often consisted of heavy metals with limited capacities.
Discovery of Layered Hydrogen Silicane (L-HSi)
A research team from Institute of Science Tokyo, Kindai University, and the University of Tsukuba, Japan, identified a new solid-state hydrogen carrier: layered hydrogen silicane (L-HSi). The discovery was published in Advanced Optical Materials on December 29, 2025.
Material Properties and Hydrogen Release Mechanism
L-HSi is composed of silicon and hydrogen in a 1:1 ratio and exhibits a gravimetric hydrogen capacity of 3.44 wt.%. This material is stable and releases hydrogen when exposed to low-intensity visible light, such as sunlight or LEDs, under ambient temperature and pressure.
Researchers synthesized L-HSi by decalcification of CaSi2. In experiments, L-HSi powder under an argon atmosphere was irradiated with a xenon lamp. Hydrogen gas formation was observed during irradiation. Further analysis confirmed that hydrogen release resulted from bandgap excitation of L-HSi, not a photothermal process. The optical bandgap of L-HSi is 2.13 eV, corresponding to 600 nm, and hydrogen was released when irradiated with wavelengths below this value. A maximum quantum efficiency of 7.3% was recorded at 550 nm.
Experimental Outcomes
Long-term irradiation tests demonstrated that approximately 46.7% of the bonded hydrogen atoms within L-HSi were released under extended visible-light exposure. The team confirmed the material's effectiveness with economical light sources like sunlight and LEDs.
Future Prospects
L-HSi is considered a promising solid-state hydrogen carrier that may offer new possibilities for safe, lightweight, and energy-efficient hydrogen storage. Future research will focus on improving its reversibility and scalability for practical applications.