High-Density Hydrogen Storage: Key to Future Energy Systems
February 19, 2024 | by indiatoday360.com

Hydrogen is a clean and renewable energy carrier that can be used for various applications, such as transportation, stationary power, and portable power. However, one of the main challenges of hydrogen utilization is how to store it efficiently and safely. Hydrogen has the highest energy per mass of any fuel, but its low ambient temperature density results in a low energy per unit volume, requiring advanced storage methods that have higher energy density. One of the promising approaches for high-density hydrogen storage is to use solid materials that can adsorb or absorb hydrogen molecules on their surfaces or within their structures.
Nanoporous Complex Hydride for High-Density Hydrogen Storage
Recently, researchers from Ulsan National Institute of Science and Technology (UNIST) reported a breakthrough in high-density hydrogen storage using a nanoporous complex hydride composed of magnesium hydride, solid boron hydride, and magnesium cation. This material can store five hydrogen molecules in a three-dimensional arrangement, achieving a remarkable hydrogen storage capacity of 144 g/L per volume of pores. This surpasses traditional methods, such as storing hydrogen as a gas in a liquid state (70.8 g/L), and exceeds the density of hydrogen molecules in the solid state .
The researchers synthesized the material by ball-milling magnesium hydride and boron hydride under an inert atmosphere. They then characterized the material using various techniques, such as X-ray diffraction, transmission electron microscopy, and nuclear magnetic resonance spectroscopy. They found that the material has a nanoporous structure with an average pore size of 0.8 nm and a large surface area of 1150 m2/g. They also discovered that the material exhibits a high-density hydrogen adsorption state, where five hydrogen molecules are arranged in a tetrahedral configuration around each magnesium cation .
Reversible Hydrogen Storage Performance and Mechanism
The researchers demonstrated that the material can reversibly store and release hydrogen by changing the temperature. They measured the hydrogen uptake and release curves of the material at different temperatures and pressures using a Sieverts apparatus. They found that the material can adsorb up to 6.5 wt.% of hydrogen at 77 K and 1 bar, and release 5.6 wt.% of hydrogen at 423 K and 1 bar. They also observed that the material has good cycling stability, maintaining its hydrogen storage capacity after 10 cycles .
The researchers attributed the high-density hydrogen storage performance of the material to the synergistic effect of the nanoporous structure and the complex hydride composition. They explained that the nanopores provide a large surface area for hydrogen adsorption, while the complex hydride offers a favorable interaction between hydrogen and magnesium cations. They also suggested that the material has a low activation energy for hydrogen desorption due to the presence of boron hydride anions .
Conclusion
This innovative research represents a significant advancement in high-density hydrogen storage for future energy systems. It offers a compelling alternative to conventional methods that have low efficiency and high cost. It also addresses critical challenges in large-scale hydrogen storage for public transportation applications, such as buses, trucks, and trains. The researchers hope that their findings will inspire further development of novel materials and technologies for efficient and sustainable hydrogen utilization.
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