How can hydrogen be stored？

With the transformation of global energy structure and the development of low-carbon economy, hydrogen energy has gradually become an important part of future energy because of its clean, efficient and renewable advantages. However, the storage of hydrogen is still one of the key technical bottlenecks in the wide application of hydrogen energy. Because hydrogen has the characteristics of extremely low density, easy leakage, inflammable and explosive, how to store hydrogen safely and efficiently is an important issue to be solved urgently in the hydrogen energy industry chain.

At present, the storage methods of hydrogen mainly include high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, solid hydrogen storage and organic liquid hydrogen storage.

1. High pressure gaseous hydrogen storage

This is the most widely used hydrogen storage method at present. Its principle is to compress hydrogen to a high pressure state (usually 35MPa or 70MPa) and then store it in a gas cylinder made of high-strength materials. This method has mature technology and fast hydrogen charging and discharging speed, and is suitable for fuel cell vehicles, hydrogen refueling stations and other fields. However, its disadvantages are also obvious, such as high manufacturing cost of high-pressure vessels, potential safety hazards and relatively low energy density of hydrogen storage.

2. Low temperature liquid hydrogen storage

The density of liquid hydrogen is much higher than that of gaseous hydrogen, so the hydrogen content per unit volume can be significantly increased by cooling hydrogen to -252.8℃ for liquefaction and storage. Liquid hydrogen storage tanks usually adopt double-layer vacuum insulation structure to reduce heat loss. This method is suitable for large-scale and long-distance transportation and aerospace fields. However, it has high energy consumption, high cost and the problem of hydrogen evaporation loss.

3. Solid hydrogen storage

Solid-state hydrogen storage is to adsorb or absorb hydrogen in some materials in the form of atoms or molecules, such as metal-organic frameworks (MOFs), coordination hydrides, carbon nanomaterials and so on. This method has high hydrogen storage density, good safety and moderate operating temperature, and is considered as one of the most promising hydrogen storage methods in the future. However, the hydrogen absorption and desorption efficiency, cycle life and cost control of solid hydrogen storage materials still need to be further optimized.

4. Organic liquid hydrogen storage

This technology generates stable compounds by the reversible chemical reaction between hydrogen and organic compounds (such as toluene, cycloalkane, etc.), thus realizing the storage and transportation of hydrogen. When in use, hydrogen is released through dehydrogenation reaction. This method has high hydrogen storage density, convenient transportation and good safety, but the dehydrogenation process needs high temperature and catalyst, and the system complexity is high.

To sum up, different hydrogen storage technologies have their own advantages and disadvantages and are suitable for different application scenarios. At present, high-pressure gaseous hydrogen storage and low-temperature liquid hydrogen storage technologies are relatively mature and have been commercialized. However, solid hydrogen storage and organic liquid hydrogen storage are in the stage of continuous research and development and gradual promotion. In the future, with the progress of materials science, chemical engineering and other fields, the storage efficiency and safety of hydrogen will be continuously improved, laying a solid foundation for building a clean and efficient hydrogen energy society.