Hydrogen energy, as one of the ideal clean energy sources, has been widely concerned in the world. High-pressure gaseous hydrogen storage and low-temperature liquid hydrogen storage are to two main traditional hydrogen storage methods, which has the shortcomings of storage volume small, easy to explode and others. Therefore, new hydrogen storage materials have been developed to solve the problems of traditional hydrogen storage methods, which mainly can be divided into hydrogen storage alloys, coordination hydride hydrogen storage materials, carbon-based hydrogen storage materials and organic liquid hydrides hydrogen storage materials.
- Hydrogen storage alloys: Hydrogen storage alloys can reversibly absorb and release hydrogen under certain temperature and pressure, which includes magnesium series, rare earth series, titanium series, zirconium series, vanadium based solid solution hydrogen storage alloys and others. For example, the typical representative of magnesium series hydrogen storage alloys is Mg2Ni and TiFe alloy is the representative of titanium series hydrogen storage alloy, which has the advantages of low dehydrogenation temperature and moderate price. Moreover, vanadium based solid solution hydrogen storage alloys have the benefits of high hydrogen storage density and moderate equilibrium pressure.
Figure 1. Example of hydrogen storage principle in alloys.
- Coordination hydride hydrogen storage materials: Coordination hydride hydrogen storage materials have the highest hydrogen storage density in volume and mass. Coordination hydride hydrogen storage materials are generally formed by alkali metal or alkali earth metal and boron element or nonmetal element. NaAlH4 is the most-well studied in this system. In this material, Al forms covalent bonds with four H atoms, and Al forms ionic bonds with Na atom.
- Carbon-based hydrogen storage materials: Carbon-based hydrogen storage materials, based on adsorption theory, mainly include super activated carbon, carbon nanofibers and carbon nanotubes. Super activated carbon hydrogen storage material is a typical supercritical gas adsorption technology, which uses activated carbon with super high specific surface area as adsorbent. Activated carbon hydrogen storage has the advantages of economy, high hydrogen storage capacity, fast desorption, long cycle life and easy to achieve large-scale production. In addition, carbon nanofibers have molecular-level pores on the surface, and hollow tubes with a diameter of about 10nm in the interior. Hydrogen can condenses in these carbon nanofibers, so they have super hydrogen storage capacity.
- Organic liquid hydrides hydrogen storage materials: The principle of organic liquid hydride hydrogen storage technology is realized by the reversible reaction of unsaturated liquid organic matter and hydrogen, namely hydrogenation and dehydrogenation. Hydrogenation reaction realizes hydrogen storage and dehydrogenation reaction realizes hydrogen release.
Figure 2. An example of organic liquid hydrides hydrogen storage material.
- Xin G, Yang J, Wang C, et al. Superior (de)hydrogenation properties of Mg-Ti-Pd trilayer films at room temperature.[J]. Dalton Transactions, 2012, 41(22):6783-6790.
- Zheng J, Wu Y, Yu H, et al. Promoting hydrogen absorption of liquid organic hydrogen carriers by solid metal hydrides[J]. Journal of Materials Chemistry A, 2019, 7(28).