The goal of the U. S. Department of Energy and the manufacturers of hydrogen fuel tanks and other storage vessels have been to find a material that bonds with H2 that is lightweight and that can be used at ambient temperature and pressures.
The problem with hydrogen atoms bonding with other elements is that either those bonds are too weak or too strong. If the bonds are too strong then heat is needed to separate the hydrogen atoms from the material. If the bonds are too weak, then there is instability in the storage.
Researchers from China and the U. S. have been using computer modeling to find a material with moderate bonding qualities.
According to Physorg.com, “As the researchers explained, the greatest difficulty in finding a sufficient hydrogen storage material for onboard storage systems lies in meeting multiple requirements with a single material. For example, in previous studies researchers have found that light metal hydrides can store hydrogen with a gravimetric density of 20 wt. %, but the material is not reversible, meaning it cannot be reused. Also, the hydrogen desorbs only at very high temperatures.
“In contrast, other materials such as carbon nanotubes and metal or covalent organic frameworks can store hydrogen reversibly, but the hydrogen adsorbs only at very low temperatures. The difference is due to bonding: in light metal hydrides, hydrogen is held in much stronger bonds than in the second group of materials. The researchers explain that, ideally, hydrogen should be bound with an intermediate binding energy.”
The article goes onto say, “The researchers systematically investigated 10 Pc-based porous sheets with transition metal atoms from scandium (Sc) through zinc (Zn), and found that porous Pc sheets with Sc atoms could store up to 4.6 wt. % hydrogen. In addition to the Sc atoms’ regular distribution in the Pc sheet, Sc has two other attractive features. First, it is lighter than other transition elements, allowing the overall storage material to be relatively light. Second, Sc atoms have a large size, so that they stick out and can capture more hydrogen molecules.”
I’ve talked about hydrogen fuel storage many times in this blog. Both inside and outside an H2 car the efficiency of hydrogen storage needs to go up and the price needs to come down in order for these vehicles and the supporting infrastructure to become commercially viable.
Sometimes I think we are just one small breakthrough away from disrupting the paradigm of fossil fueled vehicles. As long as knowledgeable scientists and researchers keep working the issue from different angles, the solution I believe will happen sooner rather than later.