Hydrogen can be a climate and environmentally friendly energy carrier if it is produced with the help of wind or solar energy. Unlike conventional fuels, its later use releases neither harmful carbon dioxide nor soot particles.
For mobile use, hydrogen is currently mostly stored in compressed gas containers, which have a relatively large volume and occupy the corresponding space in the vehicles. High pressures of up to 900 bar are also required for filling. In order to withstand the stress, special containers made of high-quality, non-recyclable fibre-reinforced polymer materials must be used.
Scientists at the Helmholtz-Zentrum Geesthacht have been working on the development of so-called solid storage facilities since the late 1990s. "We have been investigating the possibility of using complex light metal hydrides as storage media for many years," explains Dr. Claudio Pistidda, material scientist at the Helmholtz Zentrum Geesthacht. These systems can store more hydrogen in less space than high-pressure tanks.
Solids Storage Tanks Lose Capacity
But with all previous material combinations, the storage capacity was reduced after each loading. A similar problem is known with rechargeable batteries: as the number of cycles increases, they continuously lose their capacity due to mechanical tension and undesirable reactions at the electrodes, and therefore have a limited service life.
After many years, a system has now been developed in Geesthacht that can possibly solve these problems. For the first time, Pistidda and his colleagues were able to demonstrate that calcium borohydride can not only release the absorbed hydrogen by adding magnesium-nickel hydride, but that the system also returns to its original chemical structure during reloading with hydrogen. The discovered reaction path also avoids undesired side reactions, which would otherwise hinder recharging with hydrogen.
»We have thus achieved a real breakthrough on the way to developing new types of hydrogen storage materials for mobile and stationary applications,« says a delighted Dr. Claudio Pistidda.
The scientists published their results in the journal »Journal of Material Chemistry«.