Safe hydrogen storage from solids
At room temperature and low pressure, metal powders are intended to safely store green hydrogen.
Green hydrogen should be a key to the energy transition. The aim of the project „GreenH2Metals: Sustainable and recyclable metal alloys for the efficient and safe storage of hydrogen for stationary applications“, in which the Ruhr University Bochum is involved with two sub-projects, is the aim of storing it safely. The Bochum working group is studying the micro - and nanostructure of metal alloys capable of absorbing and releasing hydrogen. The raw materials for this should come from secondary sources, i.e. be and can be recycled. The project is funded with around 3.3 million euros by the Federal Ministry of Education and Research, of which a good 750,000 euros go to the Ruhr University.
Disadvantages of gas and liquid storage
If one day green hydrogen can be produced on a large scale, for example by wind power or solar energy, it will also have to be stored. This is the only way you can use it when you need it. „The storage in gas or liquid tanks that has been common up to now has various drawbacks“, explains Prof. Dr. Christian Liebscher from the Research Center Future Energy Materials and Systems. „To do this, the hydrogen must either be strongly compressed or extremely cooled down, which requires a lot of energy. In addition, thermal insulation is a problem with liquid storage, resulting in losses. Furthermore, there is a risk that hydrogen can escape very quickly due to leaks, which is associated with the risk of an explosion.“
Save securely and losslessly
The type of storage that the project team is investigating has neither disadvantage: powder particles or powder-pressed pellets made from an alloy of titanium and iron are able to absorb hydrogen under moderate pressures of less than 40 bar. At the surface of the particles, the hydrogen molecules are first split. The atoms then diffuse into the metal lattice. The metal thereby becomes a so-called hydride. If you lower the pressure around the particles or pellets again, the hydrogen emerges again. The whole thing works at room temperature and is almost lossless. If a tank were to burst, the hydrogen would only escape very slowly, so that the risk of explosion is greatly reduced.
The working group at the Ruhr University is dedicated in two subprojects to micro - and nanostructural analysis of the storage material in collaboration with the Max Planck Institute for Sustainable Materials in Dusseldorf. „For example, we want to know how the material structure manifests itself when we use raw materials from secondary sources, i.e. from recycling“, explains Christian Liebscher. „There could be contaminants in it, but some of them could even have a positive effect on the storage properties.“ Using transmission emission microscopy and atomic probe tomography, the researchers in the experiment want to investigate very closely how the alloy behaves during loading and unloading, and whether there are wear effects, for example. „Ideally, we want to optimize the storage properties in this way“, says Christian Liebscher.
Ruhr University Bochum
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