(Hamburg) – At the German Electron Synchrotron (DESY), scientists have created the basis for a new method of storing hydrogen: with tiny particles made of the precious metal palladium, just 1,2 nanometers in size. The fact that palladium can “absorb hydrogen like a sponge” has been known for a long time, says team leader Andreas Stierle. However, so far there has been the problem of “getting the hydrogen out of the material again”. That's why research was carried out with palladium particles, which only measure around one nanometer. A nanometer is a millionth of a millimeter.
The conventional way of storing hydrogen has so far been complex: either the gas is stored in pressure tanks at up to 700 bar or in liquid form, where it has to be cooled down to minus 253 degrees Celsius - both processes cost additional energy.
Iridium as a stabilizer
The potential new memories are stabilized by a core made of the rare precious metal iridium. In addition, they are fixed to graphene, an extremely thin layer of carbon. “We can anchor the palladium particles on graphene at a distance of just two and a half nanometers,” explains Stierle, who heads the DESY NanoLab. “The result is a regular periodic structure.”
Using the X-ray light source in the PETRA III ring accelerator, the researchers were able to see that when the hydrogen came into contact with palladium particles, it essentially stuck to their surfaces and hardly penetrated into the interior. “Figuratively speaking, these nanoparticles resemble a praline,” say the scientists: “In the middle there is an iridium nut, covered by a marzipan layer made of palladium, and at the very outside there is hydrogen as a chocolate coating.” A light one is enough to discharge the storage device Heating: Since the gas molecules do not have to make their way out of the interior, the hydrogen quickly detaches from the particle surface.
Clarify storage density
Next, the team wants to find out what storage density can be achieved with the new method. Research also needs to be carried out on the carrier materials before practical use can be considered. Scientists from the universities of Cologne and Hamburg are also involved in the work. The German Electron Synchrotron DESY in the Helmholtz Association is a center for basic scientific research based in Hamburg and Zeuthen.
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The palladium nanoparticles (green) are stabilized by a core made of iridium (red). Hydrogen can accumulate on their surface like a kind of chocolate icing - and can be released again when heated. © DESY / Andreas Stierle
