Grenoble (France) - Scientists working at the European Synchrotron Radiation Facility (ESRF) may have discovered a practical storage mechanism for hydrogen gas. It's a form of Lithium Borohydride, or LiBH4, and it contains 18% hydrogen by weight. Presently, it's created under enormous pressure, but is showing extreme promise as a new candidate for permanent hydrogen storage through future chemical refinement and a lower pressure system.
One of the problems existing hydrogen storage systems have today, outside of high pressure vessel storage, is that they are too stable. Once the hydrogen is chemically combined into the various substances being researched, they just don't like to give up their hydrogen. A new, and almost accidentally discovered form of LiBH4 is proving to be stable, yet unstable enough to offer what's being heralded as a breakthrough in hydrogen storage research.
In order to create the new form of LiBH4, an extremely high pressure of 200,000 bar is required. To put this pressure into perspective, the Earth's atmosphere at sea level is almost exactly 1 bar. This 200,000 bar number would be the equivalent force exerted upon the Earth by a mountain 80x the size of Mount Everest. Still, according to the press release, this pressure is not a record in the laboratory.
The researchers used something called a diamond anvil to create the high pressure environment. That device is capable of even higher pressure. Once formed, the new compound was examined using something called diffraction of synchrotron light. This, despite hydrogen's difficulty in being detected in this way, has helped researchers determine the atomic arrangement of the new material. They discovered two new formations. One of them was "truly unprecedented and reveals strikingly short contacts between hydrogen atoms". This trait is desirable because it become unstable much more easily. In this case, it requires heating to 300C to begin releasing its hydrogen gas.
While this high temperature is not unworkable, it would require a significant portion of the energy extracted from the hydrogen to be captured solely for the continued emission of the gas, thus greatly reducing its efficiency. The team has now combined experimental and theoretical research, however, to realize a potential in this newest form of LiBH4.
The team believes the current form can be chemically tweaked to release its hydrogen at lower temperatures. They also explain that this new form they're after begins to appear at only 10,000 bar. This is the commercial equivalent pressure pharmaceutical companies use today to compress "pellets".
And right now, that's exactly what the team is hoping to do. They're working on a way to chemically "freeze" the new form into something that's capable of storing and releasing even more hydrogen than this current form of LiBH4. The team believes that it may be possible to further stabilize the substance through chemical substitutions. The eventual goal is to have all of this happening at regular atmospheric pressure, and in high volume.
The scientists are hoping that by using this technology, tweaking the chemical components which make it up, they'll be able to create a process which stores enough hydrogen to be useful in something like water softener salt pellets. Instead of being salt, it will be some material which, when heated, rubbed, smacked, or whatever ultimately ends up being required to make it chemically breakdown and release its hydrogen, will provide a safe mechanism for storing the volatile gas in a dangerous vehicle like an automobile, safely enough to only extract as much gas as is needed immediately by the engine.