Metallic hydrogen

Metallic hydrogen was first “created” in 2020. It is produced at pressures above 425 gigapascals. It is the material that could store the most energy and be superconducting… at room temperature.

This article is a part of our dossier on hydrogen, innovation and ecology.

We know the hydrogen atom in gaseous form, its natural state, or liquid, used in particular in the Appolo spaceships, which brought humans to the Moon. But did you know that it exists in … solid form?

More precisely, it exists as a metal. It is found naturally…but not on Earth. There are indeed some in the depths of gas giants, such as Jupiter and Saturn. On Earth, we managed to make it in a lab recently : 2020!

What is metallic Hydrogen ?

While liquid hydrogen was first obtained in 1898, metallic hydrogen took much longer to develop. It’s possible existence was discovered in 1935! Eugene Wigner demonstrated that at sufficiently high pressures, hydrogen becomes a solid metal. This pressure was first estimated between 25 to 2,000 gigapascals. More recent research has estimated it at 400 or 620 gigapascals (GPa).

Mao and Hemley succeeded in understanding hydrogen at 250 GPa in 1989, a team from Cornell University reached 342 GPa in 1998. It was not until January 29, 2020 that Paul Loubeyre, Florent Occelli and Paul Dumas reached 425 GPa thanks to an anvil press, thus producing the famous metallic hydrogen. The result of 85 years of research!

Properties of metallic Hydrogen

The sample obtained by the 3 French researchers was a cube of less than 5 µm on a side and was compressed between 2 diamond points. It was “molecular” metallic hydrogen. Further research is needed for its “atomic” form.

The study of this metal could learn a lot about the physics theory. On a practical perspective, metallic hydrogen might achieve supra-conductivity:

“There is no theory that can precisely describe the properties of hydrogen. […]

This metallic hydrogen is a bit of an ultimate material.

– It stores a phenomenal chemical energy. There is no other chemical system that stores such energy.

– It is a superconductor at room temperature, so there is no system that conducts electricity without resistance at room temperature. It’s a bit like the dream of materials technology.

– And then it still has exotic properties like the mobility of the proton.

So, in fact, it would be a bit of a spectacular material, if we had it at ambient pressure. »

Translated from french, Paul Loubeyra (CEA), Une étape décisive vers l’hydrogène métallique