Confining Hydrogen: A Low Energy Route to Room Temperature Superconductivity

In the energy and transportation sector, it is now widely recognised that hydrogen offers a green alternative to fossil fuels. It is three times more energy dense by weight than gasoline, produces only water as a by-product and can be produced from renewable sources by electrolysis of water. However, due to hydrogen being a low-density gas at room temperatures and pressures, compact and efficient storage of ample hydrogen remains a technological problem. Naturally, the most compact and efficient way to store hydrogen is in its solid phases; however, they are classically formed at very cold temperatures (< -250˚C) or very high pressures. For instance, the densest phase, metallic hydrogen, has been predicted to form at pressures >400 GPa, to be stable upon removal of pressure, moreover it is predicted to be a room temperature superconductor. If such a phase could be formed at less costly temperatures and pressures, it would represent a supremely energy dense, clean fuel source for vehicles, rockets and even fusion reactors. Furthermore, if superconductive, it could revolutionise the energy sector with lossless energy transmission and long-term magnetic energy storage. In Bristol, by the use of nanoconfinement in a microporous material, we have developed an alternative approach to producing a dense phase of hydrogen at pressures 2000 times lower than those required for the condensation of bulk hydrogen above its critical temperature. Using our approach as a ‘pre-densification’ method and the application of additional pressure may allow our system to create metallic hydrogen at significantly lower pressures than classically observed. Working at the University of Bristol under Prof. Valeska Ting, Dr. Lui Terry is investigating the state, phase and properties of the dense-nanoconfined hydrogen. To investigate the properties of confined hydrogen and whether the density can be amplified to higher order phases (such as metallic hydrogen) at pressures lower than the bulk, Dr. Terry is combining temperature and pressure dependent neutron scattering, Raman spectroscopy, calorimetry, SQUID magnetometry, Electron transport and physisorption studies. Results indicate that the low energy – ordered solid phase of solid hydrogen is stabilised in our systems micropores at higher temperatures than associated in the bulk and at much higher density. Furthermore, upon densification the system switches from non-magnetic to magnetic with a concurrent drop in resistivity. These results indicate that confinement offers an alternative route to producing exotic dense phases of materials at less costly temperatures and pressures and indicate a potential route to room temperature metallic hydrogen.