The State and Phase of Nanoconfined H2: Neutron diffraction and spectroscopy of H2 adsorbed in micro and mesoporous activated carbons

Currently, compact storage of ample hydrogen remains a technical problem for the field and a barrier to commercialisation. Naturally, the most compact and efficient way to store hydrogen is in its solid phases. Unfortunately, solid phases are classically formed at very low temperatures (<14 K) or extremely high pressures (GPa). If the dense, solid phases of hydrogen could be prepared at lower pressures and higher temperatures, the solution to compact and efficient storage of ample hydrogen fuel could be realised. Recently, solid-like characteristics and densities of H2 has been observed at atmospheric pressure and temperatures above the critical temperature (33 K) by nanoconfinement within optimally sized micropores of activated carbons, suggesting the phase diagram can be manipulated. To understand how confinement could be used to produce and study further dense phases of hydrogen and hence increased the wt% of adsorbent storage materials, an assessment of which crystalline phases of H2 form under confinement and what causes the increased stability is needed. In this study we use pressure and temperature dependent neutron diffraction and inelastic neutron scattering to examine dynamics and crystal structure of the confined hydrogen