Restricted Dynamics and Para-Ortho Conversion of H Adsorbed in Micro- and Mesoporous Carbide-Derived Carbon: A Quasi- and Inelastic Neutron Scattering Study.

Strong confinement of hydrogen is important for adsorption-based hydrogen storage solutions, which are vital for the transition toward a hydrogen-based economy. The dynamics of hydrogen adsorbed in high-porosity TiC-derived carbon with relatively well-stacked graphenic layers for a carbide-derived carbon is investigated with inelastic and quasi-elastic neutron scattering methods. Both the para-ortho rotational transition and elastic incoherent scattering factor are investigated. Hydrogen is translationally bound at temperatures of 20-80 K. At temperatures of 50 and 80 K, the adsorbed hydrogen exhibits localized jumps over 3.4 and 3.7 Å, respectively, along or between the ultramicropore walls. The restricted jumps of hydrogen in ultramicropores show the confining influence of specific adsorption sites present in the micropores of carbon materials, which limit hydrogen mobility and localize the hydrogen molecules within these pores. These findings yield new insights into the influence of hydrogen loading and temperature on the confinement of hydrogen and the development of carbonaceous adsorbents for high-density hydrogen storage.