CTAB serves as the best kinetic promoters of H2/DIOX mixed hydrates for moderate solidified hydrogen storage via clathrates

Abstract

Although clathrate hydrates were thought to open the Pandora box of hydrogen moderate storage, poor hydration efficiency of hydrogen hydrates impedes its application in hydrogen economy. To improve the situation, an efficient kinetic promoter of cetyltrimethylammonium bromide (CTAB) was proposed to enhance the hydration efficiency of mixed H₂ and 1,3-dioxolane (DIOX) hydrates, the micro structures of which were characterized via Raman spectra. In DIOX system, when CTAB was introduced, hydrate induction time reduces by 91.4 %, hydrate growth rate increases by 185.2 %, and the storage capacity of hydrogen in hydrates is up to 0.582 wt% under a moderate condition (12 MPa, 274.15 K), which increases by 99.32 %. Potential mechanisms behind the enhancement were proposed, and it was deduced that CTAB changes the arrangement of interfacial water molecules and induces hydration shells, which decrease the nucleation energy barrier as confirmed by the profiles of differential scanning calorimetry (DSC), giving rise to fast hydrate nucleation. In addition, hydrogen molecules were thought to enter the cavity of CTAB micelles, which serve as hydrogen vehicles to enhance the mass transfer of hydrogen by interfacial capture and inner release, resulting in fast hydrate formation. To the best of our knowledge, CTAB presents the best promotion effect on the nucleation and growth of H₂/DIOX mixed hydrates among known kinetic promoters, and this finding promotes the application of clathrate hydrates on hydrogen moderate storage a small step forward.