TY - JOUR

T1 - Hydrogen densification in carbon nanopore confinement

T2 - Insights from small-angle neutron scattering using a hierarchical contrast model

AU - Stock, Sebastian

AU - Seyffertitz, Malina

AU - Kostoglou, Nikolaos

AU - Rauscher, Max

AU - Presser, Volker

AU - Demé, Bruno

AU - Cristiglio, ‪Viviana

AU - Kratzer, Markus

AU - Rols, Stéphane

AU - Mitterer, Christian

AU - Paris, Oskar

PY - 2024/2/17

Y1 - 2024/2/17

N2 - This study reports on the low-pressure hydrogen (H2) and deuterium (D2) physisorption processes in nanoporous activated carbon cloth at supercritical temperatures. In-situ small-angle neutron scattering (SANS) is employed as a hydrogen-sensitive method to determine the pore-size-dependent and isotope-dependent adsorbate densification for different gas pressures up to 1 bar. The changes of the SANS signal resulting from the physisorption of adsorbate molecules in the pore space is described by analytical pore scattering functions resembling slit-like pores. Analysis based on a hierarchical pore model allows quantifying the pore-size-dependent physical density of the confined adsorbate for three pore classes, resembling roughly the IUPAC classes of ultramicropores, supermicropores, and mesopores. While the adsorbate density within the very smallest pores approaches the bulk solid density of H2 for pressures of about 1 bar at 77 K, it remains much lower for larger pores. A high density is also found for D2 within ultramicropores, but these results are hampered by a subtle effect of an exchange of chemically bound hydrogen by deuterium in the sample. These findings contribute to a fundamentally better understanding of confinement effects on hydrogen densification, and affect materials design for efficient hydrogen storage devices working at realistic cryogenic conditions and low pressures.

AB - This study reports on the low-pressure hydrogen (H2) and deuterium (D2) physisorption processes in nanoporous activated carbon cloth at supercritical temperatures. In-situ small-angle neutron scattering (SANS) is employed as a hydrogen-sensitive method to determine the pore-size-dependent and isotope-dependent adsorbate densification for different gas pressures up to 1 bar. The changes of the SANS signal resulting from the physisorption of adsorbate molecules in the pore space is described by analytical pore scattering functions resembling slit-like pores. Analysis based on a hierarchical pore model allows quantifying the pore-size-dependent physical density of the confined adsorbate for three pore classes, resembling roughly the IUPAC classes of ultramicropores, supermicropores, and mesopores. While the adsorbate density within the very smallest pores approaches the bulk solid density of H2 for pressures of about 1 bar at 77 K, it remains much lower for larger pores. A high density is also found for D2 within ultramicropores, but these results are hampered by a subtle effect of an exchange of chemically bound hydrogen by deuterium in the sample. These findings contribute to a fundamentally better understanding of confinement effects on hydrogen densification, and affect materials design for efficient hydrogen storage devices working at realistic cryogenic conditions and low pressures.

U2 - 10.1016/j.carbon.2024.118911

DO - 10.1016/j.carbon.2024.118911

M3 - Article

VL - 221.2024

JO - Carbon

JF - Carbon

SN - 0008-6223

IS - March

M1 - 118911

ER -