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
N1 - Publisher Copyright:
© 2024 Elsevier Ltd
PY - 2024/3
Y1 - 2024/3
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.
KW - Activated carbon cloth
KW - Hierarchical pore model
KW - Hydrogen physisorption
KW - Nanoporous carbon
KW - Small-angle neutron scattering
UR - http://www.scopus.com/inward/record.url?scp=85185841321&partnerID=8YFLogxK
U2 - 10.1016/j.carbon.2024.118911
DO - 10.1016/j.carbon.2024.118911
M3 - Article
AN - SCOPUS:85185841321
SN - 0008-6223
VL - 221.2024
JO - Carbon
JF - Carbon
IS - March
M1 - 118911
ER -