Selective D2 adsorption enhanced by the quantum sieving effect on entangled single-wall carbon nanotubes

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Quantum sieving utilizes differences in quantum behavior for gas separation.
• Single-wall carbon nanotubes (SWCNTs) possess unique structural properties suitable for gas adsorption and separation.
• Understanding H2 and D2 adsorption is crucial for isotope separation and hydrogen storage applications.

Purpose of the Study:

• To investigate the quantum sieving effect of deuterium (D2) over hydrogen (H2) in different SWCNT structures.
• To compare experimental adsorption data with GCMC simulations for well-bundled and loosely-assembled SWCNTs.
• To evaluate the impact of oxidation on SWCNT performance for D2/H2 separation.

Main Methods:

• Gas adsorption experiments at 40 K and 77 K.
• Grand Canonical Monte Carlo (GCMC) simulations.
• Utilized two types of SWCNTs: well-bundled and super growth method (SG-SWCNT).
• Studied both non-oxidized and oxidized SWCNT samples.

Main Results:

• Pore-blocking and restricted diffusion in well-bundled SWCNTs limited D2/H2 selectivity.
• Non-oxidized SG-SWCNT assemblies demonstrated the highest D2 over H2 selectivity at both 40 K and 77 K.
• Selectivity in SG-SWCNT was pronounced even at higher temperatures (77 K).

Conclusions:

• The unique assembly structure of SG-SWCNTs is responsible for their high D2/H2 selectivity.
• Quantum sieving performance is strongly influenced by nanotube structure and packing.
• Oxidation can affect the accessibility of internal sites and influence separation efficiency.