Competition of quantum effects in H₂/D₂ sieving in narrow single-wall carbon nanotubes

Abstract

Nanoporous materials have the potential to be used as molecular sieves to separate chemical substances in a mixture via selective adsorption and kinetic sieving. The separation of isotopologues is also possible via the so-called quantum sieving effect: the different effective size of isotopologues due to their different Zero Point Energy (ZPE). Here we compare the diffusion coefficients of Hydrogen and Deuterium in (8,0) Single Walled Carbon Nanotubes obtained with quantum dynamics simulations. The diffusion channels obtained present important contributions from resonances connecting the potential wells. These resonances, which are more important for H${}_2$ than for D${}_2$, increase the low-temperature diffusivity of both isotopologues, but prevent the inverse kinetic isotope effect reported for similar nanostructured systems.

GRAPHICAL ABSTRACT

Keywords:

• Quantum confinement
• quantum sieving
• quantum dynamics

Acknowledgments

Financial support from the Spanish Ministerio de Economía y Competitividad (Ministry of Economy and Competitiveness) (CTQ2013-41307-P) and Generalitat de Catalunya (2014-SGR-25) is acknowledged. M.M.-M. further thanks a predoctoral grant from the FPU program (FPU2013/02210) from the Spanish Ministerio de Educación, Cultura y Deporte (Ministry of Education, Culture and Sports).

Data Availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Spanish Ministerio de Economía y Competitividad (Ministry of Economy and Competitiveness) under Grant CTQ2013-41307-P and Generalitat de Catalunya under Grant 2014-SGR-25. Ministerio de Educación, Cultura y Deporte FPU2013/02210.