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The rotational and translational dynamics of molecular hydrogen physiosorbed in activated carbon: A direct probe of microporosity and hydrogen storage performance

Georgiev, PA, Ross, DK, Albers, P and Ramirez-Cuesta, AJ 2006, 'The rotational and translational dynamics of molecular hydrogen physiosorbed in activated carbon: A direct probe of microporosity and hydrogen storage performance' , Carbon, 44 (13) , pp. 2724-2738.

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Abstract

We have measured Incoherent Inelastic Neutron Scattering (IINS) spectra of H2 physisorbed in high purity chemically activated carbon (AC) at different surface coverage and at temperatures near the triple point of bulk hydrogen. Our experimental results and DFT calculations show that at low surface coverage, due to the very low corrugation of the adsorption potential, and in the absence of H2–H2 lateral interactions, the adsorbed molecules are practically free to translate in the 2D plane parallel to the surface. Model calculations show that a complete mixing between the sub-states of the J = 1 manifold occurs on the free surface. The J = 0-to-1 rotational transition should split if the H2 molecule is adsorbed in a slit type pore. Rotational splitting of up to 13 meV is found in the narrowest pores of around 6 Å investigated. The calculated isosteric heat of adsorption for molecules adsorbed on the free surface, at different sites and molecule orientations, range between −39 and −42 meV/H2 at 77 K. In the optimum size slit pores, these numbers double up. Micropore volume of 0.34–0.45 ml/g carbon, and an upper limit of 4 wt% hydrogen storage is anticipated for the investigated material.

Item Type: Article
Uncontrolled Keywords: Activated carbon, neutron scattering, gas storage
Themes: Subjects / Themes > Q Science > QD Chemistry
Subjects / Themes > Q Science > QC Physics
Subjects outside of the University Themes
Schools: Colleges and Schools > College of Science & Technology
Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering
Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering > Materials & Physics Research Centre
Journal or Publication Title: Carbon
Publisher: Elsevier
Refereed: Yes
ISSN: 00086223
Depositing User: H Kenna
Date Deposited: 23 Aug 2007 11:35
Last Modified: 20 Aug 2013 16:47
URI: http://usir.salford.ac.uk/id/eprint/329

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