NMR studies of hydrogen motion in nanostructured hydrogen–graphite systems

Nanostructured hydrogen–graphite systems, CnanoHx (x=0.24, 0.31, 0.96), have been characterized by first nuclear magnetic resonance (NMR) measurements. The NMR spectrum of CnanoH0.96 is well represented by the sum of a Lorentzian and a Gaussian line, indicating two types of hydrogen coordinations. T...

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Bibliographic Details
Published in:Journal of alloys and compounds 2003-08, Vol.356-357, p.617-621
Main Authors: Majer, G., Stanik, E., Orimo, S.
Format: Article
Language:English
Subjects:
H motion
Nanostructured graphite
NMR
Spin–lattice relaxation
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Summary:Nanostructured hydrogen–graphite systems, CnanoHx (x=0.24, 0.31, 0.96), have been characterized by first nuclear magnetic resonance (NMR) measurements. The NMR spectrum of CnanoH0.96 is well represented by the sum of a Lorentzian and a Gaussian line, indicating two types of hydrogen coordinations. These two components may be ascribed to hydrogen in graphite interlayers and hydrogen chemisorbed at dangling bonds. Information on the hydrogen hopping frequencies is provided by the spin–lattice relaxation rate Γ1. The temperature dependence of Γ1 yields high hydrogen diffusivities and low activation energies of Ea≈0.1 eV. A change in the Γ1 data of CnanoHx with x=0.24 and 0.31 occurred after the samples had been heated to about 400–430 K. This suggests that in this temperature range hydrogen atoms start to occupy sites with different site energies, resulting in a distribution of the activation energies for hydrogen motion.
ISSN:0925-8388
1873-4669
DOI:10.1016/S0925-8388(03)00121-X