Electron spin resonance investigation of hydrogen absorption in ball-milled graphite

Smith, Christopher I., Miyaoka, Hiroki, Ichikawa, Takayuki, Jones, Martin O., Harmer, Jeffrey, Ishida, Wataru, Edwards, Peter P., Kojima, Yoshitsugu and Fuji, Hironobu (2009) Electron spin resonance investigation of hydrogen absorption in ball-milled graphite. Journal of Physical Chemistry C, 113 14: 5409-5416. doi:10.1021/jp809902r


Author Smith, Christopher I.
Miyaoka, Hiroki
Ichikawa, Takayuki
Jones, Martin O.
Harmer, Jeffrey
Ishida, Wataru
Edwards, Peter P.
Kojima, Yoshitsugu
Fuji, Hironobu
Title Electron spin resonance investigation of hydrogen absorption in ball-milled graphite
Journal name Journal of Physical Chemistry C   Check publisher's open access policy
ISSN 1932-7447
1932-7455
Publication date 2009-04-01
Year available 2009
Sub-type Article (original research)
DOI 10.1021/jp809902r
Volume 113
Issue 14
Start page 5409
End page 5416
Total pages 8
Place of publication Washington, United States
Publisher American Chemical Society
Language eng
Formatted abstract
Nanostructured hydrogenated graphite (CnanoHx) was synthesized here from graphite by ball-milling under a hydrogen (H2) atmosphere. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) show that ball milling results in the rupture of graphene sheets creating active defects and allowing hydrogen to be dissociated and then chemisorbed. Most likely small quantities of iron particles incorporated during the milling process act as a catalyst. CnanoHx thus possesses unique characteristic hydrogenated states present in nanometer scale particles, unlike standard hydride materials. Electron spin resonance (ESR) spectroscopy resolves two distinct paramagnetic components. The first is assigned to (intrinsic) delocalized π-electrons in the graphene sheets (g ~ 2.008) which disappears after approximately 32 h milling. The second ESR component grows in intensity with milling time and is assigned to localized electrons (g ~ 2.003) with a concentration of 3 × 1020 spins per gram after 80 h milling. HYSCORE spectroscopy reveals proton hyperfine couplings, and variable temperature CW ESR spectra demonstrate an unexpected magnetic ordering at low temperatures (~10 K). Formation of CnanoHx thus consists of weakly coupled localized electrons with wave functions that extends over small graphitic moieties. The radical centers do not physisorb a large quantity of H2 molecules under conditions required for practical H2 storage materials and are a product of the milling process and chemisorption of hydrogen.
Keyword Walled carbon nanotubes
Prepared nanostructured graphite
Storage properties
Room temperature
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Centre for Advanced Imaging Publications
 
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