Hydrogen Sorption Cycling Stability and Microstructure of Single-Walled Carbon Nanotube (SWCNT) Encapsulated Magnesium Hydride

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DOIResolve DOI: http://doi.org/10.1021/jp907724t
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TypeArticle
Journal titleThe Journal of Physical Chemistry C
Volume144
Issue7
Pages32653275; # of pages: 11
AbstractWe have examined comilling with unpurified single-walled carbon nanotubes (SWCNTs) as a method to promote hydrogenation/dehydrogenation cycling kinetic stability in nanocrystalline magnesium hydride (MgH2). The synthesized material was a true nanocomposite consisting of MgH2 covered by highly defective SWCNTs coupled to catalytic metal nanoparticles and mixed with amorphous carbon. The nanocomposite was hydrogen sorption cycled at 300 °C using a volumetric Sievert’s type apparatus. Identically milled pure MgH2 was used as a baseline. The microstructure of both materials was analyzed in detail using cryo-stage transmission electron microscopy (TEM) as well as other techniques. The nanocomposite shows markedly improved kinetic performance, both during initial postmilling desorption and during subsequent cycling. Activation energy analysis demonstrates that any catalytic effect due to the metallic nanoparticles is lost during cycling. Improved cycling performance is instead achieved as a result of the carbon allotropes preventing MgH2 particle agglomeration and sintering. Even after 35 absorption/desorption cycles, the SWCNTs remain covering the MgH2 surfaces. Sorption cycling creates a dramatic difference in the particle size distributions between the nanocomposite system and the baseline, whereas the two were nearly identical at the onset of testing. In a separate experiment performed at more aggressive pressure conditions, the nanocomposite received over 100 sorption cycles with fairly minor kinetic degradation.
Publication date
LanguageEnglish
AffiliationNational Institute for Nanotechnology; NRC Steacie Institute for Molecular Sciences; National Research Council Canada
Peer reviewedYes
NPARC number17653085
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Record identifier0c7f6ad2-00f4-4f0e-a08c-180bcf5e2562
Record created2011-04-01
Record modified2017-03-23
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