Hydrogen Sorption Cycling Kinetic Stability and Microstructure of Single-Walled Carbon Nanotube (SWCNT) Magnesium Hydride (MgH₂) Nanocomposites

Abstract

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=0c7f6ad2-00f4-4f0e-a08c-180bcf5e2562 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=0c7f6ad2-00f4-4f0e-a08c-180bcf5e2562 NRC, 100 Sussex DriVe, Ottawa, Ontario, Canada ReceiVed: August 10, 2009; ReVised Manuscript ReceiVed: December 20, 2009 We have examined comilling with unpurified single-walled carbon nanotubes (SWCNTs) as a method to promote hydrogenation/dehydrogenation cycling kinetic stability in nanocrystalline magnesium hydride (MgH 2 ). The synthesized material was a true nanocomposite consisting of MgH 2 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 MgH 2 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 MgH 2 particle agglomeration and sintering. Even after 35 absorption/desorption cycles, the SWCNTs remain covering the MgH 2 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.

Microstructural evolution during hydrogen sorption cycling of Mg–FeTi nanolayered composites

“…It was recently found that the addition of a mixture of single-wall carbon nanotubes, amorphous carbon and metal catalyst particles prevents coarsening of Mg particles and grains to a large extent [13]. Compared to the baseline case of milled MgH 2 without additives, grain growth of Mg was slowed by over a factor three by the addition of the carbon mixture.…”

“…Increase in absorption and desorption times during cycling was slowed down by a factor three or more for the MgH 2 -SWCNT mixture compared to the baseline. Analysis of the activation energies revealed that the catalytic activity of the metal particles was lost during cycling [13].…”

The impact of carbon materials on the hydrogen storage properties of light metal hydrides

“…35,[73][74][75][76][77] The effect of carbon as additive on the hydrogen release from ball-milled MgH 2 is illustrated in Fig. 5.…”

Catalytic Effect of Multi-Wall Carbon Nanotubes Supported Nickel on Hydrogen Storage Properties of Mg₉₉Ni Prepared by Hydriding Combustion Synthesis

“…Thus, in this respect, the HCS+MM-Mg 99 Ni+Nano-nickel/MWCNT is superior to those reported in previous works. 42,43) …”