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Copper/Molybdenum Nanocomposite Particles as Catalysts for the Growth of Bamboo-Structured Carbon Nanotubes
Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
Tyndall National Institute, University College Cork.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
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2008 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 32, 12201-12206 p.Article in journal (Refereed) Published
Abstract [en]

Bamboo-structured carbon nanotubes (BCNTs), with mean diameters of 20 nm, have been synthesized on MgO-supported Cu and Mo catalysts by the catalytic chemical vapor deposition of methane. BCNTs could only be generated using a combination of Cu and Mo catalysts. No BCNTs were produced from either individual Cu or Mo catalysts. In combination, Mo was found to be essential for cracking the methane precursor, while Cu was required for BCNT formation. Energy dispersive X-ray analysis of the individual particles at the tips of the nanotubes suggest that Cu and Mo are present as a “composite” nanoparticle catalyst after growth. First-principles modeling has been used to describe the interaction of the Cu/Mo catalyst with the nanotubes, suggesting that the catalyst binds with the same energy as traditional catalysts such as Fe, Ni, and Co.

Place, publisher, year, edition, pages
2008. Vol. 112, no 32, 12201-12206 p.
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-108265DOI: 10.1021/jp8023556ISI: 000258290100026OAI: oai:DiVA.org:uu-108265DiVA: diva2:234808
Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
Open this publication in new window or tab >>Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Density functional theory has been used to investigate cathode materials for rechargeable batteries, carbon nanotube interactions with catalyst particles and transition metal catalyzed hydrogen release in magnesium hydride nanoclusters.

An effort has been made to the understand structural and electrochemical properties of lithium iron silicate (Li2FeSiO4) and its manganese-doped analogue. Starting from the X-ray measurements, the crystal structure of Li2FeSiO4 was refined, and several metastable phases of partially delithiated Li2FeSiO4 were identified. There are signs that manganese doping leads to structural instability and that lithium extraction beyond 50% capacity only occurs at impractically high potentials in the new material.

The chemical interaction energies of single-walled carbon nanotubes and nanoclusters were calculated. It is found that the interaction needs to be strong enough to compete with the energy gained by detaching the nanotubes and forming closed ends with carbon caps. This represents a new criterion for determining catalyst metal suitability. The stability of isolated carbon nanotube fragments were also studied, and it is argued that chirality selection during growth is best achieved by exploiting the much wider energy span of open-ended carbon nanotube fragments.

Magnesium hydride nanoclusters were doped with transition metals Ti, V, Fe, and Ni. The resulting changes in hydrogen desorption energies from the surface were calculated, and the associated changes in the cluster structures reveal that the transition metals not only lower the desorption energy of hydrogen, but also seem to work as proposed in the gateway hypothesis of transition metal catalysis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 670
Keyword
Materials science, density functional theory, cathode materials, hydrogen-storage materials, carbon nanotube growth
National Category
Other Physics Topics
Research subject
Physics of Matter; Materials Science
Identifiers
urn:nbn:se:uu:diva-108261 (URN)978-91-554-7603-8 (ISBN)
Public defence
2009-10-23, Polhemsalen, Ångströmlaboratoriet, Uppsala, 13:15 (English)
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Supervisors
Available from: 2009-10-01 Created: 2009-09-10 Last updated: 2009-10-01

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Ahuja, Rajeev

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