Creating and mastering nano-objects to design advanced catalytic materials

Centi, Gabriele

doi:10.1016/j.ccr.2011.01.021

Cited by 86 publications

(63 citation statements)

References 222 publications

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“…confined catalysis | confinement effect A n increasing number of studies reveal that confinement of metal or metal oxide nanoparticles inside carbon nanotubes (CNTs) often leads to significantly enhanced catalytic activity with respect to the same bare metal nanoparticles or those deposited on the outer walls of CNTs (1)(2)(3). Such a different behavior originates from both the physical (spatial restriction of the channels) and chemical factors (electronic interaction of confined species with the curved graphene walls) inside CNTs (1)(2)(3)(4)(5).…”

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confidence: 99%

“…Such a different behavior originates from both the physical (spatial restriction of the channels) and chemical factors (electronic interaction of confined species with the curved graphene walls) inside CNTs (1)(2)(3)(4)(5). In this sense, single-walled carbon nanotubes (SWCNTs) are very interesting because they have a higher degree of uniformity and smaller channel compared with multiwalled CNTs (6).…”

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confidence: 99%

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Tuning the redox activity of encapsulated metal clusters via the metallic and semiconducting character of carbon nanotubes

Zhang

Pan

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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We demonstrate that reactions confined within single-walled carbon nanotube (SWCNT) channels are modulated by the metallic and semiconducting character of the hosts. In situ Raman and X-ray absorption near-edge structure spectroscopies provide complementary information about the electronic state of carbon nanotubes and the encapsulated rhenium species, which reveal electronic interactions between encapsulated species and nanotubes. More electrons are transferred from metallic tubes (m-SWCNTs) to oxidic rhenium clusters, leading to a lower valence state rhenium oxide than that in semiconducting tubes (s-SWCNTs). Reduction in 3.5% (vol/vol) H 2 /Ar leads to weakened host-guest electronic interaction. The high valence state Re within s-SWCNTs is more readily reduced when raising the temperature, whereas only a sluggish change is observed for Re within m-SWCNTs. Only at 400°C does Re reach a similar electronic state (mixture of Re 0 and Re 4+ ) in both types of tubes. Subsequent oxidation in 1% O 2 /Ar does not show changes for Re in s-SWCNTs up to 200°C. In comparison, m-SWCNTs facilitate the oxidation of reduced rhenium (160°C). This can be exploited for rational design of active catalysts with stable species as a desired valence state can be obtained by selecting specific-type SWCNTs and a controlled thermal treatment. These results also provide a chemical approach to modulate reversibly the electronic structure of SWCNTs without damaging the sidewalls of SWCNTs.confined catalysis | confinement effect A n increasing number of studies reveal that confinement of metal or metal oxide nanoparticles inside carbon nanotubes (CNTs) often leads to significantly enhanced catalytic activity with respect to the same bare metal nanoparticles or those deposited on the outer walls of CNTs (1-3). Such a different behavior originates from both the physical (spatial restriction of the channels) and chemical factors (electronic interaction of confined species with the curved graphene walls) inside CNTs (1-5). In this sense, single-walled carbon nanotubes (SWCNTs) are very interesting because they have a higher degree of uniformity and smaller channel compared with multiwalled CNTs (6). More interestingly, they exhibit intrinsically either metallic or semiconducting properties with different electronic structure around the Fermi level. Metallic and semiconducting SWCNTs (m-SWCNTs and s-SWCNTs, respectively) have been demonstrated to vary significantly in reactivity toward covalent and noncovalent functionalization of their sidewalls (7-9). For example, diazonium salts (10), nitronium ions (NO 2 + ) (11), and OsO 4 (12) reacted selectively with metallic tubes, which was attributed to their higher electron density near the Fermi level. Metallic tubes were also reported preferentially etched away by water and methane plasma because of their higher reactivity (13,14). On the other hand, H 2 O 2 (15), azomethineylides (16), and gaseous SO 3 (17) preferentially attacked s-SWCNTs, and recently s-SWCNTs were also shown to be preferentially...

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confidence: 99%

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confidence: 99%

Tuning the redox activity of encapsulated metal clusters via the metallic and semiconducting character of carbon nanotubes

Zhang

Pan

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Two-dimensional zeolites include those materials composed of layers with a thickness of ≤3 nm. These layer assemblies produce open architectures with enhanced accessibility and reactant/product mobility, providing the potential for activating larger molecules and suppressing catalyst deactivation through coke deposition [47]. Corma et al [48] reported the synthesis of delaminated ITQ-2 obtained from an MCM-22-layered zeolite precursor, thus providing a roadmap for the discovery of other zeolite materials in their lamellar forms (to date 10 frameworks have been recognized as having a layered precursor).…”

Section: Two-dimensional (2d) Zeolitesmentioning

confidence: 99%

Designing Porous Inorganic Architectures

Melero

Iglesias

Morales

2013

Heterogeneous Catalysts for Clean Technology

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“…can be easily reduced, and reduced species through their agglomeration can produce small metal clusters or nanoparticles of different sizes [3][4][5]. Those metal complexes confined within solid cavities can be considered as nanoreactors, charged with ordered zero-dimensional type metal oxides [6]. Controlled assembly of molecules into organized mesoscopic structures during self-assembling of oxide-based catalytic materials is an effective approach for tailoring heterogeneous catalysts and controlling their catalytic activities [7].…”

Section: Introductionmentioning

confidence: 99%