Reactions over catalysts confined in carbon nanotubes

Pan, Xiulian; Bao, Xinhe

doi:10.1039/b810994j

Cited by 243 publications

(192 citation statements)

References 70 publications

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“…14,28 The strengthened interaction between the electron-deficient inner surface of CNTs and anionic oxygen of metal oxides led to weakened bonding strength of metal oxide, and therefore, the confined metal oxides inside CNT channels presented a higher reducibility than those located on the exterior surface of CNTs. 12 However, in our study, Ru/COX with Ru particles mostly confined inside CNTs shows a similar reduction temperature to Ru/P-CNTs with Ru species deposited on the external surface. This may be because the diffusion process of hydrogen molecules (the reductant) into the channels shifts the reduction peak to higher temperature ranges.…”

Section: Metal-support Interactionsupporting

confidence: 38%

Difference in the cooperative interaction between carbon nanotubes and Ru particles loaded on their internal/external surface

Wang

Chen

et al. 2013

RSC Adv.

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This paper examines differences in the cooperative interaction between carbon nanotubes (CNTs) and Ru particles loaded on their internal/external surface. The techniques used were transmission electron microscopy, X-ray photoelectron spectroscopy, CO chemisorption, X-ray diffraction, N 2 physisorption, hydrogen temperature-programmed reduction and two probe catalysis reactions, namely ammonia decomposition and preferential oxidation of CO in H 2 -rich atmosphere (PROX). The results show that the loading of highly dispersed Ru particles on CNTs does not change the structure of the CNTs. The cooperative interaction between Ru particles and associated CNT surfaces is dependent on the position of Ru particles and the surface functional groups of CNTs. Due to the electron-deficient structure of Ru particles confined inside CNT channels, they have an inferior ammonia decomposition activity to those deposited on the CNT external surface. For PROX, the catalytic performance of Ru particles confined inside CNT channels is superior compared to that over Ru particles deposited outside CNTs, which we attribute to the selective reactant enrichment of CO over H 2 inside the CNTs.

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Section: Metal-support Interactionsupporting

confidence: 38%

Difference in the cooperative interaction between carbon nanotubes and Ru particles loaded on their internal/external surface

Wang

Chen

et al. 2013

RSC Adv.

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“…The first step corresponded to decomposition of Mn 12 Ac with the loss of all coordinated ligands and, hence, the consequent formation of Mn 3 O 4 . The second step corresponded to the catalytic oxidation of the GMWNTs in the presence of the Mn 3 O 4 formed inside the nanotubes, and the third step corresponded to thermal oxidation of the GMWNT themselves (that is, sections of nanotubes that are not in direct contact with Mn 3 O 4 ) 25,26 . The residual weight remaining at 1,000 °C was attributed to Mn 3 O 4 that does not decompose further.…”

Section: Resultsmentioning

confidence: 99%

Encapsulation of single-molecule magnets in carbon nanotubes

et al. 2011

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next-generation electronic, photonic or spintronic devices will be based on nanoscale functional units, such as quantum dots, isolated spin centres or single-molecule magnets. The key challenge is the coupling of the nanoscale units to the macroscopic world, which is essential for read and write purposes. Carbon nanotubes with one macroscopic and two nanoscopic dimensions provide an excellent means to achieve this coupling. Although the dimensions of nanotube internal cavities are suitable for hosting a wide range of different molecules, to our knowledge, no examples of molecular magnets inserted in nanotubes have been reported to date. Here we report the successful encapsulation of single-molecule magnets in carbon nanotubes, yielding a new type of hybrid nanostructure that combines all the key single-molecule magnet properties of the guest molecules with the functional properties of the host nanotube. The findings may pave the way to the construction of spintronic or ultrahigh-density magnetic data storage devices.

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“…A general conclusion can be drawn from those studies that the activity or product selectivities are improved in comparison to the metals supported on AC and conventional oxides. 1,2 However, catalysis utilizing the interior surface of CNTs has been less explored, 5,6 although theoretical studies 8 also benefited from enclosure inside CNTs due to dipolar interaction of the product and CNT surface. In addition, confinement has been demonstrated to modify the structure and properties of confined materials.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Confinement inside Carbon Nanotubes on Catalysis

2011

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T he unique tubular morphology of carbon nanotubes (CNTs) has triggered wide research interest. These structures can be used as nanoreactors and to create novel composites through the encapsulation of guest materials in their well-defined channels. The rigid nanotubes restrict the size of the encapsulated materials down to the nanometer and even the subnanometer scale. In addition, interactions may develop between the encapsulated molecules and nanomaterials and the CNT surfaces. The curvature of CNT walls causes the π electron density of the graphene layers to shift from the concave inner to the convex outer surface, which results in an electric potential difference. As a result, the molecules and nanomaterials on the exterior walls of CNTs likely display different properties and chemical reactivities from those confined within CNTs. Catalysis that utilizes the interior surface of CNTs was only explored recently. An increasing number of studies have demonstrated that confining metal or metal oxide nanoparticles inside CNTs often leads to a different catalytic activity with respect to the same metals deposited on the CNT exterior surface. Furthermore, this inside and outside activity difference varies based on the metals used and the reactions catalyzed.In this Account, we describe the efforts toward understanding the fundamental effects of confining metal nanoparticles inside the CNT channels. This research may provide a novel approach to modulate their catalytic performance and promote rational design of catalysts. To achieve this, we have developed strategies for homogeneous dispersion of nanoparticles inside nanotubes. Because researchers have previously demonstrated the insertion of nanoparticles within larger nanotubes, we focused specifically on multiwalled carbon nanotubes (MWCNTs) with an inner diameter (i.d.) smaller than 10 nm and double-walled carbon nanotubes (DWCNTs) with 1.0À1.5 nm i.d. The results show that CNTs with well-defined morphology and unique electronic structure of CNTs provide an intriguing confinement environment for catalysis.

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Reactions over catalysts confined in carbon nanotubes

Cited by 243 publications

References 70 publications

Difference in the cooperative interaction between carbon nanotubes and Ru particles loaded on their internal/external surface

Difference in the cooperative interaction between carbon nanotubes and Ru particles loaded on their internal/external surface

Encapsulation of single-molecule magnets in carbon nanotubes

The Effects of Confinement inside Carbon Nanotubes on Catalysis

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