Polyoxometalate steric hindrance driven chirality-selective separation of subnanometer carbon nanotubes

Yang, Xusheng; Zhu, Chao; Zeng, Lianduan; Xue, Weiyang; Zhang, Luyao; Zhang, Lei; Zhao, Kaitong; Lyu, Min; Wang, Lei; Zhang, Yuan‐Zhu; Wang, Xiao; Li, Yan; Yang, Feng

doi:10.1039/d2sc01160c

Cited by 15 publications

(9 citation statements)

References 79 publications

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“…Single-walled carbon nanotubes (SWCNTs), whose structure is indexed by two integers ( n , m ) (the so-called “chiral index”), could be a typical example of this aspect. To fully utilize the chirality-dependent outstanding performance of SWCNTs, the synthesis of nanotubes with identical ( n , m ) has been considered as an ultimate goal, which is, however, a considerable challenge. − …”

Section: Introductionmentioning

confidence: 99%

Atomic-Scale Evidence of Catalyst Evolution for the Structure-Controlled Growth of Single-Walled Carbon Nanotubes

Zhao

Yang

2022

Acc. Chem. Res.

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Conspectus Knowing how nanomaterials nucleate and dynamically evolve at the nanoscale is crucial to understanding and in turn controlling the structure and properties of a wide variety of materials, among which single-walled carbon nanotubes (SWCNTs) with chirality-dependent properties is a typical example. Catalyst takes a central role in guiding the SWCNT growth. An in-depth understanding of the growth mechanism of SWCNTs requires knowledge of the catalyst dynamic behavior during the chemical vapor deposition process, where real-time atomic-scale observations are needed. The high spatial, temporal, and energy resolution makes the state-of-the-art aberration-corrected environmental transmission electron microscope (ETEM) a superior tool for tracking the catalyst evolution and the SWCNT growth. Several key factors and processes, including the catalyst stability, carbon diffusion pathway, nucleation site, and growth modes of nanotubes, greatly influence the structure of SWCNTs. This Account summarizes our recent progress in the ETEM investigation of the dynamic catalyst behavior and nucleation of SWCNTs. We first compare the different growth modes of SWCNTs on two types of catalyst-stable solid intermetallic Co7W6 and unstable monometallic catalysts. Then we address the origin of different growth modes and chirality selectivity by revealing the atomic-scale stability and evolution of catalysts under carbon feed conditions and the observation of the in situ growth of SWCNTs on catalysts. We also discuss the catalyst–support interaction and the possible influence on SWCNT growth. In the end, we summarize the present achievements and future challenges. We carefully compare the difference in the ordinary Co catalyst and Co7W6 catalyst which has shown great chirality selectivity in SWCNT growth. Direct imaging by ETEM demonstrated that solid catalysts initiated the growth of SWCNTs with diameters smaller (d NT) than those of the catalyst particles (d NP) (d NT < d NP), whereas molten catalyst nanoparticles produced SWCNTs with similar diameters (d NT ≈ d NP). ETEM combined with in situ synchrotron X-ray absorption spectroscopy demonstrated that the Co7W6 catalyst maintained a solid stable structure under carbon feed conditions at 700–1000 °C, demonstrating the feasibility in acting as a structure template to grow SWCNTs. By contrast, the state and composition of the Co catalyst were changing during SWCNT growth. The near-surface lattice spacings of Co7W6 remained unchanged under carbon feed condition with carbon diffusion on the surface, whereas the solid Co catalyst underwent dynamic expansion and contraction due to carbon penetration into and precipitation out of Co nanoparticles. These two different pathways of carbon diffusion on or in catalysts indicate the distinctly different growth mechanisms of SWCNTs: the epitaxial growth of SWCNTs with specified chirality on the facets of Co7W6 nanocrystals and the nonselective growth of SWCNTs by the Co catalyst with Co/CoC3 as the active species. Besides the SWCNT–catalyst...

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Section: Introductionmentioning

confidence: 99%

Atomic-Scale Evidence of Catalyst Evolution for the Structure-Controlled Growth of Single-Walled Carbon Nanotubes

Zhao

Yang

2022

Acc. Chem. Res.

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“…One-dimensional heterostructures coupled with SWCNTs have attracted tremendous attention recently. − The use of CNTs as hosts has been widely demonstrated to encapsulate various guests in the cavity, such as molecules, − clusters, − picoperovskites, , and unusual atomic chains/crystals. ,− These fascinating findings have elaborately clarified the templating and shielding effects, allowing access to the unseen crystal structures ,, and dynamic events, ,,,− and improving electrical performance. − Moreover, the monolayer of graphite carbon of SWCNTs has also been proved to be transparent to the inner guests, which enables the guests to modulate the electronic surface structure of SWCNTs through host–guest charge communication. ,, However, the highly carbophilic metals such as W and Mo which tend to exhibit strong metal–carbon interactions , were rarely studied previously. The strong carbide-formatting elements (W, Mo) could exhibit strong interactions with carbon and result in a considerable charge communication with the host SWCNTs, providing a nondestructive way to homogeneously modify the electronic surface of SWCNTs.…”

Section: Introductionmentioning

confidence: 99%

“…47−50 Moreover, the monolayer of graphite carbon of SWCNTs has also been proved to be transparent to the inner guests, which enables the guests to modulate the electronic surface structure of SWCNTs through host−guest charge communication. 28,51,52 However, the highly carbophilic metals such as W and Mo which tend to exhibit strong metal−carbon interactions 53,54 were rarely studied previously. The strong carbide-formatting elements (W, Mo) could exhibit strong interactions with carbon and result in a considerable charge communication with the host SWCNTs, providing a nondestructive way to homogeneously modify the electronic surface of SWCNTs.…”

Section: ■ Introductionmentioning

confidence: 99%

Anisotropic Growth of One-Dimensional Carbides in Single-Walled Carbon Nanotubes with Strong Interaction for Catalysis

et al. 2023

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Tungsten and molybdenum carbides have shown great potential in catalysis and superconductivity. However, the synthesis of ultrathin W/Mo carbides with a controlled dimension and unique structure is still difficult. Here, inspired by the host−guest assembly strategy with single-walled carbon nanotubes (SWCNTs) as a transparent template, we reported the synthesis of ultrathin (0.8−2.0 nm) W 2 C and Mo 2 C nanowires confined in SWCNTs deriving from the encapsulated W/Mo polyoxometalate clusters. The atom-resolved electron microscope combined with spectroscopy and theoretical calculations revealed that the strong interaction between the highly carbophilic W/Mo and SWCNT resulted in the anisotropic growth of carbide nanowires along a specific crystal direction, accompanied by lattice strain and electron donation to the SWCNTs. The SWCNT template endowed carbides with resistance to H 2 O corrosion. Different from normal modification on the outer surface of SWCNTs, such M 2 C@SWCNTs (M = W, Mo) provided a delocalized and electron-enriched SWCNT surface to uniformly construct the negatively charged Pd catalyst, which was demonstrated to inhibit the formation of active PdH x hydride and thus achieve highly selective semihydrogenation of a series of alkynes. This work could provide a nondestructive way to design the electron-delocalized SWCNT surface and expand the methodology in synthesizing unusual 1D ultrathin carbophilic-metal nanowires (e.g., TaC, NbC, β-W) with precise control of the anisotropy in SWCNT arrays.

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“…[13] Yang and Li et al recently reported a cluster steric hindrance strategy by assembling POMs on the exterior of subnanometer SWNTs, and achieved the separation of chirality specific SWNTs. [15] To date, most studies focused on the assembly of POMs on the outer walls of CNTs. However, due to the inhomogeneous electron distribution inside and outside the CNTs wall, a comprehensive understanding of the assembly behavior of POMs within CNTs is of great significance.…”

Section: Introductionmentioning

confidence: 99%

“…Yang and Li et al. recently reported a cluster steric hindrance strategy by assembling POMs on the exterior of subnanometer SWNTs, and achieved the separation of chirality specific SWNTs [15] . To date, most studies focused on the assembly of POMs on the outer walls of CNTs.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Structural Variation and Sodium Storage Behavior of Polyoxometalates Encapsulated within Single‐Walled Carbon Nanotubes

Sha

Cao

Wang

et al. 2022

Chemistry A European J

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The host–guest interaction can remarkably alter the physiochemical properties of composite materials. It is crucial to clarify the mechanism by revealing the influence of the host on the electronic structure of the guest molecules. Herein, we study the structural variation of polyoxometalates (POMs) after being confined in single‐walled carbon nanotubes (SWNT). What we found is that in addition to the reported charge transfer from SWNT to POM, an intramolecular electron transfer within a single POM cluster can be observed in the POM@SWNT composites. Moreover, the charge density on the bridged oxygen of POMs is prominently enhanced. The structural change and electron reconfiguration of POMs upon encapsulation in SWNT significantly speed up electron and ion transport, leading to the improved electrochemical performance for sodium ions storage.

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Polyoxometalate steric hindrance driven chirality-selective separation of subnanometer carbon nanotubes

Abstract: Subnanometer single-chirality single-walled carbon nanotubes (SWCNTs) are of particular interest in multiple applications. Inspired by the interdisciplinary joint of redox active polyoxometalates and SWCNTs, here we report a cluster steric...

Cited by 15 publications

References 79 publications

Atomic-Scale Evidence of Catalyst Evolution for the Structure-Controlled Growth of Single-Walled Carbon Nanotubes

Atomic-Scale Evidence of Catalyst Evolution for the Structure-Controlled Growth of Single-Walled Carbon Nanotubes

Anisotropic Growth of One-Dimensional Carbides in Single-Walled Carbon Nanotubes with Strong Interaction for Catalysis

Insight into the Structural Variation and Sodium Storage Behavior of Polyoxometalates Encapsulated within Single‐Walled Carbon Nanotubes

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