Hidden features of the catalyst nanoparticles favorable for single-walled carbon nanotube growth

Harutyunyan, Avetik R.; Mora, Elena; Tokune, Toshio; Bolton, Kim; Rosén, Arne; Jiang, Aiqin; Awasthi, Neha; Curtarolo, Stefano

doi:10.1063/1.2730730

Cited by 65 publications

(111 citation statements)

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“…In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 . This is explained in terms of substantial inter-metallic interaction between Mo, Fe and C 20,35,36 which is congruent with previously observed solid-state reactions between these elements. In fact, the addition of Mo in mechanical alloying of powder Fe and C mixtures 38 promotes solid state reactions even at low Mo concentrations by forming ternary phases, such as the (Fe,Mo) 23 C 6 type carbides 38 .…”

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“…chemical poisoning or coating with carbon), thermal sintering (e.g. caused by highly exothermic reactions on the clusters surface 13,14,24 with insufficient heat transfer 25,26 ) and solid-state reactions (nucleation of inactive phases in the cluster 22,23,25 ).Metal alloy catalysts, such as Fe:Co, Co:Mo and Fe:Mo, improve the growth of CNTs 4,10,20,27,28,29,30,31 , because the presence of more than one metal species can significantly enhance the activity of a catalyst 20,32,33,34 , and can prevent catalyst particle aggregation 20,31,32,33 . In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 .…”

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“…Similarly to Co, Fe can dissolve a relatively large fraction of C (at least in the γ phase), but concomitantly it forms carbides at temperatures relevant to SWCNT growth (Fe 3 C) 35,36 . Nucleation of Fe 3 C and subsequent loss of C solubility 20 can be used to identify the thermodynamic lower limit for the CVD growth of very thin SWCNTs from Fe nanoparticles 22,23 . Thus, for efficient CVD growth from Fe, Mo, Fe:Mo and Co:Mo clusters, the particles must be small (dispersed) and metallic (preserved from carbidization).…”

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“…Efficient catalysts must have long active lifetimes (with respect to feedstock dissociation and nanotube growth), high selectivity and be less prone to contamination 19,20,21,22,23 . Common factors that lead to reduction in catalytic activity are deactivation (i.e.…”

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Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

et al. 2008

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We explore the role of Mo in Fe:Mo nanocatalyst thermodynamics for low-temperature chemical vapor deposition growth of single walled carbon nanotubes (SWCNTs). By using the size-pressure approximation and ab initio modeling, we prove that for both Fe-rich (∼ 80% Fe or more) and Mo-rich (∼ 50% Mo or more) Fe:Mo clusters, the presence of carbon in the cluster causes nucleation of Mo2C. This enhances the activity of the particle since it releases Fe, which is initially bound in a stable Fe:Mo phase, so that it can catalyze SWCNT growth. Furthermore, the presence of small concentrations of Mo reduce the lower size limit of low-temperature steady-state growth from ∼0.58nmf orpureF eparticlesto ∼ 0.52nm. Our ab initio-thermodynamic modeling explains experimental results and establishes a new direction to search for better catalysts.Critical factors for the efficient growth of single walled carbon nanotubes (SWCNTs) via catalytic chemical vapor deposition (CCVD) 1,2,3 are the compositions of the interacting species (feedstock, catalyst, support 4,5,6,7,8,9,10 ), the preparation of the catalysts, and the synthesis conditions 11,12,13,14,15,16,17,18 . Efficient catalysts must have long active lifetimes (with respect to feedstock dissociation and nanotube growth), high selectivity and be less prone to contamination 19,20,21,22,23 . Common factors that lead to reduction in catalytic activity are deactivation (i.e. chemical poisoning or coating with carbon), thermal sintering (e.g. caused by highly exothermic reactions on the clusters surface 13,14,24 with insufficient heat transfer 25,26 ) and solid-state reactions (nucleation of inactive phases in the cluster 22,23,25 ).Metal alloy catalysts, such as Fe:Co, Co:Mo and Fe:Mo, improve the growth of CNTs 4,10,20,27,28,29,30,31 , because the presence of more than one metal species can significantly enhance the activity of a catalyst 20,32,33,34 , and can prevent catalyst particle aggregation 20,31,32,33 . In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 . This is explained in terms of substantial inter-metallic interaction between Mo, Fe and C 20,35,36 which is congruent with previously observed solid-state reactions between these elements. In fact, the addition of Mo in mechanical alloying of powder Fe and C mixtures 38 promotes solid state reactions even at low Mo concentrations by forming ternary phases, such as the (Fe,Mo) 23 C 6 type carbides 38 .The way in which carbon interacts with transition metals depends on the metal species. Fe and Co belong to the "carbon dissolution-precipitation mechanism" group, where relatively large fractions of carbon dissolve into the cluster before stable carbides are formed, while Mo belongs to the "carbide formation-decomposition" group where carbide formation occurs rapidly at low carbon concentrations 39 . These mechanisms are governed by the interplay between solub...

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Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

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Carbon Nanomaterials: Synthetic Approaches

Tessonnier

2011

Nanotechnologies for the Life Sciences

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The sections in this article are Introduction General Concepts on the Synthesis of Carbon (Nano‐)Materials Uncatalyzed Synthesis of Carbon (Nano‐)Materials Catalyzed Synthesis of Carbon (Nano‐)Materials Synthesis from Solid Precursors Nanodiamonds Turning Graphite into Diamond Explosive Detonation Synthesis Fullerenes, Nanohorns, Single‐ and Multi‐Wall Carbon Nanotubes Catalytic Chemical Vapor Deposition Definitions Mechanistic Aspects Single‐ and Multi‐Wall Carbon Nanotubes Floating Catalyst CCVD Immobilized Catalyst CCVD Aligned Carbon Nanotubes Carbon Nanotubes Synthesized from Biocompatible Catalysts Metal‐ and PAH ‐Induced Toxicity of Carbon Nanotubes Purification Techniques Importance of Defects and Curvature for Further Functionalization Functionalization: Creating Anchoring Points for Bioactive Molecules Functionalization by Oxidation Functionalization by Coupling Reactions Noncovalent Functionalization Conclusion and Outlook

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Recent Progress on the Growth Mechanism of Carbon Nanotubes: A Review

2011

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Tremendous progress has been achieved during the past 20 years on not only improving the yields of carbon nanotubes and move progressively towards their mass production, but also on gaining a profound fundamental understanding of the nucleation and the growth processes. Parameters that influence the yield but also the quality (e.g., microstructure, homogeneity within a batch) are better understood. The influence of the carbon precursor, the reaction conditions, the presence of a catalyst, the chemical and physical status of the latter, and other factors have been extensively studied. The purpose of the present Review is not to list all the experiments reported in the literature, but rather to identify trends and provide a comprehensive summary on the role of selected parameters. The role of the catalyst occupies a central place in this Review as a careful control of the metal particle size, particle dispersion on the support, the metastable phase formed under reaction conditions, its possible reconstruction, and faceting strongly influence the diameter of the carbon nanotubes, their structure (number of walls, graphene sheet orientation, chirality), their alignment, and the yield. The identified trends will be compared with recent observations on the growth of graphene. Recent results on metal-free catalysts will be analyzed from a different perspective.

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Hidden features of the catalyst nanoparticles favorable for single-walled carbon nanotube growth

Cited by 65 publications

References 29 publications

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

Carbon Nanomaterials: Synthetic Approaches

Recent Progress on the Growth Mechanism of Carbon Nanotubes: A Review

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