Nucleation Of Single-walled Carbon Nanotubes Research Articles

Evolution Mechanism of Solid-Phase Catalysts During Catalytic Growth of Single-Walled Carbon Nanotubes.

Using solid nanoparticles (NPs) as catalysts is the most effective method to achieve catalytic growth of single-walled carbon nanotubes (SWCNTs) with ultrapure chirality. Until now, SWCNTs with a suitable chirality purity have not been prepared in experiments. That is, the evolution of solid NPs during the catalytic growth of SWCNTs is in contradiction with the original concept of a changeless structure. Hence, in this work, the evolution mechanism of solid cobalt NPs during the nucleation process of SWCNTs is analyzed through molecular dynamics. Similar to the experimental observations, the results show that a drastic structural fluctuation of the NPs occurs during the nucleation of SWCNTs. This structural fluctuation is caused by the fact that the elastic strain energy and surface energy of the NPs can be tuned when a carbon gradient exists between the subsurface and interior of the NP. Furthermore, such a carbon gradient can be reduced by changing the carbon feeding rate. This work not only reveals the evolution mechanism of solid catalysts during the nucleation of SWCNTs but also provides prospects for realizing solid catalysts with a changeless structure by tuning the experimental parameters.

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

ConspectusKnowing 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 (dNT) than those of the catalyst particles (dNP) (dNT < dNP), whereas molten catalyst nanoparticles produced SWCNTs with similar diameters (dNT ≈ dNP). 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 interface, the catalyst-support interface is also of importance in SWCNT growth. The atomic-scale information on catalyst dynamics provides a deep mechanistic understanding of SWCNT growth and will boost the development of the structure-controlled synthesis of SWCNTs and other nanomaterials.

Nucleation of Single-Wall Carbon Nanotubes from Faceted Pt Catalyst Particles Revealed by in Situ Transmission Electron Microscopy.

Revealing the nucleation and growth mechanism of single-wall carbon nanotubes (SWCNTs) from faceted solid catalysts is crucial to the control of their structure and properties. However, due to the small size and complex growth environment, the early stages and dynamic process of SWCNT nucleation have rarely been directly revealed, especially under atmospheric conditions. Here, we report the atomic-resolved nucleation of SWCNTs from the faces of truncated octahedral Pt catalysts under atmospheric pressure using a transmission electron microscope equipped with a gas-cell. It was found that the graphene layers were initially formed preferentially on (111) surfaces, which then joined together to form an annular belt and a hemispherical cap, followed by the elongation of the SWCNT. Based on the observations, an annular belt assembly nucleation model and a possible chirality control mechanism are proposed for SWCNTs grown from well-faceted Pt catalysts, which provides useful guidance for the controlled synthesis of SWCNTs by catalyst design.

Temperature-dependent selective nucleation of single-walled carbon nanotubes from stabilized catalyst nanoparticles

• Enriched (6,5) and (7,5) SWCNTs are respectively synthesized at ambient pressure. • Highly stabilized cobalt nanoparticles are generated from catalyst reduction. • Thermodynamic stability of different tube nuclei accounts for SWCNT selectivity. The utilization of metal nanoparticles supported on oxides substrate as a catalyst for rational single-walled carbon nanotube (SWCNT) growth is hindered by particle coarsening at high synthesis temperature, despite many empirical advances in supported catalyst design. In this study, a newly developed MgO-supported cobalt (Co-MgO) catalyst affords the formation of well-stabilized Co nanoparticles upon reduction, which is attributed to the electronic metal-support interaction and electrostatic stabilization at the Co-MgO interface. The highly stabilized Co nanoparticles led to the predominant growth of (6, 5) SWCNTs at 700 °C by CO disproportionation and the major SWCNT species was found to be (7, 5) SWCNTs at a reaction temperature of 800 °C. The temperature-dependent selective growth of the two SWCNT species was found, by density functional theory calculation, to be strongly correlated with the change of the relative thermodynamic stability of the SWCNT nuclei in the chirality assigning process at different temperatures.

Narrow-chirality distributed single-walled carbon nanotube synthesized from oxide promoted Fe–SiC catalyst

A SiC supported iron (Fe–SiC) catalyst was developed for chemical vapor deposition (CVD) growth of carbon nanotubes. Using CO as the carbon source, sole Fe–SiC catalyst was mostly inactive for synthesizing carbon nanotubes and only trace amount of carbon deposits was produced. In contrast, the powder Fe–SiC catalyst could be activated by pressing them onto a flat SiO2 substrate or by mixing them with porous MgO powders. Particularly, efficient growth of single-walled carbon nanotubes (SWNTs) was achieved on porous MgO promoted Fe–SiC catalyst, and predominant synthesis of (6, 5) SWNTs was realized at a reaction temperature of 650 °C. Systematic characterizations revealed that the reducibility of the Fe–SiC catalyst was enhanced by the physical contact with oxide support, which promotes the formation of small active Fe nanoparticles for the subsequent SWNT nucleation and growth. This work not only deepens our understandings to the catalyst activation mechanisms, but also helps design composite catalyst for synthesizing SWNTs.

Understanding Single-Walled Carbon Nanotube Growth for Chirality Controllable Synthesis

ConspectusChirality defines the structural and electronic properties of a single-walled carbon nanotube (SWCNT), and therefore, synthesizing SWCNT samples with single chirality is essential for future high-end applications, such as replacing silicon in next-generation electronics. Since its discovery in 1991, to realize the selective growth of SWCNTs with a unique structure has been a key focus of SWCNT research. Chirality is currently understood to be assigned at birth and might be changed during the growth process. Understanding the mechanism of chirality assignment during nucleation and chirality-dependent growth kinetics is essential for realizing the final goal of SWCNT synthesis, i.e., the large-scale synthesis of SWCNTs with a specific chiral index. From 2003, we have systematically explored chirality assignment during SWCNT nucleation, how the chirality of a SWCNT affects its growth, and how the chirality changes during growth. Together with our experimental collaborators, we have realized the chirality-specific growth of SWCNTs via a few designed experimental routes. In this account, we will review all these studies and present our perspectives on this very important research topic.We will first introduce the screw dislocation theory of SWCNT growth to elucidate how the chirality affects the growth rate of a SWCNT and the abundance of each SWCNT in the final product. Second, a modified screw dislocation theory, which describes the SWCNT’s growth kinetics on a solid catalyst and its impact on chirality control during synthesis is presented. Third, the random chiral angle assignment during SWCNT nucleation on liquid catalysts is discussed as well as why chirality control in SWCNT growth is so challenging. Together with previous experimental reports, we further demonstrate that solid catalysts have a great advantage in realizing chirality-selective SWCNT growth. Based on our current understanding, we propose three strategies to realize chirality-selective SWCNT growth, (i) controlling the symmetry of solid catalyst particles, (ii) varying the growth conditions, and (iii) controlling the feedstock and etching agent during growth. We expect this account will give the reader a comprehensive understanding of the mechanism behind SWCNT growth and motivate further studies on selective growth to achieve the best performance of SWCNT-based devices in the future.

Residence time effect on single-walled carbon nanotube synthesis in an aerosol CVD reactor

• Residence time in aerosol CVD was tuned while nanotube nucleation maintained. • Carbon nanotube length and I G /I D ratio increase with a higher residence time. • The increase in length and defectiveness drops equivalent sheet resistance. • Effect of vortices, diffusion, and thermophoresis on nanotube yield was shown. • SWCNT/HAuCl 4 thin films with equivalent sheet resistance of 51 Ω/□ were obtained. We examine an effect of residence time on the growth of single-walled carbon nanotubes (SWCNTs) in an aerosol (floating catalyst) chemical vapor deposition (CVD) process using CO as a carbon source and ferrocene as a catalyst precursor. The key feature of aerosol CVD reactors, namely stabilization of fine nanoparticles by an extreme dilution, limits the method for catalyst evolution studies. We show an approach to examine the role of the residence time while maintaining all the processes preceding the nanotube growth (catalyst formation, nanotube nucleation). Using the diameter distribution of nanotubes as a fingerprint of the SWCNT nucleation stage, we have proven the latter to be unaffected by changes in the residence time. Using SEM observations, we have revealed a quite intuitive but inspiring correlation between the carbon nanotube length and residence time. We have also found a decrease in the SWCNT yield caused by the drop in the aerosol concentration, which could be attributed to the gas-phase losses as well as the shift in the catalyst activation degree. Nevertheless, the trends observed allowed us to reach a tenfold decrease in an equivalent sheet resistance (sheet resistance of a film with 90% transmittance at 550 nm) by a threefold increase in the residence time at optimal CO 2 concentration. SWCNT films with the equivalent sheet resistance as low as 245 Ω/□ and 51 Ω/□ (for pristine and doped carbon nanotubes, correspondingly) ensure the promising future of the proposed strategy for optimization of both aerosol CVD reactors and SWCNT-based films for optoelectronic applications.

Carbon fiber-promoted activation of catalyst for efficient growth of single-walled carbon nanotubes

Carbon fibers are placed onto substrate surface with dispersed Co particles to promote the growth efficiency of single-walled carbon nanotubes (SWNTs). During chemical vapor deposition (CVD) process, micro-spaces are fabricated between the carbon fibers and the substrate surface, which modify the Knudsen number of CO and increase its efficient contact with cobalt oxide nanoparticles, enhancing the reduction of catalysts and the nucleation of SWNTs. Compared with surface grown SWNTs without covering carbon fibers, SWNTs grown under carbon fibers demonstrate a much higher catalyst efficiency, i.e. a SWNT density as high as ∼140 SWNTs/μm2. X-ray photoelectron spectroscopy characterizations confirm that the presence of carbon fibers promotes the reduction of cobalt oxide catalyst particles and carbon dissolution inside catalyst particles, which are crucial for catalyst activation and subsequent SWNT nucleation. This work provides a new strategy for the efficient growth of SWNTs, which benefits high-density growth of SWNTs required for future nanoelectronics applications.

A robust CoxMg1-xO catalyst for predominantly growing (6, 5) single-walled carbon nanotubes

Chirality-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) is one of the most challenging tasks in carbon nanotube synthesis field. During CVD growth, the catalyst plays crucial roles in governing SWCNT nucleation thermodynamics as well as growth kinetics. However, the performances of catalyst are generally sensitive to the metal loading amount in the catalyst and the reaction conditions, like the partial pressure of carbon source and the reaction time. In this work, we have systematically investigated a robust CoxMg1-xO solid solution, which can predominantly yield (6, 5) SWCNTs in a wide range of Co concentration, with a diversity of CO concentrations or a broad-ranging reaction time. Besides, the effect of reaction temperature on SWCNT chirality distribution is demonstrated, the mechanism of which is clarified with the assistance of environmental transmission electron microscopy. Finally, the chirality distribution of SWCNTs grown using CH4 as the carbon source is presented. The effects of carbon sources are discussed in view of SWCNT growth mode.

Catalyst- and Etchant-Dependent Mechanisms of Single-Walled Carbon Nanotube Nucleation during Chemical Vapor Deposition

Recent experiments have shown that single-walled carbon nanotube (SWCNT) chirality and diameter can be modulated by adjusting the carbon/hydrogen chemical potentials at the catalyst surface and also by adding chemical etchants, such as ammonia, to the chemical vapor deposition (CVD) feedstock. Here, we present nonequilibrium quantum chemical molecular dynamics simulations showing how these factors control the SWCNT nucleation mechanism in different ways on Fe and Ni catalyst nanoparticles. Polygonal carbon rings form on Ni catalysts via the collapse of extended, partially saturated carbon chains that are adsorbed weakly to the catalyst surface, while SWCNT nucleation on Fe is strongly mediated by the catalyst surface. The weaker Ni–C interaction here means that the carbon desorption rate, and hence carbon chemical potential, on Ni is consistently lower than it is on Fe. Ni also activates adsorbed C–H and N–H bonds more effectively than Fe. Nevertheless, the hydrogen chemical potential is consistently lowe...

How does acetonitrile modulate single-walled carbon nanotube diameter during CVD growth?

There is a commercial demand for single-walled carbon nanotubes (SWCNTs) with uniform diameters and (n, m) chiralities. However, controlling these structural parameters in practice remains a challenge. Recent studies have shown that acetonitrile reversibly modulates SWCNT diameter during chemical vapour deposition (CVD) growth. Here we propose a mechanism to explain this phenomenon using non-equilibrium quantum chemical molecular dynamics simulations. We reveal that acetonitrile-derived radicals actively abstract hydrogen from surface hydrocarbon species as the SWCNT nucleates. This forms hydrogen (iso)-cyanide as a principal chemical product, and decreases the overall surface carbon density during nucleation. By liberating hydrogen, the number of dangling bonds present at the interface of the nucleating carbon structure is increased, which in turn accelerates SWCNT nucleation kinetics. Critically, the number of pentagon rings formed in the SWCNT precursor cap structure increases. Because the nucleation kinetics are much faster than the kinetics of ring defect healing, the pentagons become ‘trapped’ in the growing SWCNT cap structure, and this leads to more highly-curved SWCNT caps. These more highly-curved caps, combined with the lower surface carbon density and the faster kinetics of nucleation and growth, will ultimately yield narrower-diameter SWCNTs in the presence of acetonitrile.

Designing Catalysts for Chirality-Selective Synthesis of Single-Walled Carbon Nanotubes: Past Success and Future Opportunity.

A major obstacle for the applications of single-walled carbon nanotubes (SWNTs) in electronic devices is their structural diversity, ending in SWNTs with diverse electrical properties. Catalytic chemical vapor deposition has shown great promise in directly synthesizing high-quality SWNTs with a high selectivity to specific chirality (n, m). During the growth process, the tube-catalyst interface plays crucial roles in regulating the SWNT nucleation thermodynamics and growth kinetics, ultimately governing the SWNT chirality distribution. Starting with the introduction of SWNT growth modes, this review seeks to extend the knowledge about chirality-selective synthesis by clarifying the energetically favored SWNT cap nucleation and the threshold step for SWNT growth, which describes how the tube-catalyst interface affects both the nucleus energy and the new carbon atom incorporation. Such understandings are subsequently applied to interpret the (n, m) specific growth achieved on a variety of templates, such as SWNT segments or predefined molecular seeds, transition metal (Fe, Co and Ni)-containing catalysts at low reaction temperatures, W-based alloy catalysts, and metal carbides at relatively high reaction temperatures. The up to date achievements on chirality-controlled synthesis of SWNTs is summarized and the remaining major challenges existing in the SWNT synthesis field are discussed.

Structure of Supported and Unsupported Catalytic Rh Nanoparticles: Effects on Nucleation of Single-Walled Carbon Nanotubes.

Achieving a better control of the nucleation and growth of single-walled carbon nanotubes requires understanding of the changes in the catalyst structure and the interfacial phenomena occurring at the solid surface and the gaseous phase from the early stages of the synthesis process. Carbon nanotubes produced by chemical vapor deposition typically use carbon-philic metal catalysts such as Fe, Ni, and Co, in which both surface C and dissolved C atoms contribute to the nanotube formation. We use density functional theory to investigate the interactions of Rh, a noble metal, with carbon both as individual atoms gradually deposited on the catalyst surface from the precursor gas decomposition and as a nucleating seed adhered to the catalyst. Adsorption and limited dissolution of carbon atoms in the subsurface are found to be favorable in unsupported clusters of various sizes (Rh38, Rh55, and Rh68) and in Rh32 clusters supported on MgO(100) and MgO(111) surfaces. Changes in solubility, electron density transfer, and interactions of the Rh clusters with the support and the nascent nanotube are explored for increasing contents of carbon adsorbed on or dissolved inside the particles. The adhesion energy of small Rh38 clusters on the different MgO surfaces studied can differ by as much as 1 eV compared with the same-sized Rh2C particles. Also, the adhesion of graphene differs on the Rh particles by as much as 5.7 eV with respect to Rh2C supported nanoparticles. This demonstrates the influence that the presence of dissolved carbon can have on the catalyst interactions with the support and nucleating nanotube. A discussion on how such factors affect the lattice and electronic structure of the catalyst particles is presented in the interest of obtaining insight that will allow the design of improved catalysts for controlled nanotube synthesis.

Preparation of horizontally aligned single-walled carbon nanotubes with floating catalyst

A strategy to prepare horizontally aligned single-walled carbon nanotubes (SWNTs) at moderate temperatures (≤600 °C) were developed. Using ferocene as the catalyst precursor, Fe nanoparticles are formed in the gaseous phase and catalyze the nucleation and growth of SWNTs in situ. Then the resultant SWNTs are deposited onto the substrates downstream and aligned by the surface lattice of the ST-cut single crystal quartz. The preparation of SWNT arrays at moderate temperatures is important for combining the tube growth with device fabrication.

Effect of ammonia on chemical vapour deposition and carbon nanotube nucleation mechanisms.

Chemical vapour deposition (CVD) growth of carbon nanotubes is currently the most viable method for commercial-scale nanotube production. However, controlling the 'chirality', or helicity, of carbon nanotubes during CVD growth remains a challenge. Recent studies have shown that adding chemical 'etchants', such as ammonia and water, to the feedstock gas can alter the diameter and chirality of nanotubes produced with CVD. To date, this strategy for chirality control remains sub-optimal, since we have a poor understanding of how these etchants change the CVD and nucleation mechanisms. Here, we show how ammonia alters the mechanism of methane CVD and single-walled carbon nanotube nucleation on iron catalysts, using quantum chemical molecular dynamics simulations. Our simulations reveal that ammonia is selectively activated by the catalyst, and this enables ammonia to play a dual role during methane CVD. Following activation, ammonia nitrogen removes carbon from the catalyst surface exclusively via the production of hydrogen (iso)cyanide, thus impeding the growth of extended carbon chains. Simultaneously, ammonia hydrogen passivates carbon dangling bonds, which impedes nanotube nucleation and promotes defect healing. Combined, these effects lead to slower, more controllable nucleation and growth kinetics.

Chiral-selective growth of single-walled carbon nanotubes on Fe-based catalysts using CO as carbon source

MgO supported monometallic Fe (FeMgO) and bimetallic FeMn (FeMnMgO) catalysts were developed for growing carbon nanotubes using CO as carbon source. Characterizations on the FeMgO catalyst revealed that Fe cations were well-dispersed in the porous MgO support, forming a solid solution. Since most Fe cations in the solid solution are difficult to reduce, FeMgO can only catalyze the growth of single-walled carbon nanotubes (SWCNTs) at temperatures of 700 °C and above. While Fe cations in FeMnMgO could be reduced at lower temperatures with the assistance of Mn, catalyzing the subsequent growth of SWCNTs. Compared with most SWCNTs grown on components like Co or Ni at ambient reaction pressure, the Fe-catalyzed SWCNTs demonstrate rather narrow chirality distributions. Particularly, preferential (6, 5) tube growth on FeMnMgO was achieved at 600 °C. The narrow SWCNT chirality distribution could be inherently related to the high carbon solubility of Fe nanoparticles, favoring the nucleation of SWCNTs by a perpendicular mode. The present studies not only offer essential insights into SWCNT growth mechanisms, but can guide the design of novel catalysts for chirality-controlled growth of SWCNTs.

The influence of magnetic moment on carbon nanotube nucleation

We demonstrate the impact of magnetic moment on single-walled carbon nanotube (SWCNT) nucleation, using quantum chemical molecular dynamics simulations. The mechanism of SWCNT cap formation on Fe38 nanoparticle catalysts can be manipulated by altering the total magnetic moment. When the magnetic moment is low, large cap structures dominated by pentagons are formed. Increasing the magnetic moment leads to smaller, “flatter” sp2 carbon networks with a higher proportion of hexagons, which are incapable of lifting away from the catalyst surface. These results demonstrate that SWCNT (n,m) chirality distributions can be potentially manipulated via altering the magnetic moment of the catalyst-carbon interface. We also show that higher magnetic moments leads to slower SWCNT nucleation. This is a consequence of the extent of Fe → C charge transfer, which is proportional to the total magnetic moment. As the magnetic moment is increased, the Fe38 nanoparticle has higher catalytic activity and is able to stabilise carbon in its subsurface region, thereby impeding the nucleation process.

Atomic scale simulation of carbon nanotube nucleation from hydrocarbon precursors.

Atomic scale simulations of the nucleation and growth of carbon nanotubes is essential for understanding their growth mechanism. In spite of over twenty years of simulation efforts in this area, limited progress has so far been made on addressing the role of the hydrocarbon growth precursor. Here we report on atomic scale simulations of cap nucleation of single-walled carbon nanotubes from hydrocarbon precursors. The presented mechanism emphasizes the important role of hydrogen in the nucleation process, and is discussed in relation to previously presented mechanisms. In particular, the role of hydrogen in the appearance of unstable carbon structures during in situ experimental observations as well as the initial stage of multi-walled carbon nanotube growth is discussed. The results are in good agreement with available experimental and quantum-mechanical results, and provide a basic understanding of the incubation and nucleation stages of hydrocarbon-based CNT growth at the atomic level.

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition.

We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts.

DFT study of Fe-Ni core-shell nanoparticles: stability, catalytic activity, and interaction with carbon atom for single-walled carbon nanotube growth.

Metal catalysts play an important role in the nucleation and growth of single-walled carbon nanotubes (SWCNTs). It is essential for probing the nucleation and growth mechanism of SWCNTs to fundamentally understand the properties of the metal catalysts and their interaction with carbon species. In this study, we systematically studied the stability of 13- and 55-atom Fe and Fe-Ni core-shell particles as well as these particles interaction with the carbon atoms using the density functional theory calculations. Icosahedral 13- and 55-atom Fe-Ni core-shell bimetallic particles have higher stability than the corresponding monometallic Fe and Ni particles. Opposite charge transfer (or distribution) in these particles leads to the Fe surface-shell displays a positive charge, while the Ni surface-shell exhibits a negative charge. The opposite charge transfer would induce different chemical activities. Compared with the monometallic Fe and Ni particles, the core-shell bimetallic particles have weaker interaction with C atoms. More importantly, C atoms only prefer staying on the surface of the bimetallic particles. In contrast, C atoms prefer locating into the subsurface of the monometallic particles, which is more likely to form stable metal carbides. The difference of the mono- and bimetallic particles on this issue may result in different nucleation and growth mechanism of SWCNTs. Our findings provide useful insights for the design of bimetallic catalysts and a better understanding nucleation and growth mechanism of SWCNTs.