Metallic Ni Particles Research Articles

Engineering the interfacial hetero-structure for high-current-density hydrogen evolution

Modulating the hetero-structures with abundant interfaces in catalyst is a feasible but challenging strategy to improve the catalytic performance. In this work, a highly efficient catalyst (R-CoMoOx/Ni (Co)) was prepared with plentiful interfacial structures to accelerate the hydrogen evolution reaction (HER), which contained both reduced CoO and MoO2 as a R-CoMoOx substrate and metallic Ni (Co) particles as the catalytic center. The combination of CoO and MoO2 with a Co-O-Mo local structure in R-CoMoOx led to an electron-enriched Co center to catch the dissociated H+, while the abundant interfacial interaction between R-CoMoOx and Ni (Co) could accelerate the charge transfer and then facilitate the production of H2 through a fast Volmer-Tafel pathway. As a result, the integrated R-CoMoOx/Ni (Co) catalyst could drive alkaline HER with ultra-low overpotentials of 16 mV for 10 mA cm−2 (25 °C) and 186 mV for 1000 mA cm−2 (60 °C), respectively, with a good stability over 100 h. Moreover, by coupling with RuO2 electrode in an anion exchange membrane system, it could achieve 1000 mA cm−2 at 1.78 V for overall water splitting with a high energy conversion efficiency of 70.4 %. The H2 production cost at 1000 mA cm−2 was merely $ 0.952 per gasoline gallon equivalent, much less than the target cost of the US Department of Energy.

Structure Engineering of Ni/SiO2 Vegetable Oil Hydrogenation Catalyst via CeO2.

Inspired by our finding that metallic Ni particles could be uniformly distributed on a reduced CeO2 surface and stabilized on Ce3+ sites, we suppose a possible improvement in the activity and selectivity of the MgNi/SiO2 vegetable oil hydrogenation catalyst by increasing the surface metal Ni availability via modification by ceria. The proposed approach involved the addition of a CeO2 modifier to the SiO2 carrier and as a catalyst component. Evaluation of the structure, reducibility, and surface and electronic states of the CeO2-doped MgNi/SiO2 catalyst was performed by means of the Powder X-ray diffraction (PXRD), Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) combined with High-resolution transmission electron microscopy (HRTEM), Temperature-programmed reduction with hydrogen (H2-TPR), and H2-chemisortion techniques. So far, no studies related to this approach of designing Ni/SiO2 catalysts for the partial hydrogenation of vegetable oil have been reported. The added ceria impact was elucidated by comparing fatty acid compositions obtained by the catalysts at an iodine value of 80. In summary, tuning the hydrogenation performance of Ni-based catalysts can be achieved by structural reconstruction using 1 wt.% CeO2. The introduction mode changed the selectivity towards C18:1-cis and C18:0 fatty acids by applying ceria as a carrier modifier, while hydrogenation activity was improved upon ceria operation as the catalyst dopant.

Elucidating nickel oxide reduction in a Ni-YSZ solid oxide cell via in-situ X-ray nano holo-tomography

Reducing nickel oxide in solid oxide cell (SOC) electrodes is a critical step during the early stages of cell operation. It is considered crucial in shaping the final microstructure of the fuel electrode. In this work, we investigate the NiO reduction process in a state-of-the-art Solid Oxide Cell (SOC) using in-situ X-ray nano-holo-tomography. Results show a fast reaction kinetics and a reaction front from the outer to the inner regions of the sample. NiO reduction is complete in the first few seconds and the metallic Ni particles present a sponge-like structure, with many nanocrystallites and internal nano porosity. After reduction, the Ni network undergoes coarsening, increasing its particle size. Based on the acquired data, we propose a new chain of reaction mechanisms for forming the Ni nanocrystallites observed after reduction.

Fabrication of NiTi-MMO supported on in-situ generated TiO2 for dioctyl phthalate hydrogenation: A strategy for improving the utilization efficiency of Ni

In this work, a NiTi-MMO/TiO2-R catalyst was prepared by in-situ generation of a TiO2 support during hydrothermal synthesis of the hydrotalcite precursor for NiTi-MMO. The formation of NiTi-MMO can reduce the size of metallic Ni particles, which can significantly improve the catalyst's activity, and the in-situ generated TiO2 support can enhance the dispersion of NiTi-MMO and the utilization efficiency of the active nickel species. The NiTi-MMO/TiO2-R catalyst showed high activity for the hydrogenation of dioctyl phthalate to dioctyl-1,2-cyclohexanedicarboxylate. The catalyst also exhibited good stability, maintaining the yield over 90 % after 6 cycles. Characterization results showed that a strong metal-support interaction was formed between the in-situ generated TiO2 support and the metallic Ni particles produced by the reduction of NiTi-MMO. The strong metal-support interactions formed between metallic Ni particles and the in-situ generated TiO2 played a crucial role in stabilizing the nickel species and preventing their aggregation, resulting in superior catalytic performance.

Ordered Mesoporous Carbons with Well-Dispersed Nickel or Platinum Nanoparticles for Room Temperature Hydrogen Adsorption.

A facile mechanochemical method was used for the synthesis of ordered mesoporous carbons (OMCs) with well-dispersed metal nanoparticles. The one-pot ball milling of tannins with a metal salt in the presence of a block copolymer followed by thermal treatment led to Ni- or Pt-embedded OMCs with high specific surface areas (up to 600 m2·g-1) and large pore volumes (up to ~0.5 cm3·g-1). The as-prepared OMC-based samples exhibited hexagonally ordered cylindrical mesopores with narrow pore size distributions (average pore size ~7 nm), which implies sufficient long-range copolymer-assisted self-assembly of the tannin-derived polymer upon milling even in the presence of a metal salt. The homogenous decoration of carbons with small-sized metal (Ni or Pt) particles was essential to provide H2 storage capacities up to 0.33 wt.% at 25 °C and under 100 bar. The presented synthesis strategy seems to have great potential in the practical uses of functionalized polymers and carbons for applications in adsorption and catalysis.

Carbon cycle using the CO2 conversion to methane as environmental feasibility on Ni/TiO2-Na nanotubes catalysts

xNi/TiO2-Na nanotubes catalysts were evaluated in CO2-methanation. The catalysts were characterized by FE-SEM, TEM, XRD, MS, CO2-TPD, DRIFTS and TPR. 50Ni/TiO2-Na catalyst showed better CO2 conversion and high CH4 selectivity while, the 5Ni/TiO2-Na catalyst that showed high CO selectivity, low CO2 methanation and Ni species in intimate contact with the support. In this latter, the difficulty of CO2 hydrogenation can be associated with the strength of the catalyst basic sites, which is influenced by the Ni species in intimate contact with the support, promoting the SMSI effect. According with TPD results, the CO2 is retained on the surface of the catalysts with 5 and 20 wt% Ni, and needs higher temperature than in the 50Ni/TiO2-Na nanotube sample to desorb it and liberate the active sites blocked for the reaction to proceed. Although, a high amount of the Ti0.75Ni0.23O cubic phase was observed on the 50Ni/TiO2-Na sample, a large number of metallic Ni particles remained supported on the TiO2-Na which could reduce the SMSI effect on this catalyst. DRIFTs studies showed that Ni impregnation to TiO2-Na nanotubes generated new sites for CO2 adsorption and H2 is necessary to produce carbonates, bicarbonates, formate and carboxilates as intermediaries of the reaction during CO2-hydrogenation.

Co3O4 nanosheets modified by Ni@C nanoparticles as effective flow-through electrode for electro-activation of PMS: Ni@C as electron shuttle for accelerated Co3+/Co2+ cycle in bulk Co3O4

Electro-assisted activation of peroxymonosulfate (EA-PMS) by transition metals oxides (TMOs) has been extensively studied for the removal of organic pollutants. Despite TMOs possess considerable activity and affinity to PMS, their poor bulk conductivity still limits the electron exchange during the TMδ/δ+1 redox cycle, especially the efficient reduction of TMδ+1 via cathodic process. In this study, carbon felt loaded with modified Co3O4 nanosheets (Co@FCF) was fabricated and applied as the flow-through electrode of EA-PMS process, where the Co3O4 nanosheets were embedded with numerous metallic Ni particles encapsulated within carbon layers (Ni@C). Driven by weak electric current, continuous electrons can be supplied to the bulk Co3O4 from the electron-rich Ni@C nanoparticles, resulting in accelerated Co3+/Co2+ cycle, enhanced production of SO4·− and improved energy utilization efficiency. Electrochemical tests along with density functional theory calculations indicate that the unique structure of Co@FCF played essential role in the enhanced performance.

Depositing Pd on the outmost surface of Pd1Ni/SiO2 single-atom alloy via atomic layer deposition for selective hydrogenation of acetylene

Supported Pd single-atom alloy (SAA) catalysts are selective in acetylene semi-hydrogenation. However, it is a challenge to prepare Pd SAA where Pd single atoms dispersed on the outmost surface of the catalysts because the Pd atoms on Pd SAA prepared by conventional impregnation distribute inside the alloyed particle or on the support surface after activation. In this work, we firstly synthesized Ni/SiO2 nanocatalysts by impregnation, followed by H2 reduction to generate metal Ni particles on SiO2. Subsequently, Pd single atoms are selectively deposited on the Ni particle surface by atomic layer deposition (ALD). The Pd species on the Pd1Ni/SiO2 prepared by ALD dispersed on the outmost surface of catalyst, presenting the improved catalytic performances in acetylene hydrogenation, as compared to a reference Pd1Ni/SiO2 catalyst prepared by impregnation. The Pd1Ni/SiO2 catalyst prepared by ALD with 5 cycles (0.04 wt. %Pd, 5c-Pd1Ni/SiO2) shows both superior hydrogenation activity (92 %) and selectivity (88 %) under mild temperature (80 °C) in the selective semi-hydrogenation of acetylene. Moreover, the specific activity of the 5c-Pd1Ni/SiO2 catalyst is the highest, as compared to the catalysts reported in literature. Therefore, we conclude that the metal single atoms on metal SAA catalyst prepared by ALD locate on the outmost surface of the catalyst, presenting the unusual catalytic performances in catalysis.

Brilliant blue FCF dye adsorption using magnetic activated carbon from Sapelli wood sawdust

Sapelli wood sawdust-derived magnetic activated carbon (SWSMAC) was produced by single-step pyrolysis using KOH and NiCl2 as activating and magnetization agents. SWSMAC was characterized by several techniques (SEM/EDS, N2 adsorption/desorption isotherms, FTIR, XRD, VSM, and pHPZC) and applied in the brilliant blue FCF dye adsorption from an aqueous medium. The obtained SWSMAC was a mesoporous material and showed good textural properties. Metallic nanostructured Ni particles were observed. Also, SWSMAC exhibited ferromagnetic properties. In the adsorption experiments, adequate conditions were an adsorbent dosage of 0.75g L-1 and a solution pH of 4. The adsorption was fast, and the pseudo-second-order demonstrated greater suitability to the kinetic data. The Sips model fitted the equilibrium data well, and the maximum adsorption capacity predicted by this model was 105.88mgg-1 (at 55°C). The thermodynamic study revealed that the adsorption was spontaneous, favorable, and endothermic. Besides, the mechanistic elucidation suggested that electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions were involved in the brilliant blue FCF dye adsorption onto SWSMAC. In summary, an advanced adsorbent material was developed from waste by single-step pyrolysis, and this material effectively adsorbs brilliant blue FCF dye.

Multifunctional flower-like Ni particles/silicon carbide nanowires for infrared radar compatible stealth performance

Alongside the rapid development of detection systems and improved detection accuracy, infrared/radar-compatible stealth materials have become the emphasis of current stealth technology research. Versatile flower-like Ni particles/silicon carbide nanowires (SiC NWs) composites for infrared radar stealth compatibility have been successfully prepared. Due to its special microstructure in combination with the multiple loss mechanisms of dielectric and magnetic, the minimum reflection loss (RLmin) achievable with the paraffin matrix mixture is −49.26 dB at a composite content of 50 wt%, which has a thickness of 1.9 mm and an effective absorption bandwidth (EAB) of 4.85 GHz. By increasing the absorbent content to 60 wt%, the EAB in the Ku band can attain 5.0 GHz at 1.8 mm thickness. Petal-shaped Ni particles are introduced to improve the impedance matching characteristics, increase interfacial polarisation and multiple scattering of electromagnetic (EM) wave, and enhance the microwave absorption properties. Simultaneously, the pure SiC NWs material can protect against infrared radiation emitted from the hand for more than 15 min, and the infrared (IR) reflectivity is improved in all three bands after the composite metal Ni particles. A novel formulation guide for the design of versatile and high-performance EM wave absorbing and infrared stealth materials is provided by this work.

Dry reforming of methane over silica zeolite-encapsulated Ni-based catalysts: Effect of preparation method, support structure and Ni content on catalytic performance

Dry reforming of methane (DRM) is a prospective technology for efficient utilization of CH4 and CO2, with the essential challenge being the design and synthesis of efficient catalysts. In this research, serial encapsulated Ni-based catalysts (xNi@S-1, x = 5, 7, 10) by silica zeolite (S-1) were prepared successfully. The effects of support structure, preparation method and Ni content upon the catalytic performance for DRM were investigated and diverse characterizations were utilized for revealing structural features of as-prepared catalysts. Encapsulated 7Ni@S-1 catalyst prepared using the one-pot hydrothermal method could acquire more homogeneously dispersed metallic Ni particles and more Ni species including Ni0, NiO, 1:1/2:1 Ni phyllosilicates that could facilitate forming stable Ni0 sites and Ni2+-O2- ion pairs for adsorption and activation of CH4 and CO2, respectively. Hence, 7Ni@S-1 still maintained the highest CH4 and CO2 conversions of 57.9% and 88.6% and H2/CO molar ratio of 0.90 after 52 h stability tests.

Characterization and Syngas Production at Low Temperature via Dry Reforming of Methane over Ni-M (M = Fe, Cr) Catalysts Tailored from LDH Structure

Bimetallic layered double oxide (LDO) NiM (M = Cr, Fe) catalysts with nominal compositions of Ni/M = 2 or 3 were tailored from layered double hydroxides (LDH) using a coprecipitation method to investigate the effects of the trivalent metal (Cr or Fe) and the amount of Ni species on the structural, textural, reducibility, and catalytic properties for CH4/CO2 reforming. The solids before (LDH) and after (LDO) thermal treatment at 500 °C were characterized using TGA-TD-SM, HT-XRD, XRD, Raman, and IR-ATR spectroscopies; N2 physical adsorption; XPS; and H2-TPR. According to the XRD and Raman analysis, a hydrotalcite structure was present at room temperature and stable up to 250 °C. The interlayer space decreased when the temperature increased, with a lattice parameter and interlayer space of 3.018 Å and 7.017 Å, respectively. The solids fully decomposed into oxide after calcination at 500 °C. NiO and spinel phases (NiM2O4, M = Cr or Fe) were observed in the NiM (M = Cr, Fe) catalysts, and Cr2O3 was detected in the case of NiCr. The NiFe catalysts show low activity and selectivity for DRM in the temperature range explored. In contrast, the chromium compound demonstrated interesting CH4 and CO2 conversions and generally excellent H2 selectivity at low reaction temperatures. CH4 and CO2 conversions of 18–20% with H2/CO of approx. 0.7 could be reached at temperatures as low as 500 °C, but transient behavior and deactivation were observed at higher temperatures or long reaction times. The excellent activity observed during this transient sequence was attributed to the stabilization of the metallic Ni particles formed during the reduction of the NiO phase due to the presence of NiCr2O4, opening the path for the use of these materials in periodic or looping processes for methane reforming at low temperature.

Atomically Isolated Nickel–Nitrogen–Carbon Electrocatalysts Derived by the Utilization of Mg2+ ions as Spacers in Bimetallic Ni/Mg–Metal–Organic Framework Precursors for Boosting the Electroreduction of CO2

Electrochemical CO2 reduction (CO2R) is a promising avenue for the conversion of CO2 into fuels and beneficial chemicals. Significant efforts have been devoted to the development of active and selective electrocatalysts for CO2R. Atomically dispersed transition metal electrocatalysts have recently attracted consideration for CO2R due to their unique electronic and structural properties that can impart good catalytic performance and high active metal utilization. Among different precursors used for preparing these catalysts, metal–organic frameworks (MOFs) have been utilized as templates for generating atomically dispersed transition metal active sites as they provide well-defined structures that contain transition metals isolated from each other by organic ligands, along with high surface areas. However, maintaining the isolation of the transition metal species, achieving high surface concentrations of active sites, and imparting porosity during the high-temperature heat treatment of MOFs used during synthesis remain a challenge. In this report, Mg2+ ions have been employed as spacers in a bimetallic metal–organic framework (NiMg-MOF-74) to assist in preventing the coalescence of the Ni atoms into Ni-based particles during heat treatment, which combined with the use of urea as a nitrogen source resulted in the formation of isolated Ni–Nx/C active sites. Our findings demonstrated that Mg2+ ions play a crucial role in extending the distance between the adjacent Ni sites in the precursor structure and generating atomically isolated Ni sites. On the contrary, the utilization of Mg-free Ni-MOF-74 led to the formation of metallic Ni particles embedded in a carbon nanotube-based structure. Furthermore, we investigated the impact of pyrolysis temperature on the produced catalyst morphology. The generation of isolated Ni–Nx/C sites was promoted at higher pyrolysis temperatures (900 °C), while Ni-based particles were predominantly formed at a lower temperature (700 °C). The optimized atomically dispersed Ni–N–C catalyst exhibited excellent selectivity toward CO with a Faradaic efficiency of ∼90% and a current density of −4.2 mA/cm2 at −0.76 V vs a reversible hydrogen electrode.

Modeling and characterization of the electrical conductivity on metal nanoparticles/carbon nanotube/polymer composites

Flexible conductive films have good deformability and conductivity, and are expected to be used in flexible electronic devices. In this paper, four kinds of flexible conductive films were successfully prepared by compounding nano-sized metal (Ni, Cu, Au or AuCu alloy) particles to CNT surface and then dispersing to polydimethylsiloxane matrix. Experiment results show that the conductivity of these prepared films are almost two orders of magnitude higher than that of CNT/polydimethylsiloxane films with the same CNT loadings. A simulation model based on percolation network theory and Monte Carlo technology is introduced to study the influence of nanoparticles on the composite conductivity. Results confirmed that the introduction of nanoparticles effectively reduces the effective resistance of CNT and the tunnelling resistance at CNT junctions. The intrinsic conductivity and the length diameter ratio of CNT, the intrinsic conductivity, the size and the coverage ratio of nanoparticles are the core parameters affecting the conductivity of composite. Compared with CNT/polydimethylsiloxane films, the optimized theoretical conductivity of these nano-sized particles enhanced composites can be further improved.

The properties characterization and strengthening-toughening mechanism of Al2O3-CA6-MA-Ni multi-phase composites prepared by adding calcined dolomite

Basing on the systematical research of the powder properties of calcined dolomite mineral (CM) obtained from raw dolomite mineral (RDM), a novel Al2O3-CA6-MA/Ni multi-phase composite was developed using the in-situ generated strengthening-toughening phases of calcium hexaluminate (CA6) and magnesium aluminate spinel (MA) being introduced into an Al2O3-Ni system by regulating the reaction between CM and Al2O3. Under the anisotropic growth behaviour of CA6, the composite obtained a unique “ring” microstructure, while the mechanical properties were improved. In addition, the strengthening-toughening mechanisms related to this modification and improvement were studied in depth, that is, the pull out and fracture behaviours of CA6 and MA grains promoted crack deflection, bridging and branching, and the nano precipitation behaviour of metal Ni particles at the boundaries between CA6 and Al2O3 grains realized the bonding effect. This finding has important practical significance and economic value for the deep processing and application of RDM.

Electronic Structure Investigation of GaN Nanowire Doped with Transition Metals Particles via First Principle

AbstractIn order to make GaN nanowires better used in the field of spin‐polarized electron sources, the structure and properties of transition metal (Cr, Mn, Fe, Co, and Ni) particles doped nanowires are studied through first principles. The research results show that transition metal (TM) particles are more likely to be doped on the outermost surface of GaN nanowires. The work function of Cr‐doped GaN nanowires has the largest decrease, which is 2.06 eV. For TM‐doped nanowires, magnetic moments are induced, which are mainly derived from the polarization of 3d electrons of TM atoms and 2p electrons of N atoms. Mn‐doped GaN nanowires with 100% spin polarization characteristics seem to be good candidates for spin‐polarized electron source photocathode applications.

Reversing sintering effect of Ni particles on \u03b3-Mo2N via strong metal support interaction

Reversing the thermal induced sintering phenomenon and forming high temperature stable fine dispersed metallic centers with unique structural and electronic properties is one of the ever-lasting targets of heterogeneous catalysis. Here we report that the dispersion of metallic Ni particles into under-coordinated two-dimensional Ni clusters over γ-Mo2N is a thermodynamically favorable process based on the AIMD simulation. A Ni-4nm/γ-Mo2N model catalyst is synthesized and used to further study the reverse sintering effect by the combination of multiple in-situ characterization methods, including in-situ quick XANES and EXAFS, ambient pressure XPS and environmental SE/STEM etc. The under-coordinated two-dimensional layered Ni clusters on molybdenum nitride support generated from the Ni-4nm/γ-Mo2N has been demonstrated to be a thermally stable catalyst in 50 h stability test in CO2 hydrogenation, and exhibits a remarkable catalytic selectivity reverse compared with traditional Ni particles-based catalyst, leading to a chemo-specific CO2 hydrogenation to CO.

New Insights on the Nickel State Deposited by Hydrazine Wet-Chemical Synthesis Route in the Ni/BCY15 Proton-Conducting SOFC Anode.

Yttrium-doped barium cerate (BCY15) was used as an anode ceramic matrix for synthesis of the Ni-based cermet anode with application in proton-conducting solid oxide fuel cells (pSOFC). The hydrazine wet-chemical synthesis was developed as an alternative low-cost energy-efficient route that promotes ‘in situ’ introduction of metallic Ni particles in the BCY15 matrix. The focus of this study is a detailed comparative characterization of the nickel state in the Ni/BCY15 cermets obtained in two types of medium, aqueous and anhydrous ethylene glycol environment, performed by a combination of XRD, N2 physisorption, SEM, EPR, XPS, and electrochemical impedance spectroscopy. Obtained results on the effect of the working medium show that ethylene glycol ensures active Ni cermet preparation with well-dispersed nanoscale metal Ni particles and provides a strong interaction between hydrazine-originating metallic Ni and cerium from the BCY15 matrix. The metallic Ni phase in the pSOFC anode is more stable during reoxidation compared to the Ni cermet prepared by the commercial mechanical mixing procedure. These factors contribute toward improvement of the anode’s electrochemical performance in pSOFC, enhanced stability, and a lower degradation rate during operation.

Preparation and properties of silica-coated metallic nickel particles

A simple method that suppresses the oxidation and aggregation of metallic particles has been required to be developed. In the present work, metallic nickel (Ni) particles were used as a control, and silica-coating of them was performed for the suppression. Metallic Ni particles were synthesized in water exposed to air, in which nickel(II) acetate tetrahydrate, sodium borohydride, and citric acid monohydrate (Cit) were used as the Ni source, reducing reagent, and stabilizer, respectively. The metallic Ni particles with the size of ca. 33 nm were coated with silica shells with thicknesses of 14–40 nm by adding tetraethylorthosilicate (TEOS)/ethanol to the metallic Ni particle colloid solution (Ni/SiO2). In this solution, TEOS was the silica source, and ethanol was the solvent. The morphology of Ni/SiO2 particles was dependent on the concentrations of Cit and TEOS. Both aggregation of the metallic Ni particles and their oxidation even with annealing in air were controlled by the silica shells due to their function as a physical barrier. In addition, crystallization of the cores to metallic Ni with annealing in air was exhibited. The annealed Ni/SiO2 particles showed paramagnetic behavior because of their small size, and the Ni/SiO2 particles annealed at 600 °C had a saturation magnetization of 46.5 emu/g-Ni roughly comparable to that of bulk metallic Ni, which also supported that the aggregation and oxidation of metallic Ni particles were successfully controlled with the silica coating.

Metal Cluster Size-Dependent Activation Energies of Growth of Single-Chirality Single-Walled Carbon Nanotubes inside Metallocene-Filled Single-Walled Carbon Nanotubes.

By combining in situ annealing and Raman spectroscopy measurements, the growth dynamics of nine individual-chirality inner tubes (8,8), (12,3), (13,1), (9,6), (10,4), (11,2), (11,1), (9,3) and (9,2) with diameters from ~0.8 to 1.1 nm are monitored using a time resolution of several minutes. The growth mechanism of inner tubes implies two successive stages of the growth on the carburized and purely metallic catalytic particles, respectively, which are formed as a result of the thermally induced decomposition of metallocenes inside the outer SWCNTs. The activation energies of the growth on carburized Ni and Co catalytic particles amount to 1.85–2.57 eV and 1.80–2.71 eV, respectively. They decrease monotonically as the tube diameter decreases, independent of the metal type. The activation energies of the growth on purely metallic Ni and Co particles equal 1.49–1.91 eV and 0.77–1.79 eV, respectively. They increase as the tube diameter decreases. The activation energies of the growth of large-diameter tubes (dt = ~0.95–1.10 nm) on Ni catalyst are significantly larger than on Co catalyst, whereas the values of small-diameter tubes (dt = ~0.80–0.95 nm) are similar. For both metals, no dependence of the activation energies on the chirality of inner tubes is observed.