Formation Of Carbon Nanotubes Research Articles

Magnetron carbon structures obtained by high-frequency magnetron sputtering in Argon and Nitrogen

Purpose of research. Creation and characterization of carbon nanostructures by high-frequency magnetron sputtering from a carbon target in argon on a silicon substrate and in a reactive nitrogen environment, obtained on a Ni catalyst buffer layer. Methods. High-frequency magnetron sputtering on a silicon substrate with changes in control parameters: sputtering time power and working gas pressure Ar and N. Research was carried out using X-ray phase analysis, atomic force microscopy and holographic microscopy, Raman scattering. Results. The formation of carbon nanotubes, including single-walled ones, was confirmed by the method of Raman scattering of light along the lines ID 1363 and IG 1564 cm-1, as well as ωRDМ 308 and 227 cm–1. Using atomic force microscopic images, the fractal dimension of the nanofilms was calculated, which indicated their 3D nature. Based on X-ray phase analysis of magnetron nanofilms, the dimensions of the coherence region, texture, microdeformations and interplanar deformation distortions were determined. Conclusion. In carbon magnetron nanofilms, deformations of both signs occur: both compressive (∆a < 0) and tensile (∆a > 0). Carbon magnetron nanofilms are represented, among other things, by single-walled carbon nanotubes, the chirality of which in an argon environment is (6, 6), and in a reactive mixture of nitrogen and argon on a Ni buffer layer (7, 7). It was discovered that in high-frequency magnetron mode, silicon carbide is formed in both inert and reactive environments.

Antibacterial efficacy of decorated carbon nanotubes by nano silver against pseudomonas aeruginosa

Carbon nanotubes (CNTs) are considered as a promising nanomaterial for a variety of applications. It has desirable physicochemical characteristics of high surface area, superior mechanical and thermal strength, and electrochemical activity. In this study, CNTs decorated with silver nanoparticles (AgNPs) were manufactured by an arc discharge technique. As a result, etching produces stable AgNPs-CNTs aqueous suspensions of pure silver and carbon electrodes in ethanol vapor condensed in water. UV- visible photometer, x-ray Diffraction, transmission electron microscope, and energy dispersive x-ray characterized the synthesized AgNPs-CNTs. The synthesized AgNPs-CNTs crystals showed CNTs formation of an average 9.5 nm, with intermediate length position of about 75.8 nm decorated by homogeneous spherical AgNPs of average size 15.2 nm. The antibacterial efficiency of AgNPs-CNTs against Pseudomonas aeruginosa was established at a series of concentrations (45 g ml−1: 0.0879 g ml−1) while values for the MIC and MBC were determined. The MIC and MBC levels were found to be (>5.625 μg ml−1) and (>11.25 μg/ml) respectively. The bacteria cytotoxicity was evaluated through LDH and protein leakage levels. Treated samples with 3.2 μg ml−1 AgNPs-CNTs revealed significant injuries in the cell membrane by two times greater in LDH and protein leakage levels than samples treated by 5.0 μg ml−1 AgNPs. Results in this work substantiate the synergistic effect of combining AgNPs with CNTs to enhanced antibacterial properties and performance compared to AgNPs alone. The efficiency of using synthesized AgNPs-CNTs showed high antibacterial potential against Pseudomonas aeruginosa in a concentration-dependent manner. The arc discharge method can be adapted to incorporate different materials or change the synthesis conditions, allowing for the production of AgNPs-CNTs with tailored properties for specific applications.

Carbon nanotube interweaved Fe7Se8 nanosheet/nanorod hybrids on expanded graphite for high-performance sodium storage

The construction of nano-micro scale hybrid structures by carbon materials is an effective strategy to address the issues of metal chalcogenides when used as anodes of sodium-ion batteries. Herein, we develop a carbon nanotube (CNT)-interweaved Fe7Se8/expanded graphite (EG) composite by means of a facile one-step gas-phase pyrolysis route with ferrocene, selenium and EG as the starting materials. The ex-situ monitoring of the pyrolysis process indicates that the selenium as a promoter facilitates the formation of CNTs and the carbon coated Fe7Se8 nanosheet/nanorod mixture. A competing reaction between CNT growth and the evolution of Fe7Se8 nanostructures occurs, which could be dominated by the concentration of selenium vapor. By optimizing the feeding ratio and the pyrolysis condition, the nanocomponents are homogeneously deposited on the surface of the EG matrix to realize a well-developed nano-micro hybrid configuration. The constructed three-dimensional conductive network, rich mesopores and high specific surface area (107.1 m2 g−1) contribute to substantially enhanced sodium-storage performance in ester electrolyte. Remarkably, the optimized composite electrode exhibits high reversible capacity retention of 97.5 % after 1000 cycles at 1.0 A g−1 and improved rate performance of 325 mAh g−1 at 2.0 A g−1. This study provides new avenues to develop high-performance metal chalcogenide electrodes for electrochemical energy storage.

Synthesis of carbon nanotubes via CCVD of ethylbenzene over SrFe12O19/SiO2 oxide and their application for photodegradation of the remazol red dye

Carbon-based materials have stood out due to their variety of applications such as photocatalysis. Thus, strontium hexaferrite dispersed in silica was prepared by the Pechini method and used as a catalyst in the ethylbenzene reaction to produce carbon filaments and subsequent application in the photodegradation of the remazol red dye. The presence of SrFe12O19, α-Fe2O3 and amorphous silica phases was confirmed in the XRD (X-ray diffraction), Raman and XPS (X-ray photoelectron spectroscopy) analysis. The SEM (scanning electron microscopy) and TEM (transmission electron microscopy) results of the fresh oxides indicate cluster and sponge-like morphology. The formation of carbon filaments was observed by SEM analysis as a result of catalytic chemical vapor deposition (CCVD) of ethylbenzene. TEM images confirm the generation of multi-walled carbon nanotubes with an average diameter of 27.9 nm. Besides the presence of the SrFe12O19 and SiO2 phases, the diffractograms of the samples after the reaction shows the formation of graphite carbon and Fe0, confirming the reduction of α-Fe2O3 which was also verified in the TPR-H2 profile. The growth of nanotubes occurs from metallic iron, considering that the tip of the tube contains only iron, according to EDS (energy-dispersive X-ray spectroscopy) results. The Raman spectrum exhibited the characteristic D and G bands of carbon, where the ID/IG ratio decreased with increasing temperature. The reaction with the best catalytic performance achieved an average ethylbenzene conversion of 99 % and was more selective to ethene (∼93 %) at 650 °C. Furthermore, it was possible to carry out a simple theoretical-computational study regarding the distribution of the sites in a 2D plane by constructing maps and proposing a mechanism for the formation of carbon nanotubes from the ethylbenzene conversion. Finally, the obtained materials were applied in the remazol red dye degradation, achieving complete degradation in 15 min for the material synthesized at 650 °C.

Synthesis and Mechanism Study of Carbon Nanowires, Carbon Nanotubes, and Carbon Pompons on Single-Crystal Diamonds

Carbon nanomaterials are in high demand owing to their exceptional physical and chemical properties. This study employed a mixture of CH4, H2, and N2 to create carbon nanostructures on a single-crystal diamond using microwave plasma chemical vapor deposition (MPCVD) under high-power conditions. By controlling the substrate surface and nitrogen flow rate, carbon nanowires, carbon nanotubes, and carbon pompons could be selectively deposited. The results obtained from OES, SEM, TEM, and Raman spectroscopy revealed that the nitrogen flow rate and substrate surface conditions were crucial for the growth of carbon nanostructures. The changes in the plasma shape enhanced the etching effect, promoting the growth of carbon pompons. The CN and C2 groups play vital catalytic roles in the formation of carbon nanotubes and nanowires, guiding the precipitation and composite growth of carbon atoms at the interface between the Mo metal catalysts and diamond. This study demonstrated that heterostructures of diamond–carbon nanomaterials could be produced under high-power conditions, offering a new approach to integrating diamond and carbon nanomaterials.

Dynamics of growing carbon nanotube interfaces probed by machine learning-enabled molecular simulations

Carbon nanotubes (CNTs), hollow cylinders of carbon, hold great promise for advanced technologies, provided their structure remains uniform throughout their length. Their growth takes place at high temperatures across a tube-catalyst interface. Structural defects formed during growth alter CNT properties. These defects are believed to form and heal at the tube-catalyst interface but an understanding of these mechanisms at the atomic-level is lacking. Here we present DeepCNT-22, a machine learning force field (MLFF) to drive molecular dynamics simulations through which we unveil the mechanisms of CNT formation, from nucleation to growth including defect formation and healing. We find the tube-catalyst interface to be highly dynamic, with large fluctuations in the chiral structure of the CNT-edge. This does not support continuous spiral growth as a general mechanism, instead, at these growth conditions, the growing tube edge exhibits significant configurational entropy. We demonstrate that defects form stochastically at the tube-catalyst interface, but under low growth rates and high temperatures, these heal before becoming incorporated in the tube wall, allowing CNTs to grow defect-free to seemingly unlimited lengths. These insights, not readily available through experiments, demonstrate the remarkable power of MLFF-driven simulations and fill long-standing gaps in our understanding of CNT growth mechanisms.

Electric field influence on the non-zero temperature resistance of carbon nanotube polymer nanocomposites with subbands effect

The effective electrical resistivity of carbon nanotubes (CNT)-based polymer nanocomposites is studied using an analytical model based on the percolation theory. The CNTs are considered as rod-like conductors that are aligned or randomly dispersed in the polymer to transport electrons by tunneling. When assessing non-zero temperature electrical resistivity, the tunneling effect considers the thermally energized electron transmission that occurs between each coupled pair of CNTs by the electrical transport model. The modeling technique consists of three steps: identifying the percolating network from the primary formation of CNTs, initial prediction of resistivity by equivalent resistor network, computation of the displacements of CNTs for the resistance change. Taking into consideration the behavior of tunneling in the percolation transition zone, a good agreement is obtained between the model results and experimental data. The verified code is used to investigate the sensitivity for different orientation states, aspect ratios and mode numbers. The results reveal lower sensitivity for higher mode numbers as collateral with the influence of increasing randomness.

Microstructure regulation and enhanced VOC removal performance of carbon aerogels by surface carbon nanotube grown

Carbon aerogels were newly employed in adsorption for volatile organic compounds (VOCs) as an emerging material. In contrast, the microstructure and high carbon consumption are the primary factors restricting their application scenarios. Carbon nanotubes, recognized for their controllable cylindrical hollow structure and hydrophobic walls, generally possess higher adsorption capacities than typical carbon adsorbents. In this study, carbon nanotubes were grown on the surface of carbon aerogels using the chemical vapor deposition method by controlling different deposition conditions. The results showed that the modified samples displayed the maximum adsorption capacity of 145.0 mg/g and 178.3 mg/g for toluene and 1,2- dichlorobenzene, respectively. After ten regeneration cycles, the performance decreased by 7.9 % and 5.6 %, respectively. Meanwhile, the carbon replenishment was about 0.2 g/g, which is an excellent complement for carbon consumption. Various characterization patterns showed that deposition temperature was reflected in its deposition rate, deposition times influenced the formation of multi-walled carbon nanotubes, and deposition concentration affected the length of carbon nanotubes. This study offers valuable insight into the growth patterns of carbon nanotubes and the microscale regulation of carbon material surfaces, and this method is expected to be an effective means of carbon replenishment, carbon addition to carbon-poor materials, and enhancement of VOCs removal performance, and the growth mechanisms investigated are instructive for practical applications.

Nucleation-Controlled Production of Sub-50 nm Carbon Nanotubes through Electrochemical Conversion of Carbon Dioxide in Carbonate Molten Salt

The increasing emission of carbon dioxide worldwide has emerged as a major global concern in the context of addressing climate change. Converting CO2 to high-value carbon materials is a promising solution to capture emitted carbon for achieving carbon neutrality. Furthermore, such conversion can provide carbon nanomaterials for key industries, including the lithium battery and fuel cell industries. Here, it is shown that sub-50 nm tangled carbon nanotubes (CNTs) can be synthesized by adjusting the metaborate concentration and the current density through the electrochemical conversion of carbon dioxide in a molten carbonate salt. The metaborate ion concentration affects the product selectivity and carbon morphology, and the current density is strongly related to the particle size of in situ seed catalysts supplied by the dissolution of an Ni-Fe-Cr alloy anode. The optimized process conditions control the nucleation and growth of carbon via a tip-growth mechanism, thereby promoting the formation of sub-50 nm CNTs rather than bulky irregular carbon particles. The Raman and Brunauer–Emmett–Teller analyses showed that the properties of the prepared CNTs depended on the synthetic parameters. This study provides deep insights into the mechanism underlying carbon synthesis through the electrochemical reduction of a molten carbonate salt.

CARBON NANOSTRUCTURES OBTAINING FROM POLYMER MATERIALS

As part of the expansion of raw material base used in the development of technological and productive methods for the synthesis of carbon nanostructures (CNS) and solving the problem of environmentally friendly and economical polymer recycling, the results of investigation of microwave (MW) catalytic pyrolysis of macromolecular compounds from the range of polystyrene, polypropylene, polyethylene terephthalate, polyvinyl alcohol are presented. The information about existing approaches to solving these problems is briefly considered, and the prospects for MW processing of polymers are shown. The process was carried out by microwave treatment of a mixture of polymer raw materials acting as a carbon donor and substances-precursors of metal catalysts – cobalt and nickel compounds, their mixtures, as well as metal iron and nickel. Graphite and carbon fiber were used as temperature regulator. Experiments have demonstrated that effective conversion of the studied compounds occurs only in the presence of MW energy absorbers-converters, regardless of the nature of metal catalyst precursor. According to electron microscopy data, the resulting materials are a mixture of carbon nanostructures of disordered morphology with the predominant content of carbon nanotubes (CNTs) in the reaction products for experiments with polystyrene, polypropylene and polyethylene terephthalate. The use of polypropylene and polyvinyl alcohol leads to the production of carbon nanostructures containing only a small amount of CNTs. X-ray phase analysis data confirm the formation of multi-walled carbon nanotubes as the main structural component of the obtained carbon nanomaterials. It has been suggested that transformation pathways of the investigated hydrocarbons are similar, despite the difference in pyrolysis temperatures, which may be related to the simultaneous processes of polymer cracking, carbonization of decomposition products and CNS synthesis due to the rapid growth of reaction mass temperature during microwave treatment. The efficiency of different precursors of catalytic systems based on transition metals in the processes examined is substantiated. It has been shown that the high carbon content in feedstock promotes the formation of carbon nanostructures, but is not decisive for carbon nanotubes obtaining. For citation: Zaritovskii A.N., Kotenko E.N., Grishchuk S.V. Carbon nanostructures obtaining from polymer materials. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 99-106. DOI: 10.6060/ivkkt.20246705.6957.

Mechanism on CMD reaction regulated by supports and promoters of Fe-based catalysts

Methane cracking technology for low-carbon energy conversion to produce hydrogen is a key technical approach in the pursuit of fossil energy decarbonization. Catalytic methane decomposition (CMD) is a process that accomplishes the fundamental removal of carbon from fossil energy without oxygen, producing high-quality carbon-based materials and H2. The functionality of supports and promoters was investigated using inorganic metal oxide support Al2O3, supported active metal Fe, and cocatalyst K. The results show that the Al2O3–Fe catalyst achieves the highest CH4 conversion of 65% at 850 °C, with a gas-phase H2 yield of 1189.72 mmol/gFe within 3 h, and a solid-phase carbon yield of 6.32 g/gFe, significantly higher than at 750 °C. The Al2O3–Fe–K catalyst achieves a methane conversion rate of 66.28% at 850 °C for 1.5 h, exhibiting relatively fast deactivation. The Al2O3–Fe catalyst catalyzes the formation of carbon nanotubes (CNTs) through methane cracking, resulting in mainly 'chain-locked' morphology. The promoter K acts on the surrounding metal clusters to influence the dispersion of active metal. The Al2O3–Fe–K catalyst is more favorable for the production of 'bamboo-shaped' carbon nanotubes, suggesting that K has a more significant impact on shaping the CNTs' products.

Catalytic mechanism of Co-containing layered double hydroxide (Co-LDH) as a precursor in carbon nanotube (CNT) synthesis

Abstract The synthesis of carbon nanotubes (CNTs) by water-assisted chemical vapor deposition using Co-containing layered double hydroxides (Co-LDH) as catalyst precursors and the catalytic mechanism of Co-LDH catalyst precursors during CNT synthesis were investigated. Co-Al and Co-Mg-Al LDH were prepared by the hydrothermal or homogeneous precipitation method using urea. XPS analysis indicated an increase in Co0 content after a reduction process during CNT synthesis, and the TEM images show that metallic Co nanoparticles were formed while maintaining the LDH platelet-like crystal form. Consequently, these metal particles were found to act as the catalyst for the formation of CNTs. Finally, through control of the flow rate of C2H4 gas during CNT synthesis, the formation of single-walled CNTs with diameters of 4 nm or less was demonstrated.

A universal synthesis strategy for facile and scalable of magnetic biochar composite materials for PMS activation: Catalytic mechanisms

Biochar-based catalysts have shown great promise for application in AOPs due to their wide source and good performance, while its development is limited by its complicated preparation process and large variation in performance. Herein, a series of magnetic biochar composites(Fe@NC-XX) based on different biomass (duckweed, shrimp shell, peanut shell, corncob, and pomelo peel) were fabricated via one-pot pyrolysis method. The removal of sulfadiazine (SDZ) by all materials reached more than 90% within 20 min. The characterization results indicated that the special structure of Fe encapsulated in nitrogen-doped carbon nanotubes (CNTs) was the main reason why this approach is not limited to specific biomass. Acts as a catalytic center, Fe catalyzes the formation of CNTs during annealing. Meanwhile, graphene sheets and carbon nanoparticles formed by melamine and biomass decomposition migrate to the nucleus surface to form a hollow structure of CNTs. In addition, the results of quenching experiments and ESR tests elucidated that surface-bound radicals accumulated on the surface of CNTs, which can remarkably boost the efficient removal of SDZ. Consequently, the synthetic strategy of Fe nanoparticles anchored in N-doped CNTs that are not selective for biomass provides a new pathway for a universal synthesis method of biochar-based catalysts.

Wafer-Scale Carbon Nanotubes Diodes Based on Dielectric-Induced Electrostatic Doping.

Diodes based on p-n junctions are fundamental building blocks for numerous circuits, including rectifiers, photovoltaic cells, light-emitting diodes (LEDs), and photodetectors. However, conventional doping techniques to form p- or n-type semiconductors introduce impurities that lead to Coulomb scattering. When it comes to low-dimensional materials, controllable and stable doping is challenging due to the feature of atomic thickness. Here, by selectively depositing dielectric layers of Y2O3 and AlN, direct formation of wafer-scale carbon-nanotube (CNT) diodes are demonstrated with high yield and spatial controllability. It is found that the oxygen interstitials in Y2O3, and the oxygen vacancy together with Al-Al bond in AlN/Y2O3 electrostatically modulate the intrinsic CNTs channel, which leads to p- and n-type conductance, respectively. These CNTs diodes exhibit a high rectification ratio (>104) and gate-tunable rectification behavior. Based on these results, we demonstrate the applicability of the diodes in electrostatic discharge (ESD) protection and photodetection.

Bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles for improved microwave absorption properties

High reflection loss and wide absorption bandwidth materials are in great demand to prevent electromagnetic pollution and military applications. The composites prepared by combining different components with good dielectric and magnetic losses are expected to achieve ideal absorbing performance. In this study, a composite of cobalt nanoparticles enveloped in nitrogen-doped bamboo-like carbon nanotubes (Co@N-CNTs) was prepared by one-step annealing the mixture of melamine and cobalt nitrate at 800 °C in a mixed atmosphere of hydrogen and argon. Co nanoparticles derived from the reaction between H2 and cobalt nitrate during the sintering process were used as catalysts to prompt the carbonization of melamine and the formation of the bamboo-shaped N-doped carbon nanotubes, thus forming the composite structure of bamboo-shaped N-doped carbon nanotubes encapsulated with Co nanoparticles. This Co@N-CNTs composite not only had an excellent dielectric loss and magnetic loss but also greatly improved its impedance matching, thus having good electromagnetic wave absorption performance. The coating made from the Co@N-CNTs composite had a maximum reflection loss (RL) of −35.89 dB at only 1.8 mm thickness at 14.1 GHz and possessed an effective absorption bandwidth of up to 4.91 GHz (12.35–17.26 GHz), suggesting it a high-performance and wide-absorption bandwidth composite material.

Rapid formation of carbon nanotubes–natural rubber films cured with glutaraldehyde for reducing percolation threshold concentration

Carbon nanotubes (CNTs) filled natural rubber (NR) composites with various CNT contents at 0, 1, 2, 3, 4 and 5 phr were prepared by latex mixing method using glutaraldehyde as curing agent. This work aims to improve the electrical and mechanical properties of CNT filled NR vulcanizates. The CNT dispersion of NR composites was clarified using dispersion grader, optical microscopy and scanning electron microscopy. The electrical properties of NR composites in the existing of CNT networks were studied by following the well-known percolation theory. It was observed that the NR composites exhibited low percolation threshold at 0.98 phr of CNT. Moreover, a three-dimensional network formation of CNT in the NR composites was observed and it is indicated by the t-value of 1.67. The mechanical properties of NR composites in terms of modulus, tensile strength and hardness properties were increased upon the addition of CNT to the optimum mechanical properties at 1 phr of CNT. Therefore, the present work is found the novelty of the study that the conductive rubber latex film can be produced using GA as low-temperature curing agent which enhanced good electrical properties. Moreover, this work is found to be beneficial in case of conductive rubber latex film that requires high modulus at low strain. The additional advantage of this system is the curing process occurs at low-temperature using GA and it can be easily processed.Graphical abstract

Catalytic pyrolysis of plastic waste using metal-incorporated activated carbons for monomer recovery and carbon nanotube synthesis

As the global plastic waste crisis intensifies, innovative and sustainable solutions are urgently needed. This study evaluated waste-derived metal-incorporated activated carbon (AC) catalysts for the pyrolysis of mixed plastic waste to generate value-added products, focusing on product yield distribution, composition, hydrogen, and carbon nanotube (CNT) formation. Pyrolysis-catalysis experiments were conducted using a two-stage fixed-bed reactor, wherein the temperature was maintained at 500 °C in first stage (pyrolysis) and varied (500, 600, and 700 °C) in the second stage (catalysis). The tested ACs were incorporated with nickel (Ni-AC), iron (Fe-AC), and zinc (Zn-AC) to assess the impact of metal particles distributed on the carbonaceous support in the second stage. The results from the ACs were compared to those obtained using zeolite (H-ZSM-5), Raw-AC, and non-catalytic runs. The Ni-AC and Fe-AC demonstrated superior catalytic activity, with Ni-AC being more efficient in producing hydrogen (4.24 wt%) and CNTs (34.5 wt%) with diameters of approximately 30 nm, and Fe-AC leading to higher gas yields (68.8 wt%) and CNTs (12.4 wt%) of around 60 nm. In contrast, Zn-AC and Raw-AC presented limited effectiveness, although Raw-AC moderately outperformed Zn-AC with enhanced gas yields and reduced oil/wax yields. The zeolite H-ZSM-5 exhibited the highest gas yields (78 wt%), converting heavy fractions into lighter molecules, notably the monomers ethylene and propylene. These findings provide valuable insights into catalyst selection and optimization for plastic waste pyrolysis processes, with H-ZSM-5 being the most effective catalyst for monomer recovery, and Ni-AC and Fe-AC demonstrating promising results.

The Future of 2D Materials Production: Graphene and Borophene on larger scale

The production of graphene and borophene, two distinct materials with remarkable properties, is investigated through the manipulation of charged ions in a plasma environment. Plasma, characterized by ionized atoms or molecules, offers a unique setting where diverse chemical reactions can take place. This research focuses on utilizing this environment to create longer-chain graphene and carbon nanotubes by manipulating charged carbon ions. When positively and negatively charged carbon ions coexist within the plasma, they have the potential to interact and form bonds. This interaction results in the growth of extended carbon structures, particularly graphene. By carefully controlling plasma conditions such as temperature, pressure, and composition, scientists can guide the formation of longer-chain graphene and carbon nanotubes from these charged carbon ions. Similarly, the production of borophene, a material composed of boron atoms, also takes place in a plasma state. By introducing positively and negatively charged boron ions into the plasma, these ions interact and potentially form bonds, leading to the growth of extended borophene structures. This innovative approach unlocks the potential for tailored materials with enhanced property.

Green synthesis and characterization of multiwall carbon nanotubes from sugarcane bagasse as a biogenic catalyst via chemical vapour deposition method using LPG as hydrocarbon source

In this study, sugarcane bagasse was used as an environment-friendly green catalyst for the synthesis of MWCNTs using the chemical vapour deposition method. The process was carried out at a relatively low temperature of 700 °C using liquified petroleum gas (LPG) as a hydrocarbon source. The formation of carbon nanotubes was confirmed using scanning electron microscopy (SEM). Transmission Electron microscopy (TEM) revealed that the obtained MWCNTs has a diameter in the range of 13 nm and a d-spacing of 0.33 nm. The EDAX and ICP-AES analysis confirmed the presence of various minerals like calcium, magnesium, iron and silica which have contributed to the formation of MWCNTs. The structural integrity of MWCNTs was evaluated by Raman spectroscopy and functional characterisation was done by FTIR.

Sustainable carbon-based nickel catalysts for the steam reforming of model compounds of pyrolysis liquids

Steam reforming of biomass-derived pyrolysis liquids (bio-oil) to produce hydrogen with carbon-based Ni catalysts is gaining attention due to their advantages in terms of cost, sustainability and activity. However, the catalytic activity at long times on stream is compromised by either coke deposition or gasification of the support. To face these drawbacks, two activated carbons have been studied as Ni catalyst support: a microporous carbon of high purity and a mesoporous carbon with phosphorus surface groups. The activity and long-term stability of these catalysts have been studied for the steam reforming of model compounds of bio-oil. The microporous support provided a slightly higher H2 production and lower contribution of methanation reaction. However, gasification of this support after 20 h led to a decline in the activity, and massive formation of carbon nanotubes and coke. Nevertheless, the resulting material maintained an outstanding stability with high and stable H2/CO ratio for 50 h. The P-containing catalyst showed a remarkable long-term stability, but lower H2/CO ratio. Carbon gasification was less significant in this catalyst due to the presence of surface phosphorus groups, and the generation of nickel phosphides, which hampers the growth of pyrolytic carbon and carbon nanotubes, leading to a superior stability.