Production Of Carbon Nanotubes Research Articles

Surface exsolving perovskite ceramics as catalyst for microwave methane pyrolysis to co-generate hydrogen and carbon nanotube

In this study, we have successfully developed a novel surface exsolving perovskite ceramic, which demonstrates the ability to simultaneously generate COx-free hydrogen and carbon nanotubes (CNTs) through methane pyrolysis under the influence of microwave irradiation. We conducted an extensive survey and optimization of various perovskite materials specifically tailored for microwave applications. Among the materials investigated, nickel-doped strontium titanium oxide (STON) emerged as the most promising candidate, exhibiting both a satisfactory methane conversion rate and excellent responsiveness to microwave irradiation. Refinement of STON was carried out by fine-tuning the Ni content, optimizing the reduction dwell time, and adjusting the reduction temperature. Notably, SrTiNi0.08O3 (STON8), demonstrated an impressive initial methane conversion rate of up to 40%. Transmission Electron Microscopy (TEM) provided visual evidence of the correlation between Ni content and reduction temperature, with respect to the exsolved Ni metal particle size. This finding highlights the immense potential of surface exsolving perovskite ceramics as a highly effective catalyst for the simultaneous production of CNTs and COx-free hydrogen via methane pyrolysis under microwave irradiation. It represents a step forward in the field of catalytic materials and microwave-driven processes.

Converting Carbon Dioxide into Carbon Nanotubes by Reacting with Ethane

The urgency to mitigate environmental impacts from anthropogenic CO2 emissions has propelled extensive research efforts on CO2 reduction. The current work reports a novel approach involving transforming CO2 and ethane into carbon nanotubes (CNTs) using earth‐abundant metals (Fe, Co, Ni) at 750 °C. This route facilitates long‐term carbon storage via generating high‐value CNTs and produces valuable syngas with adjustable H2/CO ratios as byproducts. Without CO2, direct pyrolysis of ethane undergoes rapid deactivation. The participation of CO2 not only enhances the durability of the catalyst, but also contributes about 30% of the CNTs production, presenting a viable solution to CO2 challenges. The CNT morphology depends on the catalyst used. Co‐ and Ni‐based catalysts produce CNT with a 20 nm diameter and micrometer length, whereas Fe‐based catalysts yield bamboo‐like structures. This work represents a pioneering effort in utilizing CO2 and ethane for CNT production with potential environmental and economic benefits.

Converting Carbon Dioxide into Carbon Nanotubes by Reacting with Ethane.

The urgency to mitigate environmental impacts from anthropogenic CO2 emissions has propelled extensive research efforts on CO2 reduction. The current work reports a novel approach involving transforming CO2 and ethane into carbon nanotubes (CNTs) using earth-abundant metals (Fe, Co, Ni) at 750 °C. This route facilitates long-term carbon storage via generating high-value CNTs and produces valuable syngas with adjustable H2/CO ratios as byproducts. Without CO2, direct pyrolysis of ethane undergoes rapid deactivation. The participation of CO2 not only enhances the durability of the catalyst, but also contributes about 30% of the CNTs production, presenting a viable solution to CO2 challenges. The CNT morphology depends on the catalyst used. Co- and Ni-based catalysts produce CNT with a 20 nm diameter and micrometer length, whereas Fe-based catalysts yield bamboo-like structures. This work represents a pioneering effort in utilizing CO2 and ethane for CNT production with potential environmental and economic benefits.

Effects of CaCO3/MgO on Fe-Co-Mo catalyst in the reprocessing of recycled polypropylene to carbon nanotubes

In recent times, there has been a global discourse on the menace of plastic waste (PW) materials on the ecosystem and ways for effective management of PW. This has resulted in the utilization of PW in the research arena in the synthesis of smart nanomaterials of high value as a sustainable solution. In this study, the catalytic-pyrolysis procedure was used to develop carbon nanotubes (CNTs) from recycled polypropylene (PP) plastic in a one-step chemical vapour deposition (CVD) reactor. The impacts of CaCO3 and MgO as supports for Fe-Co-Mo catalysts in the production of CNTs were studied. Kinetic and thermodynamic parameters were determined from the thermal profile of the catalysts to establish the nature of the reaction in CNTs synthesis. Transmission electron microscopy (TEM), energy Dispersive X-ray (EDX), selected area electron diffraction pattern, particle size distribution (PSD), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier transforms infrared (FTIR) and X-ray diffraction (XRD) were employed to characterize the catalysts and CNTs. The results obtained showed the impact of the supports on the yield, quality, and morphology of the synthesized CNTs. The CNTs yield from catalysts supported with CaCO3 and MgO were 35.12 % and 37.24% respectively. The average outer diameters of CNTs produced over the catalyst with CaCO3 and MgO supports were 36 and 29 nm respectively. The ID/IG ratio for CaCO3 and MgO supports were 0.6724 and 0.8401 respectively. The change in entropy for all phases were −274.41 and −1032.97 J/mol/K and −213.0, −318.48 and −1022.13 J/mol/K for CaCO3 and MgO supported catalyst respectively which confirmed non-spontaneous endothermic reaction. It was observed that MgO support showed better catalytic activity toward CNTs growth in terms of yield while those with CaCO3 support showed higher graphitization.

High-efficiency thermal reduction of CO2 to high-valued carbon nanotubes

To reduce the amount of carbon dioxide (CO2) already emitted into the atmosphere, various carbon capture, utilization, and storage (CCUS) technologies have been developed for climate and economic reasons in recent years. However, the state of art CCUS techniques suffer from deficiencies such as high cost, low yield, and harsh and discontinuous production conditions. In this work, we report a new thermal reduction method for continuously conversing CO2 to methane (CH4) by introducing sodium borohydride (NaBH4) as a reductant under catalyst-free conditions. Experimental results show that CO2 can be fully captured and converted to CH4 and carbon monoxide (CO) and the selectivity efficiency of CO2 to CH4 can be achieved to be as high as 90% with the optimization of experimental conditions. Such a result originates from the high activity of NaBH4 and high selectivity of the thermal reduction of CO2. To demonstrate one of the potential usages of the reduction products, we integrated the thermal reduction of CO2 with the production of carbon nanotubes (CNTs). As long as CO2 is supplied at the source end, the reduction products can undergo catalytic decomposition to produce a CNT fiber or film continuously at the final end. The present technique is featured with simple equipment setup, low cost, and continuous thermal reduction, thus providing a new pathway for the large-scale conversion of CO2 into high-valued products for wide 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.

An efficient approach toward production of near-zigzag single-chirality carbon nanotubes.

Synthesizing single-walled carbon nanotubes (SWCNTs) with a narrow chirality distribution is essential for obtaining pure chirality materials through postgrowth sorting techniques. Using carbon monoxide chemical vapor deposition, we devise a ruthenium (Ru) catalyst supported by silica for the bulk production of SWCNTs containing only a few (n, m) species. The result is attributed to the limited carbon dissociation on the supported Ru clusters, favoring the growth of only small-diameter SWCNTs at comparable growth rates. The resulting materials expedite high-purity single chirality separation using gel chromatography, leading to unprecedented yields of 3.5% for (9, 1) and 5.2% for (9, 2) nanotubes, which surpass those separated from HiPco SWCNTs by two orders of magnitude. This work sheds light on the large-quantity synthesis of SWCNTs with enriched species beyond near-armchair ones for their high-yield separation.

Effect of purification methods on the quality and morphology of plastic waste-derived carbon nanotubes

Recent innovative research efforts on the usage of plastic wastes as a cheap carbon source for carbon nanotubes (CNTs) production have emerged as a low-cost and sustainable means of producing CNTs. However, plastic waste-derived CNTs are rarely used in some purity-sensitive and high-alignment needed applications due to the poor quality of CNTs resulting from the abundance of impurities such as non-crystalline amorphous carbon, metallic nanoparticles, and other impurities. Therefore, purification is a crucial issue to be addressed to fully harness all potential applications of CNTs derived from waste plastic materials. Here, the effect of employing different purification methods on the morphology and purity of waste plastic-derived CNTs was investigated. CNTs were synthesized using waste polypropylene plastic as carbon feedstock via a single-stage catalytic chemical vapour deposition (CVD) technique. As-produced CNTs were purified using liquid-phase oxidation (chemical oxidation in nitric acid), gas-phase oxidation in air, and a combination of both liquid- and gas-phase oxidation methods. The synthesized and purified CNTs were characterized for morphology, purity, surface functional groups, thermal stability, and crystallinity using Transmission electron microscopy (TEM), Raman spectroscopy, Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD), respectively. Results obtained showed that a combination of both liquid and gas phase oxidation purification techniques resulted in purer, better quality, and less defective CNTs with an IG’/IG value of 0.89 and ID/IG value of 0.86, while chemically treated CNTs (CNT-PC) presented more structurally defective CNTs and shortened nanotubes compared to other investigated treatment methods with an ID/IG value of 0.96. CNTs purified by a multi-step protocol (CNT-PAC) showed the highest weight loss of 72.3% indicating the highest quality and the presence of filamentous carbon. This study confirms that the choice of purification techniques influences the morphology and quality of plastic-derived CNTs.

Natural biochar catalyst: Realizing the co-valorization of waste cooking oil into high-quality biofuel and carbon nanotube precursor via catalytic pyrolysis process

Valorizing renewable precursors into high-quality biofuel and functional carbon nanomaterials can considerably improve the economic viability. Here, we propose a process for integrated production of high-quality biofuel and carbon nanotubes from waste cooking oil via catalytic pyrolysis coupling with chemical vapor deposition (CVD) technology. The natural biochar catalyst demonstrates excellent deoxygenation performance and good stability in catalytic pyrolysis process. The alkali/alkaline earth metal species (AAEMs) content in biochar catalysts has a strong correlation with the selectivity of esters and hydrocarbons in bio-oil. The biofuel obtained under optimal conditions exhibited potential as a precursor for jet fuel. The CVD process convert pyrolysis gas into carbon nanotubes with yield of 2.13%. The technical–economic analysis demonstrated the feasibility of the integrated process, projecting profitability and substantial total profit over a ten-year period. Overall, this study improves the economic viability of the waste cooking oil pyrolysis process and supports its wider commercial application.

Thermochemical Valorization of Waste Plastic for Production of Synthetic Fuels, Fine Chemicals, and Carbon Nanotubes

Thermochemical Valorization of Waste Plastic for Production of Synthetic Fuels, Fine Chemicals, and Carbon Nanotubes

Upcycling of composite packaging waste to carbon nanotubes via chemical vapor deposition of pyrolysis gas

Based on the necessity of evaluating composite packaging wastes from both environmental and economic perspectives, it aimed to obtain carbon nanotube (CNT) from the pyrolysis gas product of this material by the catalytic chemical vapor deposition method (CCVD) via an upcycling approach. In the first stage, composite packaging wastes were pyrolyzed. Secondly, the composition of the gas via gas chromatography was determined. In the third stage, CNT production studies were carried out by the CCVD method in a tubular reactor at four different temperatures between 600 and 900 °C with nickel catalyst. The effects of temperature and carbon source feeding ratio on the properties of the obtained CNTs were investigated. CNTs produced in this study were compared with a commercial product. As a result, high-quality multi-walled carbon nanotube of 20–30 nm diameter and in micrometer scale length comparable to commercial products were produced from the gaseous product at 800 °C under Ni-catalysis.

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH4 Decomposition in a Pressurized Fluidized-Bed Reactor

Simultaneous and Continuous Production of Carbon Nanotubes and Hydrogen by Catalytic CH₄ Decomposition in a Pressurized Fluidized-Bed Reactor

Automated statistical analysis of raman spectra of nanomaterials.

Both at the academic and the industrial level, material scientists are exploring routes for mass production and functionalization of graphene, carbon nanotubes (CNT), carbon dots, 2D materials, and heterostructures of these. Proper application of the novel materials requires fast and thorough characterization of the samples. Raman spectroscopy stands out as a standard non-invasive technique capable of giving key information on the structure and electronic properties of nanomaterials, including the presence of defects, degree of functionalization, diameter (in the case of CNT), different polytypes, doping, etc. Here, we present a computational tool to automatically analyze the Raman spectral features of nanomaterials, which we illustrate with the example of CNT and graphene. The algorithm manages hundreds of spectra simultaneously and provides statistical information (distribution of Raman shifts, average values of shifts and relative intensities, standard deviations, correlation between different peaks, etc.) of the main spectral features defining the structure and electronic properties of the samples, as well as publication-ready graphical material.

Fe–Mo/Kaolin Catalyst Optimization and Characterization for the Production of Carbon Nanotube Using the Wet Impregnated Method

Abstract: The synthesis of the bimetallic Fe–Mo/kaolin catalyst for carbon nanotube (CNT) production involves the pre-calcination and calcination processes, employing the wet impregnated method. In the pre-calcination stage, we explored the effects of synthesis parameters such as oven drying temperature, mass of kaolin, and heating time using a 23 factorial experimental design, ultimately obtaining the highest yield sample. In the calcination phase, the effect of temperature and heating time using a 22 factorial experimental design was examined. The as-prepared nanoparticles were characterized by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), thermogravimetric analysis (TGA), differential thermal analysis (DTA), x-ray diffraction (XRD), and Brunauer-Emmet-Teller (BET). SEM/TGA revealed a well-dispersed metallic particle on the kaolin support and its ability to maintain high thermal stability. XRD analysis of the catalyst confirmed its crystal nature and the presence of mixed oxides of different intensities, conducive to CNT growth. The optimum yield obtained after oven drying was 75.25%. At the optimum calcination temperature of 300° C and calcination time of 16 hours, BET analysis determined the surface area and pore volume. For kaolin, the surface area and pore volume were 1.932x102 m2/g and 1.762x10-1 cc/g, respectively. The optimal calcine sample showed increment for both the surface area (3.103 x102 m2/g) and the pore volume (2.459 x10-1cc/g) making it more suitable for CNT production. Lastly, statistical analysis showed that heating time, calcination time, temperature, and mass of kaolin have a significant influence on the catalyst yield in CNT. Keywords: catalyst, wet impregnation, optimization, carbon nanotubes.

Review of: "For the production of nanotransistors and nanochips, one of the advantages of these methods is the ease of changing the process parameters and achieving optimal conditions for the production of carbon nanotubes."

Review of: "For the production of nanotransistors and nanochips, one of the advantages of these methods is the ease of changing the process parameters and achieving optimal conditions for the production of carbon nanotubes."

Improving the mechanical performance of low graphene content epoxy nanocomposites: investigation of hybrid and chemically modified nanofillers

Graphene is a promising nanofiller for producing polymer nanocomposites with enhanced mechanical, electrical, thermal, electromechanical, and flame retardancy properties, leading to applications in aerospace, automotive, ballistics, medicine, electronics, and smart materials. Solvent-assisted top-down methods, including mechanical exfoliation of graphite, show great potential for scale-up and mass production of graphene dispersions for use in the fabrication of nanocomposites. However, these approaches can suffer from poor efficiency, which limits the concentrations of graphene/polymer dispersions that can be produced using in situ methods. As such, it is important to find new ways of making more effective use of these low concentrations of graphene nanofillers. Possible approaches include chemical modification of the graphene or finding synergies with other nanofillers to form hybrid nanocomposites. In this work, we demonstrate results that make use of each approach. Specifically, we demonstrate a low-cost and simple method for producing carbon nanotube dispersions and creating hybrid nanocomposites with substantial enhancements to mechanical properties. We also extend the scope of our previously reported semi-in situ exfoliation method by demonstrating its application in the production of a nanocomposite that incorporates chemically modified graphene. The superior mechanical properties exhibited by the nanocomposite are attributed to increased interaction strength between the polymer and nanofiller.

Production of carbon nanotubes via catalytic pyrolysis of waste plastics over Ni/Al2O3 catalyst: The influence of plastic types

Thermochemical conversion is a promising technology to convert waste plastics into high-value chemicals from both an economic and environmental point of view. In this work, the production of carbon nanotubes (CNTs) from catalytic pyrolysis of different types waste plastics over Ni/Al2O3 catalyst was investigated in a two-stage fixed bed reactor. Polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were used as raw material. The results show that PS showed a higher solid carbon yield of 32.24 wt%. PE waste plastic led to the lowest liquid yield and the highest gas yield, which were 28.95 wt% and 39.45 wt%, respectively. In terms of obtained CNTs, PE and PP plastics obtained more high-purity, structured and intertwined multi-wall carbon nanotubes, while PS produced more amorphous carbon. PET plastic had high oxygen content, which was not conducive to the growth of CNTs during the pyrolysis process. In summary, PE and PP plastics were suitable as feedstock for the preparation of high-quality CNTs by pyrolysis catalysis. The work provides basic data support for the research of the production of valuable CNTs from waste plastics.

Influence of platinum content (X) in the LaNi5PtX catalyst and reaction conditions on the properties of ferromagnetic Ni-filled CNTs

This research highlights the synthesis of carbon nanostructures using the catalytic chemical vapor deposition (CCVD) method, a hybrid process combining chemical vapor deposition (CVD) and Gas-Solid Heterogeneous Catalysis (GSHC). Intermetallic catalysts, LaNi5Ptx (x = 0, 0.05, 0.5, 1.0), were fabricated through an arc melting procedure to serve as templates for the catalytic conversion of carbon precursors into solid materials. These catalysts, featuring the ferromagnetic transition metal Ni, tend to aggregate into larger particles, reducing the rate of hydrocarbon cracking at the catalyst surface. Rare earth metals like Lanthanum were introduced to form an alloy with a higher melting point to prevent thermal aggregation. Additionally, Pt was incorporated to modify the catalytic properties of the alloy. The study primarily explores the impact of catalyst composition on carbon nanotube (CNT) production. The introduction of platinum content to the catalyst influences the rate at which Ni is filled. The research aimed to alter the catalyst's composition by varying platinum doping in the Pauli paramagnetic lanthanum nickel alloy (LaNi5) to understand the growth mechanism and morphological variations of Ni-filled CNTs. Platinum and lanthanum oxides significantly influence nickel filling in CNTs, resulting in an increased filling rate as the catalyst's Pt content varies from 0 to 1.0. However, higher Pt doping content disrupts the CNT structure with spontaneous nickel encapsulation.

Simultaneous production of high-valued carbon nanotubes and hydrogen from catalytic pyrolysis of waste plastics: The role of cellulose impurity

Upcycling waste plastics into valuable carbon nanotubes (CNTs) and hydrogen via catalytic pyrolysis is a sustainable strategy to mitigate white pollution. However, real-world plastics are complex and generally contain organic impurities, such as cellulose, which have a non-negligible impact on the catalytic pyrolysis process and product distribution. In this study, cellulose was chosen as a model compound to distinguish the effects of oxygen-containing components on the CNTs and hydrogen production during the catalytic pyrolysis of waste polypropylene. Different amounts of cellulose were mixed with polypropylene to regulate the O/C mass ratio of the feedstock, and the relationship between the O/C mass ratio and the yield of products has been built quantificationally. The results revealed that the relative content of CNTs increased to over 95%, and the stability and purity of carbon deposition increased accordingly when the O/C mass ratio is 0.05. This could be ascribed to the etching effects caused by small amounts of H2O and CO2 on amorphous carbon. However, further increasing the amount of cellulose caused the deactivation of the Fe-Ni catalyst. This not only decreased the carbon yield but had an adverse impact on its morphology and graphitization, leading to the increase of amorphous carbon. This study can provide fundamental guidance for the efficient utilization of waste plastics that take advantage of organic impurities in waste plastic to promote the formation of high-purity CNTs.

Polyethyleneglycol-polyhydroxylbutyrate functionalized carbon nanotubes for industrial electroplating wastewater treatment

This study focuses on the production and purification of multi-walled carbon nanotubes (P-CNTs) via a catalytic chemical vapor deposition method and subsequent functionalization with amino polyethylene glycol (NH2-PEG) and its mixture with polyhydroxybutyrate (PHB) through a multi-step purification process to produce NH2-PEG-CNTs and NH2-PEG-PHB-CNTs, respectively. The developed nanoadsorbents were used to treat electroplating wastewater via batch adsorption to sorb potentially toxic metals and emerging pollutants. The nanoadsorbents were characterized before and after treatment with wastewater after thermal regeneration analyzed using HRSEM/EDS/SAED, DLS Nanozetasizer, BET, TGA/DTG, and FTIR. The nanoadsorbents showed a homogeneous distribution of clean and smooth crystalline interwoven tubular/cylindrical shapes and sizes, with broad polydispersed/high aspect ratio, large surface area, mesopores, and functional groups. The batch adsorption study showed simultaneous multi-capturing of toxic metals from industrial electroplating wastewater with a directly proportional relationship between contact time, adsorbent dosage andtemperature, and electrostatic activities via the positive surface charge of the nanoadsorbents (pH > pHzpc). The highest removal of Fe (15.86 %), Ni (79.82 %), Pb (79.82 %), and Cu (84.97 %) were obtained using NH2-PEG-PHB-CNTs. In addition, the ANOVA results show that the adsorption process depends on other parameters such as the concentration of toxic metals in the wastewater, its hydration energy, electronegativity, ionic mobility in the electrostatic activities, pH of the nanoadsorbents, water holding capacity of the polymer-functionalized nanoadsorbents, and synergistic effects of the bi-polymer. Moreover, the nanoadsorbents have a stable morphology after thermal regeneration for reusability purposes, and treated wastewater can be safely reused in the electroplating industry or for other purposes, such as agriculture.