Nanotube Precursors Research Articles

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.

MoS2 nanotubes for boosting electrocatalytic performance of nitrogen to ammonia

Under environmental conditions, molybdenum-based catalysts have been extensively studied as efficient nitrogen reduction reaction (NRR) electrocatalysts. However, the NRR performance of molybdenum-based electrocatalysts is far below expectations. In this study, MoS2-500 nanotubes were synthesized by heating the MoS2 nanotube precursor at high temperatures. These electrocatalysts exhibited a remarkable NH3 yield of 17.18 µg h−1 mg-1cat. and faradaic efficiency (FE) of 16.71 %. The enhanced performance is attributable to the increase in MoS2 dangling bonds at the edge. This work demonstrates the way to develop inexpensive and efficient NRR electrocatalysts.

Coordination compound-derived Fe4N/Fe3N/Fe/CNT for efficient electrocatalytic oxygen evolution: a facile one-step synthesis in the absence of extra nitrogen source

By annealing an Fe(III)–coordination compound (Fe–CC), [FeCl3(Hbta)2] (Hbta = benzotriazole) in the presence of a carbon nanotube precursor (PCNT) template, an Fe4N/Fe3N/Fe/CNT heterostructure was successfully synthesized without an extra nitrogen source. The decomposition of the Hbta in Fe–CC under high-temperature annealing can produce carbon sheets and reduced graphene oxide (rGO), and the presence of CNTs can alleviate the stacking of the in situ-generated carbon materials. Meanwhile, iron nitride nanoparticles (NPs) can be anchored on the carbon sheets, and the anchoring effect efficiently prevents the agglomeration of NPs and increases the amount of active catalytic sites for the oxygen evolution reaction (OER). Fe4N/Fe3N/Fe/CNT shows an excellent OER activity with a Tafel slope of 63 mV dec−1 as well as overpotentials of 121 (η 10) and 275 mV (η 100) at 10 and 100 mA cm−2, respectively — far exceeding commercial RuO2 and other catalysts. Density functional theory calculations show that the excellent OER performance of Fe4N/Fe3N/Fe/CNT is associated with the Fe4N/Fe3N heterojunction, which can improve the electron conductivity and boost the electron transfer from N to Fe. The Fe4N/Fe3N/Fe/CNT catalyst exhibits long-term OER activity during 100 h of electrolysis at 20 mA cm−2. This is related to the dual coatings of the in situ-generated thin carbon shell and few-layered rGO on the surface of the iron nitride NPs, which can protect the fast leaching of iron nitride during the OER process. Furthermore, the effects of the annealing temperature, the PCNT template and the heating rate on the calcined products were investigated.

Influence of a Novel Carbon-Based Nano-Material on the Thermal Conductivity of Mortar

The paper presents the results of research work to assess the thermal conductivity of mortar incorporating a novel carbon-based nano-material (CBN). The data from the laboratory tests served as the starting point in training an artificial neural network (ANN) based on the Levenberg–Marquardt backpropagation algorithm that was used to predict the values of the thermal conductivity at later ages. The used CBNs were essential precursors of multi-walled carbon nano-tubes but different from their counterparts in the fact that they were capped at the ends. This configuration should result in lower surface tension and should prevent the bundling even without the use of surfactants and sonication. The obtained results show that the mortar mixes with CBN exhibit higher values for the thermal coefficient at early ages compared to the reference mix, even at very low percentages of CBN by weight of cement. The ANN is able to accurately predict the experimental results both at 28 days and at later ages. The obtained results should serve as the starting point for further investigations into the microstructure of cement-based materials enhanced with CBNs.

Silicon micron cages derived from a halloysite nanotube precursor and aluminum sacrificial template in molten AlCl3 as an anode for lithium-ion batteries.

Porous nanostructures have been proposed a promising strategy to improve the electrochemical performance of Si materials as anodes of lithium-ion batteries (LIBs). However, expensive raw materials and the tedious preparation processes hinder their widespread adoption. In this work, silicon micron cages (SMCs) have been synthesized in molten AlCl3 through using spherical aluminum particles as a sacrificial template, and the earth-abundant and low-cost natural halloysite clay as a precursor. The aluminum spheres (1–3 μm) not only act as a sacrificial template but also facilitate the formation of silicon branches, which connect together to form SMCs. As anodes for LIBs, the SMC electrode exhibits a high reversible capacity of 1977.5 mA h g−1 after 50 cycles at a current density of 0.2 A g−1, and 1035.1 mA h g−1 after 300 cycles at a current density of 1.0 A g−1. The improved electrochemical performance of SMCs could be ascribed to the micron cage structure, providing abundant buffering space and mesopores for Si expansion. This promising method is expected to offer a pathway towards the scalable application of Si-based anode materials in the next-generation LIB technology.

Sulfide with Oxygen-Rich Carbon Network for Good Lithium-Storage Kinetics.

Transition metal sulfides are of great interest as electrode material for alkali metal-ion batteries due to their high theoretical capacity. However, sluggish ion migration and electron transfer kinetics lead to poor cycling stability and rate performance, which hinders their practical applications. Herein, we develop a two-step localized carbonization and sulfurization method to construct a CoS2 composite material (CoS2@CNTs@C) from an in situ integrated zeolitic imidazolate framework (ZIF-67) and multiwalled carbon nanotube precursor (ZIF-67@CNTs). The as-prepared CoS2@CNTs@C composites with a nanoscale carbon skeleton inherit a large specific surface area and suitable nanopore size distribution from ZIF-67 and incredibly abundant oxygenated functional groups from CNTs. The theoretical calculation and material characterization demonstrate that the oxygenated functional groups on the porous carbon networks accelerate lithium-ion diffusion and electron transfer and especially electrocatalyze the progressive conversion of Li2S6 to the final product Li2S. Meanwhile, the three-dimensional conductive network guarantees the conductive and structural stability of CoS2@CNTs@C during the repeated lithium-storage process. Therefore, the CoS2@CNTs@C electrode material can deliver an initial discharge capacity of 1282.3 mA h g-1 at 200 mA g-1 with a high Coulombic efficiency of 93.5% and a reversible capacity of 558.8 mA h g-1 at 2000 mA g-1 in 600 cycles with a high capacity retention of 96.1%.

Boron nitride nanotube precursor formation during high-temperature synthesis: kinetic and thermodynamic modelling

We performed integrated modelling of the chemical pathways of formation for boron nitride nanotube (BNNT) precursors during high-temperature synthesis in a B/N2 mixture. Integrated modelling includes quantum chemistry, Quantum–classical molecular dynamics, thermodynamic modelling, and kinetic approaches. We demonstrate that BN compounds are formed via the interaction of molecular nitrogen with small boron clusters, rather than through interactions with less reactive liquid boron. (This process can also be described as N2 molecule fixation.) Liquid boron evaporates to produce these boron clusters (B m with m ≤ 5), which are subsequently converted into B m N n chains. The production of such chains is crucial to the growth of BNNTs because these chains form the building blocks of bigger and longer BN chains and rings, which are in turn the building blocks of fullborenes and BNNTs. Additionally, kinetic modelling revealed that B4N4 and B5N4 species in particular play a major role in the N2 molecule fixation process. The formation of these species via reactions with B4 and B5 clusters is not adequately described under the assumption of thermodynamic equilibrium, as is demonstrated in our kinetic modelling. Thus, the accumulation of both B4N4 and B5N4 depends on the background gas pressure and the gas cooling rate. Long BN chains and rings, which are precursors of the fullborene and BNNT growth, form via self-assembly of components B4N4 and B5N4. Our modelling results—particularly the increased densities of B4N4 and B5N4 species at higher gas pressures—explain the experimentally observed effect of gas pressure on the yield of high-quality BNNTs. The catalytic role of hydrogen was also studied; it is shown that HBNH molecules can be the main precursor of BNNT synthesis in the presence of hydrogen.

Cationic ion-driven surface control of one-dimensional CeO2 nanocrystals to enhance catalytic performance of CO oxidation

Surface structures of one-dimensional CeO2 nanocrystals are tuned with different cationic ions in a facile and mild hydrothermal system with formate and carbonate. The synthetic key is to control the formation of anisotropic CeO2 precursors with the anion structure of formate and carbonate. The diluted concentration of Na+ ions with NH4+ ions can induce the formation of the CeO2 nanotube (NT) precursors, and yet Na+ ions can promote the production of the CeO2 nanorod (NR) precursors. CeO2 nanocrystals are applied in CO oxidation and show a very important effect of their surface structure on their catalytic performance. CeO2 NTs have rich cerium surface with the higher concentration of Ce3+ ions and can accelerate the mobility of more surface oxygen species than CeO2 NRs with difficultly reduced rich oxygen surface. However, after silver loading, CeO2 NRs can show the higher stability of CeO2 particles, more easily activated surface of CeO2 NRs with more Ce3+ ions, the promoted production of metallic Ag nanoparticles and higher mobility of more surface oxygen species on CeO2 surface. Therefore, CeO2 NTs have a higher catalytic activity of CO oxidation and conversely, after loading Ag, Ag/CeO2 NRs show the higher catalytic performance.

Highly transparent superamphiphobic surfaces by elaborate microstructure regulation

Superamphiphobic surfaces have attracted extensive attention from both academic and commercial communities because of their unique wettability. However, big challenge still remains as superamphiphobic surfaces frequently suffer the drawbacks of either easy adhesion of liquids with low surface tension (<27.5 mN m−1) or low transparency, which in turn seriously hinders their applications. Here, we report the exploitation of highly transparent superamphiphobic surfaces, which was prepared by chemical vapor deposition (CVD) of 1H,1H,2H,2H-perfluorodecyltrichlorosilane onto silica nanotubes, via elaborate microstructure regulation. The silica nanotubes are synthesized by coating multiwalled carbon nanotubes (MWCNTs) with a layer of polysiloxane followed by calcination in air. The effects of various parameters, including the concentration of MWCNTs, the solvents for re-dispersing the polysiloxane-modified MWCNTs and its spray-coating density, on superamphiphobicity and transparency were systematically studied. The results show that the superamphiphobicity and transparency are highly dependent on the solvents for re-dispersing polysiloxane-modified MWCNTs because the microstructure of the polysiloxane layer, i.e. the precursor of silica nanotubes, relies on the re-dispersing solvents. The superamphiphobic coatings feature extremely low sliding angles for various liquids with surface tension as low as 21.6 mN m−1 and very high optical transparency, superior to most of the reported superamphiphobic surfaces, which make them promising candidates as functional surfaces or coatings for a broad variety of applications, e.g., in situ observation using microscopes, self-cleaning windows, and so on.

Fabrication of aluminum-carbon nanotube nano-composite using aluminum-coated carbon nanotube precursor

Demand of special combination of different properties of the materials instigated the development of metal matrix composite. The carbon nanotubes being renowned for their excellent physical and mechanical properties are one of the major choices as strengthen material for metal matrix composites. To benefit their properties, the carbon nanotubes should be thoroughly dispersed and have wetting with the matrix. In the present study, a precursor of aluminum-carbon nanotubes was prepared by coating the nanotubes with titanium and used to fabricate the composite by induction melting. The precursor provided easy wetting, while induction melting facilitated dispersion of the nanotubes readily. Consequently, the composite exhibited noticeable augmentations in yield and tensile strength from 64 to 193 MPa and 81 to 227 MPa, respectively.

FeCo alloy encapsulated within carbon nanotube as efficient and stable catalyst for ammonia borane hydrolysis

Herein, commercial dicyandiamide was used as the pyrolysis precursor of carbon nanotubes. Co(NO3)2·6H2O and FeCl3 as non-precious metal precursors were mixed with dicyandiamide to in situ synthesize nitrogenated carbon nanotubes encapsulating Fe and Co nanoparticles via calcination under nitrogen atmosphere. The ratio of different metal species and thus the structure and properties of the final products were investigated in detail. As a result, the Fe0.4Co0.6-NCNTs exhibited optimal catalytic ammonia borane(AB) dyhydrogenation activity with the responding activation energy (Ea) calculated to be 19.89 KJ mol−1, and the TOF value calculated based on metals was 102 molH2 min−1 molcat−1, superior to most well-developed bimetal-based catalysts reported previously. The present method provides cost-effective, high efficiency, and stable materials in developing the sustainable energy conversion systems.

Rapid-Heating-Triggered in Situ Solid-State Transformation of Amorphous TiO2 Nanotubes into Well-Defined Anatase Nanocrystals

Fabrication of nanocrystals from their disordered solid-state precursors represents a new synthetic strategy. Compared to the widely used chemical vapor deposition and wet-chemistry based methods employing gas and liquid phased precursors, the solid-state transformation of disordered solid precursors to highly ordered crystals is a great challenge due to the severely restricted mass transport and inadequate structural directing mechanism. Herein, we report a rapid-heating-triggered in situ solid-state crystal growth method capable of transforming amorphous TiO2 nanotubes into anatase nanocrystals with well-defined facets and uniform sizes within a minute. The results obtained from in situ transmission electron microscopy and three-dimensional phase-field simulation indicate that the basic building blocks are formed through mechanical rupture of an amorphous TiO2 nanotube precursor, followed by an enhanced diffusion and concomitant oriented attachment onto TiO2 crystal nuclei mediated by the fluorine speci...

Nitrogen-doped hierarchically porous carbonaceous nanotubes for lithium ion batteries

By a novel two-step activation of the polypyrrole nanotube (PPyNT) precursor, nitrogen-doped hierarchically porous carbonaceous nanotubes (HPCNT) are successfully prepared. The as-prepared HPCNT not only exhibits an ultrahigh specific surface area of 2180 m2 g−1 and a large total pore volume of 1.22 cm3 g−1, but also possesses a rich N-doping content of 8.2 wt% which especially includes a high pyridinic-N content of 30%. As an anode for lithium-ion batteries (LIBs), the HPCNT delivers an ultrahigh reversible capacity of 1372 mAh g−1 and keeps a high retention of 89.3% over 100 cycles at 0.1 A g−1. Even at a large current rate of 1 A g−1, the reversible capacity is still as high as 630 mAh g−1 after 700 cycles. Compared with either the commercial graphite or the state-of-the-art LIB carbons in the literature, the HPCNT is quite competitive, which makes it a promising anode material for next-generation LIBs. Also, the outstanding performances of the HPCNT exhibit a great potential of this novel activation strategy for commercial application on LIBs.

Molecular Reactive Force-Field Simulations on the Carbon Nanocavities from Methane Pyrolysis

Hydrocarbon pyrolysis is the main way to achieve carbonaceous materials, while most related conversion mechanisms still remain unclear. This work images pyrolysis of methane at various temperatures and densities by molecular reactive force field (ReaxFF) simulations. First, it is interesting to find that the methane decay is dominated by intermolecular collision displacement instead of direct molecular decomposition. Second, a conversion of 1200 methane molecules into a regular carbon nanocavity (CNC) is realized at 3500 K temperature and 0.1 g/cm3 density after a simulation lasting for 10 ns, with 923 carbon atoms and a diameter of 3.4 nm. Such CNC is a perfect precursor of carbon nanotubes, which is confirmed by a sequent simulation on a larger system of 2400 methane molecules and in agreement with several experimental observations. It is found that the CNC growth obeys a polyyne model, without any single aromatic ring formed in the growth. Furthermore, the complex CNC growth appears in some successive ...

Solvent-controlled reversible switching between adsorbed self-assembled nanoribbons and nanotubes.

We have demonstrated that solutions of 3,5-bis-(5-hexylcarbamoylpentyloxy)-benzoic acid decyl ester (BHPB-10) can form metastable nanostructures on solid substrates and in the bulk. BHPB-10 is an achiral molecule involving several distinct, strongly interacting groups (SIGs), one aromatic-ester ring and two amide groups per molecule. Specific solvents affect the interactions between particular SIGs, thus promoting various nano-structures: lamellae, nanoribbons, helical ribbons, or nanotubes. In cyclohexane, a solvent allowing for both inter-amide hydrogen bonds and mutual attraction of rings, the formation of nanotubes with a diameter of 28 ± 5 nm was observed in the bulk and on surfaces. By contrast, in cyclohexanone, which suppresses inter-amide hydrogen bonds, flat nanoribbons with a specific width of 12 ± 4 nm were formed on solid substrates after drying. By annealing in cyclohexane vapor, we followed the process of switching surface structures from nanoribbons to nanotubes and observed helical ribbons as the precursor of nanotubes. We also turned nanotubes back into nanoribbons by adding cyclohexanone, thus demonstrating reversible switching along the route: tubes → lamellae → flat ribbons → helical ribbons → tubes. We propose models explaining the observed nanostructures and their transformations, including the origin of spontaneous chirality of the helical ribbons. Our findings on the self-assembly in the achiral BHPB-10 solutions provide insight into the influence of complementary inter-molecular specific SIG-based interactions and demonstrate an effective route for tailoring the shape and size of nanostructures derived from the same building unit.

Organic macromolecule assisted synthesis of ultralong carbon@TiO2 nanotubes for high performance lithium-ion batteries

Ultralong carbon coated TiO2 nanotube (500–1000nm) with well-crystallization has been synthesized via an efficient macromolecular-assisted method. Specifically, tubular TiO2 nanotube precursors synthesized via a hydrothermal method are firstly coated with polyvinylpyrrolidone (PVP). In the following crystallization heat-treatment process, PVP with a chain structure and suitable thickness restricts the stretching trend of inner TiO2 nanotube and carbonizes as high conductive substrate, finally helps nanotubes to avoid the collapse in heat-treatment. The conductive coating maintains the integrity of the electrode during the charge/discharge processes and promotes electron transport, the unique open channel structure of TiO2-B crystal gotten 400°C facilitates lithiation/delithiation paths of electrons and lithium ions, the tubular structure of TiO2 provides great electrode/electrolyte contact area. All of these factors are responsible for the remarkable rate capability (194mAhg−1 at 5C, 157mAhg−1 at 20C, 1C=334mAg−1) and high reversible charge/discharge capacity (154mAhg−1 after 100 cycles at 10C). The carbon coated TiO2 nanotube is superior to many reported TiO2 electrodes, which makes it hold great promise as an optional anode material for LIBs

A Designed TiO2 /Carbon Nanocomposite as a High-Efficiency Lithium-Ion Battery Anode and Photocatalyst.

Herein, a peapod-like TiO2 /carbon nanocomposite has successfully been synthesized by a rational method for the first time. The novel nanostructure exhibits a distinct feature of TiO2 nanoparticles encapsulated inside and the carbon fiber coating outside. In the synthetic process, H2 Ti3 O7 nanotubes serve as precursors and templates, and glucose molecules act as the green carbon source. With the alliciency of hydrogen bonding between H2 Ti3 O7 and glucose, a thin polymer layer is hydrothermally assembled and subsequently converted into carbon fibers through calcinations under an inert atmosphere. Meanwhile, the precursors of H2 Ti3 O7 nanotubes are transformed into the TiO2 nanoparticles encapsulated in carbon fibers. The achieved unique nanocomposites can be used as excellent anode materials in lithium-ion batteries (LIBs) and photocatalytic reagents in the degradation of rhodamine B. Due to the synergistic effect derived from TiO2 nanoparticles and carbon fibers, the obtained peapod-like TiO2 /carbon cannot only deliver a high specific capacity of 160 mAh g(-1) over 500 cycles in LIBs, but also perform a much faster photodegradation rate than bare TiO2 and P25. Furthermore, owing to the low cost, environmental friendliness as well as abundant source, this novel TiO2 /carbon nanocomposite will have a great potential to be extended to other application fields, such as specific catalysis, gas sensing, and photovoltaics.

Novel Au/TiO2 photocatalysts for hydrogen production in alcohol–water mixtures based on hydrogen titanate nanotube precursors

In this study, a series of titania nanorods with different phase compositions and surface areas were prepared by calcination of hydrogen titanate (H2Ti3O7) nanotubes at temperatures up to 1000°C. Gold nanoparticles were subsequently deposited on the obtained TiNTx (x=calcination temperature) nanorod supports at loadings between 0.5 and 2.0wt.%, and also onto a commercially available mixed-phase titania support (Degussa P25). TEM, XRF, UV–Vis, XPS and photoluminescence measurements confirmed the presence of gold nanoparticles of mean size 4–7nm on the surface of the Au/TiNTx (x=350–800) and Au/P25 photocatalysts, which suppressed electron–hole pair recombination in TiO2 under UV and created cathodic sites for hydrogen evolution. Hydrogen production tests were conducted on the Au/TiNTx and Au/P25 photocatalysts in various alcohol–water mixtures under UV excitation (6.5mWcm−2) with no external bias applied. The impact of the gold loading and the calcination temperatures on the structural, physico-chemical and photocatalytic properties of the TiNTx nanorods was investigated, and a comparison to P25 was made. A 0.5wt.% Au/TiNT600 photocatalyst demonstrated excellent H2 production activity in all the alcohol–water systems, performing similarly to a 1.5wt.% Au/P25 reference photocatalyst. For both the 0.5wt.% Au/TiNT600 and 1.5wt.% Au/P25 photocatalysts, H2 production rates decreased in the order triol (glycerol)>diol (1,2-ethanediol≈1,2-propanediol)>ethanol>1-propanol. Good correlations were found between the H2 production rates and alcohol properties such as the number of hydroxyl groups, polarity or standard oxidation potential.

Microwave synthesis of nitrogen-doped carbon nanotubes anchored on graphene substrates

We report a fast and facile microwave technique to synthesize nitrogen-doped carbon nanotubes anchored on graphene substrates from azobis(cyclohexanecarbonitrile), a commodity chemical, commonly used as a radical initiator in polymerization reactions as the nanotube precursor. Micrometer-long, nitrogen-doped carbon nanotubes vertically anchored on graphene was obtained to produce mesoporous, hierarchical nanostructures. X-ray photoelectron spectroscopy reveals that nitrogen moieties exist as pyridinic and graphitic nitrogen. When applied as anodes in lithium-ion batteries, our materials exhibit a high capacity of 1342mAhg−1 even after prolonged cycling reflecting the ability of the three-dimensional network to accommodate the extreme volume changes occurring during the lithiation/delithiation reactions.

Enhanced photoactivity of graphene/titanium dioxide nanotubes for removal of Acetaminophen

Acetaminophen is commonly used as an antipyretic or analgesics agent and poses threat to human health. In this research, TiO2 and graphite oxide were used as precursors of titanium dioxide nanotubes and graphene respectively. Titanium dioxide nanotube and graphene (GR-TNT) nanocomposites were synthesized through a hydrothermal method. FT-IR, UV-Vis, XRD, and TGA were used to characterize the catalysts. The acetaminophen degradation rate can reach up to 96% under UV light irradiation for 3h and with the 5% GR-TNT dosage of 0.1gL−1. Further experiments were done to probe the mechanism of the photocatalytic reaction catalyzed by the GR-TNT composite. EDTA (hole scavengers) and t-BuOH (radical scavengers) were used to detect the main active oxidative species in the system. The results showed that the holes are the main oxidation species in the photocatalytic process. This study provides a new prospect for acetaminophen degradation by using high efficiency catalysts.