Nitrogen-doped Bamboo-like Carbon Nanotubes Research Articles

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.

Development of Magnetizable, Nickel-Ferrite-Decorated Carbon Nanocomposites as Hydrogenation Catalyst for Aniline Synthesis.

Catalysts with magnetic properties can be easily recovered from the reaction medium without loss by using a magnetic field, which highly improves their applicability. To design such systems, we have successfully combined the magnetic properties of nickel ferrite nanoparticles with the positive properties of carbon-based catalyst supports. Amine-functionalized NiFe2O4 nanoparticles were deposited on the surfaces of nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) and carbon nanolayers (CNL) by using a coprecipitation process. The magnetizable catalyst supports were decorated by Pd nanoparticles, and their catalytic activity was tested through the hydrogenation of nitrobenzene (NB). By using the prepared catalysts, high nitrobenzene conversion (100% for 120 min at 333 K) and a high aniline yield (99%) were achieved. The Pd/NiFe2O4-CNL catalyst was remarkable in terms of stability during the reuse tests due to the strong interaction formed between the catalytically active metal and its support (the activity was retained during four cycles of 120 min at 333 K). Furthermore, despite the long-lasting mechanical stress, no significant palladium loss (only 0.08 wt%) was detected.

Development of Palladium and Platinum Decorated Granulated Carbon Nanocomposites for Catalytic Chlorate Elimination.

Granulated carbon nanotube-supported palladium and platinum-containing catalysts were developed. By using these, remarkable catalytic activity was achieved in chlorate ion hydrogenation. Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) loaded gel beads were prepared by using Ca2+, Ni2+ or Fe3+ ions as precursors for cross-linking of sodium alginate. The gel beads were carbonized at 800 °C, and these granulated carbon nanocomposites (GCNC) were used as supports to prepare palladium and platinum-containing catalysts. All in all, three catalysts were developed and, in each case, >99 n/n% chlorate conversion was reached in the aqueous phase by using the Pd-Pt containing GCNCs, moreover, these systems retained their catalytic activity even after repeated use.

In situ construction of FeCo alloy nanoparticles embedded in nitrogen-doped bamboo-like carbon nanotubes as a bifunctional electrocatalyst for Zn-air batteries.

The rational design and exploration of low-cost, highly efficient, and robust bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are essential for the application of zinc-air batteries. Herein, a novel highly active and stable oxygen electrode catalyst is designed based on in situ construction of FeCo alloy nanoparticles embedded in nitrogen-doped carbon nanotubes (FeCo/N-CNTs-800) with a bamboo-like structure. The unique architecture of bamboo-like nanotubes, the large surface area with abundant mesoporous structure, and the strong coupling interactions between the encapsulated alloy nanoparticle core and the nitrogen-doped graphitic carbon shell synergistically enhance the electrocatalytic activity. As a result, FeCo/N-CNTs-800 exhibits remarkable ORR (with a half-wave potential of 0.891 V in 0.1 M KOH) and OER (with an overpotential of 359 mV to deliver 10 mA cm-2 in 1 M KOH) performance, respectively. More impressively, an assembled zinc-air battery with the bifunctional FeCo/N-CNTs-800 catalyst as the air electrode demonstrates a large power density of 200.4 mW cm-2 and robust cycling performance over 445 h compared to precious-metal catalysts Pt/C∥IrO2. Thus, the electrocatalyst presented in this work holds great potential as an air cathode for practical applications of zinc-air batteries.

Fabrication of Fe/Fe3C-nanoparticles encapsulated nitrogen-doped carbon nanotubes with thin wall thickness as high-efficiency electromagnetic wave absorbing materials

Nitrogen-doped bamboo-like carbon nanotubes with embedded Fe/Fe3C nanoparticles (NPs) (Fe/Fe3C@NCNTs) were successfully fabricated by the pyrolysis of the metal organic framework. When the pyrolysis temperature was 800 °C, the length and diameter of NCNTs were in the ranges 8–20 µm and 17–130 nm, respectively. Remarkably, the wall thickness of the NCNTs was merely 5.0 nm. The Fe/Fe3C@NCNTs-800 exhibits enhanced dielectric and magnetic loss performance attributing to its excellent electrical conductivity, massive interfaces between Fe/Fe3C and NCNTs, and a large number of defects and void spaces between bamboo joints. In addition, the Fe/Fe3C@NCNTs-800 also has outstanding impedance matching characteristic, and thus its minimal reflection loss and effective absorption bandwidth reached −50.8 dB with a thickness of 1.6 mm and 4.3 GHz with a thickness of 1.4 mm, respectively. The results of this study demonstrate the Fe/Fe3C@NCNTs-800 as a promising candidate for electromagnetic wave absorption.

Atomically dispersed dual Fe centers on nitrogen-doped bamboo-like carbon nanotubes for efficient oxygen reduction

Atomically dispersed dual Fe centers on nitrogen-doped bamboo-like carbon nanotubes for efficient oxygen reduction

Second diffusion of Co particles during MoS2 incorporated in N-doped carbon nanotubes towards superior electrochemical activity

Transition metal endowed carbon nanotubes are widely used in electrochemical catalytic reactions. The distribution of transition metal affected their performance. Herein, Co particles were firstly embedded in N-doped carbon nanotubes. During the deposition of molybdenum disulfide (MoS2), the size of Co particles was drastically decreased. This phenomenon is ascribed to the reaction between Co and S2− ions. Finally, MoS2/Co/N-doped carbon heterostructures formed. Such heterostructures exhibited excellent activity for electrocatalytic water splitting. It effectively improves the electrocatalytic hydrogen evolution ability of the carbon nanotubes with an over potential of 468 mV at 50 mA/cm2 current density. In addition, the formation mechanism of the Mo–N–C interface coupling structure has also been proposed. This unique structure facilitates further design research on carbon materials. It is worth mentioning that nitrogen-doped bamboo-like carbon nanotubes have good oxygen reduction reaction activity, and the half-wave potential can reach 792 mV, the onset potential is 931 mV, and the ultimate diffusion current density is 5.3 mV/cm2, which is close to the expensive commercial Pt/C electrodes.

Influence of doping nitrogen on the catalytic performance of carbon nanotubes encapsulating cobalt for selective oxidation of arylalkanes

Efficient selective oxidation of hydrocarbons to corresponding ketones has been a significant but challenging work in the past decades. Here, a nitrogen-doped bamboo-like carbon nanotubes encapsulating cobalt catalyst (NCNTs-X) using citric acid, melamine and CoCl2·6H2O as precursors was synthesized by a simple pyrolysis method. A series of characterization techniques were employed to investigate the physicochemical properties of samples. And the results show that the as-prepared catalysts achieve a high catalytic performance for selective ethylbenzene oxidation (78.3% ethylbenzene conversion) using molecular oxygen as oxidant, especially giving a high selectivity (93.8% selectivity to acetophenone). According to the investigation of the structure-activity relationship of the catalysts, it can be deduced that the Co–Nx sites have an obvious positive effect on catalytic performance thanks to the synergistic effect between metallic cobalt and pyridinic N.

A highly effective bifunctional catalyst of cobalt selenide nanoparticles embedded nitrogen-doped bamboo-like carbon nanotubes toward hydrogen and oxygen evolution reactions based on metal-organic framework

Metal selenides as highly efficient bifunctional electrocatalysts were extensively applied to water-splitting technology. In present work, N-doped graphitized carbon wrapped CoSe2 nanoparticles (NPs) with in-situ grown bamboo-like carbon nanotube (CoSe2@N/C-CNT) was successfully synthesized via a Co-Ade (Adenine) MOF-derived selenylation strategy. Each CNT was capped with CoSe2 NP, which not only effectively avoided self-agglomeration of CoSe2 NPs but also protected the CoSe2 NPs from electrolyte etching. The synergism of bamboo-like CNT with high conductivity and the uniformly distributed CoSe2 NPs endowed CoSe2@N/C-CNT the better bifunctional electrocatalytic activities toward both HER (hydrogen evolution reaction) and OER (oxygen evolution reaction). To generate a current density of 10 mA cm−2, CoSe2@N/C-CNT exerted as low as overpotential (η) of 185 mV vs. RHE (reversible hydrogen electrode) and 340 mV vs. RHE for HER and OER, the corresponding Tafel slopes were 98 and 107 mV dec-1 respectively. In addition, CoSe2@N/C-CNT exhibited superior durability with negligible attenuation after long-term stability test.

Carbon nanotube-zeolite composite catalyst - characterization and application

“Support on support” (SoS) core-shell nanostructure was prepared by using zeolite beads as supports for nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs). The N-BCNTs were synthetized with catalytic chemical vapor deposition (CCVD) onto the surface of the beads to use later as primary catalyst support. On the SoS composite Pd, Rh, and Pt nanoparticles were successfully deposited (2 w/w%) with high dispersity. The prepared three catalytic systems (Pd-, Rh- and Pt-SoS) were characterized and tested in butene hydrogenation. The reactions were followed by FTIR spectroscopy. The butene conversion reached the maximum after about 6 minutes. Each catalyst was easy to handle and applicable in the studied reaction.

Bamboo-like nitrogen-doped carbon nanotubes encapsulated with NiFeP nanoparticles and their efficient catalysis in the oxygen evolution reaction

There is an urgent need to develop efficient, durable, earth-abundant, and low-cost electrocatalysts for the oxygen evolution reaction (OER) that occurs during the electrochemical splitting of water. Herein, we develop a method to synthesize uniform nitrogen-doped bamboo-like carbon nanotubes (NBCNT) encapsulated with NiFeP nanoparticles (NiFeP@NBCNT). When the as-fabricated nanocomposites are used to catalyze the OER, it exhibits exceptionally high activity in alkaline solution (180 mV @10 mA cm−2 and a low Tafel slope of 59 mV dec−1) and outstanding long-term stability. The turnover frequency (TOF) for NiFeP@NBCNT at an overpotential of 350 mV are calculated to 3.38 s−1. The OER reaction mechanism on the NiFeP@NBCNT modified electrode is explored by comparing the XPS spectra before and after electrochemical OER testing. The excellent catalytic properties make NiFeP@NBCNT a promising candidate for electrochemical catalysis in water splitting.

Adsorption capacity of oxidized nitrogen-doped bamboo-like carbon nanotubes

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthetized by catalytic chemical vapor deposition (CCVD) and characterized by electron microscopy. The produced nanotubes were oxidized in different degree by using of various oxidizing agents (H2O2, HClO4 and HNO3) in order to change their adsorption potential by creating dissociable functional groups (e.g. -OH) on their surface. The appearance of oxygen containing groups was confirmed by spectroscopic analysis and the zeta potential (ζ of the samples was measured. The HNO3 treatment has led to the emergence of the most polar groups on the nanotube surface (ζ = −27.1 mV), while the other two oxidizing agents were less effective (H2O2 and HClO4, ζ = −18.3 and −19.8 mV, respectively). The adsorption potential of the oxidized N-BCNT samples were tested with copper(II)-ion. Despite the difference in their surface properties, the oxidized nanotubes adsorbed copper to the same extent. The contribution of the oxidized surface for the adsorption capacity is smaller than the effects of nitrogen doping. Thus, more things involved in the adsorption mechanism not only electrostatic attraction, but sorption-precipitation, and complex formation between copper and heteroatoms of the nanotubes. Thus, it is not enough to discuss the effect of dissociable functional groups, but the contribution of e.g. heteroatoms must also be taken into account to fully understand metal ion adsorption on oxidized carbon materials.

Development of nitrogen-doped bamboo-like carbon nanotubes coated zeolite beads as \u201csupport on support\u201d catalyst for the catalytic hydrogenation of olefins

“Support on support” type catalysts were developed by applying catalytic chemical vapour deposition (CCVD). Nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) were synthetized on the surface of zeolite beads by using four different metals (Ni, Fe, Co and V). Based on the thermogravimetric analysis (TGA), the Ni, Co and Fe were catalytically active for nanotube production on the zeolite surface. It was confirmed by SEM measurements, that the surface of the beads was extensively covered by N-BCNTs. Based on the TGA and SEM results, two SoS systems were selected for further catalysts development, which differed the most in their nanotube content (difference 11.63 wt%) and surface coverage. These were two nickel containing samples with 6.72 and 18.35 wt% N-BCNT. Palladium nanoparticles were deposited (1 wt%) on the surface of the N-BCNT/zeolite systems, and the final Pd/SoS catalysts were tested in hydrogenation of 1-butene. The conversion maximum (X = 100%) was reached after 6 min in both cases independently of the nanotube content and coverage (WHSV: 5.49). To measure the lifetime of the selected catalysts, the WHSV was increased from 5.49 to 11 (by increasing the gas flow) and the systems were still active after 6 h. Thus, the lifetime of the catalysts is longer than 6 h. Furthermore, by increasing the gas flow (WHSV = 11), higher conversion was achieved (98%) with the sample which has a higher nanotube content Therefore, smaller carbon nanotube content is still as catalyst support. The final Pd/SoS catalysts were active, easy to treat and removable from the reactors and could work with smaller carbon nanotube content as well. Thus, a more economical catalysts was developed, than a solely carbon nanotube-based counterparts which lack the zeolite core.

Nitrogen-doped bamboo-like carbon nanotubes as anode material for high performance potassium ion batteries

Nitrogen-doped bamboo-like carbon nanotubes enable a simple intercalation of K+ ions and provide enough spaces to accommodate volume change.

Cobalt particles encapsulated and nitrogen-doped bamboo-like carbon nanotubes as a catalytic and adsorptive bifunctional material for efficient removal of organic pollutants from wastewater

Bifunctional materials having both good catalytic and adsorptive performances are promising in the field of wastewater treatment. Cobalt-encapsulated and nitrogen-doped bamboo-like carbon nanotubes (Co/N-CNTs) were prepared by a simple method of calcination and acid treatment with Co3[Co(CN)6]2 as a precursor. Based on a series of characterization and performance studies, Co/N-CNTs were confirmed to be able to function as both a catalyst and an adsorbent for oxidative degradation of organic pollutants in the presence of peroxymonosulfate (PMS). When rhodamine B was used as a typical dye pollutant, it was found that all the added pollutant (10mgL−1) was completely removed in 7min by using 0.1gL−1 Co/N-CNTs and 0.2gL−1 PMS. The fast and efficient degradation of the pollutant was attributed to the synergistic effect between adsorption and catalysis on the surface of Co/N-CNTs. It was confirmed that this bifunctional material provided good performances in a wide range of operation conditions, such as a wide temperature range and a wide pH range. Co/N-CNTs also exhibited a good recyclability. A mechanism study indicated that the main active species in the catalytic oxidation process was surface-bound SO4− and OH.

Nitrogen-doped bamboo-like carbon nanotubes with Ni encapsulation for persulfate activation to remove emerging contaminants with excellent catalytic stability

Nitrogen-doped bamboo-like carbon nanotubes encapsulated with nickel nanoparticles (Ni@NCNTs) were feasibly fabricated by a one-pot pyrolysis route. The characterization techniques revealed the surface morphology, structure and chemical composition of the as-prepared catalysts synthesized in different conditions. Ni@NCNTs were employed as both adsorbents and catalysts for activating persulfate to remove an emerging pollutant, antibiotic sulfachloropyridazine. The nitrogen modification enhanced both adsorption capacity and catalytic ability of Ni@NCNTs and proved to be a promising alternative to metal oxides and other carbon catalysts. Moreover, Ni@NCNTs showed an excellent stability because of nitrogen heteroatom doping and Ni nanoparticle encapsulation. Electron paramagnetic resonance (EPR) and classical radical quenching tests discovered a simultaneous radical/non-radical mechanism in Ni@NCNTs/persulfate system. The results indicated that the novel nano-architectured catalyst materials can show emerging functionalities for environmental remediation processes.

Facile Synthesis of Nickel–Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splitting

Developing active, stable, and low-cost electrocatalysts which can promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is undoubtedly a vital progress toward a hydrogen economy. Herein, we report that such electrocatalysts can be easily prepared by pyrolyzing a precursor composed of nickel and iron salts with urea under inert atmospheres without any post-treatments. The obtained products are composed of metallic nickel–iron alloy nanoparticles either encapsulated in or dispersed on nitrogen-doped bamboo-like carbon nanotubes (CNTs). This simple synthesis route could simultaneously realize nanostructuring, doping, and hybridizing with nanocarbon, which have been demonstrated as efficient strategies to optimize the catalytic activity of an electrocatalyst. The in situ formed hybrid catalysts exhibit good catalytic performances for both OER and HER under alkaline conditions, and the doping content of iron significantly affects the activities. When the bes...

Nitrogen-doped bamboo-like carbon nanotubes: promising anode materials for sodium-ion batteries.

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthesised using a facile one-step pyrolysis process. Due to their unique one-dimensional hollow structure and intrinsic high nitrogen content, N-BCNTs exhibit high capacity, superior rate capability, and excellent cycle stability and are, thus, promising anode materials for sodium-ion batteries.