Carbon Microtubes Research Articles

Facile fabrication and electrochemical oxidation of activated carbon microtube bundles for advanced all-solid-state supercapacitors

The energy density of carbon microtube bundles (CMTBs) is usually low and the preparation process is complex. After carbonization, washing and activation, the prepared metaplexis shell-based carbon microtube bundles (MS-CMTBs) not only have an open structure, but also a rich porous structure on the tube wall. The pulsed electrooxidation technology can promote the formation of functional groups on the tube wall and further enhance the energy density of the material. After assembling the electrooxidized material into an all-solid-state supercapacitor, the capacitor has a capacity of 15.1 Wh kg−1 at 0.5 A g−1 and a capacity retention rate of 95.9% after 10 000 cycles at 10 A g−1, indicating that these functional groups are relatively stable. The result shows that the MS-CMTBs before pulsed electrooxidation are more suitable as positive electrode materials, while the electrooxidized material can be either a positive or negative electrode material. This work provides an idea for the design and development of electrode materials in high-performance all-solid-state supercapacitors.

Novel porous carbon microtubes and microspheres produced from poly(CL-b-VbC) triarm block copolymer as high performance adsorbent for dye adsorption and separation

Dandelion-like and microtube-containing novel porous carbons were synthetized from brush type poly (ε-caprolactone-b-4-vinyl benzyl chloride) (poly(CL-b-VbC)) triarm block copolymer with KOH (PCLVbK) and ZnCl2 (PCLVbZn) through optimized chemical activation at low temperature. These porous carbons were used for the adsorption and separation of cationic Malachite green (MG) and anionic Congo red (CR) and Methyl orange (MO) dyes. The synthetized porous carbons were characterized by SEM, N2 adsorption-desorption isotherms, FTIR, Raman and XRD. PCLVbK and Zn porous carbons were quite effective in cationic (MG) dye adsorption from aqueous solution thanks to different functional groups, surface areas and pore volumes. The MG adsorption capacities of PCLVbZn and PCLVbK were found to be 1684 mg/g and 869.5 mg/g, and these results are considerably higher than the other adsorbents studied in the literature. Also, it was determined that while PCLVbZn could adsorb both cationic and anionic dyes, PCLVbK could only perform the adsorption of cationic dyes. The kinetic studies conducted with MG showed that both PCLVbK and Zn porous carbons fitted better with the pseudo-second-order model. At the end of the adsorption equilibrium studies, it was observed that PCLVbZn fitted with both the Langmuir and Freundlich adsorption models while PCLVbK fitted better with the Langmuir model. In conclusion, it was observed that PCLVbK could perform high and fast adsorption and separation owing to its oxygen functional groups, while PCLVbZn turned out to be effective in the adsorption of both anionic and cationic dyes thanks to its large surface area (1006 m2/g) and empty microtubes. Based on these results, it can be argued that PCLVbK and Zn porous carbons are promising adsorbents for both high adsorption and effective separation from aqueous solution.

In situ scanning electron microscopy observations of filler material transport in branched carbon microtubes by Joule heating.

Y-branched or side-by-side-branched carbon microtubes with metal filler material were fabricated, and material transport in the branched microtubes with Joule heating was investigated using in situ scanning electron microscopy with micro-electrode probes. When a voltage and electric current were applied, the material enclosed in the microtubes moved from its original position. The movement was not related to the direction of the electric current; therefore, it is concluded that the movement was not due to electromigration, but rather a temperature gradient, volume expansion and increased vapor pressure by Joule heating. In Y-branched microtubes, a part of the metal filler material moved from one branch to another branch, which would be useful for microfluidic flow switching. A cylindrical filler material was also observed to be expelled from a branch while its shape was maintained, and this phenomenon is presumably caused by vaporization-induced high pressure and could find application in micro-mechanical manipulators such as punching needles. In side-by-side-branched carbon microtubes, Joule heating caused thermal volume expansion to fill the spaces in the branches that were initially empty. The microtubes then reverted to a state almost identical to the initial state with empty spaces when the electric current was turned off. These results suggest that thermal volume expansion could be employed for flow switching.

3D hierarchical heterostructure assembled by NiFe LDH/(NiFe)Sx on biomass-derived hollow carbon microtubes as bifunctional electrocatalysts for overall water splitting

Developing highly active and stable noble-metal-free bifunctional electrocatalysts for both hydrogen and oxygen evolution is still a challenge in electrochemical water splitting technology. Herein, a three-dimensional (3D)-networked heterogeneous electrocatalyst in the form of vertically aligned NiFe layered double hydroxide (LDH) nanoflakes coupled with Fe-doped NiSx nanoparticles is supported on biomass-derived carbon microtubes (CMT). The optimal hybrid electrode exhibits superior electrocatalytic activity with low overpotentials of 210 and 157 mV to deliver a current density of 10 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1 M KOH, respectively. It is revealed that the remarkable features of the catalyst lie in the unique 3D open configuration, the high conductivity of CMT support and the strong interfacial coupling effects between NiFe LDH and (NiFe)Sx, giving rise to enhanced active sites, accelerating electron/ion transport, and further promoting reaction kinetics of OER/HER. Furthermore, an alkaline water electrolyzer is constructed with the NiFe LDH/(NiFe)Sx/CMT composite as catalyst for both anode and cathode. This electrolyzer displays excellent electrolysis performance (affording 10 mA cm−2 at 1.53 V) and long-term durability over 100 h. This work demonstrates a strategy in preparing bifunctional and cost-efficient electrocatalysts with potential application in the future.

Efficiently immobilizing and converting polysulfide by a phosphorus doped carbon microtube textile interlayer for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are regarded as the potential substitution for the lithium-ion batteries owing to the ultrahigh theoretical energy density and specific capacity. Nevertheless, the low sulfur utilization and the severe “shuttle effect” impede the commercialization of them. Herein, a phosphorus doped carbonized cotton cloth (PCCC) interlayer is proposed to handle these problems. The PCCC interlayer can not only act as an upper current collector and a physical lithium polysulfides (LIPS) barrier due to its high conductivity and knitted structure, but also chemically adsorb the LIPS and catalyze their conversion owing to the heteroatom doping of phosphorus. The synergistic effects of immobilizing and converting the LIPS lead to greatly reduced “shuttle effect” and high sulfur utilization. As a consequence, the Li-S batteries with the PCCC interlayer demonstrate decent cycling performance as well as ultrahigh rate capability by releasing a high initial discharge capacity of 1138 mA h g−1 at 0.5 C with a small capacity fading rate of 0.054% per cycle, and achieving an astonishing discharge capacity up to 642 mA h g−1 at 10 C.

Construction and electrochemical properties determination of carbon nanotubes/porous-network carbon micron tubes/silk fibroin composite film neural electrode

A novel carbon nanotubes/porous-network carbon micron tubes/silk fibroin (CPS) composite film neural electrode was presented and characterized. This electrode was fabricated through assembling dispersed carbon nanotubes (CNTs) by phytic acid onto the porous silk fibroin film. Afterward, the silk fibroin around the CNTs was carbonized by laser irradiation, producing porous-network carbon microtubes with good conductivity and biological compatibility. The structure of the CPS composite film was characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry, electrochemical impedance spectroscopy, and safe charge injection limit (Qinj) of the CPS electrode were also measured by the three-electrode system, and the results exhibited outstanding electrochemical properties with the achieved Qinj of 5.7 mC/cm2. This work provides a promising approach for the preparation of a long-term implanted neural electrode with high charge injection ability and good biocompatibility.

Heteroatom-doped hollow carbon micro-tube derived from platanus catkins fiber for sodium ion supercapacitor

Heteroatom-doped hollow carbon micro-tubes are successfully fabricated from platanus catkins fibers by simply precarbonization and then KOH activation method for sodium ion supercapacitor. The different activation temperatures (600 °C, 700 °C and 800 °C) are used to study the effect on the structural and electrochemical performance of the bio-carbon materials. As the activation temperature increases, the disorder degrees and the surface (inner and outer) roughness of the as-prepared hollow carbon tubes (with diameters of about 15–25 μm and a wall thickness around 2–3 μm) increase. Benefiting from the proper numerous pores (micro-, meso- and macro-pores), high specific surface area, unique structure and heteroatom (N and O) dual doping, hollow carbon micro-tubes activated at 700 °C exhibit superior electrochemical performance with good rate capability and high specific capacity of 195, 140, 112, 95 and 84 mAh/g at the current densities of 0.1, 0.2, 0.5, 1 and 2 A/g, respectively.

Growing NiS2 nanosheets on porous carbon microtubes for hybrid sodium-ion capacitors

NiS2 is a promising anode material for sodium-ion batteries (SIBs) and capacitors (SICs). However, the sluggish Na+ diffusion and large volume change of bulk NiS2 during sodiation/de-sodiation lead to poor rate capability and fast capacity decay, limiting its practical application. Herein, we design and prepare well-oriented NiS2 nanosheets on porous carbon microtubes (denoted as NiS2/pCMT) as a novel anode material for SIBs/SHCs. The unique porous hollow carbon tubes and NiS2 nanosheets can well relieve the repeated stress/strain and maintain the structural integrity of the composite anode during long-term charging/discharging. As a confirmation, a modelled SHC is constructed by using the NiS2/pCMT composite as anode and coupling with an activated carbon cathode, delivering a high energy density of 136 Wh kg−1 and good cycling stability. The first-principles density functional theory (DFT) calculations confirm that the NiS2 nanosheets surface has a high chemical affinity towards Na+ ions, promising the concentration of Na+ ion on/nearby the surface for fast redox reactions during sodiation/de-sodiation of NiS2. This work provides some new insights for the design and fabrication novel composite electrode materials for applications in beyond lithium-ion batteries/capacitors.

Dual potassium salt-assisted lyophilization of natural fibres for the high-yield synthesis of one-dimensional carbon microtubes for supercapacitors and the oxygen reduction reaction

Natural fibre-derived carbon microtubes exhibit excellent performances as supercapacitor electrodes and oxygen reduction electrocatalysts via dual-potassium-salt-assisted freeze-drying and post-nitrogen doping.

Biomass-derived nitrogen and sulfur co-doped carbon microtubes for the oxygen reduction reaction

Nitrogen and sulfur co-doped carbon microtubes (N,S-CMTs) demonstrate satisfactory electrocatalytic performances compared with commercial 20% Pt/C.

Carbon Microtube Aerogel Derived from Kapok Fiber: An Efficient and Recyclable Sorbent for Oils and Organic Solvents

Carbon microtube aerogel (CMA) with hydrophobicity, strong adsorption capacity, and superb recyclability was obtained by a feasible approach with economical raw material, such as kapok fiber. The CMA possesses a great adsorption capacity of 78-348 times of its weight. Attributed to their outstanding thermal stability and excellent mechanical properties, the CMA can be used for many cycles of distillation, squeezing and combustion without degration, which suggests a extremely potential pratical application in oil-water separation. In addition, the adsorption capacity still retained 98% by distillation, 97% by squeezing, and 90% by combustion after 10 cycles. Therefore, the obtained CMA has a broad prospect as an economical, efficient and environment-friendly adsorbent.

Flexible amorphous MoS2 nanoflakes/N-doped carbon microtubes/reduced graphite oxide composite paper as binder free anode for full cell lithium ion batteries

Amorphous MoS2 Nanoflakes are grown on the outer and inner surfaces of N-doped carbon microtubes prepared by the carbonization of the biomass of willow catkins to fabricate N doped carbon microtubes@amorphous MoS2 (NCMTs@A-MoS2) and subsequently the as-prepared NCMTs@A-MoS2 and 2D reduced graphite oxide cross link to form 3D NCMTs@A-MoS2/RGO composite paper by a simple vacuum filtration. This novel three dimensional nano/micro hierarchical structure has the superior advantages of nano and micro materials, such as decreasing the diffusion lengths of lithium ions and preventing the agglomeration of amorphous MoS2 and maintaining the whole structural stability, by building nanosized amorphous MoS2 coated on carbon microtubes, so as to obtain an anode material with excellent lithium ion battery (LIBs) performances. More importantly, the amorphous MoS2 provides percolation pathways through the opening of active diffusion channels, expediting the diffusion rate of lithium ions. Furthermore, the composite paper as a whole is favorable for increasing the overall conductivity and energy density of the anode material without binders. As a result, when used as anode materials for half and full cell LIBs, N-doped carbon microtubes@amorphous MoS2 delivers an ultra-long cycling life, high reversible capacities and superior rate performances.

Efficient and rapid removal of Pb2+ from water by magnetic Fe3O4@MnO2 core-shell nanoflower attached to carbon microtube: Adsorption behavior and process study

Designing highly efficient, recyclable and environmentally friendly adsorbent for the removal of heavy metal ions from wastewater plays a key role in sewage treatment system. In this study, a magnetic Fe3O4@MnO2 core-shell nanoflower attached to Aspergillus niger carbon microtube was developed as a perfect adsorbent for the removal of Pb2+ from water solution. Benefiting from the synergistic effect of high adsorption capacity of metal oxides, magnetism of Fe3O4 and large size of Aspergillus niger carbon, the synthesized adsorbent achieves an extremely high adsorption capacity of 934 mg/g and a faster adsorption speed of 5 min, which is a splendid performance among reported adsorbent of Pb2+ from water solution. Supported by FTIR spectra, a large amount of carbon dioxide and hydroxyl groups were proved to exist on the surface of the Fe3O4@MnO2/CT, where the functional groups with negative charges play a key role in facilitating the interface adsorption process. Moreover, the amorphous magnetically adsorbent with a size of about 300 nm have a specific surface area of 151 m2/g and the high saturation magnetization of the adsorbent is highly beneficial to the re-recovery of the adsorbent. After five cycles of testing, the adsorbent can still guarantee a maximum saturated adsorption capacity of more than 86%. The lead element is adsorbed on the surface of the adsorbent in the form of basic lead carbonate, which suggests that the basic adsorption mechanism is chemical adsorption.

Hierarchical carbon microtubes from willow catkins for Li–S batteries

It is crucial but quite challenging to cycle carbon waste to prepare useful carbon material for energy storage by green process. Herein, hierarchical porous carbon microtubes synthesized by directly heating willow catkins without activation were used for Li–S batteries. The carbon microtubes loaded >75.0% sulfur were used as the Li–S battery cathodes. The cathodes with high areal sulfur content of 2.6 mg/cm2 deliver an initial discharge capacity of ~800 mAh/g at 0.5 C, and stabilized at 624 mAh/g after ~150 cycles at 0.5 C, with a low degradation rate per cycle (0.13% after 150 cycles or 0.07% after 1000 cycles). Our investigation presents that the fly willow catkins air-contaminants could be collected to use for high-density energy storage.

Efficient synthesis of carbon microtubes–gold nanoparticles composite: optical and micro-analytical study

This article reports a new synthesis method for the production of carbon microtubes–AuNPs composite (CMT–AuNPs) based on sucrose. The CMT showed the ability to functionalize gold nanoparticles. The UV–Vis spectroscopy was used to determine the surface plasmon resonance (SPR) of the nanoparticles and the absorbance of the CMT. The results showed two absorption bands centered at 287 nm and 527 nm, associated to carbon and gold structures, respectively. The Raman spectra revealed two bands, D and G, located at 1345 cm−1 and 1570 cm−1. Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to obtain structural properties of the CMT, the results show an approximate diameter size of 0.8–1.5 µm. Metallic gold NPs were observed between 15 and 30 nm adhered to the CMT surface. The NPs were analyzed with high-resolution imaging HRTEM and chemical analysis through energy dispersive X-ray spectroscopy EDS. This is the first report that uses sucrose as a precursor to obtain carbon microtubes with gold nanoparticles and opens up new ways to fabricate this material.

Fabrication of eco-friendly carbon microtubes @ nitrogen-doped reduced graphene oxide hybrid as an excellent carbonaceous scaffold to load MnO2 nanowall (PANI nanorod) as bifunctional material for high-performance supercapacitor and oxygen reduction reaction catalyst

Recently, with the concept of building a resource-conserving and environment-friendly society, the idea of developing green, sustainable and multifunctional materials has become increasingly urgent. So, how to explore more possible ways for efficient and sustainable utilization of biomass resources is very important. In this paper, a novel eco-friendly and sustainable 3D bifunctional carbon microtubes@nitrogen-doped reduced graphene oxide (CMT@N-RGO) hybrid based biomass material is firstly fabricated by combining dipping and chemical vapor deposition methods. Then the CMT@N-RGO hybrid is served as an excellent carbonaceous scaffold for constructing hierarchical hybrid with high-performance in energy storage and electrocatalysis. Finally, we have successfully prepared CMT@N-RGO/MnO2 and CMT@N-RGO/PANI hybrid with good supercapacitive and excellent oxygen reduction reaction (ORR). In short, the as-fabricated hybrid served as electrodes of supercapacitor present fast charge/discharge rate, excellent rate performance, and outstanding capacitance retention of 95% (93%) and high energy efficiency of 65–77% (61–72%) for both. In addition, the hybrid acted as an efficient electrocatalyst in the oxygen reduction reaction shows a larger positive onset potential of −0.12 V and half-wave potential of −0.21 V, which can be comparable to that of commercial Pt/C electrode. The improved capacitive and electrocatalytic properties are mainly attributed to the synergistic effects between the CMT and N-RGO/PANI (MnO2). In a word, these attractive results demonstrate that the 3D CMT@N-RGO/PANI (MnO2) hybrid are promising high-performance bifunctional material for supercapacitors and ORR catalyst. Hopefully, it can open up a versatile way for us to devise and manufacture more various multifunctional biomass-based material with outstanding electrochemical properties, excellent oxygen reduction reaction performance and other outstanding properties.

Ultralight Three-Dimensional Hierarchical Cobalt Nanocrystals/N-Doped CNTs/Carbon Sponge Composites with a Hollow Skeleton toward Superior Microwave Absorption.

It is extremely desirable but remains greatly challenging to obtain high-performance microwave absorption (MA) materials with thin thickness, lightweight, wide frequency bandwidth, and strong absorption by facile and low-cost preparing methods. In this work, by utilizing an inexpensively commercial melamine-formaldehyde sponge (MFS) as a template for growth of a Co-based metal-organic framework (ZIF-67) and subsequently carbonizing this ZIF-67-decorated MFS in a nitrogen atmosphere, an ultralight (8 mg cm-3), three-dimensional hybrid carbon sponge composite with a hierarchical micro/nanostructure and hollow skeleton is successfully prepared to acquire excellent MA performances for the first time. The as-obtained composite consisted of interconnected carbon microtubes as a skeleton, intertwined N-doped carbon nanotubes (CNTs) grew on the outer surface of the carbon microtubes, and metallic Co nanocrystals encapsulated at the tips of the CNTs. Benefiting from the unique architecture and hierarchical composite which contribute to a good conductive network, moderate magnetic loss, strong matched impedance, and multiple polarization, the composite (Co/CNTs/CS) exhibited a minimum reflection loss (RL) of -51.2 dB and an effective absorption bandwidth (EAB, RL < -10 dB) of 4.1 GHz with a matching thickness of 2.2 mm at a filler loading of as low as 10 wt % in paraffin wax. Even with the thickness of 1.6 mm or at the filler loading of 5 wt %, the composites can also gain the low minimum RL value of -30.9 or -17.9 dB, respectively. In addition, the largest EAB was 5.4 GHz at the thickness of 2.0 mm, and the tunable EAB can be achieved in the range of 3.6-18 GHz, covering 90% of the measured frequency range via adjusting the absorber thickness between 1 and 5.5 mm. The results offer new insights for designing advanced microwave absorbers with lightweight, thin thickness, strong RL, and wide absorption frequency range.

Highly Active Core-Shell Carbon/NiCo2 O4 Double Microtubes for Efficient Oxygen Evolution Reaction: Ultralow Overpotential and Superior Cycling Stability.

Developing highly efficient electrocatalysts with earth abundant elements for oxygen evolution reaction (OER) is a promising way to store light or electrical energy in the form of chemical energy. Here, a new type of electrocatalyst with core-shell carbon/NiCo2 O4 double microtubes architecture is successfully synthesized through a hydrothermal method combined with the calcination process with wet tissues as the template and carbon resource. The outer NiCo2 O4 nanosheet arrays contain abundant defects, which come from reduction of the carbon in wet tissues. This indicates that carbon is a very excellent defect inducer. The inner carbon microtubes can act as the robust structure skeleton and these core-shell double microtubes provide abundant diffusion channels for oxygen and electrolyte, both of which contribute to improving the stability by avoiding damage to the electrode from produced O2 bubbles and the collapse of the outer NiCo2 O4 microtubes. Electrochemical results show that the electrode, core-shell carbon/NiCo2 O4 double microtubes loaded on carbon cloth, exhibits prominent electrocatalytic activity with an overpotential of only 168 mV at 10 mA cm-2 and a Tafel slope as low as 57.6 mV dec-1 in 1.0 mol L-1 KOH. This new type of electrocatalyst possesses great potential in water electrolyzers and rechargeable metal-air batteries.

MoS2 Nanosheets Anchored on Melamine‐Sponges‐Derived Nitrogen‐Doped Carbon Microtubes as Anode for High‐Rate Sodium‐Ion Batteries

AbstractHere we demonstrate the design and synthesis of a composite electrode material consisting of MoS2 nanosheets anchored on nitrogen‐doped (N‐doped) carbon microtubes (NCMT) for anode applications in sodium‐ion batteries (SIBs). The NCMT skeleton was derived from the common melamine sponges, which was used not only as a template but also as the source of nitrogen and carbon. This smart design can effectively shorten the diffusion length of Na+ ions, increase electric conductivity of the electrode, and provide more active sites for electrochemical reactions. When evaluated as anode for sodium‐ion batteries, the MoS2@NCMT composites exhibited a larger initial coulombic efficiency (67.9%), high rate capability (196 mA h g−1 at 10 A g−1 and 118 mA h g−1 at 30 A g−1) and better cycling stability (289 mA h g−1 after 100 cycles at 80 mA g−1).

Carbon microtubes derived from self-rolled chitosan acetate films and graphitized by joule heating

Herein, a fast and efficient approach is proposed to obtain carbon microtubes with graphitic structure. The precursor tubes are formed via self-rolling of chitosan acetate (CA) biopolymer films in water. The self-rolling capacity is imparted to the CA films by heating them at 150 °C on a hot plate for several minutes in the ambient atmosphere. The resulting differential swelling of the top and bottom layers of the films in water generates the bending moment. The amorphous carbon microtubes are produced in Ar atmosphere via thermal treatment of chitosan acetate microtubes at 900 °C. Carbon/oxygen ratio increases from 1.2 for the pristine chitosan tube to 5.3 after the pyrolysis process. Finite electrical conductivity of the so-prepared tubes (σ ≈ 1 · 103 S · m−1) allows their consecutive treatment by joule heating. The current-induced graphitization of the tubes at 2500 °C is confirmed by TEM, Raman spectroscopy and XRD techniques. Electrical conductivity of tubes raised in course of the treatment to (σ ≈ 1.8 · 104 S · m−1). In joule-heated tubes, the carbon/oxygen ratio increases to 9.4.