CNT Electrode Research Articles

A high performance polybenzimidazole–CNT hybrid electrode for high-temperature proton exchange membrane fuel cells

A well-controlled Pt/PBI–CNT electrode provides not only good interfacial continuity but also numerous edge planes, which has strong electrochemical activity in HT-PEMFCs.

Oxygen Plasma Exfoliated Vertically-Aligned Carbon Nanotubes as Electrodes for Ultrasensitive Stripping Detection of Pb2+

In the present paper we report the production of vertically aligned carbon nanotubes exfoliated (at the tips) by oxygen plasma for electrochemical applications. The fast and dry process produces graphene oxide tips and oxygen functionalization. The electrodes are evaluated by cyclic voltametry by ferri/ferrocyanide redox couple and applied for electrochemical detection of lead (II) by differential pulsed anodic stripping voltammetry. The electrode presents high sensitivity (35.47 uA.uM−1) and low detection limit (48.3 pM). As far as we know, this is the lowest LoD in comparison with other works using CNT or graphene electrodes. The high electrochemical response is attributable to high density of functionalized edges on carbon nanotubes tips.

Effects of Electrodes and Nitrogen-Atom Locations on Electron Transport in C59N Molecular Junctions: A First-Principles Study

The electron-transport properties of C59N molecular junctions with different electrodes (Au, Al, and CNT) are investigated by density functional theory (DFT) combined with the first-principle nonequilibrium Green’s function (NEGF). The current–voltage characteristics of all the models are calculated. The results show both electrode species and nitrogen-atom location may affect the transport properties of the C59N molecular junction. When the nitrogen atom of the C59N molecule is located close to one side of the junction, the rectifying behavior can be found in CNT-electrode models, while there is no observable rectification in metal-electrode models. The negative differential resistance may be observed in the C59N molecular junction using CNT electrodes when the nitrogen atom is at a certain location. The results are discussed through examining the transmission spectra, the molecular projected self-consistent Hamiltonian states, and the projection of the density of states.

CNT–PVDF composite flow-through electrode for single-pass sequential reduction–oxidation

In this study, a five-layer electrochemical CNT–PVDF filter that is thin, flexible, and stable is demonstrated to be effective and efficient for single-pass nitrobenzene mineralization by sequential reduction–oxidation. Key to the technology is development of a CNT–PVDF membrane that is mechanically stable, electrically conductive, and non-Faradaic, which is used to prevent CNT release from and electrochemical degradation of the Faradaic CNT electrodes. A five-layer electrochemical filter: (1) conductive & protective CNT–PVDF, (2) Faradaic CNT electrode, (3) insulating PVDF separator, (4) Faradaic CNT electrode, and (5) conductive & protective CNT–PVDF is formed by mechanical press. At a total cell potential of 4 V, the sequential electrochemical reduction–oxidation process is able to reduce >99% of the influent nitrobenzene to aniline then oxidize >80% of the aniline to non-aromatic products (mostly carbon dioxide) in a single-pass (∼5 s hydraulic residence time). The mineralization current efficiency is ∼20%, total cell potential is completely (>99%) distributed to the two electrodes, and the energy requirement is ∼36000 kJ per mole of nitrobenzene degraded.

Development of Stretchable PZT/PDMS Nanocomposite Film with CNT Electrode

The piezoelectric composite film of ferroelectric PZT ceramic (PbZrxTi1-xO3) and polymer (PDMS, Polydimethylsiloxane) was prepared to improve the flexibility of piezoelectric material. The bar coating method was applied to fabricate flexible nanocomposite film with large surface area by low cost process. In the case of using metal electrode on the composite film, although there is no problem by bending process, the electrode is usually broken away from the film by stretching process. However, the well-attached, flexible CNT electrode on PZT/PDMS film improved flexibility, especially stretchability. PZT particles was usually settled down into polymer matrix due to gravity of the weighty particle, so to improve the dispersion of PZT powder in polymer matrix, small amount of additives (CNT powder, Carbon nanotube powder) was physically mixed with the matrix. By stretching the film, an output voltage of PZT(70 wt%)/PDMS with CNT (0.5 wt%) was measured.

Enhanced Power and Rechargeability of a Li−O2 Battery Based on a Hierarchical-Fibril CNT Electrode

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Electrodes modified with iron porphyrin and carbon nanotubes: application to CO2 reduction and mechanism of synergistic electrocatalysis

Electrodes modified with iron porphyrin and carbon nanotubes (FeP–CNTs) were prepared and used for CO2 electroreduction. The adsorption of iron porphyrin onto the multiwalled carbon nanotubes was characterized by scanning electron microscopy and ultraviolet and visible spectroscopy. The electrochemical properties of the modified electrodes for CO2 reduction were investigated by cyclic voltammetry and CO2 electrolysis. The FeP–CNT electrodes exhibited less negative cathode potential and higher reaction rate than the electrodes modified only with iron porphyrin or carbon nanotubes. A mechanism of the synergistic catalysis was proposed and studied by electrochemical impedance spectroscopy and electron paramagnetic resonance. The direct electron transfer between iron porphyrin and carbon nanotubes was examined. The current study shed light on the mechanism of synergistic catalysis between CNTs and metalloporphyrin, and the iron porphyrin–CNT-modified electrodes showed great potential in the efficient CO2 electroreduction.

High Sensitive Electrochemical Measurements of Neurotransmitters Using Multi-Wall Carbon Nano-Tube Electrodes

In this study, we have succeeded in detecting the neurotransmitters at nM level using multi-wall carbon nanotube (MWCNT) Bamboo and Hollow electrodes. CNT electrodes were created with mineral oil and graphite powder in order to press the electrode surface. In cyclic voltammetry measurements, dopamine was detected at 1 nM level using MWCNT Bamboo electrodes and serotonin at 1 nM level using MWCNT Hollow electrode. Moreover, in chronoamperometry measurement, dose-response relationships from 10 nM to 100 µM were observed in dopamine and serotonin. These results suggest that MWCNT bamboo and Hollow electrodes have a potential for the real-time measurement of neurotransmitters from living neurons.

Carbon Nanotube Planted on Ni‐Based Alloy in Microbial Fuel Cell

The improvement of electrode materials used in microbial fuel cell (MFC) technology for enhancing the power performance of MFCs has attracted more and more attention lately. In this study, an new electrode material with a carbon nanotube planted on an Ni‐based alloy substrate is applied to the MFC. Results show that a well‐synthesized, straight CNT electrode performs the best, with a high open circuit voltage of 0.82 V and a maximum power density of 2.31 W/m2. It is believed that this new kind of electrode will have a promising future in the technology of power generation from MFCs.

Charge stabilization by reaction center protein immobilized to carbon nanotubes functionalized by amine groups and poly(3‐thiophene acetic acid) conducting polymer

AbstractA large number of studies have indicated recently that photosynthetic reaction center proteins (RC) bind successfully to nanostructures and their functional activity is largely retained. The major goal of current research is to find the most efficient systems and conditions for the photoelectric energy conversion and for the stability of this bio‐nanocomposite. In our studies, we immobilized the RC protein on multiwalled carbon nanotubes (MWNT) through specific chemical binding to amine functional groups and through conducting polymer (poly(3‐thiophene acetic acid), PTAA). Both structural (TEM, AFM) and functional (absorption change and conductivity) measurements has shown that RCs could be bound effectively to functionalized CNTs. The kinetics of the light induced absorption change indicated that RCs were still active in the composite and there was an interaction between the protein cofactors and the CNTs. The light generated photocurrent was measured in an electrochemical cell with transparent CNT electrode designed specially for this experiment.

Electrochemical Double Layer Capacitance of Metallic and Semiconducting SWCNTs and Single Layer Graphene

The specific double layer capacitance that has been achieved with single wall carbon nanotubes (SWCNTs) is below that which is predicted from calculations based on the theoretical surface area of the CNTs and the intrinsic capacitance of the electrolyte. This paper investigates the specific capacitance of metallic (M-) and semiconducting (SC-) CNTs in order to determine if density of states (DOS)/quantum capacitance is a limiting factor in the capacitances achieved. In addition, a model system composed of a large-area single-layer graphene electrode on a nonconducting substrate has been used in order to put a lower bound on the ultimate double layer capacitance that should be achievable with CNT and graphene electrodes. We find that at the specific capacitances achieved here, the quantum capacitance of SWCNTs is not the limiting factor. In addition, the single-sided single-layer graphene electrode indicates that capacitances in excess of 550 F/g should be achievable.

Tailoring structural and electrochemical properties of vertical aligned carbon nanotubes on metal foil using scalable wet-chemical catalyst deposition

A scalable process for the synthesis of vertical aligned carbon nanotubes (VA-CNT) with precise control over structural properties is described. Direct growth on metal foils is achieved using a dip-coating step for the wet-chemical catalyst layer deposition and a subsequent chemical vapor deposition step for CNT growth. Two optimized Fe/Co and Fe/Mo 2-ethylhexanoate/2-propanol solutions are applied as precursors for the catalyst layer deposition and the influence of catalyst film thickness on resulting CNT film properties is investigated. The catalyst layer thickness can be controlled by the precursor salt concentration in the dip coating solution. By using a Fe and Co (2:3 ratio) catalyst, the CNT film homogeneity dramatically drops with lowered catalyst concentration due to a strong Ostwald ripening behavior of the catalyst layer. By using the FeMo (47:3 ratio) catalyst system, homogeneous VA-CNT films are obtained and the average CNT diameter can be adjusted in a range of 5–20nm by the catalyst layer thickness. The electrochemical properties of the CNT electrodes are investigated in a symmetric supercapacitor test cell. The lowest CNT diameters of 5nm results in a specific double layer capacitance up to 60Fg−1, while the density of the films directly correlates with its pore resistance.

Self-assembly of DNA on a gapped carbon nanotube

We perform molecular dynamics simulations to analyze the wrapping process of a single-stranded (ss) DNA around a gapped CNT immersed in a bath of water. We observe the formation of a stable molecular junction with the ssDNA adopting a helical or circular conformation around one CNT electrode and a linear conformation around the opposite electrode. We find that DNA undergoes several conformational changes during equilibration of the self-assembled molecular junction. This process would allow a higher yield of successful CNT-DNA interconnections, which constitutes a novel structure of interest in chemical and biological sensing at the single-molecule level.

Hydrothermal synthesis of MnO2/CNT nanocomposite with a CNT core/porous MnO2 sheath hierarchy architecture for supercapacitors

MnO2/carbon nanotube [CNT] nanocomposites with a CNT core/porous MnO2 sheath hierarchy architecture are synthesized by a simple hydrothermal treatment. X-ray diffraction and Raman spectroscopy analyses reveal that birnessite-type MnO2 is produced through the hydrothermal synthesis. Morphological characterization reveals that three-dimensional hierarchy architecture is built with a highly porous layer consisting of interconnected MnO2 nanoflakes uniformly coated on the CNT surface. The nanocomposite with a composition of 72 wt.% (K0.2MnO2·0.33 H2O)/28 wt.% CNT has a large specific surface area of 237.8 m2/g. Electrochemical properties of the CNT, the pure MnO2, and the MnO2/CNT nanocomposite electrodes are investigated by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The MnO2/CNT nanocomposite electrode exhibits much larger specific capacitance compared with both the CNT electrode and the pure MnO2 electrode and significantly improves rate capability compared to the pure MnO2 electrode. The superior supercapacitive performance of the MnO2/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.

PEDOT-CNT Composite Microelectrodes for Recording and Electrostimulation Applications: Fabrication, Morphology, and Electrical Properties.

Composites of carbon nanotubes and poly(3,4-ethylenedioxythiophene, PEDOT) and layers of PEDOT are deposited onto microelectrodes by electropolymerization of ethylenedioxythiophene in the presence of a suspension of carbon nanotubes and polystyrene sulfonate. Analysis by FIB and SEM demonstrates that CNT–PEDOT composites exhibit a porous morphology whereas PEDOT layers are more compact. Accordingly, capacitance and charge injection capacity of the composite material exceed those of pure PEDOT layers. In vitro cell culture experiments reveal excellent biocompatibility and adhesion of both PEDOT and PEDOT–CNT electrodes. Signals recorded from heart muscle cells demonstrate the high S/N ratio achievable with these electrodes. Long-term pulsing experiments confirm stability of charge injection capacity. In conclusion, a robust fabrication procedure for composite PEDOT–CNT electrodes is demonstrated and results show that these electrodes are well suited for stimulation and recording in cardiac and neurophysiological research.

Synthesis of MWNTs using thermal chemical vapor deposition for the application of a counter electrode for DSSCs

MWNTs (Multi-wall Carbon nanotubes) were grown using thermal CVD at a low temperature of 530 °C to be fabricated as a counter electrode of dye-sensitized solar cells (DSSCs). Ammonia gas and acetylene gas were introduced as reactive gas sources with 90 sccm and 108 sccm, respectively. DSSCs using CNT and Pt counter electrodes were fabricated using conventional method to compare its efficiencies. As a result, comparable electrical and optical properties were obtained for both electrodes. UV transmittance for the fabricated CNTs was higher than that for Pt electrode. Moreover, the cell efficiency of each DSSC was measured to be 0.99% and 0.85% using CNT and Pt counter electrodes, respectively. Therefore, the cell efficiency using the CNT counter electrode was comparable to that using the Pt counter electrode. Overall, it was found that directly grown MWNTs at low temperature are a highly promising material to be used as a counter electrode for DSSC.

Fabrication of free-standing carbon nanotube electrode arrays on a quartz wafer

For this paper, the fabrication of nano-electrodes by the synthesis of multi-wall carbon nanotubes (MWCNTs) has been investigated. MWCNTs were grown on a TiN coated quartz plate with Fe catalysts patterned by UV nano-imprint lithography (NIL). The proposed study is the realization of a simple, inexpensive and reproducible method to produce nano-scale electrode arrays in large areas. The patterns were defined by an array of circles 200 nm in diameter, and 500 nm in pitch. The nano-patterned master and Fe catalyst are observed with good pattern fidelity over a large area by atomic force microscope (AFM) and scanning electron microscopy (SEM). Among various synthesis methods for carbon nanotube growth, plasma-enhanced chemical-vapor deposition (PECVD) was used for the growth of vertically aligned multi-wall carbon nanotube arrays. Ammonia (NH 3) and acetylene (C 2H 2) were used as the etchant gases and the carbon source, respectively. The carbon nanotubes were vertically aligned in high density on a large area of the plain quartz substrates. High-resolution transmission electron microscopy analysis reveals that the synthesized CNTs are multi-walled with a bamboo-like structure. Patterned catalysts made it possible to allow the precise placement of individual CNT electrodes on the substrate. These electrodes have diameters ranging from 50 nm to 100 nm and lengths of about 300 nm. A field emission test using isolated CNTs on quartz plates showed the ability of CNTs as nano-electrodes. Bio-compatibility was also investigated by cell culturing on the fabricated CNTs/quartz template for potential bio-applications.

Preparation and Electrochemical Performance of CNT Electrode with Deposited Titanium Dioxide for Electrochemical Capacitor

To reduce polarization of electrochemical capacitor based on carbon nanotube, titanium oxide nanoparticles were deposited by ultrasound. The pore distribution of TiO2/CNT nanoparticle exhibited surface area of 341 m 2 g -1 when TiO2 content was 4 wt %, which was better than that of pristine CNT with surface area of 188 m 2 g -1 . The analyses indicated that titanium oxide (particle diameter < 20 nm) was deposited on the CNT surface. The electrochemical performance was evaluated by using cyclic voltammetry (CV), impedance measurement, and constant-current charge/discharge cycling techniques. The TiO2/CNT composite electrode showed relatively better electrochemical behaviors than CNT electrode by increasing the specific capacitance from 22 Fg -1 to 37 Fg -1 in 1 M H2SO4 solution. A symmetric cell assembled with the composite electrodes showed the specific capacitance value of 11 Fg -1 at a current loading of 0.5 mAcm -2 during initial cycling.

Advanced microwave-assisted production of hybrid electrodes for energy applications

Carbon nanotubes are one of the most prominent materials in research for creating electrodes for portable electronics. When coupled with metallic nanoparticles the performance of carbon nanotube electrodes can be dramatically improved. Microwave reduction is an extremely rapid method for producing carbon nanotube-metallic nanoparticle composites, however, this technique has so far been limited to carbon nanotube soot. An understanding of the microwave process and the interactions of metallic nanoparticles with carbon nanotubes have allowed us to extend this promising functionalisation route to pre-formed CNT electrode architectures. Nanoparticle reduction onto pre-formed architectures reduces metallic nanoparticle waste as particles are not formed where there is insufficient porosity for electrochemical processes. A two-fold increase in capacitive response, stable over 500 cycles, was observed for these composites, with a maximum capacitance of 300 F g−1 observed for a carbon Nanoweb electrode.

Nanoscale Networked Single-Walled Carbon-Nanotube Electrodes for Transparent Flexible Nanogenerators

We have investigated a nanoscale networked single-walled carbon-nanotube (SWCNT) electrode as a top cathode electrode of transparent flexible (TF) nanogenerators, so as to improve the energy scavenging performance and the system stability. The morphological effect and the electrical stability of SWCNT films for TF nanogenerators are investigated. It is found that SWCNT films have a nanosized network surface with pores, exceeding 100 nm in size, which favor ZnO nanorods contacting the CNT electrode, increasing the current generation and reducing the series resistance of the device for the effective transportation of piezoelectrically generated electrons from the nanogenerators. The nanogenerator using the CNT electrode with transparency 84% (at wavelength 550 nm) and a sheet resistance of 220 Ω/square had approximately 5 times the current density as with an indium−tin oxide-based nanogenerator. Moreover, the low variation (<100 Ω) in the resistance of CNT films during bending tests, and small change of the resistance of the film before and after the bending test (less than 1.1% on average), can support durable, stable, and reliable CNT-based TF nanogenerators.