Nanotube Hybrid Electrodes Research Articles

Engineering extracellular polymer substrates biosynthesis and carbon felt-carbon nanotube hybrid electrode to promote biofilm electroactivity and bioelectricity production

Organic-rich thin stillage is a significant by-product of the liquor brewing industry, and its direct release into the environment can cause severe water pollution. Microbial fuel cells (MFCs) offer the possibility for converting organic matters in thin stillage into clean electricity. However, limited biofilm formation and conductivity are crucial bottlenecks in restricting the power harvest of MFCs. Here, to efficiently harvest electricity power from thin stillage of liquor industry, we adopted a modular engineering strategy to increase biofilm formation and conductivity of Shewanella oneidensis via enhancing the component biosynthesis of extracellular polymer substrates (EPS) matrix, regulating intracellular c-di-GMP level, and constructing of artificial hybrid system. The results showed that the constructed CNTs@CF-EnBF2 hybrid system with low charge-transfer resistance enabled a maximum output power density of 576.77 mW/m2 in lactate-fed MFCs. Also, to evaluate the capability of harvesting electricity from actual wastewater, the CNTs@CF-EnBF2 system was employed to treat actual thin stillage, obtaining a maximum output power density of 495.86 mW/m2, 3.3-fold higher than the wild-type strain. Our research suggested that engineering and regulating EPS biosynthesis effectively promoted bioelectricity harvest, providing a green and sustainable treatment strategy for thin stillage.

Electrooxidation of Methanol on Pt, Ru, and Metal Oxides Nanoparticles Modified with Polyaniline-Carbon Nanotube Hybrid Electrodes

Electrooxidation of Methanol on Pt, Ru, and Metal Oxides Nanoparticles Modified with Polyaniline-Carbon Nanotube Hybrid Electrodes

3D Printed Thick Reduced Graphene Oxide: Manganese Oxide/Carbon Nanotube Hybrid Electrode with Highly Ordered Microstructures for Supercapacitors

AbstractHigh capacitance and good rate performance supercapacitors are needed to power sensors and miniaturized electrical devices. Thick electrodes are promising to increase the mass loading of active materials in supercapacitors, but the 3D geometries and microstructures in thick electrodes still hinder the development with high electron and ion exchange rate and accessible active sites. The scaffold 3D electrodes of reduced graphene oxide:manganese oxide/carbon nanotube (rGO:MnOx/CNT) are manufactured by material extrusion 3D printing (ME3DP), where the mass ratio of rGO to MnOx/CNT composites, thickness, and mass loading per unit area are controllable. The increasing amount of MnOx/CNT composites boosts the areal capacitance. Although the rate capability decays fast with the increasing of MnOx/CNT, it remains stable at different thicknesses (1.2, 1.6, and 2 mm). 2 mm thick rGO:MnOx/CNT (weight ratio 5:3) electrode exhibits an area capacitance of 302.13 mF cm−2 at a current density of 0.5 mA cm−2, due to the highly ordered rGO networks. Compared to the casted electrodes, the microstructures in the 3D printed electrode contribute to lower resistances for the charge and ion transportation.

In-situ construction of 3D hierarchical MoS2/CoS2@TiO2 nanotube hybrid electrodes with superior capacitive performance toward water treatment

Recently, the rational design and construction of graphene-like layered transition-metal disulfides (TMDs) with chemical and physical superiorities to act as capacitive desalination (CDI) electrodes for water purification have attracted increasing interest worldwide. Herein, an advanced self-supported MoS2/CoS2@TiO2 nanotube (TNT) hybrid electrode was grown on a TNT scaffold by a hydrothermal process-assisted in-situ growth strategy, and an asymmetric CDI cell was constructed with the as-fabricated MoS2/CoS2@TNT and commercial AC electrodes as cathode and anode, respectively. Benefiting from the effective structural feature (i.e., fully open nanosheet-assembled flowers and hierarchical pore alignment) and synergy effect of metal-like CoS2, state-of-the-art MoS2 and TNTs with an efficient charge “superhighway”, the MoS2/CoS2@TNT electrode achieved a significantly high gravimetric Na+ adsorption capacity of 44.22 mg g−1 in a 600 mg L−1 NaCl solution at 1.2 V. Moreover, the hybrid electrode possessed excellent regeneration performance with a capacity retention of nearly 100% even after 20 cycles. Most notably, such electrode also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification.

Influence of La3+induced defects on MnO2–carbon nanotube hybrid electrodes for supercapacitors

A nanohybrid containing 2 mol% La3+doped MnO2and carbon nanotubes produced hydrothermally exhibits a specific capacitance of ∼1530 F g−1at 1 A g−1and a 92% capacity retention after 5000 cycles showing its potential as electrode for supercapacitors.

Facile preparation of polyaniline-carbon nanotube hybrid electrodes and dependence of their supercapacitive properties on degree of carboxylation of carbon nanotubes

This paper reports on the preparation of polyaniline-carbon nanotube (PANi-CNT) hybrid electrodes via a facile electro-co-deposition method. In the process, carboxylated CNTs, which serve as counter anions in the electrodes, are incorporated into PANi. Supercapacitive properties of PANi-CNT hybrid electrodes are observed to depend on the degree of carboxylation of CNTs. Electrochemical measurements show two key results. First, the incorporation of CNTs observably improves the supercapacitive properties of PANi electrodes. Second, the CNTs with higher degree of carboxylation result in further improvement in supercapacitive properties of the hybrid electrodes. The former observation is attributed to the high electrical conductivity and large surface area of CNTs, which improve the electrical conductivities of the hybrids and facilitate the dispersion of PANi. The latter is in line with the fact that more CNTs are incorporated into the hybrids due to higher degree of carboxylation. The PANi-CNT electrodes prepared by CNTs with higher degree of carboxylation demonstrate remarkable supercapacitive performances, including high specific capacitance of 578.2 F g−1 and good rate performance. They also have superior cycling stability, showing 88.2% of capacitance retention after 10,000 cycles.

Strongly coupled sulfur nanoparticles on graphene-carbon nanotube hybrid electrode for multifunctional sodium and aluminium ion storage

The practical utility of multiwalled carbon nanotubes in sodium and aluminium ion batteries are limited due to its low interlayer spacing of 0.34 nm. Herein, we have developed a simple approach of enhancing the interlayer spacing of multiwalled carbon nanotubes by incorporating sulfur nanoparticles into graphene-multiwalled carbon nanotube (GCNT) structure. This proof of concept is realised from its excellent specific capacity and cyclic stability for the first time in sodium and aluminium ion batteries. GCNT/S as the anode in sodium ion battery exhibits a specific capacity of about 510 mA h g−1 at a current density of 50 mA g−1 with a cyclic stability of 2500 cycles which results in about 42% enhancement in specific capacity when compared to GCNT. GCNT/S as cathode in aluminium ion battery shows a specific capacity of 507 mA h g−1 at a current density of 50 mA g−1 and a stable cyclic stability for 600 cycles. This is about 7.2 times enhancement in specific capacity when compared to GCNT. The highly durable nature is due to the small sulfur particles which offer low volume expansion and the GCNT structure acts as a buffer matrix for controlling the volume expansion. Our study provides a new and a simple strategy to enhance the specific capacity and cyclic stability of multiwalled carbon nanotubes for sodium ion batteries and aluminium ion batteries which can be a promising approach for other cost-effective battery technologies as well.

Controlling the electrochemical performance of β-Ni(OH)2/carbon nanotube hybrid electrodes for supercapacitor applications by La doping: A systematic investigation

Controlling the electrochemical performance of electrodes for application in supercapacitor has received large research interest in the recent years. Here we report the facile synthesis of a Ni(OH)2 and carbon nanotubes based nanohybrid electrode and control its electrochemical performance for application in supercapacitor by La doping. A systematic investigation of the influence of a number of electrochemical parameters of measurement on the electrode properties is also presented. Structural and morphological analyses show formation of hexagonal nanoparticles (∼35 nm) well attached on the walls of carbon nanotubes (CNT) while elemental analysis confirms the success of La doping. The nanohybrid sample doped with 1 mol% La (with respect to Ni) appears to be the best performing electrode exhibiting specific capacitance of 2731 F/g at 1 A/g, energy density of 25 Wh/kg at power density of ∼1 kW/kg and capacity retention of 84% even after 5000 cycles which are higher than previously reported values for Ni(OH)2 based electrodes and also the first of its kind in which β-Ni(OH)2 has been combined with CNT and doped with La. Increase in the specific surface area as well as electrical conductivity of Ni(OH)2 by incorporation of CNT and La dopants are the main reasons for the improved performance of the 1 mol% La doped composite whereas formation of insulating La(OH)3 is responsible for the inferior performance of electrodes containing more than 1 mol% La. The charge storage mechanism has been found to be governed by both capacitive and diffusion processes at high scan rates but dominated by only diffusion process at low scan rates.

Paper-like TiO2/graphene-carbon nanotube hybrid electrode with high mass loading: Toward high-performance lithium ion battery

One key challenge in flexible batteries lies in the development of deformable/flexible electrode with high active materials mass loading and good electronic conductivity. Herein, we report such a paper-like TiO2/graphene-carbon nanotube hybrid electrode by a facile vacuum filtration approach. In this electrode, titania nanoparticles with uniform size (9 nm) and carbon nanotubes are embedded into graphene sheet homogeneously, forming a peculiar 3D conducting network. This feature ensures 1) a high TiO2 mass loading (77.3 wt %, 2.93 mg cm−2); 2) good electric conductivity (∼1000 S m−1); and 3) good flexibility. Benefiting from these, the electrode delivers a high specific capacity (214 mAh g−1), excellent rate capability, and up to 700 cycles stability at a high rate of 1000 mA g−1. This fabrication strategy demonstrates great practical potential and opens up new idea for high-performance self-supported electrode design.

Rational design of sandwiched polyaniline nanotube/layered graphene/polyaniline nanotube papers for high-volumetric supercapacitors

The adjustment and optimization of graphene-based electrode structures are crucial to achieve both high volumetric and gravimetric capacitances for portable energy storage devices. Structures of reduced graphene oxide (RGO)-polyaniline (PANI) nanotube hybrid electrodes were facilely regulated and rationally designed by in-situ MnO2 nanowire-templated polymerization. Typically, two different architectures of RGO-PANI composites were obtained by controlling the content of MnO2 nanowires in graphene papers. The assembled symmetric device based on the porous RGO-PANI nanotube papers (0.18mgcm−2, 20.0μm), showed a high gravimetric specific capacitance of 956Fg−1 (against the mass of single electrode) at 1Ag−1 with excellent rate capability of 74.3% from 1Ag−1 to 10Ag−1. In addition, another symmetric device based on the sandwiched polyaniline nanotube/layered graphene/polyaniline nanotube papers (0.80mgcm−2, 4.02μm), provided an ultrahigh volumetric capacitance (722Fcm−3 at 2Acm−3) and a decent gravimetric capacitance (363Fg−1 at 1Ag−1) calculated against the volume and mass of single electrode. With these excellent volumetric and gravimetric capacitive performances, this polyaniline nanotube/layered graphene/polyaniline nanotube supercapacitor holds the potential for high-volumetric and gravimetric-performance energy storages.

Fabrication, characteristics and electrical model of an ionic polymer metal-carbon nanotube composite

We develop an ionic polymer metal-carbon nanotube composite (IPMCC) actuator composed of a multiwalled carbon nanotube (MWCNT)/Nafion membrane sandwiched between two hybrid electrodes, composed of palladium, platinum and MWCNTs. The surface morphology and cross-sectional structure of the metal-carbon nanotube hybrid electrode were observed using scanning electron microscopy (SEM). SEM investigation indicated that the MWCNT layer can adhere very well with the platinum–palladium metal electrode, fill the cracks in the metal surface, and prevent the oxidation of nanoscale platinum particles. These observations show that the surface resistance of the total electrode is retained and the stability of electrode property is maintained. The displacement, blocking force and nonlinear current versus voltage (V–I) characteristics were measured. Compared with an ionic polymer metal composite (IPMC), the IPMCC shows a more stable displacement and blocking force under 1, 1.2 and 2 V at 0.1 Hz, and 2.34–3.29 times higher effective air-operating time under 3 V at 0.1 Hz. It can be observed from the V–I characteristics that the change in shape becomes significant at amplitudes higher than 1.2 V. An equivalent circuit is used to model the nonlinear behavior of the IPMCC, in which the leakage current was taken into account and analyzed. The values of the components in the circuit are estimated and electrical behavior is simulated by using the Pspice software. Compared with the model with no consideration of the leakage current, the simulations obtained by the model considering leakage current showed better agreement with the experimental results. The impressive leakage current (20 mA), which is successfully simulated by the proposed model with the nonlinear circuit, is shown to play an important role in the total current.

Design and synthesis of MWNTs-TiO2 nanotube hybrid electrode and its supercapacitance performance

A new two-step method is successfully developed for the synthesis of MWNTs-TiO2 nanotube hybrid electrodes. The resulting (3-aminopropyl)triethoxysilane (APS) film was chemisorbed on the surface of TiO2 nanotubes. TiO2 nanotubes surface modified by 5, 10, and 20 mg ml−1 APS ethanol solution can determine the morphology of MWNTs-TiO2 nanotube electrodes. The morphology and surface composition were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) techniques. The zeta potential results confirm that MWNTs were deposited on APS-TiO2 nanotubes by the electrical attractive force. The electrochemical performances were evaluated by using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge measurements. The MWNTs-TiO2 nanotube hybrid electrodes (5, 10, and 20 mg ml−1 APS) exhibited a high specific capacitance of 3.5, 4.4, and 3.4 mF cm−2 in 1 M H2SO4 aqueous solution at a charge–discharge current density of 0.1 mA cm−2, respectively. Cyclic voltammetric studies indicated that the electrode has excellent stability even after 1000 consecutive CV cycles. Moreover, the galvanostatic charge–discharge experiments conducted on the MWNTs-TiO2 nanotube hybrid electrodes (10 mg ml−1 APS) exhibited long-term cycle stability, retaining about 75% specific capacitance after 1000 cycles, which suggests that it has potential as an electrode material for high-performance electrochemical supercapacitors.

Electrochemical flexible supercapacitor based on manganese dioxide-titanium nitride nanotube hybrid

The manganese dioxide-titanium nitride (MnO2-TiN) nanotube hybrid has been designed to improve its electroactivity and conductivity for a supercapacitor application. Titanium nitride (TiN) nanotube array was prepared by an anodization process of titanium in ethylene glycol (EG) solution containing ammonium fluoride, subsequent calcination process in an air atmosphere, and final nitridation process in an ammonia atmosphere. Electroactive MnO2 was then loaded into well-aligned TiN nanotubes to form MnO2-TiN nanotube hybrid with well-designed shell layer of MnO2 through a controlled cyclic voltammetry electrodeposition process, which was directly supported on ultra thin and supple titanium foil to establish a bendable electrode. The morphology and microstructure of MnO2-TiN nanotube hybrid were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical capacitance was investigated by cyclic voltammetry and galvanostatic charge/discharge measurements. The villiform MnO2 thin shell layer was fully covered on TiN nanotube walls to form a coaxial heterogeneous structure. Superior electrical conductivity and accessible nanochannels of TiN contributed to a high capacitance performance of MnO2. The specific capacitance of MnO2-TiN was determined to be 853.3Fg−1 (or 213.2mFcm−2) at a current density of 1.0Ag−1 (or 0.25mAcm−2). All-solid-state flexible supercapacitor was constructed using two symmetric film electrodes of MnO2-TiN nanotube hybrid and a polyvinyl alcohol gel electrolyte of KOH-KI-EG. The volume specific capacitance, energy and power density were determined to be 4.01Fcm−3, 1.81mWhcm−3 and 32.8mWcm−3 at a high potential window of 1.8V and a current density of 2.0mAcm−2. Such MnO2-TiN nanotube hybrid electrode material exhibited effective energy storage in flexible supercapacitor application.

Preparation and capacitance performance of polyaniline/titanium nitride nanotube hybrid

A polyaniline/titanium nitride (PANI/TiN) nanotube hybrid was prepared and used for an electrochemical supercapacitor application. Firstly, the well-aligned TiN nanotube array was prepared by anodization of titanium foil and subsequent nitridation through ammonia annealing. Then, PANI was deposited into TiN nanotube through the electrochemical polymerization process. The obtained PANI/TiN nanotube hybrid had an ordered porous structure. A high specific capacitance of 1,066 F g−1 was obtained at the charge–discharge current density of 1 A g−1 when only the mass of PANI was considered. The specific capacitance can even achieve 864 F g−1 at 10 A g−1 and still keep 93 % of the initial capacity after 200 cycles. An aqueous supercapacitor, consisting of two symmetric PANI/TiN nanotube hybrid electrodes and 1.0 M H2SO4 electrolyte solution, showed the specific capacitance of 194.8 F g−1, energy density of 9.74 Wh kg−1, and power density of 0.3 kW kg−1.

Electrochemical capacitance performance of polypyrrole–titania nanotube hybrid

In this study, the polypyrrole–titania nanotube hybrid has been synthesized for an electrochemical supercapacitor application. The highly ordered and independent titania nanotube array is fabricated by an electro-oxidation of titanium sheet through an electrochemical anodization process in an aqueous solution containing ammonium fluoride, phosphoric acid and ethylene glycol. The polypyrrole–titania nanotube hybrid is then prepared by electrodepositing the conducting polypyrrole into well-aligned titania nanotubes through a normal pulse voltammetry deposition process in an organic acetonitrile solution containing pyrrole monomer and lithium perchlorate. The morphology and microstructure of polypyrrole–titania nanotube hybrid are characterized by scanning electron microscopy, infrared spectroscopy and Raman spectroscopy. The electrochemical capacitance performance is determined by cyclic voltammetry and charge/discharge measurement. It indicates that the polypyrrole film can been uniformly deposited on both surfaces of titania nanotube walls, demonstrating a heterogeneous coaxial nanotube structure. The specific capacitance of polypyrrole–titania nanotube hybrid is determined to be 179 F g−1 based on the polypyrrole mass. The specific energy and specific power are 7.8 Wh kg−1 and 2.8 kW kg−1 at a constant charge/discharge current of 1.85 mA cm−2, respectively. The retained specific capacitance still keeps 85% of the initial capacity even after 200 cycle numbers. This result demonstrates the satisfying stability and durability of PPy–TiO2 nanotube hybrid electrode in a cyclic charge/discharge process. Such a composite electrode material with highly ordered and coaxial nanotube hybrid structure can contribute high energy storage for supercapacitor applications.

Interface Architecture Determined Electrocatalytic Activity of Pt on Vertically Oriented TiO2 Nanotubes

The surface atomic structure and chemical state of Pt is consequential in a variety of surface-intensive devices. Herein we present the direct interrelationship between the growth scheme of Pt films, the resulting atomic and electronic structure of Pt species, and the consequent activity for methanol electro-oxidation in Pt/TiO(2) nanotube hybrid electrodes. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements were performed to relate the observed electrocatalytic activity to the oxidation state and the atomic structure of the deposited Pt species. The atomic structure as well as the oxidation state of the deposited Pt was found to depend on the pretreatment of the TiO(2) nanotube surfaces with electrodeposited Cu. Pt growth through Cu replacement increases Pt dispersion, and a separation of surface Pt atoms beyond a threshold distance from the TiO(2) substrate renders them metallic, rather than cationic. The increased dispersion and the metallic character of Pt results in strongly enhanced electrocatalytic activity toward methanol oxidation. This study points to a general phenomenon whereby the growth scheme and the substrate-to-surface-Pt distance dictates the chemical state of the surface Pt atoms, and thereby, the performance of Pt-based surface-intensive devices.

Kinetics of oxygen reduction on gold nanoparticle/multi-walled carbon nanotube hybrid electrodes in acid media

In this paper, the electrochemical reduction of oxygen has been studied on gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) modified glassy carbon (GC) electrodes in 0.5 M H 2SO 4 using the rotating disk electrode (RDE) method. The AuNP/MWCNT catalysts were prepared by chemical deposition of AuNPs onto MWCNTs spontaneously grafted with 4-nitrophenyl groups. The composite electrode was characterised by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The oxygen reduction behaviour of these electrodes was compared with that of a bulk gold electrode. The AuNP/MWCNT catalyst showed a pronounced electrocatalytic activity towards O 2 reduction in acid media. The half-wave potential of O 2 reduction on the AuNP/MWCNT catalyst shifted ca 80 mV to more positive potentials as compared to that of a polished Au electrode. The kinetic parameters of oxygen reduction were determined and the specific activity of the hybrid electrode was slightly higher than that of the bulk Au electrode.