Carbon Nanotube-based Electrodes Research Articles

Extraction and electrochemical sensing of anthocyanins in berry fruits by use of carbon nanotube-based electrode

Extraction and electrochemical sensing of anthocyanins in berry fruits by use of carbon nanotube-based electrode

Optimizing cell voltage dependence on size of carbon nanotube-based electrodes in Na-ion and K-ion batteries.

Sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) are gaining extensive attention as promising alternatives to lithium-ion batteries owing to their superior energy density and cost-effectiveness. However, the larger ionic radius of Na+ and K+ ions in comparison to Li+ ions poses a challenge in designing anode materials characterized by enduring structures and elevated voltage to facilitate the efficacy of high-performance NIBs and KIBs. Carbon nanomaterials, particularly carbon nanotubes (CNTs), have emerged as a potential candidate in anode materials. Herein, we used density functional theory calculations to study the cell voltage of CNTs in relation to Na-ion and K-ion storage as a function of CNT size. The adsorption energy profiles of both Na+@CNT and K+@CNT systems exhibit a descending trend concomitant with the increase in the CNT diameter, where Na+/K+ ion primarily prefers to adsorb in the interior wall of CNT. Conversely, the cell voltage for the Na and K system gradually increases with the increasing diameter of CNT, which can be attributed to the stronger electrostatic interaction validated by energy decomposition calculation. The voltage of Na-ion adsorbed on the inter wall of (10,10) CNT attains 1.29 V, close to the previously theoretical voltage of Li-ion on the same CNT (1.35 V), while the much lower voltage pertaining to K-ion adsorption on the inter wall of (10,10) CNT just stands at 0.59 V, suggesting the viability of CNT-based electrode for NIBs but not for KIBs. These findings lay a solid foundation for delineating the interrelationship between the voltage properties of CNT as prospective anode material and their structural characteristics, thereby expanding the application of CNT-based optoelectronic devices.

An Ionic Liquid-Based Stretchable Sensor for Measuring Normal and Shear Force.

Soft and stretchable force sensors are widely used for health monitoring, robotics, prosthetics, and other applications. Soft force sensors with the capability of measuring both normal and shear force could offer even greater functionality and provide more information, particularly in the field of biomechanics. In this work, a new solid-state force sensor is proposed that can measure both normal and shear forces at the same time. The soft and stretchable sensor was fabricated using an ionic liquid (IL)/polymer network. Two separate IL-based polymer membranes were used to detect normal and shear forces. Sensor architecture and electrical wiring for normal, shear, and combined sensing were developed, and various material compositions for different sensor layers were investigated to find the combination that could achieve the optimum sensor performance. A basic material formulation for carbon nanotube-based electrodes, the IL/polymer network, and polymeric insulation layers was proposed. To configure a combined (normal and shear) sensor, separate sensors for normal and shear deformations were first designed and investigated. Later, a combined sensor was fabricated using a mold via screen printing, photocuring, and thermal curing. The combined sensor was evaluated under different force conditions. The results show that the sensor can reliably measure normal and shear forces. Moreover, the findings demonstrate a way to successfully modulate the sensitivity for normal and shear sensing by varying the material composition or geometric configuration, which provides flexibility for application-specific designs.

Review of Flexible Supercapacitors Using Carbon Nanotube-Based Electrodes

Carbon nanotube (CNT)-based electrodes in flexible supercapacitors have received significant attention in recent years. Carbon nanotube fiber fabrics (CNT-FF) have emerged as promising materials due to their high surface area, excellent conductivity, and mechanical strength. Researchers have attempted to improve the energy density and rate performance of CNT-FF supercapacitor electrodes through various strategies, such as functionalization with conductive materials like MnO2 nanoparticles and/or incorporation of graphene into them. In addition, the utilization of CNTs in combination with thin metal film electrodes has also gained widespread attention. Research has focused on enhancing electrochemical performance through functionalizing CNTs with conductive materials such as graphene and metal nanoparticles, or by controlling their morphology. This review paper will discuss the recent developments in supercapacitor technology utilizing carbon nanotube-based electrodes, including CNT fiber fabrics and CNTs on thin metal film electrodes. Various strategies employed for improving energy storage performance and the strengths and weaknesses of these strategies will be discussed. Finally, the paper will conclude with a discussion on the challenges that need to be addressed in order to realize the full potential of carbon nanotube-based electrodes in supercapacitor technology.

Non-Covalent Integration of a [FeFe]-Hydrogenase Mimic to Multiwalled Carbon Nanotubes for Electrocatalytic Hydrogen Evolution.

Surface integration of molecular catalysts inspired from the active sites of hydrogenase enzymes represents a promising route towards developing noble metal-free and sustainable technologies for H2 production. Efficient and stable catalyst anchoring is a key aspect to enable this approach. Herein, we report the preparation and electrochemical characterization of an original diironhexacarbonyl complex including two pyrene groups per catalytic unit in order to allow for its smooth integration, through π-interactions, onto multiwalled carbon nanotube-based electrodes. In this configuration, the grafted catalyst could reach turnover numbers for H2 production (TONH2 ) of up to 4±2×103 within 20 h of bulk electrolysis, operating at neutral pH. Post operando analysis of catalyst functionalized electrodes revealed the degradation of the catalytic unit occurred via loss of the iron carbonyl units, while the anchoring groups and most part of the ligand remained attached onto multiwalled carbon nanotubes.

Maximizing Energy Density of Nanostructured Electrochemical Capacitors: From Proof of Concept to Reliable Manufacturing

Currently, portable energy storage devices are lacking in the overall performance characteristics needed to meet desired energy and power density performance demands. Furthermore, these performance demands for long-lasting energy storage devices for portable electronics continue to constantly increase. Batteries remain the main source of portable energy storage, but they generally lack the pulsed-power delivery capability required by many applications, as well as have limited cycle life. Thus, improvements in devices that show a high operational cycle life in addition to delivering high energy and power densities are extremely desirable over a wide range of physical sizes, footprints, and power delivery capabilities. Conventional electrostatic capacitors provide some of these benefits compared to batteries, including high power density and extended cycle life, but are lacking in the energy density capability required to replace batteries in many applications.Electrochemically-based double-layer capacitors (EDLCs) or ultracapacitors offer a promising solution to bridging the gap between maintaining the high-power density capability of electrostatic capacitors while providing a path to improving the energy density to be comparable to batteries –significantly broadening their applicability. An EDLC’s power density and energy density are based on the highly reversible surface charge adsorption-based mechanism of energy storage. This provides benefits in terms of high frequency responses as well as providing a route to supply power for longer duration pulses. Additionally, since the stored capacity is based on the surface charge adsorption-based energy storage, it provides an essentially indefinite lifespan as long as the materials do not degrade. However, current EDLC technologies still provide significantly lower energy density than is available from batteries. This energy density gap must be narrowed if the EDLCs are going to make further inroads toward replacing batteries.The capacitance and energy density are driven by the electrode’s available solution-accessible surface area. Thus, our approach to increasing the energy density of electrochemical capacitors is through the development of carbon nanotube-based electrode structures with a precise, highly controlled and ordered nanostructured porosity. To further improve power and energy density, these electrode structures are used in combination with an ionic liquid electrolyte with high voltage window, thus providing an increased operating voltage. While traditional electrode materials are generally comprised of randomly ordered porous structures, we have developed electrodes with an adjustable and highly controlled pore structure that provide very high surface area. These electrodes are produced using a nanotemplated approach that allows for preparation of high surface area aligned and vertically oriented carbon nanotube (CNT)-based electrodes. The templated approach has the added benefit of a achieving a greater areal CNT density than available in traditional carpet-grown CNT forests as well as providing more uniform and controllable CNT outer and inner diameters. The ability to control these dimensions allows for tailoring the electrode geometry for a specific electrolyte.Ionic liquids are becoming increasingly popular in a variety of applications as a result of their unique properties and highly tailorable chemistry. In electrochemical applications, their large voltage stability window, low vapor pressure, excellent thermal stability at temperatures above most organic solvents’ boiling points, and lower temperature conductivity make them an excellent electrolyte choice. Ionic liquids are ideal for use in higher temperature electronics applications, especially in small-scale microelectronics formats where confined spaces make efficient heat removal very difficult. By making use of ionic liquid electrolytes and optimizing the interaction of the electrolyte with our templated CNT electrodes, we have developed an energy storage technology with high-energy density and high-power density.In this talk, we will discuss the challenges and solutions to scaling up the fabrication and testing of reproducible, nanostructured electrodes from 3.14 cm2 or smaller single-sided lab cells to multiple 200 cm2 electrodes on both sides of an aluminum current collector. We will discuss the electrode fabrication scale-up and performance validation from small coin or disc cells tested in a glove box to larger area sealed pouch cells with integration of an optimized ionic liquid electrolyte. We discuss cell fabrication challenges and solutions including verifying the performance of the electrodes as they are scaled up, and the cell fabrication including ensuring the electrode and separator are reliably wetted with the ionic liquid electrolyte. The challenges of optimizing the practical tradeoff of electrode active depth and minimizing the current collector thickness as we move the electrode and overall cell design to a fully packaged cell while maintaining the optimized electrochemical performance characteristics will be discussed.[DISTRIBUTION STATEMENT A. Approved for public release; Distribution is unlimited 412TW-PA-21154]

Polyimide-free liquid crystal devices with carbon nanotube-based electrodes

A novel type of polyimide-free liquid crystal (LC) device has been fabricated using layer-by-layer (LBL) deposition of carbon nanotube-based electrodes and in situ formation of self-aligning amphiphilic graft copolymer layer. The LBL-processed organic electrodes showed high transparency comparable to indium tin oxide (ITO) and the self-aligned layer of amphiphilic graft copolymer on organic electrodes provided a stable vertical alignment of LCs. Moreover, the proposed LC device resulted in voltage-dependent driving characteristics suitable for display application. This functional organic electrode layer has potential for application in a flexible display to replace conventional ITO electrode and polyimide alignment layer.

Comparative Study of Nanocarbon-Based Flexible Multifunctional Composite Electrodes.

Although nanocarbon-based nanofillers have been widely used to improve the energy-storing and sensing functions of porous materials, the comparison of the effects of different nanocarbon-based fillers on the capacitive and flexible sensing properties of nanocarbon-based porous sponge composite supercapacitor electrodes by combining a carbon nanotube, graphene, and graphene oxide with porous sponge is incomplete. The specific capacitance of carbon nanotube-based electrodes is 20.1 F/g. The specific capacitance of graphene-based electrodes is 26.7 F/g. The specific capacitance of graphene oxide-based electrodes is 78.1 F/g, and the capacity retention rate is 92.99% under 20 000 charge–discharge cycles. Under a bending load of 180°, the capacitance retention rate of graphene oxide sponge composite electrodes is 67.46%, which indicates that the prepared electrodes of supercapacitor have the advantages of high capacitance and good flexibility at the same time. To demonstrate their performance, an array of three graphene oxide supercapacitors in series was constructed, which could light up a red light-emitting diode (LED). The tensile strength of carbon nanotube sponge composite electrodes is 0.267 MPa, and the tensile linearity is 0.0169. The experimental results show that graphene oxide-based sponge composite supercapacitor electrodes have the best capacitance performance and carbon nanotube sponge composites have the most potential as a flexible sensor.

Water Freezes at Near-Zero Temperatures Using Carbon Nanotube-Based Electrodes under Static Electric Fields.

Although static electric fields have been effective in controlling ice nucleation, the highest freezing temperature (Tf) of water that can be achieved in an electric field (E) is still uncertain. We performed a systematic study of the effect of an electric field on water freezing by varying the thickness of a dielectric layer and the voltage across it in an electrowetting system. Results show that Tf first increases sharply with E and then reaches saturation at -3.5 °C after a critical value E of 6 × 106 V/m. Using classical heterogeneous nucleation theory, it is revealed that this behavior is due to saturation in the contact angle of the ice embryo with the underlying substrate. Finally, we show that it is possible to overcome this freezing saturation by controlling the uniformity of the electric field using carbon nanotubes. We achieve a Tf of -0.6 °C using carbon nanotube-based electrodes with an E of 3 × 107 V/m. This work sheds new light on the control of ice nucleation and has the potential to impact many applications ranging from food freezing to ice production.

Paper-Based Electrochemical Sensors Using Paper as a Scaffold to Create Porous Carbon Nanotube Electrodes.

Paper-based sensors and assays have evolved rapidly due to the conversion of paper-based microfluidics, functional paper coatings, and new electrical and optical readout techniques. Nanomaterials have gained substantial attraction as key components in paper-based sensors, as they can be coated or printed relatively easily on paper to locally control the device functionality. Here, we report a new combination of methods to fabricate carbon nanotube-based (CNT) electrodes for paper-based electrochemical sensors using a combination of laser cutting, drop-casting, and origami. We applied this process to a range of filter papers with different porosities and used their differences in three-dimensional cellulose networks to study the influence of the cellulose scaffold on the final CNT network and the resulting electrochemical detection of glucose. We found that an optimal porosity exists, which balances the benefits of surface enhancement and electrical connectivity within the cellulose scaffold of the paper-based device and demonstrates a cost-effective process for the fabrication of device arrays.

Carbon nanotube-based electrodes for flexible supercapacitors

Flexible supercapacitors (SCs) have attracted increasing attention as the power supply unit for portable/wearable electronics. Carbon nanotubes (CNTs) are promising candidate materials for flexible SC electrodes because of their outstanding mechanical property, high electrical conductivity, large surface area, and functionability. CNTs can assemble into various macroscopic materials with different dimensions. In this review, flexible CNT assemblies including 1D fibers, 2D films, and 3D aerogels and sponges are introduced with a focus on the design strategies and fabrication techniques. The recent developments and state-of-the-art applications of such structures as electrodes in flexible SCs are summarized based on device configurations including sandwiched, interdigital in-plane, and cable-type configurations. The flexible CNT-based electrodes have shown great advantages in bendability, stretchability and/or compressibility, as well as a long cycle lifetime. The current challenges and future research opportunities in this field are also discussed.

A novel copper(ıı) phthalocyanine-modified multiwalled carbon nanotube-based electrode for sensitive electrochemical detection of bisphenol A

A novel copper(ii) phthalocyanine (CuPc)-modified multiwalled carbon nanotube-based electrode was prepared for the sensitive electrochemical detection of bisphenol A, by the modification of a pencil graphite electrode via the adsorption method.

High energy flexible supercapacitors formed via bottom-up infilling of gel electrolytes into thick porous electrodes

Formation of thick, high energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes. Incomplete infilling results in a low capacitance and poor mechanical properties. Here we report a bottom-up infilling method to overcome these challenges. Electrodes up to 500 μm thick, formed from multi-walled carbon nanotubes and a composite of poly(3,4-ethylenedioxythiophene), polystyrene sulfonate and multi-walled carbon nanotubes are successfully infilled with a polyvinyl alcohol/phosphoric acid gel electrolyte. The exceptional mechanical properties of the multi-walled carbon nanotube-based electrode enable it to be rolled into a radius of curvature as small as 0.5 mm without cracking and retain 95% of its initial capacitance after 5000 bending cycles. The areal capacitance of our 500 μm thick poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, multi-walled carbon nanotube-based flexible solid supercapacitor is 2662 mF cm–2 at 2 mV s–1, at least five times greater than current flexible supercapacitors.

(Invited) Enzymatic Reduction of Oxygen for the Development of Biofuel Cells and Hybrid Fuel Cells

The need for clean methods of producing electricity for medical applications has stimulated the emergence of biofuel cells as a new generation of fuel cells. This subcategory of fuel cells, mainly rely on redox enzymes, which are very efficient and selective biocatalysts that can advantageously replace rare and expensive platinum-based catalysts in classic fuel cell devices. Enzymes provide exceptional specificities towards their substrates, thus enabling the assembly of both the anode and cathode electrodes of a biofuel cell without the need for membranes [1,2]. Recent advances in the design of biocathodes based on electrically wired enzymes onto carbon nanotube coatings for the reduction of oxygen will be reported. In particular, different strategies for achieving a controlled orientation of laccase or bilirubin oxidase on carbon nanotube-based electrodes will be presented [3,4]. In particular, a new generation of flexible buckypaper electrodes was produced by using linear polynorbornene polymers containing multiple pyrene groups as crosslinker. Robust buckypapers using copolymers containing both pyrene and activated ester groups for cross-linking and tethering, respectively, will be applied to the covalent binding of redox groups or enzymes [5]. Moreover, buckypapers based on bilirubin oxidase and FAD-dependent glucose dehydrogenase, were developed for the direct electron transfer and the mediated electron transfer, respectively. The resulting biofuel cell based on the O2/glucose system, provides the highest volumetric power reported until now, namely 24.07 mW cm-3 [6]. The design of hybrid biofuel cells will be also reported. In particular, cubic Pd nanoparticles were synthesized and evaluated for the catalytic oxygen reduction. These nanoparticles were employed for the development of an air-breathing cathode modified by multiwalled carbon nanotubes. The latter was combined with a phenanthrolinequinone/glucose dehydrogenase-based anode to form a complete glucose/O2 hybrid biofuel cell delivering a maximal power output of 184 ± 21 µW cm-2 [7]. Finally, an innovative approach based on the electrical wiring of enzymes in solution by redox glyconanoparticles resulting from the self-assembly of bio-sourced block copolymers will be presented [8]. We demonstrate the self-assembly, characterization and bioelectrocatalysis of redox-active cyclodextrin-coated nanoparticles. The nanoparticles with host-guest functionality are easy to assemble and permit entrapment of hydrophobic redox molecules in aqueous solution. Bis-pyrene-ABTS encapsulated nanoparticles (diameter: 195 nm) were used as electron shuttles between electrode and bilirubin oxidase. Enhanced current densities for enzymatic O2 reduction are observed with the redox nanoparticle system compared to equivalent bioelectrode cells with dissolved mediator [9]. Acknowledgements This work is partly supported by the French National Research Agency in the framework of the "Investissements d’avenir” program Glyco@Alps (ANR-15-IDEX-02), the LabEx ARCANE (ANR-11-LABX-0003-01), and Institut Carnot PolyNat (ANR-16-CARN-0025-01). References Cosnier, A. Le Goff, M. Holzinger, Electrochem. Commun. 38 19-23 (2014)Cosnier A. J. Gross, A. Le Goff, M. Holzinger, J. Power Sources 325 252-263 (2016)Lalaoui, R. David, H. Jamet, M. Holzinger, A. Le Goff, S. Cosnier. ACS Catal., 6 4259-4264 (2016)Lalaoui, M. Holzinger, A. Le Goff, S. Cosnier. Chem. Eur. J., 22 10494-10500 (2016)J. Gross, M. P. Robin, Y. Nedellec, R. K. O’Reilly, D. Shan, S. Cosnier, Carbon, 107 542-547 (2016)Gross, X. Chen, F. Giroud, C. Abreu, A. Le Goff, M. Holzinger, S. Cosnier. ACS Catalysis, 7 (2017) 4408-4416.Faggion Junior, R. Haddad, F. Giroud, M. Holzinger, C. Eduardo Maduro de Campos, J. J. S. Acuña, J. B. Domingos, S. Cosnier. Nanoscale, 8 10433-10440 (2016)J. Gross, R. Haddad, C. Travelet, E. Reynaud, P. Audebert, R. Borsali, S. Cosnier. Langmuir, 32 11939-11945 (2016). J. Gross, X. Chen, F. Giroud, C. Abreu, A. Le Goff, M. Holzinger, S. Cosnier, J. Am. Chem. Soc. accepted.

Highly conductive and transparent carbon nanotube-based electrodes for ultrathin and stretchable organic solar cells**Project supported by the National Basic Research Program of China (Grant No. 2012CB932302), the National Natural Science Foundation of China (Grant Nos. 11634014, 51172271, 51372269, and 51472264), and the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant No. XDA09040202).

In this work, we have presented a freestanding and flexible CNT-based film with sheet resistance of 60 Ω/□ and transmittance of 82% treated by nitric acid and chloroauric acid in sequence. Based on modified CNT film as a transparent electrode, we have demonstrated an ultrathin, flexible organic solar cell (OSC) fabricated on 2.5-μm PET substrate. The efficiency of OSC, combined with a composite film of poly (3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) as an active layer and with a thin layer of methanol soluble biuret inserted between the photoactive layer and the cathode, can be up to 2.74% which is approximate to that of the reference solar cell fabricated with ITO-coated glass (2.93%). Incorporating the as-fabricated ITO-free OSC with pre-stretched elastomer, 50% compressive deformation can apply to the solar cells. The results show that the as-prepared CNT-based hybrid film with outstanding electrical and optical properties could serve as a promising transparent electrode for low cost, flexible and stretchable OSCs, which will broaden the applications of OSC and generate more solar power than it now does.

Structural and Electrical Characterization of Solution-Processed Electrodes for Piezoelectric Polymer Film Sensors

Solution-processable graphene and carbon nanotube-based electrode materials were used here to provide electrodes on flexible piezoelectric polyvinylidenefluoride sensors. Piezoelectric sensitivity measurements, image-based analysis, adhesion tests, and sheet resistance measurements were applied to these printable sensors to rigorously analyze their performance and structure. The printable sensors showed electrical performance similar to metallized sensors, whereas the adhesion of the solution-processed materials to the substrate is not as high as that of the evaporated metal films. This also affects the measured sensor sensitivity values. The measurements based on optical images were found to be a promising method to capture detailed information about the electrode surface structure.

Direct Electron Transfer between a Site-Specific Pyrene-Modified Laccase and Carbon Nanotube/Gold Nanoparticle Supramolecular Assemblies for Bioelectrocatalytic Dioxygen Reduction

Strategies to maximize direct electron transfer (DET) between redox enzymes and electrodes include the oriented immobilization of enzymes onto an electroactive surface. Here, we present a strategy for achieving a controlled orientation of a fungal laccase on carbon nanotube-based electrodes. A homogeneous population of pyrene-modified laccase is obtained via the reductive amination of a unique surface accessible lysine residue engineered near the T1 copper center of the enzyme. Immobilization of the site-specific functionalized enzyme is achieved either via π-stacking of pyrene on pristine CNT electrodes or through pyrene/β-cyclodextrin host guest interactions on β-cyclodextrin-modified gold nanoparticles (β-CD-AuNPs). Contrasting with unmodified and nonspecifically modified (pyrene-NHS) laccase-electrodes, an efficient DET is obtained at these nanostructured assemblies. Modeling the direct bioelectrocatalysis of dioxygen reduction reveals a heterogeneity in ET rates on MWCNT electrodes wheras β-CD-AuNPs ...

Bridging the performance gap between electric double-layer capacitors and batteries with high-energy/high-power carbon nanotube-based electrodes

The energy/power density of EDLCs containing high surface area carbon nanotube-based electrodes bridges the performance gap between conventional EDLCs and batteries.

Fabrication and characterization of a multi-walled carbon nanotube-based counter electrode for dye-sensitized solar cells

Fabrication and characterization of a multi-walled carbon nanotube-based counter electrode for dye-sensitized solar cells

High Active Surface Area and Durable Multi-Wall Carbon Nanotube-Based Electrodes for the Bromine Reactions in H2-Br2 Fuel Cells

The commercially available carbon gas diffusion electrodes (GDEs) with low specific active area but high permeability are often used as Br2 electrodes in the H2-Br2 fuel cell. In order to increase the specific active surface area of the existing carbon GDEs, a study was conducted to grow multi-wall carbon nanotubes (MWCNTs) directly on the surface of carbon fibers of a commercial carbon electrode. Experimental fixtures were developed to promote the electrodeposition of cobalt and the growth of MWCNTs on the carbon GDE. The MWCNT growth across the carbon electrode was confirmed by SEM. The carbon GDE with a dense distribution of short MWCNTs evaluated in a H2-Br2 fuel cell has 29 times higher active surface area than a plain carbon electrode and was found to be highly durable at an electrolyte flow rate of 10 cc/min/cm2. The performance of the best single layer MWCNT GDE measured at 80% discharge voltage efficiency in a H2-Br2 fuel cell was found to be 16% higher compared to that obtained using three layers of plain carbon electrodes. Finally, the preliminary material cost analysis has shown that the MWCNT-based carbon electrodes offer significant cost advantages over the plain carbon electrodes.