Multi-walled Carbon Nanotube Electrodes Research Articles

Hydrazine Electrooxidation with PdNPs and Its Application for a Hybrid Self-Powered Sensor and N2H4 Decontamination

We report the use of cubic palladium nanoparticles (PdNPs) for the catalytic oxidation of hydrazine for use in a hybrid self-powered N2H4 sensor. Multiwalled carbon nanotube electrodes were prepared and functionalized with PdNPs by drop casting, confining the colloidal suspension of nanoparticles into the 3D-carbon nanotube matrix support. Electron microscopy and electrochemical characterization experiments were performed and confirmed the presence, uniform distribution, and accessibility of the metallic particles. Cubic PdNPs with an average diameter of 22.5 nm were investigated for their catalytic hydrazine oxidation capacities at varying hydrazine concentrations. Application of the PdNPs for electrochemical detection of hydrazine was demonstrated using a hybrid fuel cell setup with the PdNPs-based electrode as the anode and a bilirubin oxidase bioelectrode as the oxygen-reducing cathode. The self-powered hybrid sensor exhibits linear hydrazine detection from 0.02 to 4.00 mmol L−1 and a sensitivity of 53 ± 3 mW cm−2 mmol−1 L. When using the air-breathing cathode setup, the fuel cell could deliver a maximal current and power output of 1.23 ± 0.08 mA cm−2 and 267 ± 10 μW cm−2 respectively. PdNPs supported on carbon nanotube electrodes are thus promising catalytic materials for self-powered sensing and hybrid fuel cell applications via consumption of environmental contaminants.

Enzymatic versus Electrocatalytic Oxidation of NADH at Carbon‐Nanotube Electrodes Modified with Glucose Dehydrogenases: Application in a Bucky‐Paper‐Based Glucose Enzymatic Fuel Cell

AbstractIn this work, we have designed and compared functionalized carbon‐nanotube‐based electrodes for the electrocatalytic oxidation of NADH. We show that oxidation of NADH at neutral pH values can be performed by pristine multi‐walled carbon nanotubes (MWCNT) and directly wired diaphorase or ruthenium phenanthrolinequinone molecular catalysts. Glucose dehydrogenase was immobilized on these MWCNT electrodes by an activated‐ester‐modified pyrene linker. Glucose‐oxidizing bioelectrodes were compared and integrated into a bucky‐paper‐based glucose/O2 biofuel cell, using a bilirubin‐oxidase‐modified bucky‐paper cathode. The best configuration was obtained using a NADH‐oxidizing molecular catalyst at the anode. The biofuel cell exhibits an open‐circuit voltage of 0.62 V and delivers a power output of 0.47 mW cm−2.

Self-assembly of one-dimensional nitrogen-doped hollow carbon nanoparticle chains derived from zinc hexacyanoferrate coordination polymer for lithium-ion capacitors

One-dimensional nitrogen-doped hollow carbon nanoparticle chains (CNCs) featuring bimodal pore size distribution were obtained by direct thermal pyrolysis of a three-dimensional cyanide-bridged coordination polymer precursor (zinc hexacyanoferrate) without the need for additional carbon, nitrogen, and catalyst sources. Nitrogen doping turned out to play the key role in the formation of mesoporous compartment layers and structural defects in the CNCs. Small mesopores in the walls provided high surface area for charge storage and allowed the migration of electrolyte into the compartments. Large mesopores in the hollow compartments accommodated electrolyte for easy transport of lithium ions. The commercial multiwalled carbon nanotube (CNT) electrode stored lithium ions primarily through the intercalation process, while the CNC electrode stored lithium ions through both the intercalation and adsorption processes. Thus, the CNC electrode exhibited superior supercapacitive performance than the CNT electrode. The CNC electrode with low internal resistance could deliver a high capacitance of 680Fg−1 at 1Ag−1 in the working potential range of 0.01-3.50V vs. Li/Li+, which was much better than the commercial CNT electrode (252Fg−1).

Electropolymerization and energy storage of poly[Ni(salphen)]/MWCNT composite materials for supercapacitors

ABSTRACTNi(salphen), a Schiff base ligand compound, was synthesized and electropolymerized on multiwalled carbon nanotube (MWCNT) electrodes in an acetonitrile solution via the pulse potentiostatic method and then applied as a supercapacitor electrode material. The polymerization mode was investigated through methyl replacement in the para‐position of phenyl rings in the Ni(salphen) monomer, and it was found that the Ni(salphen) monomers would polymerize by the generation of CC bonds between the phenyl rings in the para‐position of the phenol moieties. The optimum condition for polymerization was evaluated, and when the polymerization time was 8 min, poly[Ni(salphen)] exhibited a specific capacitance up to 200 F g−1 at a current density of 0.1 mA cm−2, and the capacitance remains at 164 F g−1 at 20 mA cm−2. The energy density of the poly[Ni(salphen)] electrode reached 40 Wh kg−1 at 0.1 mA cm−2, about eight times greater than for a pure MWCNT electrode. Electrochemical performances were investigated, and the composites showed good redox property and ion transfer capability. This work showed that Ni(salphen) may be an attractive material in supercapacitors© 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44464.

Highly sensitive voltammetric and impedimetric sensor based on an ionic liquid/cobalt hexacyanoferrate nanoparticle modified multi-walled carbon nanotubes electrode for diclofenac analysis

ABSTRACTThis paper describes the development of 1-methyl-3-butylimidazolium chloride ionic liquid/cobalt hexacyanoferrate nanoparticle modified multi-walled carbon nanotubes nanocomposite paste electrode for the electrocatalytic and adsorptive stripping voltammetric and impedimetric determination of diclofenac (DIC) in real samples. The nanocomposite was prepared by a simple chemical method and was characterised by scanning electron microscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. Also, the electrochemical behaviours of the modified electrode and the electrocatalytic oxidation of DIC were investigated in detail by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques. The kinetic parameters such as electron transfer coefficient, and apparent rate constant for the redox reaction between DIC and the modified electrode were also determined using electrochemical approaches. It was found that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of DIC, and under the optimised conditions, the linear response range and detection limit were found to be 1.0–100.0 and 0.3 μM, respectively using the differential pulse voltammetry method. The proposed method was applied for the sensitive and selective determination of diclofenac in the urine samples and pharmaceutical formulations with satisfactory results.

Carbon-based flexible micro-supercapacitor fabrication via mask-free ambient micro-plasma-jet etching

We demonstrate a general and facile method to fabricate all-solid-state flexible micro-supercapacitors (MSCs) with micropatterned multi-walled carbon nanotube (MWNT) electrodes via mask-free micro-plasma-jet etching in ambient conditions. Localized pulsed plasma jet etches the MWNTs rapidly and produces the interdigitated electrode patterns by scanning. This mask-free patterning technique is easy operated, cost-effective, readily scalable, free from photoresist contamination and applicable to various kinds of carbon-based materials. A solid-state polyvinyl alcohol-H3PO4 gel electrolyte is introduced to realize an all-solid-state flexible MSC assembly. Cyclic voltammetry measurements exhibit the expected electrical double layer behavior. The fabricated MSC with twelve interdigitated electrodes exhibits a stack capacitance of 2.02 F cm−3 at a scan rate of 10 mV s−1. Moreover, the MSC shows stable performance under repeated bending, with retention of 98.2% of capacitance after 600 bending cycles. Furthermore, both the output voltage and the total capacitance of the MSC could be controlled via the serial or parallel connection.

5,5-Dithiobis(2-nitrobenzoic acid) pyrene derivative-carbon nanotube electrodes for NADH electrooxidation and oriented immobilization of multicopper oxidases for the development of glucose/O2 biofuel cells

We report the functionalization of multi-walled carbon nanotubes (MWCNTs) electrodes by a bifunctional nitroaromatic molecule accomplished via π-π interactions of a pyrene derivative. DTNB (5,5′-dithiobis(2-nitrobenzoic acid)) has the particularity to possess both electroactivable nitro groups and negatively charged carboxylic groups. The integration of the DTNB-modified MWCNTs was evaluated for different bioelectrocatalytic systems. The immobilized DTNB-based electrodes showed electrocatalytic activity toward the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) with low overpotential of −0.09V vs Ag/AgCl at neutral pH. Glucose dehydrogenase was successfully immobilized at the surface of DTNB-based electrodes and, in the presence of NAD+, the resulting bioelectrode achieved efficient glucose oxidation with high current densities of 2.03mAcm−2. On the other hand, the aromatic structure and the negatively charged nature of the DTNB provoked orientation of both laccase and bilirubin oxidase onto the electrode, which enhanced their ability to undergo a direct electron transfer for oxygen reduction. Due to the proper orientation, low overpotentials were obtained (ca. 0.6V vs Ag/AgCl) and high electrocatalytic currents of about 3.5mAcm−2 were recorded at neutral pH in O2 saturated conditions for bilirubin oxidase electrodes. The combination of these bioanodes and bilirubin oxidase biocathodes provided glucose/O2 enzymatic biofuel cells (EBFC) exhibiting an open-circuit potential of 0.640V, with an associated maximum current density of 2.10mAcm−2. Moreover, the fuel cell delivered a maximum power density of 0.50mWcm−2 at 0.36 V.

Understanding the Critical Role of Carbon Nanotube Surface Chemistry Towards the Electrochemical Behavior in Li-O2 Cells

The aprotic lithium-oxygen (Li-O2) battery stands alone owing to its highest theoretical specific energy (3.5 kWh/kg) of all battery chemistries.1 The electrochemistry of metallic lithium and gaseous oxygen in the negative and positive electrodes respectively gives the ideal reversible reaction (2Li + O2 ↔ Li2O2, E=2.96 V vs Li/Li+). However, translating the promise of Li-O2 batteries into reality has been stifled by the lack of thorough understanding of the Li2O2 formation and decomposition processes. Additional well-documented challenges relating to electrolyte and electrode instability, low round-trip efficiency, poor reversibility and cycleability, and lower-than-theoretical capacity will need to be tackled before practical Li-O2can be realized. Of note, to achieve the high energy densities desired, it is critical that lightweight materials be used for the positive electrode. Carbon, is the natural choice owing to its numerous advantages including abundance, cost, porosity, conductivity, and weight. Moreover, carbon has been found to be sufficiently active with low kinetic overpotentials for the formation and decomposition of Li2O2 the use of ‘catalysts’ may not be warranted.2 However, several studies have shown side product formation including lithium carbonate and lithium carboxylates originating from carbon-based electrodes, prompting researchers to explore non-carbon electrode materials. The use of non-carbon materials has been met with mixed results with McCloskey et al. demonstrating similar to worse reversibility of nanoporous Au and TiC in comparison to carbon-based electrodes.1 Therefore, provided the management and mitigation of issues relating to instability, carbon remains a promising electrode material. However, surprisingly the influence of the surface characteristics of carbon towards the behavior of Li-O2cells has not been thoroughly investigated. Carbon surfaces contain surface functional groups and vary in morphology with respect to edges, defects and degree of graphitization all of which can have influence on the electrochemical behavior. Here, we highlight the critical role of carbon nanotube surface chemistry towards the behavior of lithium-oxygen (Li-O2) cells by systematically modifying the surface morphology and surface functional groups of multi-walled carbon nanotubes (MWNT). MWNTs are ideal for this study due to their ease of surface modification and ability to fabricate binder-free electrodes. Our study utilizes a variety of techniques including scanning electron microscopy (SEM), x-ray diffraction (XRD), rotating ring disk electrode (RRDE), temperature programmed desorption (TPD) and in situ quantitative gas analysis to understand the differences in discharge capacity, recharge overpotential and reversibility (Figure 1). As seen in Figure 1 discharge capacity is dependent on the degree of disorder of the MWNT surfaces which is found to affect the discharge mechanism related to the adsorption affinity of O2 and soluble Li2O2 intermediates with the MWNT surface. Moreover, the recharge process is found to be dependent on the preceding discharge process, where O-functional groups acts as a promoter in the formation of amorphous Li2O2 which is in intimate contact with the MWNT electrode, enabling the low Li2O2 decomposition potential of 3.0-3.2 V. Our findings have broader implications that can be extended to include the general role of carbon towards capacity, recharge overpotential, and reversibility. Figure 1 – (a) Galvanostatic discharge-recharge profiles performed with 0.5M LiClO4 in tetraglyme at current density 50 mA/g of multi-walled carbon nanotubes with defective edges decorated with O-functional groups (Oxidized CNT), defective CNTs with O-functional groups removed through Ar annealing at 900oC (Oxidized CNT-900), as-received carbon nanotubes (pristine CNT), and lastly pristine CNTs annealed at 2800oC (graphitized CNT) (b) capacity normalized profiles showing trend in recharge overpotential (c) Raman (Id/Ig) ratio versus discharge capacity (d-g) Scanning electron micrographs (SEM) of discharge product morphology following discharge to 2 V. Figure 1

Graphene oxide-multiwalled carbon nanotubes composite as an anode for lithium ion batteries

AbstractNowadays reduced graphene oxide (rGO) is regarded as a highly interesting material which is appropriate for possible applications in electrochemistry, especially in lithium-ion batteries (LIBs). Several methods were proposed for the preparation of rGO-based electrodes, resulting in high-capacity LIBs anodes. However, the mechanism of lithium storage in rGO and related materials is still not well understood. In this work we focused on the proposed mechanism of favorable bonding sites induced by additional functionalities attached to the graphene planes. This mechanism might increase the capacity of electrodes. In order to verify this hypothesis the composite of non-reduced graphene oxide (GO) with multiwalled carbon nanotubes electrodes was fabricated. Electrochemical properties of GO composite anodes were studied in comparison with similarly prepared electrodes based on rGO. This allowed us to estimate the impact of functional groups on the reversible capacity changes. As a result, it was shown that oxygen containing functional groups of GO do not create, in noticeable way, additional active sites for the electrochemical reactions of lithium storage, contrary to what has been postulated previously.

Photocatalytic Activeties of Copper Oxides/Carbon Nanotube Composites

Cu2O has the advantage of absorbing visible light unlike the practical photocatalyst, TiO2. To use most of Cu2O as a photo catalyst, increase of the surface area and electro-conductivity are considered to be promising approach. For this purpose, our studies have focused on the composition of Cu2O with Multi-Walled Carbon Nano Tube (MW-CNT). In our recent studies, we demonstrated that the various morphologies of copper oxides can be electrochemically deposited on a MW-CNT film-modified electrode(*). In this paper, the photocatalytic activities of these samples are compared. CNT thin film that thickness was less than 17.5 μm was prepared on a transparent electrode by electrophoretic electrodeposition with 17.5 V at 35 ℃. And Cu2O was deposited by electrochemical deposition method, using a three electrode cell: an ITO substrate as anode electrode, Pt wire as counter electrode, and Ag/AgCl as reference electrode, at various potentials and deposition charge. The plating bath was 0.4 M CuSO4, and NaOH is used to adjust the pH to 11. Scanning Electron Microscope (SEM) and Energy Dispersive x-ray Spectroscopy (EDS) was used to observe the morphology and composition of the samples, respectively. The crystallinity and crystal structure were examined by XRD method. Photocatalytic activity was tested by photocurrent response and charge transfer resistance evaluated by electrochemical impedance spectroscopy. The results of SEM and EDS demonstrate that copper oxide was deposited over the entire surface of CNT when the deposition charge and potential is 250 mC and -0.4 V, respectively. At the lower potential, copper oxide becomes aggregated and CNT is partially exposed. In addition, CNT was also partially exposed with less and more electric charge. The copper oxide is considered to peal off by its excess deposition. For all samples, the diffraction peaks in the XRD patterns match well with those of Cu2O and Cu crystals. With 250 mC, the ratio of Cu is appeared to increase at the more negative potential than -0.4 V. At -0.4 V, the ratio of Cu2O increase with increasing the deposition charge up to 250 mC. Charge transfer resistance of the hydrogen evolution reaction was evaluated by EIS measurement at 0 V vs SHE. As a result, the sample prepared at -0.4 V with both 250 mC and 500 mC, charge transfer resistance become minimal. In addition, the charge transfer resistance also increases at the more negative potential than -0.4 V when the deposition charge is 250 mC. Based on the above-mentioned results, the ratio of Cu2O versus Cu is considered to be important to decrease the charge transfer resistance. Photocatalyc acitivity was evaluated using the cell illuminated by 50 W Xe arc lamp with a calibrated AM 1.5 solar light simulator (class A). Upon the illumination of 100 mW/cm2 light, the largest photocurrent was observed under the condition with 250 mC at -0.4 V. As discussed above, the difference between 250 mC and 500 mC is mainly the morphology of Cu2O. Thus, based on the fact that the carbon materials are known to adsorb light, the condition Cu2O was deposited over the entire surface of CNT is important to show the better performance. The details will be discussed on the day. *“Preparation of Cu2O/ CNT Composite Photocatalysts using Electrodeposition Methods,” Yuki Saito, Kensei Takahashi, Mariko Matsunaga, The 83th Annual Meeting of Japan Electrochemical Society, Osaka, Japan, Mar.2016.

Removal of Ni(II) Using Multi-walled Carbon Nanotubes Electrodes: Relation Between Operating Parameters and Capacitive Deionization Performance

Experiments were conducted to develop a statistical model which describes the relation between operating parameters and capacitive deionization performance for the removal of Ni(II) ion using multi-walled carbon nanotubes (MCNT) electrodes. The \(R^{2}\) value of 0.84 in regression analysis represents that the statistical model reproduced the data well. The factors for pH (\(a = 0.242\)), applied voltage (\(b = 0.619\)) and retention time (\(c = 0.504\)) in the statistical model revealed the significance of each parameter. The effect of initial Ni(II) concentration is best described by Langmuir isotherm. Kinetic study showed that pseudo-first-order equation fitted the data well. Modeling the performance with operating parameters for the removal of Ni(II) using MCNT electrodes is feasible, and results can be used for practical engineering applications.

Metal-free polymer/MWCNT composite fiber as an efficient counter electrode in fiber shape dye-sensitized solar cells

Highly aligned multiwall carbon nanotubes (MWCNT) as fiber were modified with a conducting polymer via a simple dip coating method. Modified MWCNT exhibited admirable improvement in electrocatalytic activity for the reduction of tri-iodide in dye sensitized solar cells. Scanning electron microscopy images confirm the successful deposition of polymer on MWCNT. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy studies were carried out to investigate the inner mechanism for the charge transfer behaviour. Results from bare and modified electrodes revealed that the MWCNT/(poly (3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composite electrode is much better at catalysing the redox couple compared to the pristine fiber electrode. The photoelectric conversion efficiency of 5.03% for the modified MWCNT electrodes was comparable with that of the conventional Pt-based electrode. The scientific results of this study reveal that MWCNT/PEDOT:PSS may be a better choice for the replacement of cost intensive electrode materials such as platinum. Good performance even after bending up to 90° and in-series connection to enhance the output voltage were also successfully achieved, highlighting the practical application of this novel device.

Freestanding Aligned Multi-walled Carbon Nanotubes for Supercapacitor Devices

We report on the synthesis and electrochemical properties of multi-walled carbon nanotubes (MWCNTs) for supercapacitor devices. Freestanding vertically-aligned MWCNTs and MWCNT powder were grown concomitantly in a one-step chemical vapour deposition process. Samples were characterized by scanning and transmission electron microscopies and Fourier transform infrared and Raman spectroscopies. At similar film thicknesses and surface areas, the freestanding MWCNT electrodes showed higher electrochemical capacitance and gravimetric specific energy and power than the randomly-packed nanoparticle-based electrodes. This suggests that more ordered electrode film architectures facilitate faster electron and ion transport during the charge–discharge processes. Energy storage and supply or supercapacitor devices made from these materials could bridge the gap between rechargeable batteries and conventional high-power electrostatic capacitors.

Microwave-assisted synthesis of sponge-like carbon nanotube arrays and their application in organic transistor devices

Multi wall carbon nanotube (MWNT) sponges were synthesized with a domestic microwave oven. The procedure involves a mixture of graphite and cobalt acetate powders enclosed in an evacuated quartz ampoule exposed to microwave irradiation. Maximum yield of MWNT sponges of about 2.2 cm2 is obtained within 12 min of microwave exposure with individual MWNTs having diameters in the 20–50 nm range. Employing MWNT obtained from synthesized sponges we construct two types of organic transistors: a field effect OFET device in which the channel material is a MEH-PPV semiconducting polymer blended with the synthesized MWNT, and a light emitting transistor OLET device in which electrodes are prepared with MWNT, the channel material being the MEH-PPV polymer alone. These devices are characterized with I–V measurements. For the OFET device the Ion/Ioff figure is considerably improved by using the polymer/MWNT blend as channel. In the OLET device, I–V characteristics with MWNT electrodes are comparable to those obtained when ITO electrodes are used.

Electrochemical properties of multi-walled carbon nanotubes treated with nitric acid for a supercapacitor electrode

The capacitances of partially oxidized multi-walled carbon nanotubes (MWNTs) electrodes treated with nitric acid were investigated for use as the electrode materials of electric double-layer capacitors (EDLCs). The oxidized MWNTs had a much higher specific surface area, pore volume and average pore width than those of pristine MWNTs. Moreover, functional groups such as hydroxyl, carbonyl and carboxyl groups were observed on the surfaces of oxidized MWNTs. The specific capacitance of the oxidized MWNTs after 3h a nitric acid treatment was 68.8F/g in the highest oxidized state, more than 7 times greater than that of the pristine MWNTs. Further, the capacitance trends apparently follow the change of the zeta potentials, not the surface areas, indicating that this trend depends on the adsorption of electrolytes as compared to the migration path structure. Further, the oxidized MWNT electrode materials showed good long-term stability during repeated cycles and no decay for more than 1000 cycles.

Ionic Liquid-Derived Imidazolium Cation Linkers for the Layer-by-Layer Assembly of Polyoxometalate-MWCNT Composite Electrodes with High Power Capability.

Imidazolium cations derived from ionic liquids were demonstrated as effective linker molecules for the layer-by-layer (LbL) deposition of polyoxometalates (POMs) to increase the charge storage of multi-walled carbon nanotube (MWCNT) electrodes. MWCNTs modified with GeMo12O40(4-) (GeMo12) via an imidazolium cation linker demonstrated highly reversible redox reactions and a capacitance of 84 F cm(-3), close to 4 times larger than bare CNT. Compared to CNT-GeMo12 composites fabricated with a conventional polyelectrolyte linker poly(diallyldimethylammonium chloride), (PDDA), the imidazolium cations resulted in lower POM loading, but higher conductivity and in turn superior performance at fast charge-discharge conditions. A polymerized imidazolium linker (PIL) was also synthesized based on the ethyl-vinyl-imidazolium monomer. CNT-GeMo12 composites fabricated with this PIL achieved high POM loading comparable to PDDA, while still maintaining the good conductivity and high rate capabilities shown by the monomer imidazolium units. The high conductivity imparted by the PIL is especially valuable for the fabrication of multilayer POM composites. Dual-layer GeMo12 O40(4-)-SiMo12O40(4-) (GeMo12-SiMo12) electrodes built with this PIL demonstrated a combined contribution of the individual POMs resulting in a capacitance of 191 F cm(-3), over nine times larger than bare MWCNT. The PIL dual layer composites also maintained 72% of this capacitance at a fast rate of 2 V s(-1), compared to just over 50% retention for similar electrodes fabricated with PDDA.

Simultaneous recording of the action potential and its whole-cell associated ion current on NG108-15 cells cultured over a MWCNT electrode

It is well known that, in excitable cells, the dynamics of the ion currents (Ii) is extremely important to determine both the magnitude and time course of an action potential (Ap). To observe these two processes simultaneously, we cultured NG108-15 cells over a multi-walled carbon nanotubes electrode (MWCNTe) surface and arranged a two independent Patch Clamp system configuration (Bi-Patch Clamp). The first system was used in the voltage or current clamp mode, using a glass micropipette as an electrode. The second system was modified to connect the MWCNTe to virtual ground. While the Ap was recorded through the micropipette electrode, the MWCNTe was used to measure the underlying whole-cell current. This configuration allowed us to record both the membrane voltage (Vm) and the current changes simultaneously. Images acquired by atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicate that cultured cells developed a complex network of neurites, which served to establish the necessary close contact and strong adhesion to the MWCNTe surface. These features were a key factor to obtain the recording of the whole-cell Ii with a high signal to noise ratio (SNR). The experimental results were satisfactorily reproduced by a theoretical model developed to simulate the proposed system. Besides the contribution to a better understanding of the fundamental mechanisms involved in cell communication, the developed method could be useful in cell physiology studies, pharmacology and diseases diagnosis.

Tin Selenide – Multi-Walled Carbon Nanotubes Hybrid Anodes for High Performance Lithium-Ion Batteries

A simple dry physical grinding and solvent mixing approach was used to prepare tin selenide – multiwalled carbon nanotube (MWCNT) hybrid as an anode material for high performance lithium ion batteries (LIBs). The pure tin selenide and their composites with carbon black or graphene oxides were previously reported, however no other groups have reported tin selenide/MWCNT composite as anode materials for LIBs. The new hybrid had superior electrochemical cycling performance with higher reversible (lithiation) capacity of 882 to 651mAhg−1 over 50 cycles compared to pure tin selenide (602 to 58 mAhg−1) or pure MWCNT (339 to 171 mAhg−1) electrodes. The enhanced performance of the tin selenide/MWCNT hybrid was attributed to various factors including alleviation of volume change of tin selenide during lithiation/delithiation by nanoscale network of MWCNT which helped to preserve the electrical connectivity between active particles, reversible decomposition of tin selenide, lithiation/delithiation of MWCNTs and conductive electronic transport pathways provided by MWCNTs.

Encapsulated, High-Performance, Stretchable Array of Stacked Planar Micro-Supercapacitors as Waterproof Wearable Energy Storage Devices.

We report the fabrication of an encapsulated, high-performance, stretchable array of stacked planar micro-supercapacitors (MSCs) as a wearable energy storage device for waterproof applications. A pair of planar all-solid-state MSCs with spray-coated multiwalled carbon nanotube electrodes and a drop-cast UV-patternable ion-gel electrolyte was fabricated on a polyethylene terephthalate film using serial connection to increase the operation voltage of the MSC. Additionally, multiple MSCs could be vertically stacked with parallel connections to increase both the total capacitance and the areal capacitance owing to the use of a solid-state patterned electrolyte. The overall device of five parallel-connected stacked MSCs, a microlight-emitting diode (μ-LED), and a switch was encapsulated in thin Ecoflex film so that the capacitance remained at 82% of its initial value even after 4 d in water; the μ-LED was lit without noticeable decrease in brightness under deformation including bending and stretching. Furthermore, an Ecoflex encapsulated oximeter wound around a finger was operated using the stored energy of the MSC array attached to the hand (even in water) to give information on arterial pulse rate and oxygen saturation in the blood. This study suggests potential applications of our encapsulated MSC array in wearable energy storage devices especially in water.

The Influence of Carbon Cathode in Rechargeable Li-O2 Batteries Based on a LiNO3-Litfsi/DMSO Electrolytes

Rechargeable Li-O2 batteries have been considered one of the most promising candidates as the power source for electric vehicles due to their extremely high energy density [1,2]. In spite of this great prospect, there are still many obstacles such as the degradation of the electrode, huge polarization, low energy efficiency and poor reversibility [3]. Thus, developing stable and effective cathode catalysts is important as they can be utilized to decrease the polarization and increase the reversibility. Carbon materials are known to advantageous air electrodes for Li-O2 batteries with nonaqueous electrolyte due to their good conductivity and site of reversible electrode reaction. However, the influence of carbon materials on electrochemical performance in Li-O2 batteries is not clear. Furthermore, recent research focused on selecting a combination of lithium salt and electrolytes by challenge in improving the electrochemical performance of Li-O2 batteries. In this study, we select four different kinds of carbon materials such as multi-walled carbon nanotubes (MWCNTs), CMK-3, Graphene nanosheets (GNSs), and KB as air electrodes and further examine their electrochemical performance in Li-O2 batteries with 0.7 M LiNO3-0.3 M LiTFSI/DMSO electrolytes. We find that the Li-O2 cell with a MWCNTs electrode in a 0.7 M LiNO3-0.3 M LiTFSI/ DMSO electrolyte demonstrates good rate performance and cycle stability comparison with other carbon electrodes. The result shows that the Li-O2 cell based on MWCNTs electrodes with a cut-off capacity of 1000 mAg-1 at 500 mAg-1 can undergo around 90 cycles without obvious capacity loss. Even when the discharge depth is increased to 2000 mAhg-1, stable cycling is maintained for 45 cycles with a charge potential below 4.0 V vs. Li/Li+. Moreover, when the rate performance of Li-O2 cell with MWCNTs electrodes is examined at different current densities from 200, 400, 500, and 1000 mAg-1 with a cut-off capacity of 2000 mAhg-1, interestingly, the discharge voltage is not drastically increased even the current density is 1000 mAg-1. And then, the chare voltage remains at around 3.85 V, which is similar to the current density of 200 mAg-1 (about 3.82 V). Therefore, these results demonstrate that the MWCNTs maintain excellent activity and stability of catalysts toward the reversible formation-decomposition of Li2O2. Reference [1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J. M. Tarascon, Nat. Mater. 2012, 11, 172– 172 [2] J. Lu, L. Li, J.-B. Park, Y.-K. Sun, F. Wu, K. Amine, Chem. Rev. 2014, 114, 5611 – 5640. [3] L. Grande, E. Paillard, J. Hassoun, J.-B. Park, Y.-J. Lee, Y.-K. Sun, S. Passerini,