High Scan Rates Research Articles

Structural and Electrochemical Relationships of Bicontinuous Polysorbate-20 Microemulsions

Research and discovery of new electrolytes is crucial for advancing the fundamental understanding and development of new opportunities in electrochemical systems. Through an Energy Frontier Research Center (EFRC) for Breakthrough Electrolytes for Energy Storage (BEES), the approach we are taking is to establish a system for decoupling the nature and solubility of electroactive material from the conductivity and transport of ions in the surrounding solution. We accomplish this with microemulsions as a technique to solubilize hydrophobic redox active materials in an aqueous solvent. Microemulsions are isotropic, nanoscale dispersions of two immiscible liquids, stabilized by a surfactant, and cosurfactant. Microemulsions are an interesting electrolyte because they possess several properties that make them useful as an energy storage medium – they are thermodynamically stable, have fast dynamics, possess large interfacial areas, and can solubilize large concentrations of hydrophobic redox-active compounds in an aqueous electrolyte solution. Cyclic voltammetry experiments have shown reversible behavior in microemulsions up to 22 V/s with a double layer capacitance less than expected with such high scan rates. In order to understand the electrochemical behavior, we have begun with understanding the nanoscale structure of the microemulsion. Presented here are the small angle neutron scattering results on microemulsion systems with increasing surfactant loading and how the nanostructure correlates with the electrochemical response. That is as the strength of the amphiphile increases the maximum current density peak decreases and the half-wave potentials shift to lower potentials suggesting the local environment of the redox active species changes as the composition of the microemulsion is varied. Figure 1

Block-Copolymer Derived Nanoporous Thin Films for the Development of a L-BMAA Aptamer-Based Electrochemical Biosensor

Produced by diverse cyanobacteria, b-N-methylamino-l-alanine (L-BMAA) is a non-protein neurotoxic cyanotoxin that has been linked to an elevated incidence of neurodegenerative diseases such Parkinson’s and Alzheimer’s disease and Multiple Lateral Sclerosis. The continuing rising of water temperatures and eutrophication of the water bodies propitiate the increment and size of harmful algal blooms, subsequently increasing the production of L-BMAA and other cyanotoxins. This toxin is known to bioaccumulate in plants, animals and humans. Currently, the detection of L-BMAA in water is limited by its hydrophilicity, absence of ultraviolet and fluorescent properties, and the isomers that cause false positives. Given the threat that this cyanotoxin could represent to the long-term human health, it is imperative to develop new analytical techniques for its detection in water. Therefore, this project proposes the development of an impedimetric aptamer-based biosensor, using block-copolymer (BCP’s) derived nanoporous thin films as the electrode, for the detection of L-BMAA. Our hypothesis is that the development of such aptasensor will lead to the advancement of an innovative device for a sensitive, portable, economic and flexible way to achieve the detection of the cyanotoxin in water. To achieve this, we used BCP polystyrene-poly(methylmethacrylate) (PS-b-PMMA), known to form cylinder-like structures, to create recessed nanodisk-array electrodes (RNEs). These cylindrical nanostructures provide primary mass transport pathways for ionic and redox active species which changes upon analyte binding, making them ideal to use in biosensing applications. The nanoporous electrodes were prepared by spin-coating a PS-b-PMMA solution in toluene over gold-coated silicon wafers, followed by thermal annealing and UV etching. Different annealing times, temperatures and UV exposure has been used in order to produce the alignment of the cylindrical polymer microdomains in a vertical fashion over the surface of the electrode. The prepared films were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), to confirm the formation of RNE’s. Under specific sets of conditions, CV data shows sigmoidal curves at high scan rates characteristic of RNE’s, suggesting the formation of this type of nanopores with a sufficiently large distance among them to attain radial diffusion. Atomic force microscopy (AFM) images of the samples evidence the formation of vertical nanopores but mixed with horizontal alignments. Furthermore, grazing incident small angle x-ray scattering (GISAXS)11 suggests that the polymer was well-dispersed among the surface although the expected scattering profile for RNEs is missing. Future work includes the optimization of the electrode preparation methods and the selection of a L-BMAA specific aptamer through graphene oxide-assisted selection evolution of ligands by exponential enrichment (GO-SELEX).

Organic Cathode Based on Quinone-Sulfide Polymer for Both Li and Mg Batteries

The undeniable benefit of lithium-ion (LIB) batteries for the development of a more environmentally friendly economy was recognized by the 2019 Nobel Prize in Chemistry. However, relying only on LIBs to energy storage will put considerable strain on lithium and cobalt resources used in these batteries. Therefore, alternative battery technologies other than LIBs are desirable to satisfy our growing demand for energy. Magnesium-ion batteries offer many distinct advantages over LIBs, including the high earth-abundance of magnesium, its high energy density and reversible dendrite-free Mg deposition1. In parallel, organic materials are receiving an increasing amount of attention as electrode materials for future post lithium-ion batteries due to their versatility and sustainability2. In order to propose organic cathode with both high potential and specific capacity, new polymer based on hydroquinone sulfide, poly(benzoquinone disulfide) (PBQDS), were prepared in view to be applied in both lithium and magnesium batteries. Diglyme and sulfolane solvents associated with both LiTFSI (lithium bistrifluomethane sulfonimide) and Mg(TFSI)2 salts were selected, as electrolytes, in order to evaluate the potentiality of the active material3. First of all, the electrochemical responses of PBQDS in lithium and magnesium based electrolytes was performed in a cavity micro-electrode. Whereas in both case the cyclic voltammetry exhibit a close to reversible redox stem (Fig. 1a), The electrochemical characteristics of the material are very similar in term of potential and ΔEpeak in both lithium and magnesium systems at a relative high scan rate i.e. 1 mV s-1. An improvement of the redox couple reversibility seems to be observed in Mg form, with a ΔEpeak= 400 mV at E° of 0.3 V vs Fc+/Fc (3.5 vs Li+/Li). Given this interesting behavior, PBQDS in a coin cell configuration using glyme + LiTFSI electrolyte, was analyzed. . A stable capacity of 160 mAh g-1 was obtained at C/10 after 70 cycles, whereas a value of 120 mAh g-1 was maintained at C rate (Fig. 1b). In order to improve, the electrochemical performances, especially at high C-rate, the impact of the particle sizes (controlled grinding) of the cathodic material is in progress in view to approach its theoretical capacity value. In addition, the electrochemical investigations in both Mg and Li based electrolytes will be presented in regard to the electrolyte nature and the PBQDS morphology. 1. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci., 2013, 6, 2265–2279.2. P. Poizot, F. Dolhem, Energy Environ. Sci., 2011, 4, 20033. H. Dong, Y. Liang, O. Tutusaus, R. Mohtadi, Y. Zhang, F. Hao, Y. Yao, Joule 2019, 3, 1–12 Figure 1

Enhancing Catalytic Activity and Selectivity by Plasmon-Induced Hot Carriers.

SummaryPlasmon-assisted chemical transformation holds great potential for solar energy conversion. However, simultaneous enhancement of reactivity and selectivity is still challenging and the mechanism remains mysterious. Herein, we elucidate the localized surface plasmon resonance (LSPR)-induced principles underlying the enhanced activity (∼70%) and selectivity of photoelectrocatalytic redox of nitrobenzene (NB) on Au nanoparticles. Hot carriers selectively accelerate the conversion rate from NB to phenylhydroxylamine (PHA) by ∼14% but suppress the transformation rate from PHA to nitrosobenzene (NSB) by ∼13%. By adding an electron accepter, the as-observed suppression ratio is substantially enlarged up to 43%. Our experiments, supported by in situ surface-enhanced Raman spectroscopy and density functional theory simulations, reveal such particular hot-carrier-induced selectivity is conjointly contributed by the accelerated hot electron transfer and the corresponding residual hot holes. This work will help expand the applications of renewable sunlight in the directional production of value-added chemicals under mild conditions.

Electrochemical properties of ascorbic acid and folic acid under acidic solution

Ascorbic acid and folic acid are very important vitamins which have some crucial roles in human body’s metabolism, including enhancing iron absorption. Regardless of its roles, these vitamins are also known to be unstable and easily degraded in the processing by oxygen, pH, temperature, and UV light. Nowadays, microencapsulation may be a proper technique to overcome some of these shortcomings. However, there is a possibility of the changes in vitamin stability during encapsulation processes, particularly while using chitosan and acetic acid as wall material and solvent, respectively. In this study, cyclic voltammetry method was carried out for investigating the electrochemical properties of ascorbic acid and folic acid under acidic medium. The effect of scan rate (0.1; 0.2; 0.3 V/s) on the observed current was also studied. Furthermore, vitamin-aquadest solutions were also studied as a referred sample. Cyclic voltammetry was conducted using a three electrodes configuration connected to an electrochemical analyser. Platinum wire, graphite, and Ag/AgCl were employed as the working, auxiliary and reference electrodes, respectively. All the solutions were maintained for free oxygen by the degassing process. In general, the recorded currents of all solutions were increased while using a higher scan rate. Cyclic voltammogram also showed that ascorbic acid had two anodic peaks and two cathodic peaks which indicated that ascorbic acid undergoes reversible reaction. However, folic acid only had one anodic peak in water which represented an oxidation reaction. Furthermore, the electrochemical properties of ascorbic acid have a similar profile with folic acid while were in acidic solutions. Both vitamins have more positives anodic peak; hence depicted that acid could suspend the oxidation reaction.

Pinus nigra pine derived hierarchical carbon foam for high performance supercapacitors

Biomass comprises an attractive source of carbon materials for energy conversion and storage applications, because it provides a low cost and sustainable approach for the production of carbon-based electrode materials at large scale. Here, we demonstrate the preparation of a three-dimensional and hierarchical carbon foam (3DCF) from bio-renewable Pinus nigra pine, using a chemical degradation method followed by two simple carbonization steps in presence of argon gas. The as-prepared 3DCF in supercapacitor electrode shows high scan rate capability up to 10 V s−1, specific capacitance of 165 F g−1 at the specific current of 3.3 A g−1 in 6 M KOH electrolyte in three-electrode cell configuration, and retains 69.6% of its initial capacitance when the specific current increased to 13.3 A g−1. Furthermore, a 3DCF based symmetrical two-electrode cell has been constructed that shows a satisfactory specific energy of 6.6 Wh kg−1 at specific power of 2.3 kW kg−1, and maintains the specific energy of about 50% at high specific power of 7.3 kW kg−1 under an operating voltage of 1.4 V in 2 M LiClO4 aqueous electrolyte. These results reveal a sustainable and low-cost electrode fabrication at large quantity for fabricating high performance supercapacitors with both KOH and Li-ion based electrolytes.

Tunable electrochemical activity of polyaniline salt by doping anion exchange

The exchange of mobile anion of chemically synthesized polyaniline with counter anions of electrolyte solutions is studied by using cyclic voltammetry (CV). The synthesized polyaniline (PANI) doped with sulfuric acid (H2SO4) and dodecyl benzenesulfonic acid (DBSA) is soluble in a wide range of organic solvents which makes it appealing for further processability. The exchange of dopant anions (of H2SO4 and DBSA) with a variety of counter anion has been inspected by electrochemical cycling in aqueous sodium sulfate (Na2SO4), sodium perchlorate (NaClO4), and sodium hydroxide (NaOH) solution. The CV measurements have revealed that PANI remains redox active at higher scan rate and there is exchange of dopant anion with SO42- and ClO41- of electrolytes. In NaOH solution, the emeraldine salt form of PANI is transformed into emeraldine base due to deintercalation of the anion form polymer matrix. The results indicate a significant change in electrochemical conductance and behavior of PANI in each electrolyte. Furthermore, the polymer film displayed a high specific capacitance value of 588 F/g in 1.0 M NaClO4 solution in the optimized potential window of -0.2 V to 0.9 V at 20 mV/s.

Flexible and stretchable polyaniline supercapacitor with a high rate capability

AbstractFlexible electronics are currently highly favored because of their promising applications in flexible displays, artificial electronic skin, wearable devices etc. Exploiting flexible energy storage systems, which are supercapacitors, that have a decent electrochemical performance as well as flexibility and stretchability is essential to promote the development of flexible electronic products. In this work, a flexible and stretchable polyaniline (PANI) supercapacitor based on a conductive stainless steel mesh was developed via a simple electrodeposition route with an elastic gel polyvinyl alcohol polymer (PVA)/phosphoric acid (H3PO4) electrolyte, which exhibits a considerable rate capability and mechanical properties. The as‐prepared capacitor delivers a specific capacitance of 282 F g−1 under a specific current of 2.5 A g−1. Meanwhile, the PANI capacitor exhibits perfect pseudocapacitance behavior at low scan rates (up to 50 mV s−1) and great capacitive characteristics at high scan rates up to 5000 mV s−1. More impressively, this supercapacitor displays excellent tolerance against mechanical deformation, including bending, folding and stretching, even to 20%, with a well‐maintained capacitance. This stretchable PANI supercapacitor with a high rate capability provides a facile and cost‐effective route for the design of flexible energy storage devices. © 2020 Society of Chemical Industry

Non-targeted method to detect honey adulteration: Combination of electrochemical and spectrophotometric responses with principal component analysis

Detecting adulteration in honey is not an easy task and most of the traditional methods are usually unaffordable. Thus, we describe the use of cyclic voltammetry using Cu/CuO electrode and UV–vis spectrophotometry along with chemometric tools to detect adulteration of honey with corn syrup. Both honey and corn syrup samples presented an anodic peak at +1.1 V, but the current is variable and depends on the sample composition in relation to the honey and syrup content. A cathodic peak at +0.42 V arises at higher scan rates, which is more pronounced for syrup samples and can be used to discriminate between pure and adulterated samples. This response can be combined with UV/vis absorbance peaks at 285 and 216 nm to identify adulteration. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) allowed differentiating between honey and corn syrup samples and simulated mixtures of them, in which the first two principal components together explain 100.0 % of the data variability, specifically 98.47 % by PC1 and 1.53 % by PC2. The method requires a minimum amount of sample and generates a low amount of waste. Furthermore, it is possible to use portable and cheap equipment, making it more accessible to the beekeeper sector.

Capacitive and diffusive contribution in strontium phosphide-polyaniline based supercapattery

Abstract The statistics of capacitive and diffusive contribution in the supercapattery performance is analyzed via numerical approach. In this regard's strontium phosphide has been synthesized through sonochemical technique whereas PANI is obtained through polymerization. The optimized composite of strontium phosphide and PANI is designated for supercapattery device by coupling it with activated carbon. Structural, morphological, crystallinity, and elemental analysis is carried out through SEM, XRD and EDX. The electrochemical performance in three as well as two electrode assembly is investigated through CV, GCD and EIS. Supercapattery expresses excellent performance by showing 122.4 C/g specific capacity, 28.9 W h/kg energy density and 1020 W/kg power density. This device also delivered outstanding power density of 5100 W/kg in parallel with 10.95 W h/kg energy density. Later, the capacitive/diffusive contribution in the supercapattery is analyzed through a systematic approach. A total of 87.95% diffusive contribution is recorded at the scan rate of 3 mV/s which reaches up to 57.90% at 100 mV/s. On other side capacitive contribution in the device is 12.04% at lower scan rate that raises up to 42.09% at 100 mV/s. The decrease in the diffusive part and increase in the capacitive part is due to the ion's interaction time offered with electrode material at lower and higher scan rates.

Flash glucose monitoring reduces glycemic variability and hypoglycemia: real-world data from Spain.

ObjectiveObservations in real-world settings support and extend findings demonstrated in randomized controlled trials that show flash glucose monitoring improves glycemic control. In this study, Spain-specific relationships between testing frequency and glycemic parameters were investigated under real-world settings.Research design and methodsDeidentified glucose and user scanning data were analyzed and readers were rank ordered into 20 equal sized groups by daily scan frequency. Glucose parameters were calculated for each group: estimated HbA1c, time below range (<70 and ≤54 mg/dL), within range (70–180 mg/dL), and above range (>180 mg/dL). Glycemic variability (GV) metrics were described and data obtained from sensors in Spain and worldwide were compared.ResultsSpanish users (n=22 949) collected 37.1 million glucose scans, 250 million automatically recorded glucose readings, and checked glucose values via a mean of 13 scans/day. Estimated HbA1c, time below 70 mg/dL, at or below 54 mg/dL, above 180 mg/dL, and GV metrics were significantly lower in the highest compared with lowest scan rate group (39.6 to 3.9 scans/day). Time-in-range was higher for the highest versus lowest scan rate group at 15.6 vs 11.5 hours/day, respectively. GV metrics correlated positively with time below 70 mg/dL, at or below 54 mg/dL, above 180 mg/dL, and negatively with time-in-range. The relationship between glucose metrics and scan rate was similar in Spain and worldwide. However, time in hypoglycemia in Spain was higher in the groups with lower scan rates.ConclusionsAs seen in clinical trials, flash glucose monitoring in real-world settings allows frequent glucose checks. High scan rates are associated with the favorable glycemic markers of increased time-in-range and reduced time in hyperglycemia and hypoglycemia, and GV. The same trends, with unique nuances, are observed in both Spanish and global data.

Voltammetric behaviour of cationic redox probes at mesoporous silica film electrodes

The effect of vertically aligned silica nanochannels on the electrochemical response of various cationic redox probes has been investigated. To this end, an oriented mesoporous silica thin film has been generated by electro-assisted self-assembly onto a fluorine-doped tin oxide (FTO) electrode, which was then used to characterize the voltammetric behaviour of redox cations of different nature, size and charge. Methylene Blue (MB+), paraquat (PQ2+), diquat (DQ2+), ruthenium trisbipyridine (Ru(bpy)32+) and ruthenium hexamine (Ru(NH3)63+) were selected for that purpose. Multisweep cyclic voltammetry experiments showed significant accumulation of these cations thanks to favourable electrostatic interactions with the negatively-charge silica surface, but the enhancement of the votammetric signals compared to the bare FTO electrode was strongly dependent on the probe type, according the following trend: MB+ > PQ2+ > DQ2+ > Ru(bpy)32+ > Ru(NH3)63+. The accumulation processes were very fast owing to the vertical orientation of the mesopore channels ensuring fast diffusion from the solution to the electrode surface. Operating at various potential scan rates and different probe concentrations enabled to quantify the relative ratio between surface-confined and diffusion-controlled processes, the adsorption phenomena being clearly more prominent in diluted media and also accentuated at high potential scan rates. The mesoporous silica film electrodes exhibited higher sensitivities at lower concentrations, which can give benefits for sensor applications at trace levels.

Drying-Mediated Self-Assembly of Graphene for Inkjet Printing of High-Rate Micro-supercapacitors

HighlightsBased on the drying-mediated self-assembly behavior of passivated graphene, a new kind of 2D micro-flake inks is developed to directly print high-resolution patterns with multiscale porous microstructure.The new ink allows to directly print complex 3D structures comprising multiple layers of heterogeneous materials.High-rate all-solid-state 3D micro-supercapacitors have been fully inkjet-printed with an areal capacitance surpassing 10 mF cm−2 at a high scan rate of 1 V s−1.

3D hierarchical carbon nanofibers/TiO2@MoS2 core-shell heterostructures by electrospinning, hydrothermal and in-situ growth for flexible electrode materials

Design and synthesis of unique core-shell heterostructures for flexible electrode materials have recently attracted intensive attention. In this work, 3D flexible carbon nanofibers (CNFs)/TiO2@MoS2 core-shell hierarchical nanostructures were prepared on the surface of CNFs by combining electrospinning, hydrothermal method and in situ growth. We investigated the behavior of CNFs/TiO2@MoS2 as electrode material, which showed desirable electrochemical performance in terms of ultrahigh specific capacitance and long-term stability. The CNFs/TiO2@MoS2 exhibited ultrahigh specific capacitance (510.4 F g−1 at 0.5 A g−1) superior to CNFs/TiO2 (53.8 F g−1 at 0.5 A g−1) and prominent rate capability at high scan rates. Specifically, the capacitance retention of CNFs/TiO2@MoS2 remained about 95.7% even after 3000 cycles at 3.5 A g−1, which indicates considerable cycling stability. Hence, this work presents a novel strategy for the construction of cost-effective, flexible and high-performance 3D electrode materials, and confers in-depth understanding of nanocomposites with relatively light quality. The fabricated nanocomposite can have attractive application prospects in energy storage systems and can even be extended to wearable and portable energy storage equipment.

Novel diverse-structured h-WO3 nanoflake arrays as electrode materials for high performance supercapacitors

Hexagonal tungsten trioxide (h-WO3) nano-materials can be widely used in many fields of optics, electrics and chemistry. In this work, three types of h-WO3 (single crystal, polycrystal and hierarchical) nanoflake arrays (WNFs) are synthesized through a simple hydrothermal method. The morphologies, crystalline degree and exposed faces of these WNFs can be controlled with simple adjustments of reaction parameters. The relationships between the crystal structures and supercapacitive properties of these WNFs are systematically investigated and the results show that: the single crystal WNFs with a fast electron transmitting channel exhibits a high rate performance at high voltage scan rate, while the polycrystal and hierarchical WNFs with more oxygen vacancies and ion storage spaces have relatively high specific capacitances at low scan rate. These WNFs are used to fabricate supercapacitors, which show specific energy density as high as 88.2 W h kg−1 at a power density of 400 W kg−1. It is concluded that the electrode materials should have single structure facilitating the electrons transfer at current collector side and a porous structure for ion storage at the electrolyte side.

Supercapacitors with Prussian Blue Derived Carbon Encapsulated Fe/Fe3C Nanocomposites

A one-step synthesis of carbon encapsulated Fe/Fe3C nanoparticles by pyrolyzing single source precursor of Prussian Blue (Iron (III) ferrocyanide) for its usage as anode material in high-performance supercapacitors is reported. The synthetic method produces 3D doughnut shaped porous structures comprising numerous interconnected Fe/Fe3C nanoparticles entirely encapsulated within layers of graphitic carbon. Such a porous structure facilitates electrolytic ion diffusion during charge storage on Fe/Fe3C nanoparticles through surface or near surface- based faradaic reactions, while the metallic iron helps enhancing the electronic conductivity of the electroactive material. Accordingly, the charge storage in such carbon encapsulated Fe/Fe3C nanoparticles is governed by capacitive as well as diffusion-controlled processes at lower scan rates, and is taken over by capacitive processes at higher scan rates. The material achieves a specific capacitance of 223 F g−1 at a scan rate of 10 mV s−1 along with compelling cycling performance exhibiting a little decay in capacitance over 20,000 cycles. When coupled with activated-carbon cathode, Fe/Fe3C//activated-carbon asymmetric supercapacitor out-performs many recently reported supercapacitors.

Effective electrocatalytic methanol oxidation of Pd-based metallic glass nanofilms.

Compared to their conventional polycrystalline Pd counterparts, Pd79Au9Si12 (at%) - metallic glass (MG) nanofilm (NF) electrocatalysts offer better methanol oxidation reaction (MOR) in alkaline medium, CO poisoning tolerance and catalyst stability even at high scan rates or high methanol concentrations owing to their amorphous structure without grain boundaries. This study evaluates the influence of scan rate and methanol concentration by cyclic voltammetry, frequency-dependent electrochemical impedance spectroscopy and a related equivalent circuit model at different potentials in Pd-Au-Si amorphous NFs. Structural and compositional differences for the NFs are assessed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray (EDX) mapping and X-ray diffraction (XRD). The ratio of the forward to reverse peak current density ipf/ipb for the MG NFs is ∼2.2 times higher than for polycrystalline Pd NFs, evidencing better oxidation of methanol to carbon dioxide in the forward scan and less poisoning of the electrocatalysts by carbonaceous (e.g. CO, HCO) species. Moreover, the electrochemical circuit model obtained from EIS measurements reveals that the MOR occurring around -100 mV increases the capacitance without any significant change in oxidation resistance, whereas CO2 formation towards lower potentials results in a sharp increase in the capacitance of the Faradaic MOR at the catalyst interface and a slight decrease in the corresponding resistance. These results, together with the high ipf/ipb = 3.37 yielding the minimum amount of carbonaceous species deposited on the thin film during cyclic voltammetry and stability in the alkaline environment, can potentially make these amorphous thin films potential candidates for fuel-cell applications.

45° Linearly Polarized and Circularly Polarized High-Scanning-Rate Leaky-Wave Antennas Based on Slotted Substrate Integrated Waveguide

A class of 45° linearly polarized and circular polarized high scanning rate leaky wave antennas are proposed in this paper, which is based on slow-wave substrate integrated waveguide structure. High scanning rate leaky wave antennas have recently become attractive for imaging applications and automotive radar. These applications also require a continuous scanning range without an open stopband, as seen at broadside for ordinary leaky wave antennas. Furthermore, both 45° linearly polarization and circularly polarization are required in practical applications. In this paper, we propose an all-in-one leaky wave antenna design, which features high scanning rate, continuous scanning capability across the broadside, 45° linear polarization or circularly polarization, single-layer configuration, and single-side radiation. Two design examples are provided to illustrate the proposed principle. Both simulation and experimental validation are given.

Regenerated Bamboo-Derived Cellulose Fibers/RGO-Based Composite for High-Performance Supercapacitor Electrodes

Bamboo-derived cellulose fibers/RGO carbon aerogel composite was prepared by using a facile aerogel-based method, in which bamboo pulp fibers were dissolved and incorporated in an ionic liquid system, and RGO was introduced by thermal reduction approach. The obtained bamboo-derived cellulose fibers/RGO carbon aerogel composite shows a large specific surface area, and excellent electrochemical performance. When the GO content was 2.5 wt%, the obtained composite showed a high specific surface area of 1957 m2/g, and high specific capacitance of 351 F/g in 6 M KOH electrolyte solution even with a more than 90% capacitance retention at a high scan rate of 200 mV/s. The bamboo-derived cellulose fibers/RGO composite electrodes show the low equivalent series resistance of 5.0 Ω and small charge transfer resistance of 0.30 Ω which further demonstrate the excellent electrochemical behaviors.

Ternary nanocomposite of cobalt oxide nanograins and silver nanoparticles grown on reduced graphene oxide conducting platform for high-performance supercapattery electrode material

The ternary nanocomposite of cobalt oxide (Co3O4) and silver (Ag) nanoparticles with reduced graphene (rGO) was successfully synthesized via single-step hydrothermal method and applied as a positrode material in supercapattery. The successful synthesis of ternary nanocomposite (rGO-Co3O4–Ag) and uniform distribution of Co3O4 nanograins over graphene matrix decorated with Ag nanoparticles was confirmed using X-ray diffraction, field emission scanning electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy. From electrochemical studies such as cyclic voltammetry, galvanic charge-discharge and impedance spectroscopy, it was found that the prepared ternary nanocomposite exhibited excellent performance compared to its counterparts (Co3O4, rGO-Co3O4). The rGO-Co3O4–Ag ternary nanocomposite showed a specific capacity of 94.20 C g−1 that is remarkably higher than the rGO-Co3O4 (63.98 C g−1) and Co3O4 (58.92 C g−1) in a three-electrode cell system using 1 M KOH electrolyte. The two electrodes cell assembly (supercapattery) was fabricated using rGO-Co3O4–Ag nanocomposite as a positrode and activated carbon as a negatrode. The assembled supercapattery (rGO-Co3O4–Ag/activated carbon) was able to run in a potential range of 0–1.5 V even at the higher scan rate. The two electrodes cell studies demonstrated that the assembled supercapattery at a current density of 0.6 A g−1 achieved energy density and power density of 23.63 Wh kg−1 and 440 W kg−1 respectively. It also displayed excellent cycling stability with capacity retention around 85.5% after 3000 cycles at a current density of 3 A g−1.