Increase In Capacitance Research Articles

Gamma radiation impact on dielectrics and RH sensitivity of nylon–carbon–GNP–epoxy composites

AbstractComposites of carbon–graphene nanoplatelets (GNP) epoxy with nylon‐66 interleaving were fabricated and investigated to understand the impact of γ‐irradiation on their dielectrics and relative humidity (RH) sensitivity by capacitance and water absorption measurements. The moisture sensitivity was investigated by measuring memory effect (hysteresis) and response time of the capacitance. Composites were γ‐irradiated at doses of 1000 and 3000 kGy and studied by the same set of measurements. X‐ray diffraction analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to understand the impact of γ‐irradiation on the morphology and surface roughness of the composites. Results of these measurements suggest that 3000‐kGy dose γ‐irradiation produces good chain scission and cross‐linking, resulting in reduced water absorption and a 360% increase in capacitance values. The sensitivity of capacitance for 3000‐kGy γ‐irradiated composite was found to be highest at 40 pF/%RH, and hysteresis was 1.8% RH and not observed in non‐irradiated composites. Based on these observations, it seems that 3000‐kGy γ‐irradiated composite could be a potential candidate for moisture content diagnostics during condition monitoring of the carbon–epoxy structures in several industrial applications and needs to be further investigated.Highlights Composites of carbon–GNP epoxy with nylon‐66 interleaving were γ‐irradiated. 3000‐kGy dose γ‐irradiated composites exhibit 360% increase in capacitance. Sensitivity and hysteresis were higher than those of 1000‐kGy and non‐irradiated samples. Good chain scission and cross‐linking resulted in reduced water absorption.

Influence of conductive carbon and MnCo2O4 on morphological and electrical properties of hydrogels for electrochemical energy conversion.

In this work, a strategy for one-stage synthesis of polymer composites based on PNIPAAm hydrogel was presented. Both conductive particles in the form of conductive carbon black (cCB) and MnCo2O4 (MCO) spinel particles were suspended in the three-dimensional structure of the hydrogel. The MCO particles in the resulting hydrogel composite acted as an electrocatalyst in the oxygen evolution reaction. Morphological studies confirmed that the added particles were incorporated and, in the case of a higher concentration of cCB particles, also bound to the surface of the structure of the hydrogel matrix. The produced composite materials were tested in terms of their electrical properties, showing that an increase in the concentration of conductive particles in the hydrogel structure translates into a lowering of the impedance modulus and an increase in the double-layer capacitance of the electrode. This, in turn, resulted in a higher catalytic activity of the electrode in the oxygen evolution reaction. The use of a hydrogel as a matrix to suspend the catalyst particles, and thus increase their availability through the electrolyte, seems to be an interesting and promising application approach.

Ceramic matrix composite based on silicon carbide and nanostructured nitrogen-doped carbon for supercapacitor electrodes

The results of studies on the production of a porous ceramic-matrix composite material C–N/SiC from silicon carbide and nitrogen-doped nanostructured carbon for subsequent use as supercapacitor electrodes are presented. The material is formed by pressing silicon carbide micropowder (1 µm) and impregnating with a solution of carbamide (nitrogen source) in phenol-formaldehyde varnish (carbon source), curing and pyrolysis in a nitrogen atmosphere. The maximum concentration of carbamide was obtained in the solution (16 wt.%) at 50 ºС with a viscosity of 134.3 mPa⋅s. Thermogravimetric analysis in nitrogen of the cured solution revealed multistage decomposition with a residual mass of C–N of 48 % at 1000 ºС. Studies of the elemental composition showed a nitrogen content of 1.4 wt.% in C–N/SiC composite (up to 7 % of C–N active mass). In the composite structure, the C–N carbon-nitrogen layer (up to 12 wt.%) distributed inside the matrix pores and covering the SiC grains is X-ray amorphous has a complex nanoscale relief with an average pore size of 1.0–1.5 nm. According to electrochemical studies, the specific capacitance of the C–N/SiC material and the C–N active layer is 16.84 and 153.2 F/g respectively, and the equivalent resistance of the test supercapacitor cell with C–N/SiC electrodes is 0.567 Ohm for samples with maximum doping. The electrodes operate according to the sorption-desorption mechanism of charge accumulation and release, which is typical for a classic supercapacitor based on a double electric layer without the presence of redox reactions on the electrodes. The influence of technological regimes of pyrolysis on the electrophysical parameters of the cell is revealed: lower values of the pyrolysis temperature and nitrogen pressure in the chamber lead to an increase of the material specific capacitance and reduction of the cell equivalent resistance. The obtained results demonstrate the possibility of utilizing C–N/SiC material for the manufacture of supercapacitor electrodes.

Low-Pressure Plasma-Processed NiCo Metal–Organic Framework for Oxygen Evolution Reaction and Its Application in Alkaline Water Electrolysis Module

Ar, Ar/H2 (95:5), and Ar/O2 (95:5) plasmas are used for treating the NiCo metal–organic framework (MOF), and the plasma-processed NiCo MOF is applied for catalyzing the oxygen evolution reaction (OER) in a 1 M KOH electrolyte. Linear sweep voltammetry measurements show that after plasma treatment with Ar/H2 (95:5) and Ar gases, the overpotential reaches 552 and 540 mV, respectively, at a current density of 100 mA/cm2. The increase in the double-layer capacitance further confirms the enhanced oxygen production activity. We test the Ar plasma-treated NiCo MOF as an electrocatalyst at the OER electrode and Ru as an electrocatalyst at the hydrogen evolution reaction (HER) electrode in the alkaline water electrolysis module. The energy efficiency of the electrolyzer with the Ar plasma-processed NiCo-MOF catalyst increases from 54.7% to 62.5% at a current density of 500 mA/cm2 at 25 °C. The alkaline water electrolysis module with the Ar plasma-processed catalyst also exhibits a specific energy consumption of 5.20 kWh/m3 and 4.69 kWh/m3 at 25 °C and 70 °C, respectively. The alkaline water electrolysis module performance parameters such as the hydrogen production rate, specific energy consumption, and energy efficiency are characterized at temperatures between 25 °C and 70 °C. Our experimental results show that the NiCo MOF is an efficient OER electrocatalyst for the alkaline water electrolysis module.

Advancing Photoelectrochemical Systems: Unleashing the Remarkable Performance of In : SnO2/Nd4In5S13 for Sustainable Energy Applications

AbstractNeodymium Indium sulphide (Nd4In5S13) photoactive electrode was produced by spin‐coating for photoelectrochemical cell. The photoactive electrode is analysed for its crystalline, structural and elements makeup in addition to its optical and electrical responses. A 56 nm sized orthorhombic crystallite was found and geometrical compact structures were observed. The presence of chief elements with core levels of In3d, Nd4d and S2p were detected. The bandgap energy was found to be 4.1 eV. Electrochemical investigations were performed to evaluate the photoactive efficiency of the electrode. Photo‐cyclic voltammetry present a specific capacitance under illumination to be 570 Fg−1, as contrasting to 481 Fg−1 when in dark. A photocurrent density of 282 mA cm−2 was obtained from photo‐linear sweep voltammetry. It had also been discovered that the transient chronoamperometry provided a photocurrent density of 46.1 mA cm−2. Whereas electrical impedance spectroscopy presented internal resistance (Rs) to be 232 Ω. All scan rates show an increase in the specific capacitance of photo‐electrode when illuminated. The research created an effective photo‐electrode for renewable energy structures. It can be posited that the study presented a pragmatic photoelectrode, which had the potential to be employed in sustainable energy frameworks, including but not limited to photovoltaics, supercapacitors, and photoelectrochemical solar cells.

Capacitance breakthroughs in free-standing electrodes through MXene functionalization

The discovery of the large group of 2D materials called MXenes has gathered much attention due to their potential applications in various fields as well as the evergrowing discoveries about their nature. One of the most interesting applications is energy storage devices. Herein, we demonstrated the impact of the functionalization with two different silanes on the electrochemical and structural properties of Ti3C2Tx MXene. Materials are prepared and characterized as free-standing films obtained by a simple vacuum filtration method. The structure of the modified MXene electrodes was confirmed via SEM, FTIR, and XPS analysis. At the same time, the electrochemical properties were determined by cyclic voltammetry and galvanostatic charge-discharge in a two-electrode setup in aqueous electrolyte. Capacitance values at lower scanning speeds revealed the benefits of PEG silane functionalization (25.38 F/g), showing higher values compared to pure MXene (23.95 F/g) and MEMO silane (23.37 F/g). Capacitance retention decreased with the addition of silanes, but there was a significant increase in capacitance in the first 100 cycles. This study clarifies the benefits of adding different silanes to the structural and electrochemical properties of MXene for energy storage applications.

Online monitoring of epithelial barrier kinetics and cell detachment during cisplatin-induced toxicity of renal proximal tubule cells.

Real-time and non-invasive assessment of tissue health is crucial for maximizing the potential of microphysiological systems (MPS) for drug-induced nephrotoxicity screening. Although impedance has been widely considered as a measure of the barrier function, it has not been incorporated to detect cell detachment in MPS with top and bottom microfluidic channels separated by a porous membrane. During cell delamination from the porous membrane, the resistance between both channels decreases, while capacitance increases, allowing the detection of such detachment. Previously reported concepts have solely attributed the decrease in the resistance to the distortion of the barrier function, ignoring the resistance and capacitance changes due to cell detachment. Here, we report a two-channel MPS with integrated indium tin oxide (ITO) electrodes capable of measuring impedance in real time. The trans-epithelial electrical resistance (TEER) and tissue reactance (capacitance) were extracted from the impedance profiles. We attributed the anomalous initial increase observed in TEER, upon cisplatin administration, to the distortion of tight junctions. Cell detachment was captured by sudden jumps in capacitance. TEER profiles illuminated the effects of cisplatin and cimetidine treatments in a dose-dependent and polarity-dependent manner. The correspondence between TEER and barrier function was validated for a continuous tissue using the capacitance profiles. These results demonstrate that capacitance can be used as a real-time and non-invasive indicator of confluence and will support the accuracy of the drug-induced cytotoxicity assessed by TEER profiles in the two-channel MPS for the barrier function of a cell monolayer.

Rational design of conductive metal-organic frameworks and aligned carbon nanofibers for enhancing the performance of flexible supercapacitors.

Carbonaceous materials are attractive active materials for the manufacture of flexible electrochemical double-layer capacitors (EDLCs) because of their high electrical conductivity, large surface area, and inherent resilience against deformation. However, compared to pseudocapacitors, which store electrochemical energy via faradaic redox reactions, EDLCs generally exhibit inferior energy density. One potential approach to addressing this issue is to incorporate highly porous and electrically conductive materials into carbonaceous material-based EDLCs. In this paper, we present a hybrid electrode consisting of a conductive metal-organic framework (c-MOF) with high electrical conductivity and unique porous structure combined with a mat of aligned carbon nanofibers (ACNFs). Its highly ordered structure facilitates electronic/ionic transport, increasing the areal capacitance by up to 3.9 times compared to randomly-oriented carbon nanofibers (RCNFs). An additional increase in areal capacitance (+64%) is achieved by introducing c-MOF (RCNFs: 25.4 mF cm-2; ACNFs: 98.7 mF cm-2; c-MOF/ACNF: 161.8 mF cm-2). Additionally, an ACNF mat exhibits excellent mechanical flexibility and electrochemical reliability, making it highly suitable for the assembly of freestanding flexible supercapacitors. By optimizing the electrochemical performance of c-MOF/ACNF and its suitability for utilization in flexible energy storage systems, this study presents a promising avenue for the practical implementation of c-MOF-based supercapacitors.

Negative capacitance based on isomeric polythiophene in action.

In this study, we demonstrated that arranging positive and negative capacitance materials in series, based on isomeric polythiophene, led to a notable increase in total capacitance. Furthermore, the application of negative capacitance (NC) technology in supercapacitor (SC) construction offers the potential for energy storage capabilities surpassing fundamental limits. Our findings suggest the feasibility of developing all-organic based energy storage devices with high capacitance.

Self‐Micropatterned Wood Hydrophone for Underwater Detection

AbstractA hydrophone is a core component of sonar and plays a significant role in underwater detection. High sensitivity and wide‐frequency responsiveness are crucial parameters for underwater mechanosensors. This study introduces an innovative wood‐based hydrophone for precise detection of water wave spectra and a wide range of underwater sounds. The wood hydrophone consists of a conductive wood electrode with deposited polypyrrole (PPy) microbranches (polypyrrole wood (PW)) and a cellulosic micropatterned anti‐swelling hydrogel (MPASH) serving as the dielectric layer. As pressure increases within the range of 6.4 Pa to 1.2 kPa, the densely distributed PPy microbranches within the wood fiber cell lumina contact with more tips of the self‐wrinkled micropatterns of MPASH. This interaction results in a four‐order‐of‐magnitude increase in capacitance, leading to an unprecedented sensitivity of 1153 kPa−1 toward microstresses. Due to the presence of multisized configurations in both PW and MPASH, the sensitivity of the wood hydrophone decreases gradually (268 kPa−1 up to 37 kPa). The receiving sensitivity of the wood hydrophone for acoustic waves is greater than ‐174 dB within the frequency range of 250–2300 Hz. This work presents a promising avenue for the development of underwater detection devices utilizing graded wood channels and micropatterned cellulosic hydrogels.

Stretchable Zn‐Ion Hybrid Capacitor with Hydrogel Encapsulated 3D Interdigital Structure

AbstractTo enhance the areal energy density of current flexible energy storage devices, hybrid capacitors combining the advantages of supercapacitors and batteries are proposed and further enhanced by incorporating the 3D interdigital structure design. However, uneven electric field distribution and hindered ion diffusion kinetics due to the non‐electroactive components in these devices limit the enhancement of areal electrochemical performances when expanding the electrodes longitudinally. Herein, hydrogels with high ionic conductivity and high mechanical stability are designed to accommodate Zn2+‐containing electrolytes and integrated with Ti3C2Tx‐MXene electrodes to assemble flexible Zn‐ion hybrid capacitors (ZIHCs). Fully encapsulated by ionic conductive hydrogels, 3D interdigital electrodes enable omnidirectional ion transport and unimpeded ionic accessibility, facilitating adequate electrode reactions, rapid energy storage, and uniform energy distribution. Hence, the all‐hydrogel‐encapsulated ZIHC achieved a 50‐fold increase in capacitance with a quadrupled electrode thickness, exhibiting a large areal capacitance of 1432 mF cm−2 and an energy density of 389.7 µWh cm−2 without sacrificing power density and rate performance. Finite element simulations further illustrate the uniform distribution of potential, electric field intensity, and energy density in this structure. In addition, the device shows great stability under deformation, excellent adhesion, and underwater workability, demonstrating great promise for next‐generation wearable energy storage devices.

Fabrication of Large-Area Metal-on-Carbon Catalytic Condensers for Programmable Catalysis.

Catalytic condensers stabilize charge on either side of a high-k dielectric film to modulate the electronic states of a catalytic layer for the electronic control of surface reactions. Here, carbon sputtering provided for fast, large-scale fabrication of metal-carbon catalytic condensers required for industrial application. Carbon films were sputtered on HfO2 dielectric/p-type Si with different thicknesses (1, 3, 6, and 10 nm), and the enhancement of conductance and capacitance of carbon films was observed upon increasing the carbon thickness following thermal treatment at 400 °C. After Pt deposition on the carbon films, the Pt catalytic condenser exhibited a high capacitance of ∼210 nF/cm2 that was maintained at a frequency ∼1000 Hz, satisfying the requirement for a dynamic catalyst to implement catalytic resonance. Temperature-programmed desorption of carbon monoxide yielded CO desorption peaks that shifted in temperature with the varying potential applied to the condenser (-6 or +6 V), indicating a shift in the binding energy of carbon monoxide on the Pt condenser surface. A substantial increase in capacitance (∼2000 nF/cm2) of the Pt-on-carbon devices was observed at elevated temperatures of 400 °C that can modulate ∼10% of charge per metal atom when 10 V potential was applied. A large catalytic condenser of 42 cm2 area Pt/C/HfO2/Si exhibited a high capacitance of 9393 nF with a low leakage current/capacitive current ratio (<0.1), demonstrating the practicality and versatility of the facile, large-scale fabrication method for metal-carbon catalytic condensers.

One step production of phosphorene from red phosphorus and investigation of their supercapacitor applications with conducting polymers

In this work, phosphorene, which was used as an additive to the conductive polymer (polyaniline), was produced in a single step using the chemical method at 80 °C in 6 h for the first time in the literature. In addition, composites of polyaniline with phosphorene have also been produced for the first time in the literature, and these materials have been used as electrode materials in supercapacitors. The parameters of supporting electrolyte concentration, monomer concentration and cycle number, which are the factors affecting the success of electrochemical synthesis, were optimized and the optimum values for these parameters were determined for polymers. The structural and morphological properties of the produced 2D phosphorene were investigated using spectroscopic and microscopic methods. After that, phosphorene was simultaneously and electrochemically incorporated into the structure of polyaniline (Pani), which was produced by the electrochemical method, likewise. Finally, the phosphorene-based materials produced have been used as electrode components in supercapacitors. Hybrid supercapacitor electrodes (Phosphorene@Pani/PGEs) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy methods and the changes in the capacitive behavior of these systems according to the number of cycles were examined using the galvanostatic charge-discharge technique. Specific capacitance value of phosphorene-doped composite material was 335.54 F·g−1 at a charge-discharge current density of 1.6 A·g−1.Capacitance retention of the composite material was 85 % at end of 1000 cycles with 1.6 A·g−1. It was also around of 80 % after 4000 cycles with 2.5 A·g−1 charge/discharge current densities. A significant increase in specific capacitance of 259.21 % was seen when compared with the electrode without phosphorene added. By adding of phosphorene in the conducting polymer structure, specific capacitance of the system is improved.

Electrochemical sulfur-doping as an efficient method for capacitance enhancement in carbon-based supercapacitors

Cost-efficient fabrication of electrochemical supercapacitors can herald high-capacity energy storage devices. In this work, a simple electrochemical sulfur doping in activated carbon (AC) is introduced, where the specific capacitance of the electrochemically sulfur-doped (ECD) supercapacitor is increased significantly from 147 to 440 F g−1 at 1 A g−1. Surface characterizations, especially high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDAX), and Fourier transform infrared spectroscopy (FTIR) confirm induced sulfur element in the carbon electrode after doping, as result of which the electrochemical measurement shows an increase of the specific capacitance. Moreover, a high energy density of ∼15 Wh kg−1 at 1 A g−1 and almost 90 % capacitance retention at 20 A g−1 after 5000 cycles is achieved. In addition, joint density functional theory (JDFT) is used for the rational design and verification of high-energy-density supercapacitors, supporting our experimental observations. This result paves the way toward further investigations on acid-assisted elemental doping of AC materials for energy storage devices.

Amorphous Carbon Monolayer: A Novel and Effective Interlayer for Metal/Oxide Interface

We investigate the effect of one-atom thick Amorphous Carbon Monolayer (ACM) as an interfacial layer (IL) for high-k/Ge MOS structure, with the aim of suppressing the dangling bonds on the Ge surface and reducing the interfacial defects between high-k oxide and Ge layers. The frequency-dependent C-V characteristics indicated that the ACM layer eliminates the weak inversion response resulting in a steeper C-V slope and an increase in accumulation capacitance. The G-V analysis further confirmed the lower density of interface traps in the ACM layered device. The Dit values were extracted as 1.2×10¹¹ cm⁻²eV⁻¹ for Al2O3/ACM/Ge structure, which is almost two orders of magnitude lower than that of the Al2O3/Ge structure without the ACM layer. The observed improvements are attributed to the effective blocking role of the ACM interlayer against the in-diffusion of oxygen and out-diffusion of Ge and the suppression of dangling bonds at the Ge surface. Our findings suggest that the Al2O3/ACM/Ge structure exhibits superior electrical quality with lower hysteresis and interface charge trapped density, which has important implications for the development of high-performance ultra-small-scale devices based on Ge substrates.

A Stable Fe3O4-Based Hybrid Anodes for High Performance Li-Ion Batteries

There is an increasing demand for high-performance Li-ion batteries especially due to environmental concerns. To meet the high-performance requirements of the Li-ion batteries, conversion-type anodes stand out with their capacities. The crystal structure of magnetite (Fe3O4) benefits from its empty interstitial sites which hinders volume changes during the insertion and extraction of lithium ions. Combined with its high theoretical lithium storage capacity and abundance, Fe3O4 has great potential as an alternative anode. Yet in its practical use, the material suffers from severe capacity degradation, mainly due to the formation of a passive metallic iron layer on the electrode [1]. Another suggested mechanism responsible for the deterioration of the performance is the formation of electrochemically inactive FeO-based side products upon delithiation process [2].In this study, we utilize reduced graphene oxide (rGO) as a substrate for the ultrafine Fe3O4 nanoparticles to form a two-dimensional hybrid material with improved characteristics. Under a mild hydrothermal condition, nanoparticles were deposited by a simple redox process in an interconnected porous network of graphene. Graphene aids in improving the Fe3O4 performance not only by reducing the charge transfer resistance, buffering the volume change induced stresses and facilitating the ion transport but also by forming an effective interface with the delocalized electrons of Fe3O4 to further result in the increase of battery capacitance by the interfacial conjugation mechanism, as confirmed by in-situ EIS measurements. The Fe3O4 particles have been effectively stabilized on the rGO surface, becoming less prone to agglomeration during cycling. Consequently, the deliverable specific capacity of the hybrid material was gradually improved upon extended cycling, reaching from 1500 mAh/g up to 2200 mAh/g at 0.5 A/g at the end of 100 cycles of operation. The increase of the specific capacity during the extended cycling was attributed to the chemical and structural changes of the electrode material evaluated by TEM and ex-situ EELS measurements. It was confirmed that the particle size is greatly reduced to 1-2 nm scale, improving the lithium-ion diffusion kinetics by the increased surface area and reversibility of the redox reaction upon graphene contribution. Moreover, the aged cells were observed to still deliver around 1100 mAh/g capacity upon more than 250 times cycling at 1 A/g, indicating the great potential of the ultrafine Fe3O4 decorated reduced graphene hybrids as superior performance Li-ion battery anode materials.

Acetamiprid's degradation products and mechanism: Part II – Inert atmosphere and charge storage

Reuse and/or recycling of spent adsorbents is taking a central role in modern thinking and catalyzed carbonization is the way forward. Herein we explore the carbonization of adsorbed acetamiprid, in an inert atmosphere, as a way of recycling and producing nitrogen-rich carbon material for potential use in supercapacitors. Added value material and the reuse of the adsorbent were achieved by carbonization at 700 °C under argon. The formation of a nitrogen-doped carbon layer as an active material on the adsorbent, bonded through a C-Si linkage, has been conclusively verified through elemental composition quantification using XPS and EDX measurements. Two-stage catalytic decomposition and condensation of the adsorbed pesticide is followed by TGA and TPD-MS. Attained carbon-based materials give stable Faradaic capacitance with a slight dependency on the number of adsorbing cycles. Capacitance calculated with respect to the adlayer carbon material reaches values as high as 610 F g−1. Galvanostatic Charge/Discharge measurement confirmed the stability of explored materials with a slight increase in capacitance over 1000 cycles. The presented results envisage electroactive materials preparation from environmental pollutants, adding value to spent adsorbents.

A comprehensive study on effect of carbon nanomaterials as conductive additives in EDLCs

This study performs a comprehensive investigation to objectively analyze the effects of various carbon nanomaterials using as conductive additives (5 wt%) in activated carbon (AC) based electrodes for electrical double-layer capacitors (EDLCs). A variety of carbon nanomaterials including carbon black (CB), single-walled carbon nanotubes (SWCNT), graphene nanoplatelets (GNP), fullerenes (C60), and activated carbon nanofibers (ACNF) are considered in this work as they provide a diverse combination of intrinsic properties such as specific surface area, conductivity, micro-mesoporous structures, and geometry of nanomaterials. These additives are incorporated into freestanding carbon electrodes, and their EDLC performance in a neutral aqueous electrolyte is investigated by means of electrochemical measurements. The findings from this work provide useful insight into how the properties of various carbon nanomaterials influence EDLC performance in different aspects such as capacitive behavior, resistivity, performance at different current densities, charge propagation properties, and stability over long-term cycling. The results show that each carbon additive has its own strengths and limitations for different performance parameters considered. The unfavorable material properties of C60 cause a significant decrease in capacitance at high current density, leading to the lowest device performance incorporated with C60 as additives. While GNP and SWCNT show high crystallinity, low ID/IG ratios, the EDLCs still exhibit decreased specific capacitance and moderate energy densities due to their relatively limited specific surface area and high resistivity of the resultant composite electrodes compared to the pristine AC. The CB additives-based samples demonstrate the highest conductivity of dry electrodes and low equivalent series resistance (ESR) in EDLCs. On the other hand, a reduction in capacitance at high current densities and material degradation during long-term cycling are observed for CB samples, which could be attributed to the high dispersibility of CB causing limited interparticle voids and thus increasing diffusion resistance. In contrast, the use of ACNFs significantly reduces the diffusion resistance and improves the cyclic stability compared with CB based samples due to the advantages of larger specific surface area and superior micro-mesoporous structures of ACNFs. In particular, EDLCs with ACNFs demonstrate an increase in specific capacitance and energy density by 99 % and 76 %, respectively compared to CB based EDLCs at a current density of 20 A/g. This work elucidates the complex interplay between carbon nanomaterials using as additives and corresponding EDLC performance. These results provide important information to the community for future development of new energy conversion and storage devices.

Left ventricular remodeling in twin pregnancy, noninvasively assessed using hemodynamic forces and pressure-volume relation analysis: prospective, cohort study.

This study was designed to prospectively investigate the pattern of intraventricular hemodynamic forces (HDFs) associated with left ventricular (LV) function and remodeling in women with uncomplicated twin pregnancy. Transthoracic echocardiography was performed on 35 women (aged 35.9 ± 4.7-yr old) during gestation (T1, <14 wk; T2, 14-27 wk; T3, >28 wk) and 6-7 mo after delivery (T0). LV HDFs were computed from echocardiography long-axis data sets using a novel technique based on endocardial boundary tracking, both in apex-base (A-B) and latero-septal (L-S) directions. HDF distribution was evaluated by L-S over A-B HDF ratio (L-S:A-B HDF ratio). At T1, L-S:A-B HDF ratio was higher than in T0 (P < 0.05) indicating HDF misalignment. At T2, a slight impairment of cardiac function was then recorded with a reduction of global longitudinal strain (GLS) and left ventricular end-systolic elastance (Ees) at pressure-volume relationship analysis versus T1 (both P < 0.05). Finally, at T3, when HDF misalignment and LV contractility reduction (GLS and Ees) were all restored, a rightward shift of the end-diastolic pressure-volume relationship (EDPVR) with an increase of ventricular capacitance was documented. In twin pregnancy, HDF misalignment in the first trimester precedes the slight temporary decrease in left ventricular systolic function in the second trimester; at the third trimester, a rightward shift of the EDPVR was associated with a realignment of HDF and normalization of ventricular contractility indexes. These coordinated changes that occur in the maternal heart during twin pregnancy suggest the role of HDFs in cardiac remodeling.NEW & NOTEWORTHY These changes indicate that 1) the misalignment of hemodynamic forces (HDFs) precedes a mild reduction in systolic function in twin pregnancy and 2) the positive left ventricular (LV) response to hemodynamic stress is mainly due to an improved diastolic function with enhanced LV cavity compliance.

Conversion of the Bi2O3 to Bi2S3: An ion exchange strategy for tailoring the surface morphology with accrued energy storage performance

A novel salt-mediated ion exchange strategy for changing the crystal structure and surface morphology of the bismuth oxide (Bi2O3) to bismuth sulfide (Bi2S3) with accrued energy storage performance has been investigated. Upright standing nanoplates of the Bi2O3 obtained at room-temperature (27 °C) on 3D nickel-foam (NiF) using successive ionic layer adsorption and reaction (SILAR) method after immersing it in thermal autoclaves in different sulphur salts at 120 °C for 8 h convert into nanocrystalline Bi2S3 having walnut, network, nanowire, and nanoflower-type surface morphologies. The electrochemical investigations carried out using electrochemical measurements reveal a noteworthy increase in the specific capacitance (SC) of the Bi2O3 nanoplates after forming Bi2S3 i.e. changing the phase and surface morphology. Compared to pristine Bi2O3 (221F g−1), the SC performances of network (1576 F g−1), walnut (358 F g−1), nanowire (296 F g−1), and nanoflower (836.6 F g−1)-type Bi2S3 electrode materials are higher in a 6.0 M KOH electrolyte solution. Furthermore, the network-type Bi2S3 of 22.02 m2 g−1 surface area exhibits remarkable stability, as evidenced by its 93 % capacitance retention even after 2000 redox cycles over other electrodes. The as-manufactured Bi2S3//nickel hydroxide (Ni(OH)2) asymmetric supercapacitor device, wherein the Bi2S3 acts as a negatrode and Ni (OH)2 positrode, delivers an outstanding energy density of 65.9 Wh/ kgat a power density of 988 W Kg−1. A twin cell assembly is envisaged for glowing the ‘CNED’ panel comprising approximately 42 LEDs with full luminosity. This idea of changing the crystal structure and surface morphology can be applied to other metal oxides to change their structures, surface areas, and morphologies for higher energy storage performance.