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The synthesis of a pectin biopolymer and ionic salt (KI)-incorporated biopolymer composite electrolyte system is reported in this communication for electrochemical device fabrication. The solution cast technique is used to create composite electrolyte films of synthesized pectin biopolymer with KI salt at different concentrations. The conductivity achieved for the pectin biopolymer-based electrolyte films is up to the order of 8.1 × 10−6 S/cm, which is an increase of three orders over the conductivity (2.7 × 10−9 S/cm) of pure pectin. Electrical, structural, and optical studies of the biopolymer electrolyte films are carried out and described. The optical properties are represented by polarized optical microscopy images which show the amorphous nature of the electrolytes films. The electrochemical stability window (ESW) presents a potential window of 1.82 V, which makes the electrolyte film suitable for device fabrication. The maximum cationic transference number reveals the ionic nature of the biopolymer electrolyte films. [ABSTRACT FROM AUTHOR]

In large-scale all-solid-state storage technologies, solid polymer electrolytes (SPEs) provide greater safety and longer cycle life than traditional liquid or gel polymer electrolytes. Polymer electrolytes (PEs) derived from biopolymers have been intensively explored for use in electrochemical devices due to their great flexibility, low cost, and environmental sustainability. However, biopolymer-based electrolytes cannot meet the expectations of practical applications at room temperature due to their low ionic conductivity. Over the years, improving the performance of this class of electrolytes has been the focus of intense research and development, notably polymer blending, plasticization, and structural functionalization. Here, we investigate the performance of an all-biopolymer solid electrolytes based on a methylcellulose-pectin blend doped with potassium phosphate. FESEM micrographs, as well as the shifting and changing intensity of FTIR bands in the electrolyte specimens confirm the polyblend homogeneity with no phase separation. The increased amorphous fraction of the composite polymer electrolytes (CPEs) is seen in the XRD and DSC patterns of the plasticized and unplasticized samples. Impendence studies performed on the system recorded a maximum ionic conductivity of 1 × 10–5 Scm−1 by doping with 50 wt.% K3PO4. This value further increased to 5.9 × 10–4 Scm−1 upon adding 25 wt.% EC to the polymer system. This sample also possesses an electrochemical stability window of 4.24 V and an ion transference number of 0.95. [ABSTRACT FROM AUTHOR]

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NaTi2(PO4)3 (NTP) and Na0.44MnO2 (NMO), and their derivatives, have emerged as the most promising materials for aqueous Na‐ion batteries. For both, NTP and NMO, avoiding the evolution of hydrogen and oxygen is found to be mandatory in order to mitigate material dissolution. Intriguingly, however, no direct determination of the hydrogen and oxygen evolution reactions (HER and OER) has yet been carried out. Using differential electrochemical mass spectrometry (DEMS) we directly identify the onset potentials for the HER and OER. Surprisingly, the potential window is found to be significantly smaller than suggested by commonly employed cyclic voltammetry measurements. CO2 evolution, upon decomposition of carbon black, is observed at an onset potential of 1.61 VRHE, which is 0.25 V more cathodic than the OER for the NMO electrode. Our results show that the state‐of‐the‐art carbon additive plays a crucial role in the stability of the positive NMO electrode in the ion battery. [ABSTRACT FROM AUTHOR]

Present studies basically focused on preparation a system by using polymer which can show high value of conductivity and can be used as an efficient electrolyte in the formation of electrostatic double layer capacitor cell (EDLC). Here, polyvinylpyrrolidone (PVP) polymer‐H2SO4 acid‐based electrolyte system have been synthesized. H2SO4 as acid is diluted using double distilled (DD) water for maximum conductivity. Various wt% of PVP as polymer added in optimized H2SO4 (1.0 M). Different types of electrical studies such as: electrical conductivity, dielectric analysis, potential window stability have been analyzed for good results. Selected system (PVP‐H2SO4) shows highest conductivity in the range ≈10−1 S cm−1. [ABSTRACT FROM AUTHOR]

An aqueous capacitor has been developed mainly for the purpose of recovering the regenerating energy for automobiles. A rapid charging within few seconds is required as well as the safety and the considerably large energy density. We have made two types of capacitors using a saturated sodium perchlorate aqueous solution (SSPAS) as an electrolyte, i.e., one consisted of a mixture of graphite and activated carbon, and the other mixtures of graphite and metal oxides. The former was an electric double layer type its energy density being 23 Wh/kg under the 70% of activated carbon and the applied voltage of 2.5 V. The generation of gases was not detected until the cut-off voltage 2.7 V using a SS444 foil as a current collector. Experiments using a titanium foil as a current collector revealed that the charge and discharge capacities were independent of temperatures from 0 to 60°C. In the applied electric current density of 20 mA/cm2, the capacity was determined to be 0.03 mAh/cm2 with the coulombic efficiency of 100% leading to the charging time of 5.4 s. The present result confirms a feasibility of recovering the regenerating energy for automobiles.

The energy density of aqueous asymmetric supercapacitors (ASCs) is confined by the narrow voltage and the mismatching between cathode and anode. Vanadium dioxide (VO2) can contemporaneously operate in both negative and positive potential windows for efficient aqueous ASCs. Nonetheless, their intrinsically inferior cycling stability and capacity seriously restrain the overall capacitive properties. Herein, a novel manganese dioxide (MnO2) coated VO2 (VO2@MnO2) with hierarchical structure is firstly fabricated as cathode with enlarged potential (0 to 1.2 V) and superb specific capacitance (608.9 F g−1 at 1.0 A g−1). Subsequently, VO2 coated by a thin layer of carbon (VO2@C) owning high electric conductivity and superb structure stability is designed to match with VO2@MnO2 cathode. Eventually, the VO2@C//VO2@MnO2 aqueous ASCs exhibit stable voltage (2.2 V), maximal energy density (77.1 Wh kg−1) and favourable cycling stability. This research inspires the design and preparation of matchable electrode materials, providing a feasible method for the development of aqueous ASCs with broad voltage. [ABSTRACT FROM AUTHOR]

Research and development of innovative energy storage and conversion devices are being actively pursued, such as supercapacitors, metal- air batteries, fuel cells, redox flow batteries, and rechargeable batteries using ions other than lithium ions as carrier ions. This review describes in detail the advantages and disadvantages of magnesium rechargeable batteries using magnesium ions as carrier ions. In addition, the key points of electrolyte development are explained. Furthermore, the progress and future challenges of electrolyte research, one of the most important elements of magnesium rechargeable batteries, are discussed in detail. [ABSTRACT FROM AUTHOR]

• A model based on the electrochemical potential of all ions at the liquid–liquid interface. • Evaluation of the voltammograms affected by the IR drops. • Estimation of capacitive currents under the voltammetric condition. • Reproduction of electrocapillary curves that satisfy thermodynamic requirements. The liquid–liquid interface between two immiscible electrolyte solutions is an important subject in electrochemistry because ion-transfer reactions can be controlled externally. The electrochemical potentials of ions determine their behavior in a liquid–liquid two-phase system. The electrochemical potential is a continuous function of the system assuming a linear transition region at the interface. A simulation model that considers the electrochemical potential of all ions in the system was constructed for the liquid–liquid interface under electrochemical-measurement conditions. This model facilitates evaluating ion-transfer voltammograms affected by IR drops and separating charging currents from Faraday currents. Moreover, the model enables electrocapillary curves to be determined. [ABSTRACT FROM AUTHOR]

In terms of supercapacitor electrode materials, biomass derived carbon electrodes are gaining much attention as a viable option for practical applications. Obtaining unique carbon nanostructures can significantly promote the electrochemical performance. Waste potato peel (WPP) derived hierarchical porous carbon materials with heteroatoms doping can boost the development of efficient and economical electrodes with improved charge storage capabilities. Here, we report sulfur and phosphorus co-doped porous activated carbon (S, P/PAC) as an effective supercapacitor electrode material with a large specific surface area. More importantly, the S, P/PAC not only acquires dual heteroatoms doping for promoting capacitive performance but also possesses fascinating porous features which are beneficial to shorten ion adsorption distances and enlarge the contact area. The electrode exhibits a high specific capacitance of 323 F g−1 at 1 A g−1, acceptable rate capability and good cycling stability after 5000 cycles. The constructed symmetric supercapacitor device with a wide operational potential window of 1.6 V achieves a maximum energy density of 45.5 Wh kg−1 at a power density of 800 W kg−1 with an improved long cycle life (94.3 retention after 10 000 consecutive cycles). • WPP biomass derived unique hierarchical porous co-doped carbon nanoarchitectures. • The carbon shows advantageous features with multifunctional macro/meso/micropores. • Heteroatoms doping improves conductivity and induces disorders into carbon microstructure. • S, P/PAC electrode delivers a high specific capacitance and good rate capability. • The symmetric supercapacitor device achieves synergetic energy/power performances. [ABSTRACT FROM AUTHOR]

A modified ionic liquid (IL)-based electrolyte, with conventional carbonates as the support solvent and lithium salt as the additive, was designed for a high-voltage electrochemical double-layer capacitor (EDLC). It is found that the employment of carbonate solvents enhances the ionic conductivity and decreases the viscosity of the electrolyte. At the same time, the addition of lithium salt plays a key role in the stabilization of the operating potential window and the modification of the passivation layer on the electrode. As a result, increased specific capacitance, improved cycle stability, and rate capability are demonstrated in the EDLC with an EMI-BF4/LiPF6/PC/DMC electrolyte at the upper voltage of 3 V, in contrast to that with pure IL and IL/carbonate mixture. This study primarily stresses the combination effect of Li salt and organic solvent in an IL electrolyte system for constructing advanced 3 V-class EDLC with excellent overall performance.

Concentrated aqueous electrolytes have been widely explored for high-voltage aqueous batteries. To achieve higher voltage, even higher alkali-ion molalities are being pursuit up to 55.5 mol kg−1 (m) that corresponds to monohydrate, but the sacrificially lowered ionic conductivity is problematic. Here we report a 61.7 m K-ion aqueous electrolyte composed of KN(SO2F)2 (KFSI) and KSO3CF3 (KOTf). The pioneered beyond-monohydrate realm is unique to K-ion systems, in which [FSI]− anion is stable to hydrolysis. The K-ion electrolyte has two-order higher ionic conductivity (12 mS cm−1 at 30 °C) than a comparable 55.5 m Li-ion system (0.1 mS cm−1) while exhibiting a 2.7 V potential window on Pt being among the widest in all alkali-ion aqueous electrolytes. This work suggests the superior overall performance of aqueous K-ion batteries over other alkali-ion batteries.

Purpose: Novel coronavirus disease has become such an escalating epidemic that the exponential growth of infected patients has overloaded the health-care systems in many countries. Determination of early assessments for patients with a risk of clinical deterioration would benefit the management of COVID-19 outbreaks. Patients and Methods: A total of 214 confirmed COVID-19 patients were enrolled from January 11th to February 11th 2020. Medical records including laboratory parameters, clinical outcomes and other characteristics of the admitted patients were analyzed retrospectively. Results: The critical patients experienced a significantly prolonged onset–admission interval and presented with lymphopenia (r=− 0.547, p=0.015) and lower albumin level (p< 0.001) 6 days after symptom onset. Early admission of critical patients significantly reduced the duration of hormone therapy. Starting from 9 days of hospital stay, the reduced lymphocyte counts exhibited linear growth. Furthermore, on days 9 and 12, significant correlations were demonstrated between immunological manifestations and duration of hormone therapy in critical patients, and length of hospital stay in severe patients. In addition, the virus negative conversion rate was more significantly correlated with increased lymphocytes in critical patients. Conclusion: Early intervention, within 6 days of symptom onset, benefited patients' recovery from critical illness. The 9– 12 days of hospital care represented a valuable window during which to evaluate the therapeutic effects on physical recovery and virus clearance. [ABSTRACT FROM AUTHOR]

A design of a fully solid-state thin-film lithium-ion battery prototype and results of its being tested are presented. It is shown that the specific features of its charge–discharge characteristics are associated with the change of the Fermi level in the electrodes and are due to changes in the concentration of lithium ions in the course of charge–discharge. The specific capacity characteristics of the prototype were determined and found to be comparable with the characteristics of commercial lithium-ion batteries. [ABSTRACT FROM AUTHOR]

• Synthesis of PT/MC/K 2 CO 3 /EC solid polymer electrolytes (SPE) • Design of experiment and analysis of data by RSM. • Optimization and interaction studies by RSM. • Prediction by RSM and experimental validation of optimum response. • Structural studies of optimum sample. • Electrochemical studies of optimum sample. • Fabrication and testing of electrochemical capacitor based on optimum response. In this study, we developed an eco-friendly solid electrolyte by blending pectin (PT) with methylcellulose (MC) and complexed with potassium carbonate (K 2 CO 3) salt and ethylene carbonate (EC) plasticizer. The goal of the study was to understand the salt-plasticizer interaction and to optimize the electrochemical performance using response surface methodology (RSM) within the central composite design (CCD). RSM approach unveiled that K 2 CO 3 and EC interact significantly, impacting the ionic conductivity and potential window of the solid biopolymer electrolytes (SBEs). After optimization, this work achieved ideal conditions with 35.05 wt% K 2 CO 3 and 16.78 wt% EC, yielding an ionic conductivity of ∼ 1 × 10-3 Scm−1 and a 4.77 V potential window. Structural analysis confirmed coordination among constituents and increased amorphous content. This work, therefore, highlights PT/MC/K 2 CO 3 /EC's potential for electrochemical device applications. An electrochemical cell constructed using the optimized sample exhibited the highest specific capacitance of 50.74 Fg–1, as determined by cyclic voltammetry (CV) analysis. [ABSTRACT FROM AUTHOR]

The increasing demand on smart miniaturized electronics has greatly boosted the development of high‐performance micro‐supercapacitors (MSCs). However, the unsatisfied electrochemical performance (e. g. narrow potential window, low areal energy density) impedes their wide applications. Here, we demonstrate a novel type of nonaqueous Na‐ion hybrid MSC, using VS2 nanosheets grown on electrochemically exfoliated graphene (VS2@EG) as the negative electrode and activated carbon as the positive electrode in nonaqueous sodium‐ion electrolyte. Such constructed nonaqueous Na‐ion hybrid MSCs show a remarkable areal capacitance of 110.7 mF cm−2 at 0.2 mA cm−2 in a wide potential range of 0.01–3.5 V and an outstanding areal energy density of 188.3 μWh cm−2. Besides, an impressive cycling stability up to 5000 cycles without noticeable decay is also achieved for the nonaqueous Na‐ion hybrid MSCs. This new hybrid MSC holds great potential application in on‐chip electronics. [ABSTRACT FROM AUTHOR]

Core-shell structural Ni(OH) 2 @MnO 2 electrodes with widened potential window and great stability are prepared through a two-step strategy, in which freestanding Ni(OH) 2 discs grow on nickel-foam as core and wrinkled MnO 2 coatings are electrodeposited as shell. The MnO 2 shell successfully inhibits the O 2 evolution process at the high oxidation potential so that the potential window of Ni(OH) 2 @MnO 2 electrode is up to 1 V. Besides, the Ni(OH) 2 @MnO 2 electrode presents a high specific capacity of 642.3 C g−1 at 1 mV s−1 and a long cyclic life without capacity fading, which is a breakthrough against the poor stability of reported Ni(OH) 2 /MnO 2 electrodes Remarkably, an asymmetric supercapacitor (ASC) constructed by Ni(OH) 2 @MnO 2 electrode and activated carbon electrode delivers a high energy density of 66.7 Wh kg−1 at a power density of 485.7 W kg−1 under potential window of 1.7 V. Furthermore, the ASC exhibits an energy density of 17.8 Wh kg−1 at a high power density of 14571.4 W kg−1 and a capacitance retention of 101.4% after 15,000 cycles, showing great rate capability and stable cyclic performance. • A novel Ni(OH) 2 /MnO 2 composite with core-shell structure is synthesized. • The Ni(OH) 2 /MnO 2 electrode shows a high specific capacity of 642.3 C g−1 at 1 mV s−1. • The asymmetric supercapacitor (ASC) presents enhanced energy density (66.7 Wh kg−1). • The ASC possesses a capacitance retention of 101.4% after 15,000 cycles. [ABSTRACT FROM AUTHOR]

Abstract In capacitive deionization (CDI) systems, more Faradaic reactions generally occur at a higher cell voltage, resulting in the poor ion-removal efficiency and high energy consumption, but a low cell voltage may lead to a low deionization capacity. In this study, an integrated strategy, consisting of (1) selecting the acceptable charge/discharge time ratio, (2) finding the potential windows of both positive and negative electrodes, and (3) using the charge-balanced method for determining the optimal mass ratio between the positive and negative electrodes (denoted as (m+)/(m−)), is proposed to find the optimal cell voltage of a CDI system with a high desalination efficiency and low energy consumption. According to this strategy, two newly designed cells using two types of activated carbon (AC) show excellent CDI performances; cell 1 with AC = ACS679, (m+)/(m−) = 1:1.4, and cell voltage = 1.4 V: salt adsorption capacity of 12 mg g−1, charge efficiency of 62%, and energy consumption of 109 kJ mol−1 and cell 2 with AC = ACS25, (m+)/(m−) = 1:1, and cell voltage = 1.2 V: salt adsorption capacity of 13 mg g−1, charge efficiency of 81%, and energy consumption of 72 kJ mol−1 although the potential window of water decomposition for such AC-coated electrodes in 8 mM NaCl is about 2 V. This universal strategy is applicable to all CDI systems utilizing various electrode materials. Graphical abstract Image 1 Highlights • We demonstrate a universal strategy for constructing the AC//AC cell with high CDI performances. • The same charge/discharge time ratio with high reversibility on both electrodes is the key. • Influences of two-electrode mass ratio on the desalination performances are studied. • The pH change is affected by the Faradaic reactions from the potential windows of electrodes. [ABSTRACT FROM AUTHOR]

Abstract Graphite intercalation compounds of bis(fluorosulfonyl)amide (FSA-GICs) are electrochemically synthesized in a highly concentrated aqueous solution. While only water decomposition occurs at the graphite electrode in a dilute aqueous solution (1 mol kg−1 NaFSA), redox peaks clearly appear in a highly concentrated aqueous solution (19 mol kg−1 NaFSA). Under the application of a constant current, the electrode potential reaches 1.7 V (vs. Ag/AgCl), which is far beyond the upper limit of the potential window, in 19 mol kg−1 NaFSA aq., and the formation of FSA-GIC is confirmed by X-ray diffraction patterns. Acceptor-type GICs using organic anions are observed for the first time in highly concentrated aqueous solutions of NaFSA. Highlights • Graphite intercalation compound (GIC) of bis(fluorosulfonyl)amide is synthesized. • Highly concentrated aqueous solutions are used as an electrolyte for GIC formation. • Stability of aqueous solutions is determined by the concentration. [ABSTRACT FROM AUTHOR]

Abstract Non-volatile superbased-derived protic ionic liquids are thermally stable and highly conductive, thus hold great promises for electrochemical applications. However, systematic accounts of their electrochemical properties are yet to be established. In this contribution, five hydrophobic superbase-derived protic ionic liquids (PILs) have been prepared from Brønsted superbases and the salts of strong acids, and their decomposition temperature, density, conductivity and viscosity have been measured. The greatest viscosity was observed with the superbased PILs, [MTBDH][NfO] (2212 cP) and the least with [MTBDH][NTf 2 ] (121 cP). Greatest conductivity was measured for [MTBDH][NTf 2 ] (1.54 mS cm−1) and the least for [MTBDH][NfO] (0.089 mS cm−1). By combining density, conductivity and viscosity, a Walden plot was set up to demonstrate the degree of ionization, or 'ionicity' of each of the five PILs is greater than 10%. Their electrochemical characteristics were determined using cyclic voltammetry. Two IUPAC-recommended internal potential reference systems, ferrocene/ferrocenium and cobaltocenium/cobaltocene, were assessed for use in the five PILs. Potential windows of the five PILs were established at glassy carbon, gold and platinum electrodes, where the widest potential window was observed with glassy carbon electrodes with no direct correlation found between the Δp K a values and the potential windows. The widest potential window was measured in [MTBH][beti] (4.3 ± 0.1 V) and the shortest in [HNC(dma)H][beti] (2.7 ± 0.1 V). The double layer capacitance was also investigated for potential applications in supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract We have newly designed five kinds of polyvalent solute that have two to four quaternary ammonium functional groups in one cation. Their molecular structure is designed to be as compact as possible, with either two or three cationic groups on a linear molecular structure, or three or four cationic moieties on three strands in a star-shape. The prepared solutes have a bis(trifluoromethylsulfonyl)imide anion in common and a flexible molecular structure that can easily adsorb onto the electrode surface of an electric double layer capacitor (EDLC). Since a single polyvalent solute molecule can accumulate more electric charge by adsorption than can a monovalent solute, a high capacitance is possible even at a low solute concentration compared with conventional cells. We evaluated some electrochemical properties of these polyvalent solutes as an electrolyte and their EDLC performance, including initial capacitance, rate characteristics and cycle durability. All the polyvalent solutes had a potential window of 5 V or more, and in particular the divalent salt showed a capacitor performance equivalent to that of the monovalent salt even at half salt concentration in the electrolyte. On the other hand, the trivalent and tetravalent solutes had a lower charge utilization rate compared with a monovalent solute. Graphical abstract Image 1 Highlights • Five kinds of newly designed polyvalent cations were prepared for capacitor use. • All the polyvalent solutes have a wide electrochemical stability. • The divalent solute has the same capacitance as a monovalent, even at half concentration. • The polyvalent electrolytes have high cycle durability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent progress (2017–2022) in the detection of pesticides at boron-doped diamond electrodes has been reviewed. • Tuning of crucial boron-doped diamond properties, voltametric potential limits and the analytical performance has been accented. • Surface modification of boron-doped diamond electrodes targeted to the quantification of pesticides is described. • Interplay of tuneable BDD properties and gaps in the research is discussed. Boron-doped diamond (BDD) is a versatile carbon material widely utilized in electroanalysis for detecting various organic compounds. In comparison to commonly employed carbon electrode materials, BDD possesses interesting and unique properties. This review article explores important role of adjustable - tuneable BDD characteristics, including boron concentration, sp3/sp2 carbon ratio, and surface treatments, in the electrochemical determination of pesticides. Through an intricate interplay of these properties, BDD's performance in term of sensitivity, selectivity, and resistance to fouling can be optimized. Notably, the exceptional potential window of BDD electrodes extends the detection capabilities into regimes where other materials falter due to oxygen evolution reactions. Furthermore, in the reduction potential range, BDD electrodes (BDDE) offer a safer alternative to toxic mercury-based electrodes. Despite the considerable progress, gaps remain in understanding the comprehensive effects of tuneable BDDE properties on pesticide analysis. Comparative studies exploring the interplay between these properties and their impact on detection, particularly in multianalyte systems and under challenging conditions, are crucial. Addressing issues related to matrix interference and fouling would contribute significantly to the development of robust pesticide sensors. This review provides insights into the critical role of BDD's properties in pesticide detection and highlights avenues for future research. [ABSTRACT FROM AUTHOR]

A ZnO nanofiller-based polymer gel electrolyte was prepared using solution-cast technique by incorporating PVDF-HFP as the polymer, ethylene carbonate (EC)-propylene carbonate (PC) as plasticizers, tetraethylammonium tetrafluoroborate (TEABF4) as salt, and ZnO as nanofiller. A maximum ionic conductivity value 6.3 × 10−3 Scm−1 was obtained by adding 12 wt% of ZnO nanoparticles in complex [{PVDF-HFP (20 wt%) + {EC-PC (v/v)-TEABF4 (1.0 M)} (80 wt%)}]. From the temperature-dependent conductivity plot, the activation energy is found to be equal to Ea ~ 0.07 eV. The amorphous structure is confirmed by SEM and XRD analysis. Electrochemical potential window and ionic transference number were calculated and found to be equal to ~3.3 V and 0.84, respectively. Optimized NCPGE is utilized in the fabrication of the electrical double-layer capacitor (EDLC) cell using market parched activated charcoal as electrode material. The specific capacitance of the fabricated EDLC cell is found to be equal to 162.9 mFcm−1 and ~ 67.8 Fg−1 for the single-electrode system. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol)/poly(3,4-ethylenedioxythiophene) (PVA/PEDOT) nanofibers were synthesized as a positive electrode for high-performance asymmetric supercapacitor (ASC). PVA/PEDOT nanofibers were prepared through electrospinning and electrodeposition meanwhile reduced graphene oxide (rGO) was obtained by electrochemical reduction. The PVA/PEDOT nanofibers demonstrated cauliflower-like morphology showing that PEDOT was uniformly coated on the smooth cross-linking structure of PVA nanofibers. In addition, the ASC showed a remarkable energy output efficiency by delivering specific energy of 21.45 Wh·kg−1 at a specific power of 335.50 W·kg−1 with good cyclability performance (83% capacitance retained) after 5000 CV cycles. The outstanding supercapacitive performance is contributed from the synergistic effects of both PVA/PEDOT//rGO, which gives promising materials for designing high-performance supercapacitor applications.

The voltage of carbon-based aqueous supercapacitors is limited by the water splitting reaction occurring in one electrode, generally resulting in the promising but unused potential range of the other electrode. Exploiting this unused potential range provides the possibility for further boosting their energy density. An efficient surface charge control strategy was developed to remarkably enhance the energy density of multiscale porous carbon (MSPC) based aqueous symmetric supercapacitors (SSCs) by controllably tuning the operating potential range of MSPC electrodes. The operating voltage of the SSCs with neutral electrolyte was significantly expanded from 1.4 V to 1.8 V after simple adjustment, enabling the energy density of the optimized SSCs reached twice as much as the original. Such a facile strategy was also demonstrated for the aqueous SSCs with acidic and alkaline electrolytes, and is believed to bring insight in the design of aqueous supercapacitors. [ABSTRACT FROM AUTHOR]

• A polymeric ionic liquid is synsthesized and served as an electrolyte additive. • PVEIm.TFSI can improve the electrochemical stability of EMIm.TFSI/PC based electrolytes. • The operational voltage of EDLC with PIL additive increases from 2.8 V to 3.2 V. • Equivalent circle model and bode plots demonstrate changes in interface behaviors. • PIL additive reduces each element of impedance and improves the ions diffusion. Improving the energy density of electrochemical double layer capacitors (EDLC) is an important but challenging research topic. Electrolytes with wide operating potential windows are key materials for current EDLC technology. In this work, an ether branch polymeric imidazole ionic liquid (PVEIm.TFSI) is synsthesized and served as an electrolyte additive in common electrolyte to optimize the working potential ranges of carbon-based EDLC. The addition of PVEIm.TFSI can improve the electrochemical stability of electrolytes and effectively adjust the upper limit potential (P U), lower limit potential (P L). Under the optimal addition ratio of 10%, the operational voltage of EDLC increases from 2.8 V to 3.2 V, which lead to an approximately 41.5% energy density increase compared with EDLC without additive. Cycling stabibity of EDLC containing 10% PVEIm.TFSI is significantly enhanced under both 3.0 V and 3.2 V. Furthermore, an equivalent circuit model and Bode plots are proposed from the electrochemical impedance spectroscopy (EIS) measurements. Both simulated and measured date dedicate that PVEIm.TFSI reduces each element of resistance, which result in more ions movement and smaller energy barrier for the diffusion processes, thereby improving the electrochemical performance of cells. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous PANI with satisfactory CO 2 capture and spillover capability triggers CO 2 activity of TcPcCo in thermodynamics and kinetics. • PANI-TcPcCo/CP delivers over 95% FE CO at a potential range of 450 mV, ranking foremost among the reported phthalocyanine-based catalysts. • This work presents a new perspective on advancing the catalytic capability of molecular materials by regulating the local chemical environment. Metallophthalocyanines (MPcs) with the especially active metal-N 4 catalytic sites have the great potential for the electrocatalytic CO 2 -to-CO conversion. However, the masking of metal-N 4 catalytic sites attributed to the strong π-π interaction and the difficulty in capturing CO 2 severely limits their catalytic efficiency. Herein, we designed a self-supported electrode that tetra-β-carboxy phthalocyanine cobalt(II) (TcPcCo) was anchored into polyaniline (PANI) chain in isolation using the carbon paper (CP) as a support. The PANI with unique porous structure provides large surface area, rapid electron transfer, and unimpeded pathways for CO 2 diffusion. More importantly, sufficient CO 2 captured by PANI can continuously spill over to metal-N 4 active sites and be reduced into CO. The synthesized electrode for CO 2 reduction reaction (CO 2 RR) could maintain a high CO Faraday efficiency of over 95% (maximum 99.3%) at an extraordinary wide potential range of 450 mV (from -0.50 V to -0.95 V vs. RHE), ranking foremost among the previously reported phthalocyanine-based electrocatalysts. Furthermore, relative to TcPcCo, the CO turnover frequency (TOF) of PANI-TcPcCo/CP significantly improves, especially at the more negative operating potential (about 7 ∼ 68 times). Theoretical calculations further reveal that the introduce of PANI optimizes the free energy barrier of CO 2 RR intermediate at Co-N 4 site, thus accommodating the*COOH formation, and also suppresses the competition of hydrogen evolution reaction. This work presents a new perspective on advancing the catalytic CO 2 RR capability of molecular materials by regulating the chemical environment surrounding a catalytically active site. [Display omitted] [ABSTRACT FROM AUTHOR]

Bipolar supercapacitors that can store many fold higher capacitance in negative voltage compared to positive voltage are of great importance if they can be engineered for practical applications. The electrode material encompassing high surface area, better electrochemical stability, high conductivity, moderate distribution of pore size, and their interaction with suitable electrolytes is imperative to enable bipolar supercapacitor performance. Apropos of the aforementioned aspects, the intent of this work is to ascertain the effect of ionic properties of different electrolytes on the electrochemical properties and performance of a porous CNT-MoS 2 hybrid microstructure toward bipolar supercapacitor applications. The electrochemical assessment reveals that the CNT-MoS 2 hybrid electrode exhibited a two- to threefold higher areal capacitance value of 122.3 mF cm -2 at 100 μA cm -2 in 1 M aqueous Na 2 SO 4 and 42.13 mF cm -2 at 0.30 mA cm -2 in PVA-Na 2 SO 4 gel electrolyte in the negative potential window in comparison to the positive potential window. The CNT-MoS 2 hybrid demonstrates a splendid Coulombic efficiency of ∼102.5% and outstanding stability with capacitance retention showing a change from 100% to ∼180% over 7000 repeated charging-discharging cycles.

Activated carbon fibers (ACFs) with large surface area were easily prepared from melt-spun fibers of polyethylene glycol lignin (PEGL). To fabricate electric double-layer capacitors (EDLCs) with a wide potential window and a high energy density in an EDLC package, electrodes (mainly composed of ACFs) were internally laminated and connected in series, in parallel, or in a series/parallel combination. Such resultant EDLCs are termed internal tandem (IT) EDLCs. As expected, the potential window was expanded by the series connection, and the capacitance was increased by the parallel connection. As a result, the energy density in the parallel-connected EDLC was remarkably increased by 66% (16.6 Wh kg−1) compared with that of a single-cell EDLC. The EDLC with the combination connection showed both advantages. Thus, based on the package weight, the electrochemical performance of the EDLCs was remarkably improved by the IT-type lamination of electrodes. [ABSTRACT FROM AUTHOR]

The upper limit of the double-layer potential window for the propylene carbonate/carbon black interface is effectively extended from 0.1 to 1 V (vs. Ag/AgNO 3 ), compared with activated carbon. Commercial carbon black with low defects and activated carbon are respectively employed as positive and negative electrode materials to construct an advanced asymmetric supercapacitor with cell voltage reaching 3 V in propylene carbonate. This asymmetric supercapacitor of the double-layer type with a cell voltage of 3 V is very stable in 10,000-cycle charge-discharge tests. [ABSTRACT FROM AUTHOR]

The performance of supercapacitors electrode materials depends on not only their structures but also selected electrolyte as well as proper potential window. The 3D hierarchical NiCo 2 O 4 @MnO 2 hybrid nanomaterial was grown on stainless-steel mesh through a two-step electrodeposition process. The resultant interconnecting network consisting of porous nanosheets possesses open geometry and porous nature. When being employed in supercapacitor, the pseudocapacitive contributions (redox reaction on surface or near-surface) of two components are taken into account comprehensively in a wide potential window. This makes such a hybrid network deliver a high specific capacitance of 913.6 F/g at 0.5 A/g and 12.9% capacitance loss after 3000 cycles in KOH solution. Remarkably, an asymmetric supercapacitor based on NiCo 2 O 4 @MnO 2 hybrid networks as the positive electrode and activated carbon (AC) as the negative electrode achieves an energy density of 37.5 Wh/kg and a maximum power density of 7500 W/kg. These attractive findings make this NiCo 2 O 4 @MnO 2 hybrid networks hold promise in energy storage device as an efficient electrode. [ABSTRACT FROM AUTHOR]

Free-standing nanoporous Ni-Cu-Mn mixed metal oxides on metal with a high surface area was fabricated by chemically dealloying a Ni 8 Cu 12 Mn 80 single-phase precursor, followed by electrochemical oxidation in an alkaline solution. Electrochemical analysis shows that first Cu and Mn-based metal oxides formed by the electrochemical oxidation. Ni-based oxides grow later with the increase of electrochemical CV cycles and mix with the Cu/Mn oxides, forming a relatively stable mixed metal oxides thin film on metal ligament network. Due to the different electrochemical properties of each metal and the synergetic effect between them, the mixed ternary metal oxides formed on metal nano-ligament can operate stably between a wide potential window (1.5 V) in 1.0 M KOH aqueous solution when tested as a free-standing supercapacitor electrode. Due to the high volumetric surface area, wide operating potential window and excellent conductivity, the nanoporous metal oxides@metal composite exhibits a high volumetric capacitance (∼500 F cm −3 ), high energy density (∼38 mW h cm −3 ) and good cycling stability. [ABSTRACT FROM AUTHOR]

Flexible wearable multifunctional devices such as cellulose loaded with electroactive components are in the focus of modern research for electrochemical energy storage, sensors and actuators. In this report, the multifunctional response of cellulose with 50 wt% MWCNT formed into Cell-CNT composite fibers is demonstrated. The effect of (aqueous) electrolyte choice on the electro-mechanical response of Cell-CNT was studied. Aqueous electrolytes such as tetramethylammonium chloride (TMACl), sodium perchlorate (NaClO 4), and 1-ethyl-2,3-dimethylimidazolium trifluoromethanesulfonate (EDMITF) were considered, with the resulting stress and strain decreasing in the order Cl− > ClO 4 − > TF−, matching the order of the size of the ions. Upon negative charging, the cations of the electrolytes showed electromechanical response in the order: TMA+ > EDMI+ > Na+, where the solvation strength of the cations had stronger influence than their size without solvation shell. The highest specific capacitance was shown by TMACl in the range of 74 mF cm−2 upon positive charging, with also the best retention of capacitance of 86% in long-term measurements. Chronopotentiometric measurements of Cell-CNT fibers where conducted to evaluate if the composites can also act as sensors for different electrolytes. The Cell-CNT fibers were characterized with scanning electron microscopy, energy dispersive X-ray, FTIR and Raman spectroscopy. [Display omitted] • MWCNT cellulose fiber investigate in three different aqueous electrolytes. • Potential ranges 0.8 V to 0.0 V anions and 0.55 V to −0.8 V cations can be differentiated. • Multifunctional properties: actuator, sensor (cations and anions) and energy harvester. [ABSTRACT FROM AUTHOR]

In this paper we prove the existence of isolated eigenvalues of finite multiplicity below the essential spectrum of a straight waveguide with a curved potential window in the three dimensional space. We give also some asymptotic results for these eigenvalues and their counting function. We illustrate our results by some numerical computations. [ABSTRACT FROM AUTHOR]

The pseudocapacitive properties of an electrochemically modified graphite electrode (MGE) in electrolytes with different pH are investigated, and the transformation of the corresponding reaction mechanism and contribution of pseudocapacitance to the overall capacitance are analyzed in detail by cyclic voltammetry, electrochemical impedance spectroscopy and self-discharge tests. At low pH, the pseudocapacitance is attributed to the redox reaction among hydroxyl, carbonyl and carboxyl groups, which takes up nearly 61% of the overall capacitance. As the pH increases from 0 to 2, the carboxyl groups begin to ionize, the proportion of the redox reaction between carbonyl and carboxyl groups is decreased, and the contribution of pseudocapacitance to the overall capacitance decreases too. With the pH further increasing, the carboxyl groups are almost completely ionized and the redox reaction occurs only between hydroxyl and carbonyl groups, the contribution of pseudocapacitance drops to 33% and the double layer capacitance begins to play a dominate role. Despite of a lower specific capacitance for MGE in neutral solution, a broader potential window is obtained and the energy density would be increased nearly 1.33 times as large as that in acidic solution. The results indicate that the electrochemical system of MGE with the neutral electrolyte may be a promising candidate for a high energy density supercapacitor. [ABSTRACT FROM AUTHOR]

Bimetallic oxides with multiple redox states and high theoretical capacitances have attracted attention as efficient electroactive material of supercapacitors (SC). MnCo 2 O 4 is applied on SC due to high oxidation potential and multiple oxidation states. One-dimensional nanotube can provide efficient charge-transfer path, large surface area and voids for ions confinements. In this study, it is firstly to synthesize MnCo 2 O 4 nanotubes using electrospinning and hydrothermal techniques for SC. Hydrothermal duration determines redox extents of ZIF67 and Mn precursor, while Mn concentration dominates particle amounts on nanotubes. The optimized MnCo 2 O 4 electrode shows the highest specific capacitance (C F) of 101.9 ​F/g at 20 ​mV/s and the best high-rate performance, due to complete conversion of ZIF67 and KMnO 4 as well as well-constructed particle-assembled wall. The symmetric SC presents a maximum energy density of 3.40 ​Wh/kg at 350 ​W/kg, and excellent cycling stability with Coulombic efficiency of 91.2% and C F retention of 91.2% in 5500 cycles. [Display omitted] • MnCo 2 O 4 nanotube is made via electrospinning and hydrothermal techniques for SC. • Hydrothermal duration decides redox extent of ZIF67 and Mn precursor in nanotubes. • Mn concentration dominates particle amounts on the wall of MnCo 2 O 4 nanotubes. • Optimal MnCo 2 O 4 electrode shows C F of 101.9 ​F/g and good high-rate performance. • SC shows Coulombic efficiency of 91.2% and C F retention of 91.2% in 5500 cycles. [ABSTRACT FROM AUTHOR]

Amorphous MnO x thin films were prepared on flexible substrates by electron beam evaporation, with the aim of using them as electrodes in supercapacitors. The material properties of the MnO x films were characterized by scanning electron microscopy, atomic force spectroscopy, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. Cyclic voltammetry was then employed to study the electrochemical reaction mechanism. A large potential window was employed (–0.4 to 1.0 V vs. SCE) to investigate the possibility of increased energy density. When the lower potential limit was expanded from 0.0 to –0.4 V vs. SCE, faradaic redox waves were observed in the expanded region, suggesting that the redox reaction was mainly controlled by cation diffusion into the bulk structure. The galvanostatic cycle test demonstrated that capacitance was retained up to 500 cycles for a potential window of –0.1 to 1.0 V vs. SCE. [ABSTRACT FROM AUTHOR]