Wide Potential Window Research Articles

Metal organic framework MOF-74 based solid-state electrolytes for all-solid-state sodium metal batteries

The all-solid-state sodium metal batteries (ASSMBs) are highly promising for their low cost. MOFs have emerged as potential solid electrolyte materials due to their abundant pores and open metal-active sites, enabling fast ion conduction. In this study, a solid electrolyte membrane Na/Mg-MOF-74 was synthesized using a simple method. The stable ion-conducting channel of Mg-MOF-74 contributed to the excellent electrochemical performance of ASSMBs coupled with Na/Mg-MOF-74 electrolyte, including high ionic conductivity (8.53 × 10−4 S cm−1 at 70 °C) and a wide potential window (1–4.3 V). This study represents the first utilization of Mg-MOF-74 for ASSMBs, marking a significant milestone in the field.

CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes.

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm-2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg-1 at a power density of 330.5 W kg-1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.

A Novel Thin-Layer Flow Cell Sensor System Based on BDD Electrode for Heavy Metal Ion Detection.

An electrochemical sensor based on a thin-layer flow cell and a boron-doped diamond (BDD) working electrode was fabricated for heavy metal ions determination using anodic stripping voltammetry. Furthermore, a fluidic automatic detection system was developed. With the wide potential window of the BDD electrode, Zn2+ with high negative stripping potential was detected by this system. Due to the thin-layer and fluidic structure of the sensor system, the electrodepositon efficiency for heavy metal ions were improved without using conventional stirring devices. With a short deposition time of 60 s, the system consumed only 0.75 mL reagent per test. A linear relationship for Zn2+ determination was displayed ranging from 10 μg/L to 150 μg/L with a sensitivity of 0.1218 μA·L·μg-1 and a detection limit of 2.1 μg/L. A high repeatability was indicated from the relative standard deviation of 1.60% for 30 repeated current responses of zinc solution. The system was applied to determine Zn2+ in real water samples by using the standard addition method with the recoveries ranging from 92% to 118%. The system was also used for the simultaneous detection of Zn2+, Cd2+, and Pb2+. The detection results indicate its potential application in on-site monitoring for mutiple heavy metal ions.

Mesoporous nanoplates consisting of seamless graphene frameworks

Electric double-layer capacitors (EDLCs) have attracted significant attention in the field of energy storage due to their high specific power, superior safety, and long cycle life. However, commercially available electrode materials, such as activated carbons, are still facing the challenge of low energy density. Graphene mesosponge (GMS) has shown promise as an electrode material for EDLCs due to its mesoporous structure, large specific surface area, and edge-free properties that allow operation under wide potential windows. Nevertheless, GMS materials reported so far consist of large micro-particles above 30 μm, which is unfavorable in terms of the long ion-diffusion path within the particles. In this study, a novel nanoplate GMS (np-GMS) is synthesized via a template carbonization approach, where chemical vapor deposition is performed onto a nanoplate MgO. The np-GMS exhibits a nanoplate structure with a lateral nanoplate size of approximately 1 μm and a nanoplate thickness of less than 100 nm. When employed as an electrode for EDLCs, the np-GMS shows a specific capacitance of 132 F g−1 in the potential window of −0.5 V to 1.5 V vs. Ag/AgClO4. Moreover, the np-GMS-included EDLCs demonstrate a specific energy of 59 Wh kg−1 under a voltage window of 3.5 V, which outperforms the counterpart GMS with a larger particle size and commercialized activated carbon. The introduction of np-GMS is believed to open up new possibilities for improving the performance and industrial feasibility of GMS in EDLCs.

Solvothermal growth of silver-doped vanadium pentoxide microurchins as a cathode material for all-solid-state asymmetric supercapacitors

This study aims to improve the electrochemical properties of vanadium pentoxide by inserting silver cations into the vanadium oxide lattice. The porous silver-doped V2O5 (Ag-V2O5) microurchins were grown via a facile one-step solvothermal process. The enhanced mesoporosity and interlayer d-spacing upon silver-doping, as confirmed by Brunauer–Emmett–Teller (BET) and X-ray diffraction analyses, played an important role in facilitating the intercalation/de-intercalation of electrolyte ions and thus enhancing the capacitive performance of V2O5. The Ag-V2O5 electrode delivered a superior capacitance of 535.6 F/g at 0.5 A/g and a higher rate capacity of 78.8% in non-aqueous lithium perchlorate electrolyte compared to sodium perchlorate electrolyte. Furthermore, the specific capacitance of V2O5 was remarkably increased by ∼56% upon 5.33 at% Ag-doping. An all-solid-state asymmetric supercapacitor (ASC) was fabricated using Ag-V2O5 as the cathode, activated carbon cloth as the anode, and LiClO4-loaded poly(acrylonitrile-co-1-vinylimidazole-co-itaconic acid) as a solid electrolyte. The ASC was stably operating in a wide potential window of 0–1.6 V and delivered a high energy of 53.8 Wh kg−1. Most importantly, the ASC exhibits a slow self-discharge rate with only 7.7% voltage loss after 17 h when charged at 1.6 V. Hence, these impressive electrochemical performances of Ag-V2O5 make it a promising cathode material for next-generation supercapacitors.

Halide precursor reduction strategy to modulate bismuthene with high selectivity and wide potential window for electrochemicalCO2reduction

AbstractDeveloping high‐performance electrocatalysts for CO2reduction reaction (CO2RR) is vital in achieving a carbon‐neutral society by converting CO2into valuable chemicals. CO2RR electrocatalyst with lower overpotential, higher selectivity and wider working potential range is urgently desired, but it is still challenging to realize these factors simultaneously. Here, high‐performance bismuthene‐based electrocatalysts were synthesized by reducing bismuth precursors like BiCl3, BiBr3, and BiI3in liquid phases. Especially, bismuthene‐I derived from BiI3showed a nanosheet morphology (around four‐layer) with significantly enhanced (110) surfaces. It enabled an ultrawide potential window (0.7 V) for high formate selectivity (>90%) in a H‐type cell and achieved an ultralow potential (−0.46 V vs. reversible hydrogen electrode) to attain a current density of 200 mA cm−2in a gas‐diffusion flow cell. The prominent long‐term operational capability of bismuthene‐I was demonstrated in both H‐type and gas‐diffusion cells. Density functional theory calculations revealed that bismuthene‐I possessed abundant topological Bi(110) surfaces states that can reduce the CO2RR overpotential, suppress the competitive hydrogen evolution reaction, and facilitate electron donation during CO2electrocatalysis. The bismuthene‐I realized low overpotential, high selectivity and wide working potential range simultaneously for electrochemical CO2RR. This work unfolds the broader plausibility of facilely reducing precursors for the scalable fabrication of high‐performing CO2RR electrocatalysts.

Development of dicationic 1,2,4-triazolium salts and their application as solid-state electrolyte for energy storage

Here, in this study we report the synthesis and characterizations of novel electrolyte based on dicationic salts 1,3-bis(1-alkyl-1,2,4-triazolium)mesitylene bis(tetrafluoroborate). Two cations were linked by mesitylene as spacer. Using 1H NMR, 13C NMR, FTIR and RAMAN spectroscopy methods the structural characterization of synthesized salts were done. Cyclic voltammetry, electrochemical impedance spectroscopy, thermogravimetry analysis, and differential scanning calorimetry have all been used to examine their thermal, electrochemical, and transport properties. Their suitability for energy storage was examined by fabricating a cell out of it in a Swagelok, where ionic liquid gel polymer electrolyte (ILGPE) was used as electrolyte and the graphite-PTFE sheet functioned as an electrode to construct a symmetrical EDLC. A wide working electrochemical potential window range of 0 to 4.5 V was obtained after studying the electrochemical cell performance, indicating that the dicationic salts can be employed as a promising electrolyte. It provided an effective areal capacitance of 63.13 F/cm2. Even after 2000 consecutive cycles of charging and discharging, the fabricated device continues to retain about 80 % of its initial capacitance. The GCD curves provided computed values for energy and power density of 1.1 μWh and 317.5 μW/cm2, respectively.

Proton-rich two-dimensional defective Bi2S3-derived nanosheets for boosting CO2 electroreduction

Bismuth (Bi)-based catalysts have attracted great attention in electrocatalytic CO2 reduction into formate, but suffer from modest activity due to insufficient active sites and slow protonation process. Here, two-dimensional (2D) defect-rich Bi2S3 nanosheets are first achieved through chemical vapor sulfurization of Bi2O3 solids. It is found that the defects enable the stable immobilization of S heteroatoms into 2D Bi lattice. A combination of computational and experimental analyses reveal that S dopants can not only facilitate water dissociation to construct proton-rich surface, but also concentrate potassium cations to stabilize *OCHO intermediates. Further cooperating with defects, the *OCHO formation can be both kinetically and thermodynamically boosted. Remarkably, the constructed Bi2S3 nanosheets exhibit a high formate Faradaic efficiency (>90%) over a wide potential window and a high intrinsic stability over 200 h. The excellent performance in flow cell as well as promising solar-driven CO2 electrocatalysis further demonstrate the great potential for practical implementation.

Uncovering Photoelectronic and Photothermal Effects in Plasmon-Mediated Electrocatalytic CO2 Reduction.

Plasmon-mediated electrocatalysis that rests on the ability of coupling localized surface plasmon resonance (LSPR) and electrochemical activation, emerges as an intriguing and booming area. However, its development seriously suffers from the entanglement between the photoelectronic and photothermal effects induced by the decay of plasmons, especially under the influence of applied potential. Herein, using LSPR-mediated CO2 reduction on Ag electrocatalyst as a model system, we quantitatively uncover the dominant photoelectronic effect on CO2 reduction reaction over a wide potential window, in contrast to the leading photothermal effect on H2 evolution reaction at relatively negative potentials. The excitation of LSPR selectively enhances the CO faradaic efficiency (17-fold at -0.6 VRHE ) and partial current density (100-fold at -0.6 VRHE ), suppressing the undesired H2 faradaic efficiency. Furthermore, in situ attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals a plasmon-promoted formation of the bridge-bonded CO on Ag surface via a carbonyl-containing C1 intermediate. The present work demonstrates a deep mechanistic understanding of selective regulation of interfacial reactions by coupling plasmons and electrochemistry.

Uncovering Photoelectronic and Photothermal Effects in Plasmon‐Mediated Electrocatalytic CO2 Reduction

AbstractPlasmon‐mediated electrocatalysis that rests on the ability of coupling localized surface plasmon resonance (LSPR) and electrochemical activation, emerges as an intriguing and booming area. However, its development seriously suffers from the entanglement between the photoelectronic and photothermal effects induced by the decay of plasmons, especially under the influence of applied potential. Herein, using LSPR‐mediated CO2 reduction on Ag electrocatalyst as a model system, we quantitatively uncover the dominant photoelectronic effect on CO2 reduction reaction over a wide potential window, in contrast to the leading photothermal effect on H2 evolution reaction at relatively negative potentials. The excitation of LSPR selectively enhances the CO faradaic efficiency (17‐fold at −0.6 VRHE) and partial current density (100‐fold at −0.6 VRHE), suppressing the undesired H2 faradaic efficiency. Furthermore, in situ attenuated total reflection‐surface enhanced infrared absorption spectroscopy (ATR‐SEIRAS) reveals a plasmon‐promoted formation of the bridge‐bonded CO on Ag surface via a carbonyl‐containing C1 intermediate. The present work demonstrates a deep mechanistic understanding of selective regulation of interfacial reactions by coupling plasmons and electrochemistry.

Ce4+-Doped CuO Mesoporous Nanosheets for CO2 Electroreduction to C2H6 with High Selectivity under a Wide Potential Window in a Flow Cell

Ce⁴⁺-Doped CuO Mesoporous Nanosheets for CO₂ Electroreduction to C₂H₆ with High Selectivity under a Wide Potential Window in a Flow Cell

Electrocatalytic Co‐Upcycling of Nitrite and Ethylene Glycol over Cobalt–Copper Oxides

AbstractElectrocatalytic nitrite (NO2−) reduction reaction (NO2−RR) for ammonia (NH3) synthesis is a promising alternative for NO2− resource utilization. Herein, a dual‐site copper‐cobalt oxide catalyst is reported for the efficient electrocatalytic reduction of NO2− to NH3, exhibiting NH3 Faradaic efficiency that remained above 95% (0.1 m NaNO2) over a wide potential window (−0.1 to −0.6 V vs reversible hydrogen electrode, vs RHE). More importantly, the high NH3 Faradaic efficiency maintains an over 85% (−0.1 to −0.3 V vs RHE) at a low concentration of NaNO2 (0.01 m). Theoretical calculations demonstrate that CuO serves the *NO2 to *NO and is subsequently converted to NH3 on Co3O4. Coupled anodic ethylene glycol (EG) oxidation reaction endows low cell voltage (ΔU = 480 mV, 10 mA cm−2) and energy consumption saving (>23%) in a two‐electrode system. This work provides a reference for a co‐upcycling electrolyzer for NO2− and EG.

Unraveling the Pseudocapacitive Charge Storage Mechanism of NiCo2O4 Nanoflakes for Advanced Quasi Solid-State Hybrid Supercapacitor

Design and development of battery-type electrode materials with high capacitance, wide potential window, and desirable cycle stability are essential to enhance the performance of hybrid supercapacitors (HSC). In this study, a simple sol-gel synthesis strategy has been adopted to fabricate spinel NiCo2O4 nanoflakes. The morphological and structural analysis shows that the NiCo2O4 is formed with nanoflakes morphology having high phase purity and good stoichiometry. The electrochemical study of the NiCo2O4 electrode in 1 M Na2SO4 aqueous electrolyte reveals that the electrode has a maximum specific capacitance of 488 F g−1 at 2 A g−1. Detailed electrochemical examinations of cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS) profiles reveal the pseudocapacitive charge storage kinetics of NiCo2O4 electrode. Furthermore, a hybrid supercapacitor device is constructed by employing molybdenum-disulfide (MoS2) & reduced graphene oxide (rGO) nanocomposite and NiCo2O4 as the negative and positive electrodes, respectively. PVA-Na2SO4 is utilized as the polymer gel electrolyte. The HSC device delivered the highest specific capacitance of 106 F g−1 at a current density of 0.8 A g−1 with superior cyclic stability. Thus, exploring strategies for superior performance through material modification and selection of suitable electrolyte has been useful and makes this study significant among the reported related works.

Regulating oxygenated groups and carbon defects of carbon-based catalysts for electrochemical oxygen reduction to H2O2 by a mild and self-recycled modification strategy

It is a green route to prepare H2O2 through electrochemical oxygen reduction at normal temperature and pressure using only oxygen and water as feedstock. This method is suitable for the distributed production of H2O2, avoiding the safety problems caused by long-term storage and long-distance transportation. We propose a mild strategy modulating carbon materials i.e., the carbon black is treated by a low-concentration H2O2, where the oxidation reactions occur by hydroxyl radicals. The oxygenated groups and carbon defects were regulated by adjusting the concentration H2O2 used. The modified carbon black showed excellent selectivity and stability in the electrosynthesis of H2O2 under neutral conditions. The optimal catalyst had a selectivity of 99% for H2O2 at a potential of 0.25 V vs. reversible hydrogen electrode and remained above 90% in a wide potential window. The activity of optimal catalyst was increased by 19% compared to the pristine carbon black. It was found that the improvement of catalytic activity and selectivity was mainly ascribed to carbon defect. The concentration of H2O2 produced was 0.33 mol L−1 with 80% Faradaic efficiency at 4.5 V in the flow cell. The productivity of H2O2 could reach 2.23 mol g−1 h−1 during a continuous operation of 10 h.Graphical

Breaking the scaling relationship via lattice expansion of Ag for CO2 electroreduction over a wide potential window

AbstractThe achievement of excellent catalytic activity for electricity‐driven CO2 reduction over a wide potential window is significant for the mature applications. However, the efficient potential range is always limited by the dilemma in CO2 activation and product desorption at different potentials, due to the scaling relationships of adsorption energy. Herein, we developed a nanostructured Ag‐CO3 electrocatalyst featuring metallic Ag with Ag(220) orientation on the surface and Ag2CO3 beneath. The interactions between Ag and Ag2CO3 lead to lattice expansion on the surface of Ag, resulting in electron localization and accordingly enhanced CO2 activation to *COOH on Ag. Furthermore, this lattice expansion induces a change in the *CO adsorption geometry from a bridge mode to a linear mode, which compensates the promotion effect of electron localization on *CO adsorption energy. As a result, the scaling relationship between *COOH and *CO adsorption energy was disrupted, leading to enhanced *COOH adsorption and inferior *CO adsorption. Consequently, the Ag‐CO3 catalyst exhibited a high FECO (>80%) over a robust potential window of −0.8 to −1.8 V (vs. RHE), with a maximum FECO of 95% at −1.2 V (vs. RHE). The mechanism described herein offers a universal design principle for the development of high‐efficiency CO2 electroreduction catalysts that operate effectively within a broad potential range.

Charge‐switchable ligand ameliorated cobalt polyphthalocyanine polymers for high‐current‐density electrocatalytic CO2 reduction

AbstractMetallic phthalocyanines are promising electrocatalysts for CO2 reduction reaction (CO2RR). However, their catalytic activity and stability (especially under high potential) are still unsatisfactory. Herein, we synthesized a covalent organic polymer (COP‐CoPc) by introducing charge‐switchable viologen ligands into cobalt phthalocyanine (CoPc). The COP‐CoPc exhibits great activity for CO2RR, including a high Faradaic efficiency over a wide potential window and the highest CO partial current density among all ligand‐tuned phthalocyanine catalysts reported in the H‐type cell. Particularly, COP‐CoPc also shows great potential for practical applications, for example, a FECO of >95% is realized at a large current density of 150 mA/cm2 in a two‐electrode membrane electrode assembly reactor. Ex situ and in situ X‐ray absorption fine structure spectroscopy measurements and theory calculations reveal that when the charge‐switchable viologen ligands switch to neutral‐state ones, they can act as electron donors to enrich the electron density of Co centers in COP‐CoPc and enhance the desorption of *CO, thus improving the CO selectivity. Moreover, the excellent reversible redox capability of viologen ligands and the increased Co–N bonding strength in the Co–N4 sites enable COP‐CoPc to possess outstanding stability under elevated potentials and currents, enriching the knowledge of charge‐switchable ligands tailored CO2RR performance.

A high-performance asymmetric supercapacitor based on morphologically tuned CoB anode and heterostructured graphitic carbon nitride/MoSe2 cathode

Transition metal borides (TMBs) are among the fascinating electrode materials for supercapacitors. TMBs have high theoretical capacity, however the narrow potential window, structural deterioration during redox cycling, and fairly small surface area remains a major limitation. To resolve these, we synthesize cobalt boride (CoB) in different morphologies by initiating the reaction with different precursors namely, zeolitic imidazolic framework-67 (ZIF-67), Co layered hydroxide (SLH), and CoCl2. CoB synthesis from ZIF-67, SLH, and CoCl2 results in nanoflower, nanoplate, and nanowire morphology. CoB in nanowire morphology, shows highest charge storage of 273 F g−1 at 1 A g−1 due to 1D structure that endow plentiful surface area, high conductivity, ample electroactive sites and structural stability. We also engineer layer structure of molybdenum selenide (MoSe2) to favorably expand interlayer distance to enhance atomic surface exposure by successfully inserting graphitic carbon nitride (gCN) nanosheets into adjacent MoSe2 layers. Herein, asymmetric supercapacitor, CoB||gCN/MoSe2 displays a wide potential window of 1.5 V, remarkable energy density of 97.44 Wh kg−1 at 621.3 W kg−1 along with 93 % capacitance retention after 10 k GCD cycles. The research reported here demonstrates the great application potential for the asymmetric devices based on CoB||gCN/MoSe2 for the future of electrochemical charge storage devices.

Optimizing Bi active sites by Ce doping for boosting formate production in a wide potential window

CexBi1−x@C NRs were obtained by the pyrolysis method. Catalysts show desirable faradaic efficiencies of over 90% towards formate formation in a wide potential window from −0.9 to −1.9 Vvs. RHE, with the maximum value of 96.1%.

Alloying Pd with Ru enables electroreduction of nitrate to ammonia with ∼100% faradaic efficiency over a wide potential window.

Electrocatalytic nitrate (NO3-) reduction reaction (eNO3-RR) to ammonia under ambient conditions is deemed a sustainable route for wastewater treatment and a promising alternative to the Haber-Bosch process. However, there is still a lack of efficient electrocatalysts to achieve high NH3 production performance at wastewater-relevant low NO3- concentrations. Herein, we report a Pd74Ru26 bimetallic nanocrystal (NC) electrocatalyst capable of exhibiting an average NH3 FE of ∼100% over a wide potential window from 0.1 to -0.3 V (vs. reversible hydrogen electrode, RHE) at a low NO3- concentration of 32.3 mM. The average NH3 yield rate at -0.3 V can reach 16.20 mg h-1 cm-2. Meanwhile, Pd74Ru26 also demonstrates excellent electrocatalytic stability for over 110 h. Experimental investigations and density functional theory (DFT) calculations suggest that the electronic structure modulation between Pd and Ru favors the optimization of NO3- transport with respect to single components. Along the *NO3 reduction pathway, the synergy between Pd and Ru can also lower the energy barrier of the rate-determining steps (RDSs) on Ru and Pd, which are the protonation of *NO2 and *NO, respectively. Finally, this unique alloying design achieves a high-level dynamic equilibrium of adsorption and coupling between *H and various nitrogen intermediates during eNO3-RR.

Peanut Oil Cake Biomass‐Derived Hierarchical Porous Carbon by Dual Step Activation as Potential Electrodes for Fabrication of Prototype Symmetric Supercapacitor Device

Peanut oil cake biomass is a major by‐product of oil industry and can be a suitable precursor for the production of biomass‐based porous carbon. Herein, dual‐stage activation, physical activation at 400°C, and chemical activation using KOH between 600 and 900°C are adopted to prepare hierarchical porous carbons (HPCs) from peanut oil cake biomass for use as electrode material in electrochemical supercapacitors. The textural and structural properties of the HPC were evaluated by N2‐adsorption/desorption, X‐ray diffraction, Raman, FT‐IR spectroscopy, and scanning electron microscopy. The prepared HPC inherited sufficient micropores and mesopores distribution with a maximum BET surface area of 640 m2/g. The electrochemical properties of the HPC electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopic analysis. Among different HPC electrodes prepared, the carbon prepared at 800°C (HPC‐P8) electrode material exhibited a high specific capacitance of 187 F/g at 0.5 A/g in 1M Na2SO4 electrolyte in three‐electrode systems. Symmetric supercapacitors were also fabricated using HPC‐P8//HPC‐P8 as positive and negative electrodes using 1M Na2SO4 electrolyte, in a two‐electrode cell configuration via split cell method. Maximum specific capacitance of 30 F/g was achieved with superior cycle stability of 93.8% capacitance retention over 5,000 cycles for the symmetric device. The device operated at a wide potential window (0–2.0 V) resulted in appreciable specific energy and power density of 15.89 Wh/kg and 493 W/kg, respectively. HPC‐P8 had an ion diffusion coefficient of 7.79 × 10−8 cm2/s which is higher than the other prepared carbon samples. The symmetric device showed relatively high charge storage capacity and cyclic stability without any material degradation. The fabricated prototype portable supercapacitor module was tested for red LED glow with maximum intensity brightness up to 4 min. Thus, the present study reveals that HPC derived from peanut oil cake biomass can behave as a promising electrode material for supercapacitor applications.