High Capacitance Research Articles

Six polyoxotungstate-based transition metal compounds for electrochemical capacitor application and a comparative analysis of factors affecting capacitances.

Six different polyoxotungstate-based transition metal complexes were synthesized, namely [Cu5(2,2'-bpy)5(μ2-Cl)2(PO4)2(H2O)2][HPW12O40]·2H2O (1), [Cu1.5(2,2'-bpy)1.5(inic)2(H2O)1.5]3[H1.5PW12O40]2·16.25H2O (2), [Cu(2,2'-bpy)2]2[SiW12O40]·10H2O (3), [Zn(phen)3]2[PWVWVI11O40]·5H2O (4), [Zn(phen)2(H2O)]2[SiW12O40]·2H2O (5), and [Zn(2,2'-bpy)2]2[SiW12O40] (6) (2,2'-bpy = 2,2'-bipyridine, inic = isonicotinic acid, phen = 1,10-phenanthroline). Compound 1 is based on [HPW12O40]2- anions, which are accommodated within the open channels of a supramolecular network formed by novel Cu-P-Cl coordination clusters. Compound 2 is constructed from [H1.5PW12O40]1.5- and novel [Cu1.5(2,2'-bpy)1.5(inic)2(H2O)1.5]+ coordination fragments, and polyoxoanions are encapsulated within the pores created by the copper coordination fragments, resulting in a unique three-dimensional supramolecular architecture. Compound 3 is a two-dimensional structure formed through the covalent linkage between [SiW12O40]4- and [Cu(2,2'-bpy)2]2+. Compound 4 is a supramolecular architecture formed by [PWVWVI11O40]4- and [Zn(phen)3]2+ coordination fragments, while compound 5 is a supramolecular structure based on POM bi-supported Zn coordination complexes. Compound 6 is a two-dimensional framework structure constituted by [SiW12O40]4- and [Zn(2,2'-bpy)2]2+via covalent interactions. In addition, electrochemical measurement results show that the copper-based tungstate compounds 1-3 and zinc-based tungstate compounds 4-6 exhibit different performances and durabilities as electrochemical capacitors (compound 1 shows the highest specific capacitance of 94.0 F g-1 at 1.5 A g-1, whereas compound 6 maintains the best cycling stability with the capacity retention of 80.7% after 1000 cycles at 4 A g-1.). This study contributes to the development of POM-based transition metal complexes with high capacitance by providing insights into the design and synthesis process.

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.

Experimental and theoretical insights into the supercapacitive performance of interconnected WS2 nanosheets.

Transition metal dichalcogenides (TMDs) are fascinating and prodigious considerations in the electrochemical energy storage sector because of their two dimensional chemistry as well as heterogeneous characteristics. Herein, we synthesized interconnected WS2 nanosheets by a hydrothermal method followed by sulphuration at 850 °C in an argon atmosphere. The ultrathin WS2 nanosheet array is endowed with an excellent specific capacitance of 74 F g-1 at the current density of 3 A g-1 up 7000 cycles. Moreover, a symmetric supercapacitor was fabricated using WS2 nanosheets, which provided the admirable high specific capacity of 6.3 F g-1 at 0.05 A g-1 with the energy and power density of 5.6 × 102 mW h kg-1 and 3.6 × 10 5 mW kg-1, respectively. Density functional theory (DFT) simulations revealed the presence of populated energy states near the Fermi level resulting in a high quantum capacitance value, which supports the experimentally achieved high capacitance value. The attained results recommend interconnected WS2 nanosheets as a novel, robust, and low-cost electrode material for supercapacitor energy storage devices.

Flexible silk-fibroin-based microelectrode arrays for high-resolution neural recording.

High-precision neural recording plays a pivotal role in unraveling the intricate mechanisms that underlie information transmission of the nervous system, raising increasing interest in the development of implantable microelectrode arrays (MEAs). The challenge lies in providing a truly soft, highly conductive and low-impedance neural interface for precise recording of the electrophysiological signals of individual neurons or neural networks. Herein, by implementing a novel topological regulation strategy of silk fibroin (SF) crosslinking, we prepared a flexible, hydrophilic, and biocompatible MEA substrate, facilitating a biocompatible neural interface that minimizes mechanical mismatch with biological tissues. Additionally, we established a strategy involving screen-printing combined with post-coating to prepare MEAs with high conductivity, low impedance and high capacitance, by coating PEDOT:PSS on titanium carbide (Ti3C2) microarrays. The Ti3C2 nanosheets, as the conductive track of the MEAs, avoided the charge drifting associated with metals and facilitated the processing of the MEAs. Further coating PEDOT:PSS on the electrode points reduced the impedance 100-fold, from 105 to 103 Ω. Experimental validation confirmed the superior electrophysiological signal recording capabilities of the SF-based MEA (SMEA) in peripheral and cerebral nerves with a much higher signal-to-noise ratio (SNR) of 20. In particular, we achieved high-precision recording of the action potential (AP) induced by flash visual stimulation, demonstrating high performance in weak signal recording. In summary, the development of SMEA provides a robust foundation for future investigations into the mechanisms and principles of neural circuit information transmission in complex nervous systems.

Sustainable design of high-performance multifunctional carbon electrodes by one-step laser carbonization for supercapacitors and dopamine sensors.

Laser carbonization is a rapid method to produce functional carbon materials for electronic devices, but many typical carbon precursors are not sustainable and/or require extensive processing for electrochemical applications. Here, a sustainable concept to fabricate laser patterned carbon (LP-C) electrodes from biomass-derived sodium lignosulfonate, an abundant waste product from the paper industry is presented. By introducing an adhesive polymer interlayer between the sodium lignosulfonate and a graphite foil current collector, stable, abrasion-resistant LP-C electrodes can be fabricated in a single laser irradiation step. The electrode properties can be systematically tuned by controlling the laser processing parameters. The optimized LP-C electrodes demonstrate a promising performance in supercapacitors and electrochemical dopamine biosensors. They exhibit high areal capacitances of 38.9 mF cm-2 in 1 M H2SO4 and high energy and power densities of 4.3 μW h cm-2 and 16 mW cm-2 in 17 M NaClO4, showing the best performance among biomass-derived LP-C materials reported so far. After 20 000 charge/discharge cycles, they retain a high capacitance of 81%. Dopamine was linearly detected in the range of 0.1 to 20 μM with an extrapolated limit of detection of 0.5 μM (S/N = 3) and high sensitivity (13.38 μA μM-1 cm-2), demonstrating better performance than previously reported biomass-derived LP-C dopamine sensors.

Synthesis of SiO2/ZnO/Fe2O3/ZnFe2O4 from Spent Alkaline Batteries and Mining Tailings Applied as a Photocatalyst and Pseudocapacitor

In this study, a mixed oxide (SiO2/ZnO/Fe2O3/ZnFe2O4) was prepared using the anode recycled from alkaline batteries and the silt fraction of mining tailings and applied as a photocatalyst under solar irradiation and as a pseudocapacitor. The structure and morphology of the mixed oxide revealed clusters of nanometric particles with rhombic and octahedral shapes. A 23 full factorial design was performed to determine the effect of pH, hydrogen peroxide (H2O2), and photocatalyst on methylene blue (MB) decolorization. The maximum efficiency was 96%, obtained using 2.35 × 10−5 mol H2O2 and 20 mg of photocatalyst at pH 3 for 30 min under solar irradiation. This efficiency remained even after four successive decolorization cycles. Pseudocapacitive properties showed that the mixed oxide exhibited favorable characteristics for application as electrochemical pseudocapacitors due to its high capacitance (87.16 F g-1), energy density (27.24 Wh kg-1) at 524.41 W kg-1 of power density, and reversibility (93%). The studied mixed oxide has excellent potential for use in photocatalytic reactions and electrochemical devices, contributing to environmental sustainability and circular economy

Nonylphenol polybenzoxazines-derived nitrogen-rich porous carbon (NRPC)-supported g-C3N4/Fe3O4 nanocomposite for efficient high-performance supercapacitor application.

In this work, a straightforward and scalable method was used to generate nitrogen-rich porous carbon (NRPC), which was then incorporated with a graphitic carbon nitride and magnetite (g-C3N4/Fe3O4) nanocomposite, fabricated with Fe3O4 nanoparticles as an eco-friendly and economically viable component. The fabricated NRPC/g-C3N4/Fe3O4 nanocomposite was applied as an electrode in supercapacitor applications. The synthesized NRPC/g-C3N4/Fe3O4 nanocomposite, NRPC, g-C3N4, and Fe3O4 were characterized by analytical and morphological analyses. The spherically shaped Fe3O4 nanoparticles were analyzed by field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The specific surface area of NRPC/g-C3N4/Fe3O4 was determined to be 479 m2 g-1. All the crosslinked composites showed exceptional electrochemical performance and exhibited a pseudo-capacitance behaviour. In comparison to the Fe3O4 and g-C3N4/Fe3O4 electrodes, the NRPC/g-C3N4/Fe3O4 electrode showed a lower charge-transfer resistance and higher capacitance. The prepared NRPC/g-C3N4/Fe3O4 electrode exhibited the highest specific capacitance of 385 F g-1 at 1 A g-1 compared to Fe3O4 (112 F g-1) and g-C3N4/Fe3O4 (150 F g-1). Furthermore, the cycling efficiency of NRPC/g-C3N4/Fe3O4 remained at 94.3% even after 2000 cycles. The introduction of NRPC to g-C3N4/Fe3O4 improved its suitability for application in high-performance supercapacitors.

The Analytical Models of Fringe Parasitic Capacitance of FinFET - A Review

When planar MOSFET encounters its own scaling limit, FinFET was introduced and successfully replaced the traditional MOSFET. FinFET owns its privilege over the planar MOSFET for its high tolerance to short channel effect. However, due to FinFET’s 3D structure, high parasitic capacitance compared to planar MOSFET significantly degrades the transistor speed because of RC delay. This paper provides a review on the fringe capacitance of FinFET device based on the accuracy to experimental data of the two-dimensional and three-dimensional analytical models. Those models take the external and internal parasitic capacitance component into account. The three-dimensional model outperforms the two-dimensional model in levels of precision but requires more parameters and time to establish.

Facile and scalable fabrication of flexible micro-supercapacitor with high volumetric performance based on ultrathin Co(OH)2 nanosheets

Flexible and in-plane micro-supercapacitor with high volumetric capacitance based on ultrathin Co(OH)2 nanosheets.

Co3O4/activated carbon nanocomposites as electrocatalysts for the oxygen evolution reaction.

The Oxygen Evolution Reaction (OER) is crucial in various processes such as hydrogen production via water splitting. Several electrocatalysts, including metal oxides, have been evaluated to enhance the reaction efficiency. Zeolitic Imidazolate Framework-67 (ZIF-67) has been employed as a precursor to produce Co3O4, showing high OER activity. Additionally, the formation of composites with carbon-based materials improves the activity of these materials. Thus, this work focuses on synthesizing ZIF-67 and commercial activated carbon (AC) composites, which were used as precursors to obtain Co3O4/C electrocatalysts by calculating ZIF-67/CX (X = 10, 30, and 50, the mass percentage of AC). The obtained materials were thoroughly characterized by employing X-ray powder diffraction (XRD), confirming the cobalt oxide structure with a sphere-like morphology as observed in the TEM images. The presence of oxygen vacancies was confirmed by infrared spectroscopy and EPR measurements. The electrocatalytic performance in the OER was investigated by linear sweep voltammetry (LSV), which revealed an overpotential of 325 mV at 10 mA cm-2 and a Tafel slope value of 65.32 mV dec-1 for Co3O4/C10, superior in activity to several previously reported studies in the literature and electrochemical stability of up to 8 hours. The reduced value of charge transfer resistance, high double-layer capacitance, and the presence of Co3+ ions justify the superior performance of the Co3O4/C10 electrocatalyst.

Composite MAX phase/MXene/Ni electrodes with a porous 3D structure for hydrogen evolution and energy storage application.

MXenes, a family of two-dimensional (2D) transition metal carbides, have been discovered as exciting candidates for various energy storage and conversion applications, including green hydrogen production by water splitting. Today, these materials mostly remain interesting objects for in-depth fundamental studies and scientific curiosity due to issues related to their preparation and environmental stability, limiting potential industrial applications. This work proposes a simple and inexpensive concept of composite electrodes composed of molybdenum- and titanium-containing MAX phases and MXene as functional materials. The concept is based on the modification of the initial MAX phase by the addition of metallic Ni, tuning Al- and carbon content and synthesis conditions, followed by fluoride-free etching under alkaline conditions. The proposed methodology allows producing a composite electrode with a well-developed 3D porous MAX phase-based structure acting as a support for electrocatalytic species, including MXene, and possessing good mechanical integrity. Electrochemical tests have shown a high electrochemical activity of such electrodes towards the hydrogen evolution reaction (HER), combined with a relatively high areal capacitance (up to 10 F cm-2).

Rational synthesis of 3D coral-like ZnCo2O4 nanoclusters with abundant oxygen vacancies for high-performance supercapacitors.

Transition metal oxides with high theoretical capacitance are regarded as desired electrode materials for supercapacitors, however, the poor conductivity and sluggish charge transfer kinetics constrain their electrochemical performance. The three-dimensional (3D) coral-like ZnCo2O4 nanomaterials with abundant oxygen vacancies were synthesized through a facile hydrothermal method and chemical reduction approach. The introduced oxygen vacancies can provide more active sites and lower the energy barrier, thereby facilitating the kinetics of surface reactions. Furthermore, the abundant oxygen vacancies in metal oxides can function as shallow donors to facilitate charge carrier diffusion, resulting in a faster ion diffusion rate and superior electrochemical conductivity. The electrochemical performance of ZnCo2O4 was optimized by the introduction of oxygen vacancies. The ZnCo2O4 nanoclusters, reduced by 0.5 M NaBH4 (ZnCo2O4-0.5), exhibit a specific capacitance of 2685.7 F g-1 at 1 A g-1, which is nearly twice that of the pristine ZnCo2O4 (1525.7 F g-1 at 1 A g-1). The ZnCo2O4-0.5 exhibits an excellent rate capacity (81.9% capacitance retention at 10 A g-1) and a long cycling stability (72.6% specific capacitance retention after 10 000 cycles at 3 A g-1). Furthermore, the asymmetric supercapacitor (ASC, ZnCo2O4-0.5 nanoclusters//active carbon) delivers a maximum energy density of 50.2 W h kg-1 at the power density of 493.7 W kg-1 and an excellent cycling stability (75.3% capacitance retention after 3000 cycles at 2 A g-1), surpassing the majority of previously reported ZnCo2O4-based supercapacitors. This work is important for revealing the pivotal role of implementing the defect engineering regulation strategy in achieving optimization of both electrochemical activity and conductivity.

Fabrication and Electrochemical Analysis of NiCo2O4@Ni-MOF Nanoarchitectonics Composites on Ni-Foam Substrate for Supercapacitor Electrodes

To produce the free-standing electrodes, a binder-free direct growth method was employed for electrode fabrication. A NiCo2O4@Ni-MOF (metal–organic framework) composite was synthesized using a one-pot hydrothermal method. Initially, a NiCo2O4 nanowire array was cultivated on Ni foam, serving as a connecting bridge to ensure robust adherence of the Ni-MOF to the substrate. The structures of NiCo2O4 nanowire arrays exhibit the capacity for numerous redox reactions. Hybridizing MOF with transition metal oxide (TMO) nanoarchitectures can significantly alleviate the small specific surface area and aggregation tendency of TMOs. The highest energy storage capacity was obtained when the ratio of nickel to terephthalic acid (TPA) was 4:1. NiCo2O4@Ni-MOF (Ni:[Formula: see text]:1) exhibited a high storage capacitance of 1700[Formula: see text]F/g. The integration of MOF with TMO nanoarchitectonics as materials for supercapacitor electrodes can enhance porous structure and facilitate diffusion during both charging and discharging processes.

Two biomass material-derived self-doped (N/O) porous carbons from waste coriander and lilac with high specific surface areas and high capacitance for supercapacitors

In this study, two kinds of 3D self-doped (N/O) lilac-based and coriander-based porous carbons with high performance have been prepared.

Polypyrrole and activated carbon enriched MnCo2O4 ternary composite as efficient electrode material for hybrid supercapacitors.

The development of proficient electrode materials is one of the major tasks faced by modern techniques for energy storage. Integrating different materials with synergistic effects can be a valuable strategy for designing storage devices with high capacity and energy density. The spinel manganese cobaltite (MnCo2O4) is an outstanding candidate for supercapacitors owing to its remarkable pseudocapacitive behavior. However, it suffers from low electric conductivity and limited cyclic stability. To overcome its limitations, activated carbon with superior cyclic stability and polypyrrole with high electric conductivity can be incorporated in MnCo2O4. The synergistic effect of these components offers high capacitance, better conductivity, and superior cyclic performance to the ternary composite. Herein, the MnCo2O4/AC/PPY ternary composite has been synthesized by a facile approach. The optimized ternary composite (MAP-20) exhibited a wonderful capacitance of 945.77 F g-1 at five mV s-1 compared to pristine MnCo2O4 (254.98 F g-1). The real-time applicability of the optimized composite was tested with asymmetric device configuration. The asymmetric device with MAP-20 and MnO2/AC electrodes exhibited a wonderful Ed of 88.12 W h kg-1 (Pd ∼ 1.6 kW kg-1). The asymmetric device also exhibited excellent cyclic performance of 89.68% for 10 000 cycles. Further, the real-time applicability of the device was tested by illuminating a 39 red LED panel. Three asymmetric cells connected in series illuminated the panel for about 45 minutes. All these results suggest that the synergistic integration of various efficient electrode materials leads to enhanced electrochemical performance of supercapacitors.

Linking water‐use strategies with drought resistance across herbaceous crops

AbstractWoody plants minimize xylem embolism formation during drought essentially by closing stomata at higher water potentials and/or by increasing the xylem resistance to embolism. Both of these mechanisms result in a higher stomatal safety margin (SSM), which is the water potential difference between stomatal closure and embolism formation. Here, we investigated whether increasing SSM represents a drought resistance mechanism for herbaceous plants and how the different water‐use strategies impact their survival. For that, we exposed four herbaceous crops with contrasting drought resistance to severe water deficit to assess drought‐induced damage and mortality. Unlike woody species, SSM was not associated with plant survival for herbaceous crops. Soybean, which presented the largest SSM across the four crops (1.67 MPa), exhibited the earliest mortality of leaves and whole plants as well as the highest rate of plant mortality (100%) at the end of the drought period. Cowpea, with an SSM of 0.63 MPa, was the most drought‐resistant species, with the latest leaf damage and the highest plant survival (100%). The most effective traits ensuring survival in herbaceous crops under severe drought were those related to drought avoidance mechanisms such as (1) early stomatal closure, (2) very low residual transpiration post‐stomatal closure, and (3) high capacitance pre‐ and post‐turgor loss.

Self-supporting electrodes of lithium aluminium oxide–carbon nanocomposites synthesized from dicarboxylate-intercalated layered double hydroxide for supercapacitors

A three-dimensional hybrid structure of Al/LiAl5O8/C electrodes with uniform graphite nanosheets, prepared by calcination of organic species intercalated LDH, exhibits high capacitance and excellent cycling stability for supercapacitors.

Direct ink writing 3D printing of low-dimensional nanomaterials for micro-supercapacitors.

Micro-supercapacitors (MSCs) have attracted significant attention for potential applications in miniaturized electronics due to their high power density, rapid charge/discharge rates, and extended lifespan. Despite the unique properties of low-dimensional nanomaterials, which hold tremendous potential for revolutionary applications, effectively integrating these attributes into MSCs presents several challenges. 3D printing is rapidly emerging as a key player in the fabrication of advanced energy storage devices. Its ability to design, prototype, and produce functional devices incorporating low-dimensional nanomaterials positions it as an influential technology. In this review, we delve into recent advancements and innovations in micro-supercapacitor manufacturing, with a specific focus on the incorporation of low-dimensional nanomaterials using direct ink writing (DIW) 3D printing techniques. We highlight the distinct advantages offered by low-dimensional nanomaterials, from quantum effects in 0D nanoparticles that result in high capacitance values to rapid electron and ion transport in 1D nanowires, as well as the extensive surface area and mechanical flexibility of 2D nanosheets. Additionally, we address the challenges encountered during the fabrication process, such as material viscosity, printing resolution, and seamless integration of active materials with current collectors. This review highlights the remarkable progress in the energy storage sector, demonstrating how the synergistic use of low-dimensional nanomaterials and 3D printing technologies not only overcomes existing limitations but also opens new avenues for the development and production of advanced micro-supercapacitors. The convergence of low-dimensional nanomaterials and DIW 3D printing heralds the advent of the next generation of energy storage devices, making a significant contribution to the field and laying the groundwork for future innovations.

High-entropy-based nano-materials for sustainable environmental applications.

High entropy materials (HEMs), epitomized by high entropy alloys (HEAs), have sparked immense interest for a range of clean energy and environmental applications due to their remarkable structural versatility and adjustable characteristics. In the face of environmental challenges, HEMs have emerged as valuable tools for addressing issues ranging from wastewater remediation to energy conversion and storage. This review provides a comprehensive exploration of HEMs, spotlighting their catalytic capabilities in diverse redox reactions, such as carbon dioxide reduction to value-added products, degradation of organic pollutants, oxygen reduction, hydrogen evolution, and ammonia decomposition using electrocatalytic and photocatalytic pathways. Additionally, the review highlights HEMs as novel electrode nanomaterials, with the potential to enhance the performance of batteries and supercapacitors. Their unique features, including high capacitance, electrical conductivity, and thermal stability, make them valuable components for meeting crucial energy demands. Furthermore, the review examines challenges and opportunities in advancing HEMs, emphasizing the importance of understanding the underlying mechanisms governing their catalytic and electrochemical behaviors. Essential considerations for optimizing the HEM performance in catalysis and energy storage are outlined to guide future research. Moreover, to provide a comprehensive understanding of the current research landscape, a meticulous bibliometric analysis is presented, offering insights into the trends, focal points, and emerging directions within the realm of HEMs, particularly in addressing environmental concerns.

Modulation of Cu/Cu2O nanoparticles to promote the photocurrent response for light-enhanced pseudocapacitive charge storage

Bifunctional CC@Cu/Cu2O photoelectrodes are prepared for light-enhanced pseudocapacitive charge storage, and have achieved a high capacitance retention of 92% after 5000 cycles under light irradiation.