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The motion of ions in supercapacitor electrodes produces internal stresses that cause viscoelastic strains. In addition, stresses may be due to external forces applied to structural supercapacitors, which are multifunctional materials that simultaneously store energy and carry structural loads. There are currently no thermodynamics-based models for the coupled electro-chemo-viscoelastic response of electrodes. Here, the same thermodynamics model is used for both the viscoelastic response and the electrochemical response. This mathematical equivalence is a reference from which to study coupling between the viscoelastic and electrochemical responses. The model has two inputs (stress or strain and electric potential or specific charge) and two outputs (strain or stress and specific charge or electric potential). The coupling is studied by adding three constants in the free energy. The convexity of the free energy and the stability of the free response limit the magnitude of the coupling. The unit response matrix is derived, and results are given for the time and frequency domains. The effect of an applied potential on stress is shown to be much more significant than the converse effect. The model compares well to an experiment consisting of a cyclic electric current applied during stress relaxation. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) reduced graphene oxide (rGO)/Ti2CTx MXene hybrid aerogels were effectively prepared by a two-step method involving hydrothermal reaction and freeze-drying. The intimately coupled rGO/Ti2CTx hybrid aerogel combined high electrical conductivity, large interlayer spacing, and excellent mechanical stability of Ti2CTx, which not only effectively prevents the self-restacking of Ti2CTx nanosheets, exposes more active sites exposed, and improves the volume change during the charge/discharge process but also increases the accessibility of ions and promotes the rapid transfer of ions/electrons. As a result, rGO/Ti2CTx 17.5–2.5 as the working electrode of electric double layer capacitors delivers a large specific capacity (107.05 F g−1 at 0.5 A g−1 in a 1M Na2SO4 electrolyte), a high rate capability (maintains 30% of its initial capacitance at 10 A g−1, which is much better than rGO and Ti2CTx), and excellent long-term large-current cycle stability (the initial capacitance remains above 71.1% after 10 000 cycles at 1 A g−1). In addition to providing a high-performance electrode for supercapacitors, this study proposes an efficient and time-saving strategy for constructing 3D structures from 2D materials. [ABSTRACT FROM AUTHOR]

The electric double layer (EDL) has a pivotal role in screening charges on surfaces as in supercapacitor electrodes or colloidal and polymer solutions. Its structure is determined by correlations between the finite-sized ionic charge carriers of the underlying electrolyte, and, this way, these correlations affect the properties of the EDL and of applications utilizing EDLs. We study the structure of EDLs within classical density functional theory (DFT) in order to uncover whether a structural transition in the first layer of the EDL that is driven by changes in the surface potential depends on specific particle interactions or has a general footing. This transition has been found in full-atom simulations. Thus far, investigating the in-plane structure of the EDL for the primitive model (PM) using DFT has proved a challenge. We show here that the use of an appropriate functional predicts the in-plane structure of EDLs in excellent agreement with molecular dynamics simulations. This provides the playground to investigate how the structure factor within a layer parallel to a charged surface changes as a function of both the applied surface potential and its separation from the surface. We discuss pitfalls in properly defining an in-plane structure factor and fully map out the structure of the EDL within the PM for a wide range of electrostatic electrode potentials. However, we do not find any signature of a structural crossover and conclude that the previously reported effect is not fundamental but rather occurs due to the specific force field of ions used in the simulations. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylene dioxythiophene) (PEDOT) is a conducting polymer that can be used in flexible bioelectronic devices. The electrode/electrolyte interface interaction is one of the most important factors in improving the electrochemical performance of energy storage materials, and these polymers are often combined with a negatively charged poly(styrene sulfonate) (PSS) chain to improve their interaction with alkali metal cations such as sodium and potassium. In this work, we performed a one‐step electrochemical synthesis of PEDOT on carbon fabric using the molecule 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) to create highly effective materials for supercapacitor electrodes. The electrode had a significant increase in capacitance value, measured 16.4 times higher than that of the PEDOT electrode. The 2‐electrode system exhibited a specific capacitance value of 495.2 F g−1 at a scan rate of 5 mV s−1. It exhibited a high operating voltage of 2.3 V in aqueous electrolyte system. It showed a significant energy density of 109.0 Wh kg−1 when operating at 6.1 kW kg−1 power density and 85.2 Wh kg−1 when operating at 30.6 kW kg−1 power density. Recent findings reveal that the capacitance retention performance value of the device increased significantly to 113.9% after 25,000 cycles in 3.0 M NaCl aqueous electrolyte, demonstrating its outstanding long‐term durability. Thus, the creation of the synthesized supercapacitor electrode is a significant advance in the study of conducting polymers, which often have a limited lifetime in real‐world electronic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • An assisted liquid-phase plasma electrolysis is applied for synthesis of composite. • The synergy of CNFs, NiCo 2 O 4 and NiCo-LDH improves the electrochemical properties. • The specific capacitance of electrode can reach 1534.7 F/g at 1 A/g. • The ASC device has an energy density of 33.8 Wh/kg at 400 W/kg. • Deposition dynamics of NiCo 2 O 4 /NiCo-LDH/CNFs composites is explored. Nickel cobaltate/NiCo-layered double hydroxides (NiCo 2 O 4 /NiCo-LDH) as energy storage materials offer considerable potential for various applications. However, many of current methods for synthesizing NiCo 2 O 4 /NiCo-LDH suffer from long synthesis times, complex preparation process, and high temperatures and high pressures. In this study, we present a green, simple, and efficient approach known as assisted liquid-phase plasma electrolysis, which realizes the rapid fabrication of ultra-fine NiCo 2 O 4 /NiCo-LDH nanoparticle-decorated electrospun carbon nanofibers (NiCo 2 O 4 /NiCo-LDH/CNFs) composites. Ultra-fine NiCo 2 O 4 /NiCo-LDH nanoparticles (<70 nm) are uniformly deposited on the CNF surface. The CNFs are intertwined to form a highly conductive three-dimensional mesh structure, which synergizes the NiCo 2 O 4 /NiCo-LDH nanoparticles with a high specific capacitance in favor of ion/electron transport efficiency. In addition, the cooperative effect between the two phases of NiCo 2 O 4 and NiCo-LDH further improves the electrochemical properties. The NiCo 2 O 4 /NiCo-LDH/CNFs composites exhibit a high specific capacitance of 1534.7 F/g at 1 A/g and a capacitance retention of 93.9 % after 5000 cycles. An assembled asymmetric supercapacitor using activated carbon and NiCo 2 O 4 /NiCo-LDH/CNFs composites achieves an energy density of 33.8 Wh/kg at a power density of 400 W/kg and a capacitance retention of 93.0 % after 5000 cycles. Notably, two series-connected NiCo 2 O 4 /NiCo-LDH/CNFs ASC supercapacitors can light up an LED bulb, which maintains a certain brightness even after 50 min. Hence, this work provides a new and efficient route for synthesizing carbon-based NiCo 2 O 4 /NiCo-LDH composites for use as advanced energy storage materials. [ABSTRACT FROM AUTHOR]

This work proves that the Mo-doping is an efficient strategy for boosted NH 4 +-storage of VO 2 (B). Mo-doped VO 2 (B) delivers the specific capacitance of 1403 F g−1 (390 mAh g−1) at 0.1 A g−1. This strategy is like a Chinese idiom "like adding wings to a tiger" to guide the design of electrode materials for high-efficient NH 4 +-storage. [Display omitted] Supercapacitors (SCs) using ammonium-ion (NH 4 +) as the charge carrier (NH 4 +-SCs) have attracted continuous attention and vanadium-based materials are proved to have high-efficient NH 4 +-storage properties. Monoclinic vanadium dioxide, VO 2 (B), as an anode material applied to SCs has been rarely reported and modulating its electronic structure for boosted NH 4 +-storage is full of challenge. In this work, molybdenum-doped VO 2 (B) (Mo-doped VO 2 (B)) is designed and synthesize to enhance its NH 4 +-storage. The introduction of Mo atom into the crystal structure of VO 2 (B) can modulate its crystal structure and bring in some defects. Experimental results manifest that Mo-doped VO 2 (B) with 2 % Mo-doping shows the best electrochemical properties. Mo-doped VO 2 (B) achieves the specific capacitance of 1403 F g−1 (390 mAh g−1) at 0.1 A g−1 and the capacitance retention of about 98 % after 5000 cycle, superior to that of VO 2 (B) (893 F g−1, 248 mAh g−1 at 0.1 A g−1 and 60 % capacitance retention. The hybrid supercapacitor (HSC) assembled by Mo-doped VO 2 (B) and active carbon delivers good electrochemical performance with the energy density of 38.6 Wh kg−1 at power density of 208.3 W kg−1. This work proves that the Mo-doping is an efficient strategy for boosted NH 4 +-storage of VO 2 (B) and this strategy is like a Chinese idiom "like adding wings to a tiger" to guide the design of electrode materials for high-efficient NH 4 +-storage. [ABSTRACT FROM AUTHOR]

[Display omitted] The selection of highly efficient materials and the construction of advantageous structures are essential for realizing high-performance electrode materials. In this paper, electrode material Cu 2 S/C@NiMnCe-LDH/CF with excellent morphology and high performance has been successfully designed and prepared by simple hydrothermal and calcination techniques. First, ZIF-67 is loaded on the outer layer of Cu 2 S rods to obtain core–shell structured Cu 2 S@ZIF-67 rods, whose ZIF-67 MOF shell is carbonized to obtain Cu 2 S@C rods. Then, NiMnCe-LDH are epitaxially loaded on the outer layer of Cu 2 S@C to obtain Cu 2 S/C@NiMnCe-LDH rods. At a current density of 2 mA cm−2, Cu 2 S/C@NiMnCe-LDH/CF exhibits an area capacitance of 5176.4 mF cm−2. The mass capacitance and the energy density of the Cu 2 S/C@NiMnCe-LDH/CF//AC asymmetric supercapacitor (ASC) reach 150.82F g−1 at a sweep rate of 0.8 A/g and 53.62 Wh kg−1 at a power density of 639.99 W kg−1, respectively. Meanwhile, after 8000 electrochemical cycles, the specific capacitance of Cu 2 S/C@NiMnCe-LDH/CF//AC still has a retention rate of 86.32 %, which proves its excellent cycling stability. These results demonstrate a new strategy for the preparation of novel core–shell structured Cu 2 S/C@NiMnCe-LDH/CF nanocomposite material for electrode materials of energy storage devices with superb performance. [ABSTRACT FROM AUTHOR]

Supercapacitors, an innovative energy storage technology, combine the strengths of batteries and capacitors, enabling diverse applications in sectors such as communications, transportation, and aerospace. Porous carbon materials derived from biomass have excellent electrical conductivity, customizable dimensions, high surface area, and robust electrochemical stability, rendering them ideal candidates for supercapacitor electrodes. This research utilized edamame shells as the carbon precursor and KOH as the activating agent to synthesize a series of N/O co-doped porous carbons (ESC-x-800) through a combined pre-carbonization and activation process. This study thoroughly investigated the effect of KOH addition on the morphology, structure, and electrochemical performance of the materials. The result showed that the ESC-3-800 stood out as the top performer, distinguished by its unique self-doping characteristic with N and O atoms and a unique hierarchical porous structure. The ESC-3-800 boasted an impressive specific surface area of 3188.98 m2 g−1, coupled with a substantial pore volume of 1.86 cm3 g−1. When evaluated in a three-electrode system, ESC-3-800 demonstrated a remarkable specific capacitance of 301 F g−1, and a capacitance retention rate of 73.1% at a high current density of 20 A g−1. In a two-electrode setup, the ESC-3-800 achieved a notable high energy density of 37.6 W h kg−1 (at a power density of 200 W kg−1) in the 1 M Na2SO4 electrolyte. Remarkably, after enduring 12 000 charge–discharge cycles in 6 M KOH, it maintained an impressive 96.68% of its initial capacity (8 A g−1), demonstrating exceptional long-term stability and durability. The straightforward preparation method and outstanding performance of the edamame shell-derived N/O co-doped porous carbon underscore its immense potential for practical applications in supercapacitors. [ABSTRACT FROM AUTHOR]

Developing high-performance carbon-based materials for environmental and energy-related applications produces solid waste with secondary pollution to the environment at the end of their service lives. It is still challenging to utilize these functional materials in a sustainable manner in different fields. In this study, we demonstrate a cascaded utilization of an Fe3O4@onion-like carbon (Fe3O4@OLC) structure from wastewater adsorbents to a supercapacitor electrode. The structure was formed by carbonizing Fe3O4@oleic acid monodisperse nanoparticles into interconnected Fe3O4@OLCs and subsequent insufficient acid etching. The hollow OLCs in the outside region of the hybrid structure provide high surface area and the encapsulated Fe3O4 nanoparticles in the inside region offer high ferromagnetism. The three-dimensionally interconnected graphitic layers are advantageous for efficient separation and high conductivity. As a result, the maximum saturation adsorption capacity of insufficiently etched interconnected Fe3O4@OLCs can reach up to 90.2 mg g−1 and they can be efficiently separated under a magnetic field. Furthermore, the hybrid structure is thermally transformed into N-doped HOLCs, which are demonstrated to be a high-performance supercapacitor electrode with high specific capacitance and high electrochemical stability. The cascaded utilization of the hybrid structure in this study is meaningful for eco-friendly development of functional materials for environmental and energy storage applications. [ABSTRACT FROM AUTHOR]

This study investigates the potential of cerium (Ce) doping to improve the performance of cobalt oxide (Co₃O₄) nanoparticles as battery-type supercapacitor electrodes. Pure Co₃O₄ nanoparticles were synthesized via a solution combustion method and then doped with 2.5 % (Ce-Co 3 O 4) and 5 % Ce (CeO 2 -Co 3 O 4). Comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), was used to analyze the impact of Ce doping on the material properties. XRD analysis confirmed the successful incorporation of Ce into the Co₃O₄ structure, with distinct CeO 2 phases forming at higher doping levels. Ce doping resulted in decreased crystallite size and peak intensity, indicating reduced crystallinity and increased defect concentration. Raman spectroscopy corroborated these findings, showing a redshift that suggests weakened metal-oxygen bonds and smaller grain sizes due to Ce³⁺ incorporation. FESEM images demonstrated that Ce doping effectively reduced nanoparticle agglomeration, with 2.5 % doping leading to smaller particles and 5 % doping promoting a 2D flake-like morphology with increased porosity. Nitrogen adsorption-desorption measurements revealed a significant increase in surface area and pore volume for CeO 2 -Co₃O₄, facilitating improved electrolyte diffusion and reduced resistance, thereby enhancing electrochemical performance. Evaluation of the electrochemical properties of undoped and Ce-doped Co₃O₄ materials revealed a battery-like response in a three-electrode configuration. Notably, the CeO 2 -Co 3 O 4 exhibited a superior specific capacity of 603.3 C g−1 at a current density of 1 A g−1, significantly exceeding the values of 368.5 C g−1 and 127.1 C g−1 achieved by Ce-Co 3 O 4 and undoped Co 3 O 4 , respectively. Furthermore, the CeO 2 -doped Co 3 O 4 demonstrated exceptional cyclic stability, retaining 87 % of its initial capacity after undergoing 5000 charge-discharge cycles at a high current density of 10 A g−1. These results suggest that Ce doping is a promising strategy for optimizing Co₃O₄-based battery-type electrode materials, potentially leading to the development of high-performance and cost-effective energy storage systems. [ABSTRACT FROM AUTHOR]

In the contemporary landscape of technological advancements, the burgeoning demand for portable electronics and flexible wearable devices has necessitated the development of energy storage systems with superior volumetric performance. Tungsten oxide (WO3), known for its high density and theoretical capacitance, is a promising electrode material for supercapacitors. However, low conductivity and poor cycling stability are still the key bottlenecks for its application. Herein, a novel composite comprising hollow porous WO3 spheres (HPWS) derived by template method was electrostatic self-assembled on the surface of the Ti3C2T x nanosheets. The resulting electrodes exhibited ultra-high volumetric capacitance of 1930 F cm−3 at 1 A g−1 and rate capability of 46% at 50 A g−1, attributed to enhanced ion accessibility from microporous structure and electron transport from conductive network of Ti3C2T x even at a high packing density of 3.86 g cm−3. Utilizing HPWS/Ti3C2T x as the negative electrode and porous carbon as the positive electrode, the assembled asymmetric supercapacitor achieved an energy density of 31 Wh kg−1 at a power density of 650 W kg−1 with over 107% capacitance retention after 5000 cycles. This work provides a promising approach for developing next-generation supercapacitors with ultra-high volumetric capacitance. [ABSTRACT FROM AUTHOR]

As the world shifts towards renewable energy and more efficient energy storage systems, the demand for advanced materials that can support these technologies has increased. One such promising material class is High Entropy Alloys (HEAs). Unlike conventional alloys, which are typically composed of one or two principal elements, HEAs consist of multiple principal elements in near-equiatomic proportions. Their unique atomic structure, characterized by high configurational entropy, endows them with enhanced stability, tunability, and a high specific surface area—qualities that are highly desirable in supercapacitor applications. HEAs offer significant advantages as supercapacitor electrodes, including increased energy storage capacity, superior electrochemical stability, and the potential for synergistic effects that improve overall performance such as higher energy density, longer cycle life, and greater reliability. FeCoNiCuZn) 3 O 4 has been synthesized by utilizing multiple induction melting process in a quartz tube at 1100 °C , followed by ball milling in order to transform the small pieces into nanostructured powder. The highest specific capacitance obtained is 245.7 F g−1 at 1.5 A g−1 in three electrode measurement system. In addition, plastic biochar was prepared using pyrolysis techniques from plastic wastage. Moreover, it is utilized for supercapacitor application, which shows a maximum specific capacitance of 180 F g−1 at 1 A g−1 for three electrode system. The combing above two electrode materials, the fabricated asymmetric device shows a maximum specific capacitance of 58 F g−1 at 1 A g−1 for 3M KOH electrolyte with maximum specific energy of 23.44 Wh kg−1 at specific power of 1700 W kg−1. [ABSTRACT FROM AUTHOR]

The green energy storage of polyaniline, without major wastages excreted into the environment is effectively demonstrated by using the polyaniline as supercapacitor electrode and the by-product obtained during the synthesis of polyaniline as its electrolyte. This green approach to the energy storage properties of sulphuric acid doped polyaniline (H-PANI) exhibited a substantial improvement in its energy storage, compared to the conventional approach of using an ionically conducting liquid as electrolyte like 1 M H2SO4 (SA), separately. The amelioration of 40.44% was achieved when the by-product obtained as supernatant liquid (SL) was used as electrolyte compared to SA. The H-PANI provided a specific capacity (Q) of 146.4 C g−1, a specific energy (E) of 24.40 W h kg−1 and a specific power (P) of 1.200 kW kg−1 at 1 A g−1 in the presence of SA. The Q of 205.6 C g−1, E of 34.26 W h kg−1 (similar range of E of Pb-acid batteries), P of 1.200 kW kg−1 were achieved in the presence of SL at 1 A g−1 and a high rate capability of 29.18% retention of initial Q up to 25 A g−1 was also achieved. This approach is useful to harvest high energy characters from PANI. [ABSTRACT FROM AUTHOR]

Supercapacitors' high power density and extended life cycle have drawn a lot of interest in energy storage devices. In this study, different nanostructures of nickel oxide (NiO) and zinc oxide (ZnO) were synthesized using the hydrothermal method by treating the corresponding metal precursors in a high-temperature aqueous solution. The XRD and SEM were used to analyse crystal structure and morphology, respectively. The absorption of ZnO and NiO materials is found to be in the visible range of 300–400 and 200–300 nm, respectively. The band gap of ZnO was calculated as 3.04 eV, while that of NiO was 3.93 eV. The supercapacitor electrode was fabricated on nickel foam with developed nanostructure and carbon materials. The composite ZnO and NiO materials showed an increase in capacitance compared to the bare NiO and ZnO electrodes. This enhancement could be related to improved charge transfer kinetics and increased surface area for electrolyte interaction. Galvanostatic charge–discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements were conducted to assess the electrochemical efficiency of nanomaterials and their composites. At the current density of 2 A g−1, the specific capacitance of the NiO/ZnO composite is found to be 351.54 F g−1, which is ~2 times of the bare NiO and ~3.34 times of bare ZnO. The maximum energy density of ZnO nanoparticles, NiO nanoflakes and the composite are found to be 3.96, 6.58 and 13.90 Wh kg-1, respectively. The charge storage process is the result of diffusion and redox reactions. This paper explores a binary oxide composites method for creating efficient supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

Due to the depletion of fossil fuels, extensive CO2 emissions, and growing demand for electrochemical energy, it is important to develop further utilization of renewable energy, as well as advanced energy storage techniques. To this end, the optically chargeable supercapacitor, which can convert the photon energy of solar light into electrochemical energy and store it for long‐term usage, attracts extensive investigations. Among these, heterojunction construction was revealed as an effective method to enhance capacity. Recent works have reported the implementations of precipitation in ceramics, where the introduced matrix‐precipitate two‐phase structure is inspiring for constructing heterojunction, whereas it was seldom reported. In this work, Li‐doped NaNbO3 electrode material was prepared by adopting a multi‐step solid reaction to precipitate LiNbO3 and construct LiNbO3/NaNbO3 heterojunctions. The electrochemical measurement demonstrates an enhanced optically chargeable capacity of roughly 85% increase at a scan rate of 1 mV/s and a four‐fold increase at a charging–discharging current density of 1 A/g, as well as outstanding stability by introducing precipitates and constructing heterojunctions. This finding proposes a novel methodology design of heterojunction construction via precipitation to enhance the optically chargeable capacity of supercapacitor electrode materials and, therefore, may open up a potentially new application field for precipitate‐tuned functionality in functional ceramics. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of CuxCo1-xFe2O4 nanoparticles as potential supercapacitor electrode materials via a sol–gel auto-combustion process. The electrochemical properties were systematically evaluated as Cu was gradually substituted with Co. Using 1 M KOH electrolyte, we characterized the electrochemical performance of CuxCo1-xFe2O4 through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among the compositions, Cu0.5Co0.5Fe2O4 spinel ferrite nanoparticles demonstrated an impressive specific capacitance of 1755 F/g at a current density of 5 mA/cm2, along with a power density of 320 W/kg and an energy density of 38.40 Wh/kg. Additionally, the supercapacitor showcased remarkable cycling stability, retaining over 88.60% of its initial capacitance after 5000 GCD cycles. These findings suggest that CuxCo1-xFe2O4 is a highly promising candidate for supercapacitor applications. [ABSTRACT FROM AUTHOR]

The rapidly expanding global population and fast economic growth has led to a shortage of energy and electricity resources. The scarcity of effective energy storage technologies and environmentally friendly electrical power alternatives is one of the greatest concerns in the modern era. Asymmetric supercapacitors have garnered considerable attention due to their versatility in energy storage devices. However, they still require more effective electrode materials with superior electrochemical characteristics to improve their charge storage capacity, energy, and power parameters. To this end, in this work, nickel oxide (NiO), lanthanum phosphate (LaPO4), and nickel oxide-decorated lanthanum phosphate (NiO/LaPO4) nanosheets were synthesized by a facile hydrothermal method. The purity, crystallinity, and morphology of the materials were investigated using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). The NiO-decorated LaPO4 exhibited superior performance, providing higher specific capacity (Qs) of 1054.4 C/g at 2.0 A/g. The developed electrode also demonstrated excellent electrical conductivity and stability (88% galvanostatic charge/discharge [GCD] retention for 1500 cycles) as determined by electrochemical impedance spectroscopy. The capacitive and diffusive contributions indicate that the fabricated material has an asymmetric storage nature. The results suggest that the prepared material could be used in asymmetric supercapacitor applications. [ABSTRACT FROM AUTHOR]

To address the escalating demand for electrical energy, developing high-performance electrochemical energy storage materials is crucial. Metal oxides represent promising materials for high-energy-density supercapacitors. Among these materials, transition metal-based tungstates exhibit significantly enhanced electrical conductivity compared to pure oxides. However, their low inherent conductivity, restricted electrochemically active sites, significant volume expansion, lower capacity, and deprived cycling stability undermine their electrochemical properties. Herein, we synthesised an oxygen vacancy-enriched NiCoWO4 electrode by a simple solid-state, solvent-free grinding process using NaBH4. The Ov-NiCoWO4 electrode displays an impressive capacitance of 703.66 F g−1 at 1 A g−1 and exceptional cycling stability with 87% retention over 2000 cycles at 7 A g−1. This excellent performance is attributed to the oxygen vacancy in the Ov-NiCoWO4 material, which increases the electron carrier density, accelerates electron transportation, enhances the active surface area, and boosts the redox reactivity of the material. In the as-prepared real-life supercapacitor configuration of Ov-NiCoWO4//AC, a determined capacitance of 129.10 F g−1 at 1 A g−1 is achieved. Additionally, it exhibits an energy density of 37.699 W h kg−1 with a power density of 724.98 W kg−1, signifying exceptional performance. Furthermore, it maintains an impressive cycle life, retaining approximately 88.5% over 1000 cycles. [ABSTRACT FROM AUTHOR]

The increasing global energy demands, rapid consumption of fossil fuels, and rising environmental crisis are all crucial challenges requiring immediate attention. Maximizing supercapacitor performance necessitates superior electrochemical performance and outstanding stability in the electrode materials. Altering the structural and electrochemical characteristics of transition metal selenides by substituting cations and subsequently hybridizing them with MXenes is a potential strategy for designing efficient supercapacitors. Herein, facile solvothermal technique was employed to synthesize cation-substituted CoMoSe2 nanoparticles, which were subsequently hybridized with Ti3C2 before being employed as a supercapacitor electrode. This novel attempt to substitute molybdenum (Mo) in the CoSe2 lattice and the subsequent hybridization resulted in a supercapacitor electrode that exhibited enhanced electrochemical properties owing to its improved charge transfer kinetics, multivalences, and enhanced active sites. The outstanding faradaic redox characteristics of the fabricated electrodes show remarkable pseudocapacitive behaviour within a potential range between −0.2 and 0.45 V. The developed electrodes in a standard three-electrode setup show a specific capacitance of 520 F g−1 at a current density of 1 A g−1, which is greater than that of pure CoMoSe2 and mono-metal selenide CoSe2. Over 5000 cycles at 5 A g−1, the optimal CoMoSe2@Ti3C2 electrode maintains 97.43% of its initial specific capacitance. Furthermore, the designed asymmetric supercapacitor device (ASC) exhibited exceptional performance and stability with an energy density of 73.7 W h kg−1 at 740 W kg−1 power density and 93.3% retention after 15 000 cycles. This work thus demonstrates that metal selenides are a suitable material for supercapacitors. Furthermore, the cation substitution and MXene hybridization could potentially be employed as performance-enhancing strategies. [ABSTRACT FROM AUTHOR]

ABSTRACT The redox active organometallic compounds are the prominent supercapacitor electrode materials due to the attractive properties like stable redox scheme, good electron transfer mediator, and low oxidation potential. The key advantage of the organometallic compounds is that the electronic property of the electrode can be modified by altering and functionalizing the ligands around the metal atom. In this work, we synthesized cobalt‐oxyquinolinate (Co‐Q) organometallic compound by solvothermal method. To improve the electrical conductivity, the reduced graphene oxide (RGO) is grafted on Co‐Q. The electrochemical behaviour of Co‐Q is improved by the addition of RGO. The specific capacitance of Co‐Q layered on RGO is greater (1206 mF cm−2) than Co‐Q (670 mF cm−2) at current density of 1 mA cm−2. This is due to the increase in active sites after the incorporation of RGO on Co‐Q; further, this promotes the diffusion process. The fundamental electrochemical analyses, including cyclic voltammetry, galvanostatic charge–discharge analysis, and electrochemical impedance analysis, provided the information about the electrochemical energy storage performance. Dunn's method is used to understand the diffusion and capacitive contributions of the electrode material during energy storage. From the electrochemical analysis, Co‐Q layered on RGO is a suitable material for the energy storage application due to its high diffusion and stability. [ABSTRACT FROM AUTHOR]

A sugarcane molasses, a promising source of polysaccharides, was used in this study in order to modify the size, shape orientation, surface area, and charge transport properties of Co 3 O 4 nanostructures. Several methods have been used to obtain structural information on nanostructures, including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectrometry, and Fourier transform infrared spectroscopy (FTIR). Furthermore, cyclic voltage measurements (CV), linear sweep voltage measurements (LSV), galvanostatic charge-discharge measurements (GCD), and electrochemical impedance measurements (EIS) were performed on Co 3 O 4 nanostructures in conjunction with various electrochemical measurements. The major contribution of this study was focused on the development of an asymmetric supercapacitor using Co 3 O 4 nanostructures. The oxygen evolution reaction (OER) activity of Co 3 O 4 nanostructures was investigated in an aqueous solution containing 1 M KOH, and an asymmetric supercapacitor was tested in an electrolyte containing 3 M KOH. An optimal Co 3 O 4 nanostructure with OER activity has an overpotential of 330 mV at 10 mA cm−2 and a Tafel slope of 92 mVdec−1. The optimized Co 3 O 4 nanostructure demonstrated excellent durability during OER activity for 40 h. Among the three electrode-based supercapacitors, sample 1 had the highest specific capacity with 1070C/g, the highest capacitive retention percentage at 100%, and the highest columbic efficiency at 101%. Thus, ASC devices based on optimized Co 3 O 4 nanostructures exhibit exceptional specific capacities of 301C/g and 6.4 Wh/Kg at 1.5A/g. The retained capacitance was observed to be 99% after 40000 galvanostatic charge-discharge cycles (GCD). The transformation of Co 3 O 4 nanowires into nanoparticles having large specific surface area were synthesized in the sugarcane molasses and their enhanced electrochemical performance was demonstrated. [Display omitted] • Sugarcane molasses was used to synthesize functional Co 3 O 4 nanostructures. • Electrochemical performance of Co 3 O 4 nanostructures was highly improved. • An overpotential of 330 mV was noticed at 10 mAcm−2 during water oxidation. • Asymmetric supercapacitor exhibited specific capacity of 310C/g. [ABSTRACT FROM AUTHOR]

The advancement of energy storage and conversion technologies critically depends on developing superior electrode materials characterized by high specific capacitance and exceptional electrocatalytic properties. In this study, we successfully synthesized a novel ZnCo 2 O 4 @NiCo-LDH nanoelectrode material using the hydrothermal method. This composite exhibited an impressive specific capacitance of 1118 C g−1 at a current density of 1 A g−1. The resulting supercapacitor demonstrated a high energy density of 15.56 μWh cm−2 at a power density of 0.825 mW cm−2. Notably, after 10000 cycles, the material retained 79.7% of its initial capacity, underscoring its substantial cyclic stability and potential for supercapacitor applications. Furthermore, the ZnCo 2 O 4 @NiCo-LDH material displayed excellent electrocatalytic properties, with an overpotential of 54.2 mV for the Hydrogen Evolution Reaction (HER) at a current density of 10 mA cm−2 and a Tafel slope of 48.69 mV dec−1. For the Oxygen Evolution Reaction (OER), it showed an overpotential of 296.1 mV and a Tafel slope of 24.13 mV dec−1. These results indicate that the ZnCo 2 O 4 @NiCo-LDH nanoelectrode material is highly promising for high-performance supercapacitors and electrocatalytic water splitting applications, paving the way for new developments in energy storage and conversion technologies. • Composite: High specific capacitance of 1118 C g−1 at 1 A g−1 current density. • Supercapacitor: 15.56 μWh cm−2 energy density at 0.825 mW cm−2 power density. • For HER, the overpotential is 54.2 mV with a Tafel slope of 48.69 mV dec−1. • For OER, the overpotential is 296.1 mV with a Tafel slope of 24.13 mV dec−1. • ZnCo 2 O 4 @NiCo-LDH: High performance for supercapacitors and water splitting. [ABSTRACT FROM AUTHOR]

Supercapatteries combine the high-power density characteristic of supercapacitors with the high energy density typically found in batteries, offering a promising solution for advanced energy storage applications. We present an efficient two-step method to fabricate hierarchical, binder-free NiCo layered double hydroxide (LDH) nanosheet arrays supported on polyaniline layered nickel foam (NF). A PANI@NiCo-LDH/NF nanocomposite serves as the anode in the supercapattery, leveraging the high capacitance and improved conductivity of the combined materials, yielding a significantly high specific capacity of 1481 C g−1 (3703.33 F g−1). Coffee grounds derived reduced graphene oxide (rGO), providing a sustainable and environmentally friendly material with excellent electrical conductivity and high mechanical strength, serves as the cathode. The synergy between the PANI@NiCo-LDH/NF anode and the rGO cathode creates a novel and highly efficient supercapattery system. The fabricated supercapattery device offers an energy density of 54.44 W h kg−1 at a power density of 0.702 kW kg−1 and exhibits good cyclability with capacitance retention of 84.88% and Coulombic efficiency of 77.68% over 5000 charging/discharging cycles. This innovative approach addresses the limitations of traditional energy storage devices, paving the way for more versatile and sustainable energy solutions. [ABSTRACT FROM AUTHOR]

Vanadium oxide has become a promising electrode material for supercapacitors because of its high capacitance and multiple redox states. However, low intrinsic conductivity, narrow interlayer spacing and poor structural stability limit its practical application. The study reports the construction of Co-doped V2O3 using asparagic acid-functionalized graphene quantum dots (GQD) and biomass carbon (BC). V5+ and Co2+ were combined with GQD to form the Co/V-GQD complex. Then, it was adsorbed on cotton, dried and annealed. The resulting Co–V2O3-GQD@BC shows the three-dimensional carbon framework. The formed V2O3 nanocrystals with rich edges and corners are dispersed on the carbon sheets. V5+ was partly reduced to form low-valent V2+ species. V2+ and Co2+ self-doping narrows the bandgap and creates new electron transfer pathways. Graphene modification accelerates the electron transfer from V2O3 to graphene and improves structural stability. The integration of double doping with graphene modification realizes a significant improvement in electrical conductivity and a safe voltage window (1.8 V). The specific capacitance of V2O3 in Co–V2O3-GQD@BC reaches 2182.89 F g−1, which is more than that of the other vanadium oxide electrodes. The symmetrical supercapacitor with Co–V2O3-GQD@BC electrodes provides a high capacitance (664.89 F g−1 at current density of 1 A g−1), rate capacity (366.67 F g−1 at 50 A g−1), cycling stability (97.65% capacitance retention after 10 000 cycles) and energy density (74.8 W h kg−1 at a power density of 425 W kg−1). [ABSTRACT FROM AUTHOR]

Creating the porous Zinc-Zeolitic Imidazolate Framework (Zn-ZIF) using a solvothermal technique addresses the need for advanced materials with distinctive properties and cost-effectiveness in modern applications. The PXRD, SEM, UV-DRS, TEM, and TGA/DTG are used to characterize different concentrations of Zn-ZIF. Zn-ZIF's crystalline structure and phase purity have been verified by PXRD. Using diffuse reflectance spectra, the Kubelka-Monk function determined the band gaps of the Zn-ZIF samples, and scanning electron microscopy revealed a more porous structure. At 77 K and 1 bar, the Zn-ZIF solution with a 2:1 ratio had the highest hydrogen storage capacity (1.71 wt%). The electrochemical behavior of several Zn-ZIF electrodes in a 6 M KOH electrolyte was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments. The Zn-ZIF electrode with a 2:1 ratio exhibits a low charge transfer resistance and a high proton diffusion coefficient (D) of 1.687 × 10−4 cm2 s−1. The characteristics of the 2:1 synthesized Zn-ZIF electrode as a supercapacitor were investigated. Our analysis of the generated Zn-ZIF material's specific capacitance values after 2000 cycles revealed an impressive retention rate of nearly 89 %, with values of 296.6 Fg-1. In addition, we examined the photocatalytic activities of the as-synthesized material by exposing it to ultraviolet light and seeing how it degraded organic dyes such as Cango-Red (CR) dye. With a photocatalytic efficacy of 95.06 % for CR dye, Zn-ZIF (2:1 ratio) is the most effective. These findings should provide new knowledge for researchers interested in developing novel Zn-ZIF materials for photocatalytic, energy storage, and hydrogen storage applications. [ABSTRACT FROM AUTHOR]

In order to develop advanced energy storage devices, it is necessary to manufacture supercapacitor electrode that have both long electrochemical cycle lifetimes and high energy densities. These properties can only be obtained by developing heterostructure pseudo-capacitive materials. The combination of MnO 2 nanorods and ZnCr 2 O 4 nanoparticles resulted in a synergistic effect, which increased the electroactive surface area for charge storage. This effect was not observed when each component utilized individually. The material ZnCr 2 O 4 nanoparticles facilitated the MnO 2 nanorods. In present study, ZnCr 2 O 4 , MnO 2 and their composite was fabricated by simple sonication process. These fabricated samples were tested by using different techniques which includes X-ray diffraction (XRD), Raman analysis, Brunauer Emmett Teller (BET) and scanning electron microscopy (SEM). Electrochemical analysis of fabricated materials exhibited an exceptional specific capacitance (C sp = 1175.35 F g−1), energy density (E d = 15.95 Wh Kg−1) and power density (P d = 869.4 W kg−1). These materials are anticipated to act as the support for electrochemical energy storage devices that utilize an ideal electrode structure, meticulously select the appropriate transition metal oxide (TMO) and analyse electrochemical characteristics for supercapacitive performance. This study exhibits the remarkable efficiency of the nanostructured ZnCr 2 O 4 /MnO 2 electrode in supercapacitors with high energy density (E d). [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis of MFe 2 O 4 @SiO 2 (M = Cu, Ni, Co) nanostructures by microwave-assisted sol-gel synthesis utilizing rice husk as a cost-effective silica precursor and polyethylene glycol (PEG) as a soft template. Structural and electrochemical properties were characterized using XRD, FTIR, FESEM, EDS, HRTEM, BET, and electrochemical techniques. The result revealed the formation of well-defined MFe 2 O 4 spherical nanoparticles decorated mesoporous silica spheres. Electrochemical studies indicate that the CoFe 2 O 4 @SiO 2 electrode performs better than the CuFe 2 O 4 @SiO 2 and NiFe 2 O 4 @SiO 2 electrodes in faradaic redox processes and supercapacitor performance, having a specific capacitance of 1263 F/g at 1 A. Asymmetric supercapacitor (ASC) with CoFe 2 O 4 @SiO 2 as positive electrode exhibits high specific capacitance of 135.66 F/g at 1 A/g with good cycle stability retention (70.83 % at 10 A/g), high energy density (50.4 Wh/kg) and power density (891.522 W/kg). CoFe 2 O 4 @SiO 2 performs better than CuFe 2 O 4 @SiO 2 and NiFe 2 O 4 @SiO 2 because cobalt ferrite (CoFe 2 O 4) has higher electrical conductivity, superior redox activity, and better electrochemical stability. This study offers cost-effective potential electrode materials for electrochemical energy storage, combining environmental sustainability with superior electrochemical performance. [ABSTRACT FROM AUTHOR]

Supercapacitors, as promising energy storage devices, have gained significant attention due to their ability to deliver high power and efficient charge storage mechanisms. In this work, we report the synthesis and electrochemical characterization of pristine NiO and Ni 1-x Ce x O (x = 0.01, 0.02, 0.03) nanoparticles using a single-step auto ignition combustion method. Preliminary investigations indicate that Ni 1-x Ce x O (x = 0.02) nanoparticles (2 % Ce doping) exhibit superior specific capacitance compared to other compositions. Therefore, we focused on structural, morphological, and vibrational studies on pristine and 2 % Ce-doped NiO. XPS and BET techniques were explored to assess the electronic state and porosity of the samples. Subsequent electrochemical performance evaluations included Cyclic Voltammetry (CV) at various scan rates, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopic (EIS) techniques. From CV at a scan rate of 5 mVs−1, specific capacitance values of 419 Fg-1 and 604 Fg-1 were obtained for pristine and 2 % Ce-doped NiO, respectively. GCD studies revealed a specific capacitance of 381 Fg-1 for 2 % Ce-doped NiO at a current density of 1 Ag-1 and demonstrated capacitance retention of 95.1 % over 3000 GCD cycles for a current density of 4 Ag-1. The symmetric two-electrode supercapacitor cell demonstrates exceptional electrochemical performance, exhibiting a high specific capacitance of 122 Fg-1, an impressive energy density of 8.17 WhKg−1, a power density of 700 WKg-1 at 1 Ag-1, and a remarkable 88 % capacitance retention after 5000 GCD cycles. DFT calculations suggest that Ce doping significantly alters pristine NiO's electronic and structural features due to lattice strain. Our work highlights the enhanced electrochemical performance of 2 % Ce-doped NiO and its potential as a good-quality supercapacitor material. [ABSTRACT FROM AUTHOR]

Sm3+ doped β-wollastonite (β-CaSiO 3) nanoparticles (β-CSO:Sm3+ NPs) are effectively synthesized through agricultural waste. Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL), and electrochemical analyses are utilized to validate the synthesis, structural, luminescence, and supercapacitor characteristics of the NPs. The diffraction analysis unveiled a monoclinic crystal structure nested within a rhombohedral lattice system in the synthesized samples. The excitation spectrum of β-CSO doped with 7 mol % of Sm3+ ions exhibited a prominent peak at 404 nm, while the emission spectrum revealed four distinct peaks. The most intense emission peak, observed at 645 nm, corresponds to the radiative transition from 4G 5/2 to 6H 9/2 states of Sm3+ ions. Analysis of emission spectra across different doping concentrations identified 7 mol % as the optimal optical doping concentration. The phenomenon of concentration quenching is attributed to dipole-dipole interactions. Exploration into energy storage and biosensor technologies is crucial for addressing societal challenges, expanding scientific understanding, and promoting sustainable progress across various domains including energy and healthcare. In this investigation, we successfully synthesized pristine RGO@β-CSO:Sm3+ nanocomposites (NCs) using a hydrothermal approach. Through cyclic voltammetry (CV) analysis, it is observed that these NCs exhibited markedly higher specific capacitance (C sp) of 152.15 F/g at a scan rate of 2 mV/s. Moreover, they demonstrated a notable energy density of 35.77 Wh/kg, alongside enhanced capacity retention of 82.27 % and exceptional Coulombic efficiency of 95.77 % compared to undoped RGO@β-CSO. Subsequently, these NCs are utilized to fabricate modified carbon paste electrodes (MCPE) for electrochemical dopamine (DA) detection at an optimal pH of 7.4. The modified electrodes demonstrated favorable current responses for DA voltammetry, achieving low limits of detection (LOD) and quantification (LOQ) values of 9.226 μM and 30.75 μM, respectively. Additionally, they showcased improved selectivity between dopamine and uric acid, with a deterioration rate of only 97.83 % over 20 cycles. These findings suggest that the developed electrode holds significant promise for applications in supercapacitors and dopamine detection, thereby contributing to advancements in energy storage technology and biosensor applications. [Display omitted] • Economically feasible, reduced graphene oxide based β-CaSiO 3 :Sm3+ nanocomposites are synthesized from agricultural and food waste materials. • Structural, morphological, luminescence and electrochemical studies are performed using XRD, FE-SEM, TEM, XPS, PL, I QE CH instruments. • Electrochemical studies of synthesized RGO@β-CaSiO 3 :Sm3+ nanocomposites were performed to evaluate parameters like specific capacitance, energy density, coulombic efficiency, capacity retention etc. • Biosensor studies of the synthesized materials, using dopamine and uric acid proves to be a boon for biomedical applications. • Reduced graphene oxide based β-CaSiO 3 :Sm3+ nanocomposite can be used for future technologies, particularly in wearable/integrated electronic devices, smart sensor opto-electronic devices. [ABSTRACT FROM AUTHOR]

This work describes the fabrication of a composite supercapacitor electrode made of Cu-doped BiFeO 3 (Cu-BFO) films on an activated carbon (AC) electrode using radio-frequency (RF) magnetron sputtering. To prevent exfoliation of Cu-BFO and AC upon immersion in an electrolyte, the nickel foam sandwiching electrode technique was introduced. The Cu-BFO films significantly enhanced electrochemical properties, increasing specific capacitance by up to 151% compared to that of an AC electrode. This was attributed to Faradaic reactions and specific surface area in the Cu-BFO/AC electrode. The highest specific capacitance achieved was 169 F g - 1 at 0.5 A g - 1 , and cycling stability retention was 93.12% after 500 cycles. However, the remaining percentage of the specific capacitance decreased differently with increasing thickness, which is also discussed. Furthermore, an asymmetric supercapacitor using Cu-BFO/AC and AC electrodes demonstrated a high energy density of 4.71 Wh kg - 1 , power density of 2.66 kW kg - 1 , and over 90% retention after 1000 cycles, highlighting its durability. The uniform RF magnetron sputtering deposition is vital for mass production. Combined with impressive retention in asymmetric supercapacitors, this scalability suggests a promising pathway for large-scale manufacturing. Consequently, this work could pave the way for the large-scale production of supercapacitors. [ABSTRACT FROM AUTHOR]

Herein, spin‐polarized calculation is performed based on density‐functional theory in the frame of generalized gradient approximation to examine the quantum capacitance (CQ) and surface charge storage of graphene(G)‐based supercapacitor electrodes modified with molybdenum, sulfur, nitrogen, and monovacancy. In total, 15 electrode models, including graphitic doping, monovacancy doping, and Mo adsorption on pristine and single‐vacancy graphene structures are analyzed. In the results, it is demonstrated that vacancy defects and N/S/Mo doping enhances the CQ of graphene. Among all configurations, pyrrolic‐S (d1S) shows the lowest CQ performance due to few states at the Fermi level. Electrodes with Mo adsorption exhibit the highest CQ, particularly when Mo is adsorbed at the top site of graphene. However, formation and adsorption energy calculations suggest that Mo is more likely to adsorb at hollow sites. Optimally, Mo can be most effectively utilized by loading it onto vacancy or N/S‐decorated vacancy sites. The significant contribution of Mo's 4dz2 and 4s states to CQ, along with the charge‐redistribution around the Mo complexes, may facilitate proton‐coupled electron transfer to enhance pseudocapacitance. In these findings, valuable insights into designing high quantum capacitance of 2D materials with electroactive sites for improved energy storage are offered. [ABSTRACT FROM AUTHOR]

The majority of carbon materials on the market are produced from polyacrylonitrile precursor fibers using high‐temperature oven processes. Despite approaches for green carbon fiber precursors, current stabilization and carbonization processes require large amounts of energy and render carbon materials costly and environmentally not sustainable. Here, a plasma carbonization treatment is employed for papers made from lignin/polyvinylpyrrolidone precursor fibers. The process provides carbonization within a timeframe of a few seconds, while the degrees of porosity, conductivity, and hydrophobicity can be tuned. It is shown that the properties of these carbonized papers are suitable for application as supercapacitor electrodes with capacitances in the range of 40 mF g−1 with very good cycling stability dropping by less than 20% over 4000 cycles. [ABSTRACT FROM AUTHOR]

This study presents a simple and an environmentally friendly approach to make Laser-Induced Graphene (LIG) based supercapacitor electrodes anchored with abundant Silver Nanoparticles (AgNPs). LIG, was synthesized using a CO2 laser writing technique on polyimide substrate. The LIG-Ag composite was prepared using two techniques, drop-coating, and screen-printing. Ag nanoparticles prepared using the plant extract of Swietenia Macrophylla was utilized to drop-coat AgNP on LIG substrate. Screen-printing was done by using a commercial Ag-ink and a suitable mesh. The supercapacitor made from screen-printed electrodes and supercapacitor made form drop-coated electrodes showed a high specific capacitance of 118 mF/cm2, 38 mF/cm2, and a high energy density of 2.42 mWh/cm2, 0.05 mWh/cm2 respectively. The screen-printed composite of LIG and AgNP was further studied for its anti-fungal properties and proved to be effective against Candida sp. [ABSTRACT FROM AUTHOR]

Combining different metals in coordination compounds is an efficient strategy to improve their various properties. Herein, mixed nickel–cobalt hexacyanoferrate (NixCoyHCF) microcubes of varying x : y molar ratios are synthesized via a co-precipitation route and comprehensively characterized to study their material and electrochemical properties. NixCoyHCF microcubes display the battery-type electrochemical energy storage mechanism in aqueous electrolytes. Among the samples, Ni1Co2HCF microcubes deliver the highest specific capacity of 134 mA h g−1 (1068 F g−1) at a specific current of 1 A g−1. This significant enhancement in the capacity indicates the synergistic and cooperative effects between Ni and Co sites in Ni1Co2HCF microcubes. The asymmetric supercapacitor device assembled with Ni1Co2HCF microcubes delivers an excellent energy density of 74.4 μW h cm−2 at a power density of 750 μW cm−2 and retains 87.7% of its initial capacity after 2000 cycles at a current density of 5 mA cm−2, indicating its robust structural integrity and electrochemical durability. This study highlights the promising potential of mixed-metal hexacyanoferrates as high-performance electrodes for aqueous supercapacitors. [ABSTRACT FROM AUTHOR]

The PPy-coated Na 0.67 Ni 0.33 Mn 0.67 O 2 cathode undergoes reversible structural evolution during charging/discharging process. The Na-ion full cell exhibits a high capacity retention of 88.2% after 150 cycles. [Display omitted] • PPy-coated P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 is prepared by in situ polymerization process. • The PPy-coated cathode showed enhanced cycling stability and rate capability. • The PPy coating layer can inhibit side reactions stemming from the electrolyte. P 2-Na 0.67 Mn 0.67 Ni 0.33 O 2 is a promising cathode material for sodium ion batteries (SIBs) due to its low cost, high theoretical capacity, and non-toxicity. However, it still suffers from unsatisfactory cycling stability mainly incurred by the Jahn-Teller effect of Mn3+ and electrolyte decomposition on the electrode/electrolyte interface. Herein, the P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 @PPy (NNMO@PPy) composite applied as cathode materials for SIBs is obtained by introducing conductive polypyrrole (PPy) as coating layer on the P 2-Na 0.67 Ni 0.33 Mn 0.67 O 2 (NNMO) microspheres. Numerous physical characterization methods indicate that the PPy layer was uniformly coated on the surface of NNMO microspheres without change in phase structure and morphology. The PPy coating layer can alleviate Mn dissolution and effectively suppress the side reactions between the electrolyte and electrode during cycling. The optimal NNMO@PPy-9 with 9 wt% PPy delivers a high capacity of 127.4 mAh/g at the current density at 150 mA g−1, an excellent cyclic stability with high capacity retention of 80.5 % after 300 cycles, and enhanced rate performance (169.3 mAh/g at 15 mA g−1 while 89.8 mAh/g at 600 mA g−1). Furthermore, hard carbon (−)//NNMO@PPy-9 (+) full cell delivers a high energy density of 305.1 Wh kg−1 and superior cycling stability with 88.2 % capacity retention after 150 cycles. In-situ X-ray diffraction experiment and electrochemical characterization verify the highly reversible structure evolution and robust P 2-type phase structure of NNMO@PPy-9 for fast and stable Na+ diffusion. This effective strategy of using conductive PPy as a coating layer may provide a new insight to modify NNMO surface, improving the cycling stability and rate capability. [ABSTRACT FROM AUTHOR]

In this study, activated carbon (PPAC) is produced from pomegranate peel waste by activation of sodium hydroxide (NaOH) in the first stage. In the second stage, ammonia activation for nitrogen doping is carried out on PPAC (N-doped PPAC). In the third stage, zinc oxide (ZnO) doping is carried out on the obtained N-doped PPAC sample (ZnO@N-doped PPAC). The surface properties of the produced composite are examined by scanning electrode microscope (SEM), X-ray diffraction analysis (XRD), Energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy(XPS), micro Raman and nitrogen adsorption analyses. The electrochemical performance of the supercapacitor is investigated by cyclic voltammetry (CV), charge-discharge curves(GCD), and electrochemical impedance spectroscopy (EIS). N-doped PPAC and ZnO@N-doped PPAC composite materials are used as supercapacitor electrodes. Specific capacitance values of 207.4 and 265.2 F/g in 1 M sulfuric acid(H 2 SO 4) are obtained with N-doped PPAC and ZnO@N-doped PPAC electrodes, respectively. Additionally, cycle stability is achieved with a capacitance retention of approximately 86% after 5000 cycles at 0.6 A/g. The maximum energy density and power density of ZnO@N doped PPAC were calculated as 7.29 Wh/kg and 3600 Wh/kg, respectively. [Display omitted] • Ammonia and ZnO incorporated into PPAC based on biomass waste were performed. • There is an increase in the capacitance value of 28% by ZnO doping on N-doped PPAC. • Specific capacitance of 265.2 F/g at 1 A/g for ZnO@N-doped PPAC was obtained. • The cycle stability was achieved with a capacitance retention of 86% after 5000 cycles. [ABSTRACT FROM AUTHOR]

Organic frameworks coupled with hydrogen bonds known as Hydrogen bonded organic frameworks (HOFs) emerged as materials with great potential in the fabrication of supercapacitors based on their structural and chemical characteristics. HOFs are crystalline porous materials where arrays of hydrogen bonding form highly stable frameworks with tunable porosity. These frameworks possess several benefits for the application of supercapacitor electrodes with high surface area, chemical flexibility and potential facile functionalization. The synthesis, characterization, organic building blocks at creation, hydrogen bonding motifs and applications of HOFs in supercapacitors are the main topics of this paper. These methods include solvothermal synthesis, mechano-chemical methods and self-assembly processes, where the specific features of HOFs in terms of their porosity and surface functionality enhance the electrochemical performance such as specific capacitance, cycling stability, power density and energy density. Hence, the large surface area and the efficient charge storage ability are exhibited by H-bonded networks. The porosity and functional groups facilitate accurate and rapid ion conduction and enable better access to the electrolytes, resulting in enhanced battery rate performance and energy density. Furthermore, the tendency for hydrogen bond formation depicts robust cycling performance because of the structural integrity during the charge-discharge cycling. This review extends an evaluation of possible further developments in supercapacitors, with emphasis on combined HOFs and composite electrode materials like conductive polymers, carbon-based materials and metal oxides, that reveal synergistic effects in improved impact on conductivity, capacitance and performance. Thus, the HOFs are identified as versatile materials with high potential for use in supercapacitors because of their adjustable characteristics and high electrochemical activity. Research on hybrid materials will be of paramount importance in achieving future enhancement of supercapacitor technology due to the increasing global need for effective energy storage systems. • HOFs offer high surface area, tunable porosity, and flexibility for supercapacitors. • Unique HOF structure boosts capacitance, power, and energy density performance. • Strong hydrogen bonds ensure excellent cycling stability during charge-discharge. • Synthesis methods include solvothermal, mechanochemical, and self-assembly. • HOF hybrids with polymers, carbons, and oxides enhance overall device performance. [ABSTRACT FROM AUTHOR]

Despite aqueous electrolytes offer a great opportunity for large‐scale energy storage owing to their safety and cost‐effectiveness, their practical application suffers from the parasitic side reactions and poor temperature adaptability stemming from weak hydrogen‐bond (HB) network in free water. Here, we propose the guiding thought “strong replaces weak” to design hydrogen bond‐anchored electrolyte by introducing sulfolane (SL) for disrupting the regular weak HB network and contributing to superior temperature tolerance. Judiciously combined experimental characterization and theoretical calculation confirm that SL can remodel the primary solvation shell of metal ions, customize stable electrode interface chemistry and restrain the side reactions. Consequently, symmetric supercapacitor constructed by activated carbon (AC) electrodes is able to fully work within a voltage range of 2.4 V and reach high capacitance retention of 89.8 % after 60000 cycles. Additionally, Zn anodes exhibit ultra‐stable Zn plating/stripping behaviors and a wide temperature range (−20–60 °C), and zinc‐ion capacitor (Zn//AC) also delivers an excellent cycling stability with capacity retention of 99.7 % after 55000 cycles, implying that the designed electrolyte has practical application potential in extreme environments. This work proposes a novel critical solvation strategy that paves the route for the construction of ultra‐stable and wide‐temperature aqueous energy storage devices. [ABSTRACT FROM AUTHOR]

This study presented the electrochemical deposition of potassium nitrate-doped polypyrrole (Ppy:KNO 3) on stainless steel (SS), graphite sheet (GRs), and carbon fiber (CF) substrates, Ppy:KNO 3 /SS, Ppy:KNO 3 /GRs, and Ppy:KNO 3 /CF supercapacitor electrodes. Structural, morphological, and molecular analyses were conducted using X-ray diffraction (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). SEM images exhibited distinct morphologies of Ppy:KNO 3 films, varying with cycles, scan rates, and Ppy:KNO 3 concentrations. Ppy:KNO 3 /CF film displayed a unique structure with minimal particle aggregation. Electrochemical performance was assessed through Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS). Notably, Ppy:KNO 3 /CF demonstrated a specific capacitance of 1020 F/g at 1 A/g. It exhibited 92 % capacitance retention after 1000 cycles, along with impressive power and energy densities of 310 W/kg and 71.2 Wh/kg, respectively. These results represented a significant progress in the development of high-performance, durable supercapacitors. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of Mn doping on the performance of polyvinyl alcohol/borax‐structured (PMB) supercapacitor electrodes for high‐capacity, flexible, and self‐healing supercapacitor electrodes. The PMB electrodes were characterized by x‐ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Electrochemical characterization was conducted using cyclic voltammetry (CV), which revealed that redox reactions, which are evident at low scan rates, enhance capacitive performance. However, high scan rates introduce limitations owing to the increased vibrations of the PVA chains and incomplete electrolyte polarization. The PMB electrodes exhibited remarkable electrochemical properties and capacitive performances, which were significantly affected by the MnO₂ structure. The electrodes exhibited self‐healing properties and demonstrated flexibility to stretch by up to 40%. In addition, the results indicate that the electrode capacity of the PVA/borax system increased by 2.03 times after 1000 cycles with manganese doping. The solid electrolyte interface (SEI) layer formed on the electrode surface plays a critical role in stabilizing the capacity loss during prolonged charge–discharge cycles. The study concluded that PMB supercapacitors offer higher capacitance in 0‐2 V applications compared to other PVA/borax combination hydrogels. Moreover, the incorporation of metal‐based additives, particularly manganese, enhanced the capacitive performance, and operating voltage levels. [ABSTRACT FROM AUTHOR]

Pseudocapacitors (PSCs) have attracted researcher's attention due to their potential electrochemical performance as the power source for electronic devices. However, to maintain the high electrochemical properties of pseudocapacitive materials becomes critical. Therefore, the active electrode materials design and synthesis is a challenging task. To tackle these problems, herein, we rationally designed new polymer based on benzoquinone with azo linker. The polymer AZO‐BQ‐P was synthesized and tested for their energy storage applications in combination with graphite foil (GF). In three‐electrode supercapacitor (SC) device, the AZO‐BQ‐P/GF electrode exhibits excellent specific capacitance (Csp) of about 306.27 F g−1 at 0.5 A g−1 current density and higher cycling stability. The pseudocapacitive performance of SC cells result from synergistic effect of AZO‐BQ‐P and GF and due to faster electrolyte ion diffusion and increased availability at electrode/electrolyte interfaces. Furthermore, AZO‐BQ‐P/GF electrode was employed to fabricate two‐electrode AZO‐BQ‐P/GF//AZO‐BQ‐P/GF symmetric SC device. The optimal SSC device shows a Csp reaching 200 F g−1 at 0.5 A g−1, which is an impressive value. Also, it exhibits remarkable cycling stability with 86.18% Csp retention after 5000 galvanostatic charging–discharging (GCD) cycles at 3 A g−1. The SSC device applying AZO‐BQ‐P/GF electrode delivers an excellent energy density (ED) of 25.00 Wh kg−1 at 900.00 W kg−1 power density (PD). Thus, the novel polymer design offers efficient electrode materials to enhance the pseudocapacitive electrochemical performance of the SSC device. This concept can be extended for fabricating other electrochemical systems and accelerate its applications for modern electronic devices. [ABSTRACT FROM AUTHOR]

To enhance the inherent poor conductivity and low cycling stability of dimetallic layered double hydroxides (LDHs) materials, designing a synergistic effect between EDLC capacitors and pseudocapacitors is an efficient strategy. In this paper, we utilized a solvothermal technique employing Co‐glycerate as a precursor to prepare sea urchin‐like NiCo‐LDH hollow spheres anchored on a 3D graphene aerogel. The unique morphology of these hollow microspheres significantly expand the specific surface area and exposes more active sites, while reducing the volume changes of materials during long‐term charging and discharging processes. The 3D graphene aerogel serves as a conductive skeleton, improving the material's electrical conductivity and buffering high current. The sea urchin‐like NiCo‐LDH hollow spheres anchored on 3D graphene aerogel (H‐NiCo‐LDH@GA) has a specific surface area of 51 m2 g−1 and the ID/IG value is 1.02. The H‐NiCo‐LDH@GA demonstrate a significant specific capacitance of 236.8 mAh g−1 at 1 A g−1, with a remarkable capacity retention rate of 63.1 % even at 20 A g−1. Even after 8000 cycles at 10 A g−1, the capacity retention still remains at 96.3 %, presenting excellent cycling stability. [ABSTRACT FROM AUTHOR]

NASICON electrode materials exhibit a broad spectrum of electrochemical potentials, robust ionic conductivity, and structural and thermal stabilities. Using solid state reaction method, Li2Cu2(MoO4)3 was synthesized, a member of NASICON family of compounds based on molybdenum. Various analytical techniques employed to assess structural and morphological properties of synthesized nanomaterial. X‐ray diffraction (XRD) pattern indicated that generated Li2Cu2(MoO4)3 nanomaterial exhibited orthorhombic crystalline structure, with crystallite size of approximately 48 nm. The nanomaterial morphology was evaluated using field emission scanning electron microscopy (FESEM), showing columnar‐ or fiber‐like morphology composed of some conductivity points. The elemental composition of Li2Cu2(MoO4)3 was analyzed by EDAX analysis, confirming the presence of elements lithium, copper, molybdenum, and oxygen. The optical properties and band gap of Li2Cu2(MoO4)3 were analyzed by ultraviolet visible diffuse reflectance spectroscopy (UVDRS). Elemental composition of surface along with electronic states and oxidation states of component present in the nanomaterial Li2Cu2(MoO4)3 were investigated from X‐ray photoelectron spectroscopy (XPS). Electrochemical evaluation using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopic (EIS) showed a specific capacitance of 250 F g−1 at 3.5 A g−1 with the high retention rate of 95.82% after 3000 cycles, indicating its potential for high performance supercapacitors. [ABSTRACT FROM AUTHOR]

The nanocomposite material Sb2S3: SnS:MnS2 was fabricated by single precursor technique by using dithio‐carbamate ligand as Sb2S3:SnS:MnS2 (DDTC) complex. An internal and external look at the anatomy and activity of the substance was obtained by using a variety of analytical techniques like XRD, FTIR, UV‐Vis and SEM. Additionally, various electro‐analytical tools like LSV, CV, GCD and EIS were applied to confirm material's rich electro‐active capability for photoactive electrode. XRD revealed its average crystallite size of 12.33 nm with 82.8 % crystallinity. Optical characteristics represented describe effective semiconducting nature of nanomaterials with optimum band gap of 2.65 eV. By using electrochemical processes, LSV and CV demonstrated fertile opto‐electrical nature of Sb2S3: SnS: MnS2 (DDTC) material with specific capacitance, Csp, of 1080 F/g at scan rate of 2 mV/s. With a high specific power density of 2656 W/kg, the GCD technique attempted to validate the nature of the material as an electrode with a good charge‐discharge mechanism. In EIS, low series resistance, Rs=0.73 Ω, was observed to be very beneficial argument in validating the nanocomposite synthesized in this research project as effective and low‐cost material which can be applied in different energy producing and storing devices like solar system and super‐capacitors etc. [ABSTRACT FROM AUTHOR]

Designing potential architectures by the modification of conventional electrode materials is an effective approach in the development of high performance supercapacitor electrodes. The present study investigated the effect of varying anodization voltages (50, 75, and 100 V) on the morphology and electrochemical properties of titanium nanotubes (TNT). Molybdenum was doped onto TNT using a simple hydrothermal procedure, followed by thermal treatment at 450 °C. The study effectively demonstrated control over the dimensions of the nanotube structure by adjusting the anodization voltage. Additionally, it was found that the tube diameters were increased due to etching during the hydrothermal treatment with the Mo precursor, which potentially enhanced the supercapacitive performance of Mo‐doped TNT. Further, structural analysis revealed that Mo doping improved both crystallinity and electrode stability. With an optimal anodization voltage of 100 V, TNT and Molybdenum‐doped TNT could exhibit capacitance value of 13.34 and 326.54 mF cm−2 respectively, at a current density of 1 mA cm−2. Furthermore, the electrode demonstrated good cyclic stability with 88% capacitance retention and 97% coulombic efficiency after 5000 cycles. An impressive energy density of 87.03 µWh cm−2 and a power density of 799.99 µW cm−2 could be achieved with this sample in an asymmetrical device. [ABSTRACT FROM AUTHOR]

In order to solve the problem of low energy density of previous cement-based supercapacitors, the capacitor performance was optimized in four aspects: positive electrode performance, positive and negative capacity matching, and electrolyte performance. The effects of electrodeposition solution ratio and scan rate on the electrochemical properties of nickel–cobalt double hydroxide were investigated. The microscopic morphology and elements of nickel–cobalt double hydroxide were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The optimized nickel–cobalt double hydroxide electrode demonstrates an excellent areal capacitance of 10.53 F cm−2 and excellent cycling stability (106% capacitance retention after 10 000 cycles) at a current density of 1 mA cm−2. In this paper, an electrode made of activated carbon was used as the negative electrode and the loading of activated carbon was strictly controlled to better match the high specific capacitance of the nickel–cobalt double hydroxide electrode. An optimally proportioned cementitious-polymer electrolyte was selected as the electrolyte for the supercapacitor. The three-step optimized supercapacitor exhibits a high areal capacitance of 1.442 F cm−2, good cycle retention (69.4%), and a remarkable energy density of 0.444 mW h cm−2 (0.75 mW cm−2). This paper is expected to provide a new way to mitigate the issue of "curtailed light" and to construct large-scale buildings integrating light, electricity, and energy storage. [ABSTRACT FROM AUTHOR]

Thanks to their good redox activity properties and exceptional conductivity, metal selenides (MSs) have attracted great attention as prospective positive electrodes for hybrid supercapacitors. However, they demonstrate low-rate capacities and poor endurance. Nanomaterials fabricated from MSs and reduced graphene oxide (rGO) with a porous skeleton can effectively mitigate the above-mentioned problems. Herein, porous MnSe@CoSe@FeSe2 nanowires wrapped with rGO on nickel foam (NF@MCFS-rGO) are manufactured as a binder-free electrode for a hybrid supercapacitor. The obtained NF@MCFS-rGO, acting as a positive electrode, has distinct advantages such as (1) the porous nanowires are helpful for fast electrolyte penetration, (2) the conductivity of the MCFS is further improved when combined with rGO, and (3) wrapping MCFS within the rGO endows the nanomaterial with much better structural durability. Capitalizing on the high conductivity of the rGO and the porous morphology, the fabricated NF@MCFS-rGO manifests impressive characteristics with a capacitance of 1830 F g−1 at 1 A g−1 and only 6.75% capacitance loss within 10 000 cycles. By matching NF@MCFS-rGO with activated carbon (AC), the fabricated apparatus (AC\\NF@MCFS-rGO) reveals an energy density (ED) of 64.6 W h kg−1 and a long lastingness of 90.55% after 10 000 cycles. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage devices with high specific capacity are of utmost important for the next-generation electronic devices. Supercapatteries (SCs) are highly demanded energy storage devices nowadays as these bridge the low energy supercapacitors and low power batteries. Herein, we report a rapid synthesis of cobalt manganese phosphate (COMAP) by microwave-assisted hydrothermal method and facile fabrication of SCs using electrodes comprising of COMAP as positrode material. The effect of precursor concentration on the microstructure and surface morphology of the COMAP samples are examined initially. Further, the electrochemical performance of COMAP electrodes is studied systematically in 3 M KOH (aqueous) electrolyte. COMAP exhibits excellent charge storage capabilities where type of charge storage mechanism is found to be battery-type based on the calculation obtained from Dunn's method. The SC electrode fabricated with COMAP synthesized using cobalt: manganese precursor ratio as 80:20 exhibits a highest specific capacity of 191.4 C/g at a scan rate of 1 mV/s. An asymmetric SC (ASC) cell fabricated with COMAP as positrode and activated carbon (AC) as negatrode exhibits a specific capacity of 165.5 C/g at a current density of 1.8 A/g. The COMAP//AC ASC cell exhibits an energy density of 34.1 Wh/kg at a corresponding power density of 1875 W/kg at a current density of 1.8 A/g. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage is one of the effective ways that can address the mentioned issues as alternative energy/power produced through solar or windmills can effectively be stored for continuous usage. Hybrid/Asymmetric supercapacitors can deliver a significant amount of power density as well as increased energy density with better rate capability and longer lifespan. The fluffy carbonized hexagonal KCoPO4 synthesized via a simple sol‐gel method accompanied by calcination has delivered high capacitance and longer cyclibility as a positive electrode in aqueous asymmetric supercapacitors. The fluffy carbonized hexagonal KCoPO4 exhibited a specific capacitance equal to 725 F/g at 0.5 A/g current density with excellent cyclic stability. The predominant intercalative pseudocapacitive charge storage behavior seems to be the reason behind the high capacitance of the electrode due to the active involvement of Co2+/3+ redox couple mediate charge storage as intercalative (inner) and capacitive, (outer) surface charges storage on the electrode were close to 37 % and 63 % respectively. Aqueous Asymmetric supercapacitor mode with KCoPO4 being a positive electrode and activated carbon being a negative electrode (KCoPO4//AC) was designed to address its performance in 2 M KOH aqueous electrolyte. The fabricated device in AASc mode (AC//KCoPO4) achieved the highest energy density close to 121.1 Wh/kg with a high power density of 6945 W/kg in the potential window of 1.5 V in 2 M KOH electrolyte. [ABSTRACT FROM AUTHOR]

Exploring the electrochemical performance of metal/metal oxide nanoparticle composites is vital for enhancing the charge storage capability of supercapacitors. Herein, electrodes coated with ZnO/CoO x are fabricated by soaking cotton fabric seeded with 2-methylimidiazole in an ethylene glycol–based solution containing Zn and Co salts. The use of cotton fabric can reduce textile industrial waste while achieving high capacitance and sustainable energy for wearable electronics. In addition, the three-dimensional network of conductive flexible carbon derived from cotton fabric facilitates rapid ion transport kinetics at interlayers. The concentrations of Zn and Co salts are varied to produce ZnO/CoO x samples and determine the optimal salt ratio for superior electrochemical performance. The optimal sample exhibits a capacitance of 1.95 F cm−2 at 5 mA cm−2 and an energy density of 725 μWh·cm−2 over a wide potential window of 1.6 V. The long-term stability test results of the symmetric cells indicate 94 % capacitance retention after 12,000 charge–discharge cycles, emphasizing the advantages of mixed metallic oxides with cellulose-derived carbon fabric for supercapacitor electrodes. This study offers valuable insights into the fabrication of high-performance, flexible, and binder-free supercapacitor electrodes as a scalable alternative for practical applications. [ABSTRACT FROM AUTHOR]