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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]

Tantalum oxide has emerged as an important electrode material for supercapacitors due to its multiple redox capabilities, high capacitance and structural stability, but the low electrical conductivity prevents its practical applications. This study reports the synthesis of Co- and V-doped Ta1.1O1.05 using tryptophan- and aspartic-acid-functionalized boron-doped graphene quantum dots (DWB-GQD). Ta5+, V5+ and Co3+ were combined with DWB-GQD to form water-soluble complexes. The complex was then soaked in cotton, dried and annealed at 850 °C in an N2 atmosphere. The resulting Ta1.1O1.05 nanocrystals showed a cube-like nanostructure. The self-doping of low-valent Ta, V and Co species induced the production of oxygen vacancies. The presence of oxygen vacancies narrowed the bandgap and created new electron transfer pathways. The graphene surface modification accelerated the electron transfer from Ta1.1O1.05 to graphene and improved the structural stability. The unique structure significantly improved the conductivity and led to a wide safe voltage window of 1.9 V. The symmetrical supercapacitor with Co/V–Ta1.1O1.05@DWB-GQD electrodes and a 1 M Li2SO4/PVA gel electrolyte exhibited high specific capacitance (560.9 F g−1 at a current density of 1 A g−1), high-rate capacitance (365.55 F g−1 at a current density of 10 A g−1), cycling stability (99.5% capacitance retention over 10 000 cycles), and energy density (140.63 W h kg−1 at a power density of 475 W kg−1). Based on these results, the soft supercapacitor shows a wide application prospect in wearable electronic devices. [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]

The sulfuric acid-doping polyaniline (H-PANI-HSO4) are applied to conduct the electrochemical measurement and simulation calculation to investigate the capacitance, electronic structure and energy band properties. The H-PANI-HSO4 growing on graphite carbon paper (H-PANI-HSO4/GCP) is applied as an electroactive electrode to investigate electrochemical properties. The Faradaic capacitance of H-PANI-HSO4/GCP electrode is ascribed to the reversible redox reaction of bisulfate anion doping/dedoping protonated PANI (H-PANI). Cyclic voltammetry measurement at a scan rate of 5 mV s − 1 determines an equivalent mean response current of 0.64 A g − 1 and a capacitance of 128.35 F g − 1 . Galvanostatic charge–discharge measurement determines specific capacitance from 129.06 to 116.88 F g − 1 at current densities from 0.5 to 2.5 A g − 1 . Cyclic voltammetry-based capacitance at equivalent current density of 0.64 A g − 1 is in accordance with galvanostatic charge–discharge-based capacitance at the current density of 0.57 A g − 1 . Electrochemical impedance spectrum measurements indicate that H-PANI-HSO4/GCP exhibits lower charge-transfer resistance, much lower Warburg resistance, higher quasicapacitance than H-PANI-HSO4 to approaching ideal capacitor. Density functional theory calculations indicate that H-PANI-HSO4 has a higher density of states (10.6 electron/eV) and lower bandgap energy (0.481 eV) than H-PANI (5.24 electron/eV, 1.449 eV), indicating its enhanced electronic conductivity. The electronic bandgap energy is accordingly decreased from 0.263 eV for H-PANI-HSO4/GCP to 0 for H-PANI-HSO4/GCP. Electrochemical measurement and simulation calculation investigation proves that H-PANI-HSO4/GCP electrode with anion-doped and protonated state exhibits higher electronic conductivity and capacitance performance to act as superior electroactive material. The LiClO4-interacted oxygen-containing carbon paper is designed to act as electroactive supercapacitor electrode substrates for energy storage application, which involves the polarized electrostatic force-induced interfacial adsorption between LiClO4 and hydroxyl and epoxy groups of OCP substrate. [ABSTRACT FROM AUTHOR]

The two-dimensional layered materials (for example MoS 2) are potential electrodes for supercapacitors with their excellent lamellar structure, high surface area, mechanical flexibility, and potential redox activity. However, due to restacking of chemical structure and low electrical conductivity of the pure MoS 2 electrodes are prevented for energy storage applications. Therefore the electrodes are made up of a composite by a mixture of MoS 2 and rare-earth metals significantly addressing these issues with improved electrical conductivity, large electrochemical active surface, and shorter ion-diffusion kinetics. In the present study, the MoS 2 and MoS 2 /Nd 2 O 3 composite were synthesized by hydrothermal method. The structural phase identification of prepared samples was accomplished by using an X-ray diffractometer (XRD) and Raman spectra. Furthermore, TEM reveals changes in the shape of nanosheets and interlayer spacing. The GCD of symmetric MoS 2 /Nd 2 O 3 composite electrodes displayed remarkable charging/discharging performance, with increased stability and rate capability. The MoS 2 /Nd 2 O 3 composite shows utmost C sp of 2528.18 Fg-1 at 1 Ag-1. In addition, the CV and GCD studies suggest that the electrodes exhibit pseudocapacitive behavior and excellent energy density(E) of 191 Wh kg−1 at 1474.1 W kg−1 power density(P) in 1M H 2 SO 4. The supercapacitor device made up of MoS 2 /Nd 2 O 3 composite shows greater performance in practical LED glowing applications. Therefore, the composites make advancements in energy storage devices like batteries and supercapbatteries due to their excellent energy storage, high electrochemically active surface area, and stability. [Display omitted] [ABSTRACT FROM AUTHOR]

MXenes, a type of two-dimensional nanomaterials consisting of transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. Especially, Ti 3 C 2 T x MXene prepared from Ti 3 AlC 2 MAX phase shows great application potential in flexible supercapacitors due to its facile synthesis, excellent conductivity and film-forming property. In contrast to conventional Ti 3 AlC 2 , excessive aluminum is incorporated in the synthesis process to produce Al-Ti 3 AlC 2. In this study, Ti 3 AlC 2 and Al-Ti 3 AlC 2 MAX phases are used to synthesize Ti 3 C 2 T x and Al-Ti 3 C 2 T x MXenes, respectively, by the same method of HF:HCl etching and LiCl intercalation. The freestanding Ti 3 C 2 T x and Al-Ti 3 C 2 T x film electrode is separately prepared through simple vacuum filtration. The presence of excess aluminum during the Al-Ti 3 AlC 2 synthesis facilitates to form more homogeneous grains structure with relatively larger particle sizes and an improved stoichiometric MAX phase with a Ti:C ratio closer to 3:2. The resulting Al-Ti 3 C 2 T x nanosheets show improved oxidation resistance with relatively uniform and larger dimensions, which facilitate the higher conductivity with slightly increased interlayer spacing for the Al-Ti 3 C 2 T x film. Therefore, the Al-Ti 3 C 2 T x film electrode shows more efficient ions transport and charge transfer, and thus achieves significantly enhanced capacitance (399 F g−1 at 1 A g−1) and rate performance (63.6 % retention from 1 to 10 A g−1) compared to the Ti 3 C 2 T x film electrode (342 F g−1 at 1 A g−1, 55.6 % retention from 1 to 10 A g−1). Moreover, the Al-Ti 3 C 2 T x -based flexible sandwiched supercapacitor also exhibits superior energy storage performance. The impressive results indicate that Al-Ti 3 C 2 T x MXene synthesized from Al-Ti 3 AlC 2 MAX phase possesses the great application potential in flexible supercapacitors. [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]

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g−1 in supercapacitor and specific capacitance of 260 F g−1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC. [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]

Herein, the single‐phase Ni‐based bimetallic spinel oxide (NiM2O4, M = Mn, Fe, Co) nanoparticles are successfully synthesized by sol–gel method and coated on a carbon cloth substrate to form flexible electrodes for supercapacitor applications. The effects of transition metal activity, calcination temperature, surface, and textural properties on the electrochemical properties of spinel electrode materials are demonstrated. It is found that lowering the calcination temperature results in a decrease in crystallite size and particle size, leading to an increase in surface area and pore volume. X‐Ray absorption spectroscopy reveals the presence of Mn2+/3+, Fe2+/3+, and Co2+/3+ in materials. According to the electrochemical studies, NiMn2O4 electrode in Na2SO4 electrolyte exhibits electrical double‐layer capacitance behavior, while NiFe2O4 and NiCo2O4 electrodes in KOH electrolyte exhibit pseudocapacitive behavior. All electrode materials have low solution resistance and charge transfer resistance. NiCo2O4 provides the highest specific capacitance (85.60 F g−1 at 2.5 A g−1) followed by NiFe2O4 and NiMn2O4. It seems likely that the high electrochemical activity of Co2+/3+ and small particle size of NiCo2O4 nanoparticles play an important role in improving the redox process and charge transfer, which may enhance the electrochemical performance of this electrode material. [ABSTRACT FROM AUTHOR]

Energy storage technology plays a critical role in integrating variable energy sources into the grid and ensuring energy consistency. Electrochemical supercapacitors are one of the most promising energy storage devices, as they present multiple advantages of high power density, rapid charge/discharge characteristics, and long‐term cycle stability. Herein, the NiCo2O4/molybdate nanocomposites are developed as electrode materials for supercapacitor applications. The NiCo2O4/molybdate nanocomposites are synthesized by a facile single‐pot hydrothermal method and are coated on a carbon cloth substrate to form flexible supercapacitor electrodes. The structures, chemical compositions, morphologies, and textural properties of these materials are carefully studied by X‐Ray diffraction, X‐Ray absorption spectroscopy, scanning electron microscopy/energy‐dispersive X‐Ray spectroscopy mapping, and N2 adsorption–desorption isotherms. The formation of spinel NiCo2O4 nanorods decorated with molybdate (AMoO4, A = Co, Ni) particles is confirmed for all samples. The NiCo2O4/CoMoO4 electrode exhibits pseudocapacitive behavior and provides the highest specific capacitance (287.28 F g−1 at current density 6 A g−1), about 5.5 times as high as that of NiCo2O4, with excellent cycle stability (107% specific capacitance retention after 1000 charge/discharge cycles at 1 A g−1). Therefore, the NiCo2O4/CoMoO4 composites can be considered as a promising pseudocapacitor electrode material. [ABSTRACT FROM AUTHOR]

This paper studied the preparation method of graphene carbon nanotube supercapacitor electrode material for new energy vehicles. By analyzing the characteristics of electrode materials graphene and carbon nanotubes, combined with the working principle of supercapacitors, we designed an effective preparation process based on Hummers method. First, high-quality graphene was synthesized by chemical vapour deposition and characterized to confirm its structure and properties. Then, carbon nanotubes were uniformly dispersed in a graphene matrix by solvothermal method to form graphene-carbon nanotubes composite material. The electrochemical properties of the composites were optimized by adjusting the preparation parameters. The experimental results showed that the electrode material of graphene carbon nanotube supercapacitor has excellent conductivity, high specific surface area and good cycle stability. The material also shows excellent rate performance and long cycle life, making it an ideal electrode material for supercapacitors in new energy vehicles. This study provides a potential new electrode material for the energy storage system of new energy vehicles. [ABSTRACT FROM AUTHOR]

With the growing demand for high performance energy storage devices, the advanced manufacturing technology of electrodes, which is a crucial component, has become increasingly essential in academic research and industrial applications. Activated carbon fiber cloth (ACFC) is a promising candidate for lithium‐ion capacitor (LIC) electrodes due to its abundant internal space and pores. However, the wider application of ACFC is restricted by its inferior conductivity. The conventional coating process is costly in terms of both materials and time and is only applicable to surface treatment with limitations in treating shaped substrate such as ACFCs. To overcome the applications obstacles of ACFC in batteries and capacitors, we propose a novel strategy for modification that utilizes electrophoretic deposition (EPD) to deposit Super P onto the surface, thus enhancing its conductivity. After being deposited for 10 min at 80 V, the modified ACFC exhibited higher conductivity. When matched with Si@C anode, the assembled LIC demonstrates excellent initial specific areal capacitance (710 mF cm−2) and cycling retention, with 76.92% remaining after 100 cycles at a current density of 7 mA cm−2. When matched with Si@C anode, the assembled LIC demonstrates excellent initial specific areal capacitance (26.91 F g−1) and cycling retention, with 85.21% remaining after 100 cycles at a current density of 0.2 A g−1. This work showcases the potential of EPD technology in the realm of electrode preparation and offers insights for electrode manufacture in other systems. [ABSTRACT FROM AUTHOR]

Tin disulfide (SnS2) is a prominent candidate in the class of transition metal dichalcogenides (TMD), whose multiple electrical and electrochemical applications have recently steered much attention to energy storage devices like batteries and supercapacitors. Previous studies on the material came under the efforts to improve its applications by doping, creating composites, and other heterogeneous structures, which are complicated and less economical. Thus, pristine SnS2, utilizing its morphological features in conjunction with a suitable synthesis method, was investigated to improve efficiency and reduce cost without confusing processes or structural iterations. In this work, SnS2 is synthesized in its bare form using the hydrothermal method to investigate its potential supercapacitor application. The synthesis route followed a cost‐efficient and simple protocol, and the material shows a porous morphology favoring electrode–electrolyte interaction desirable for supercapacitors. A comprehensive study on the structural, morphological, and surface features done by XRD, FESEM, EDX, XPS, and nitrogen adsorption–desorption analysis confirmed the formation of SnS2 and interior structure. Supercapacitor analysis by CV, GCD, EIS, and cyclic stability tests reveal an intermittent energy storage mechanism, with a capacitance of 109.6 F g−1 at 1 A g−1 and high cyclic retention of 106% at 5 A g−1 after 7000 cycles. [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]

A simple and energy‐saving synthesis process for the high‐performance Si/C anode material of lithium‐ion batteries is advantageous for application. In this paper, the layered Si/C composite was synthesized by a low temperature one‐pot synthesis from industrial Ca−Si alloy and CCl4. The effect of synthesis temperature on the structure and performance of the products was investigated. We found that low temperature favors to the multilayer structure of Si/C. Taking the advantage of the layered structure, the Si/C‐300 anode material prepared at the temperature of 300 °C has good electrochemical performance of a reversible capacity of more than 1000 mAh g−1 at a current density of 2 A g−1 for 300 cycles, with a capacity retention ratio of 82.8 %, and an ICE of 77.0 %. At a high current density of 6 A g−1, the specific discharge capacity of 721.6 mAh g−1 can be achieved. The synthesis method provides a promising route to high performance silicon‐carbon anode materials. [ABSTRACT FROM AUTHOR]

High surface area porous activated carbons obtained from sustainable biomass are excellent functional materials for energy storage applications. This is the first report on snake gourd (Trichosanthes cucumerina) pericarp as a raw material of activated carbon and supercapacitor electrode material. Herein, a simple KOH activation and carbonisation method is used. The obtained SGC900 sample has a surface area of 1841 m2/g and an average pore volume of 0.52 cm3/g. SGC900 based supercapacitor exhibits good electrochemical storage capacity in 1 M H2SO4 with a specific capacitance of 206 F/g at 1 A/g. The symmetric device delivered an energy density of 11 Wh/kg at a power density of 1.6 kW/kg. It provides a series resistance (Rs) of 1.2 Ω and a charge transfer resistance Rct of 1.9 Ω. Furthermore, the device retains 95 % of capacitance over 5000 cycles. This work presents an easy and feasible approach for producing value‐added activated carbon from sustainable biomass, potentially used in high‐performance energy storage. [ABSTRACT FROM AUTHOR]

Here, we describe the analysis of the capacitive performance of activated carbon materials derived from the biowaste of lemon. Lemon peel discarded by restaurants after juice extraction is carbonized at 400 0C followed by chemical activation using ZnCl2. The porosity of carbon materials is tailored by varying activation conditions, such as the mass ratio of carbonized lemon peel and ZnCl2, duration of heating, and temperature. The Brunauer–Emmett– Teller (BET) surface area and pore volume of carbon materials prepared at different activating conditions range from 1380 to 2120 m2g−1 and 0.38 to 0.69 cm3 g−1 respectively. The derived carbon materials are amorphous indicated by the broad peaks in the XRD pattern as well as disordered structure of the carbon materials is revealed by the Raman spectroscopic analysis. The systematic analysis of capacitive performance of activated carbons by employing electrochemical techniques like Cyclic Voltammetry (CV), Galvanostatic charge/Discharge (GCD) cycles, and electrochemical impedance spectroscopy (EIS) in acidic (H2SO4) and alkaline (KOH) media indicates that optimum condition for activation of lemon peel is 600 °C for 60 min with 1:1 mass ratio of carbonized lemon peel and ZnCl2. The superior performance of (ALP-600) is attributed to its high surface area and well-connected hierarchical porous structure. The tiny hump at ~ 0.2 V in CV might be due to the pseudocapacitive nature of oxygen functional groups indicated by FTIR. ALP-600 exhibits the highest specific capacitance of 180 Fg−1 and retains 99.7% of its initial capacitance after 5000 cycles in the acidic electrolyte. The maximum capacitance achieved with ALP-600 symmetric cell in CR2032 coin cell configuration is 0.90F. [ABSTRACT FROM AUTHOR]

Developing supercapacitor materials that are both efficient and durable, with high cycle life and specific energy, poses a significant challenge due to issues in electrodes such as volume expansion and electrode degradation that occur over time. This work reports a simple, novel, and cost-effective synthesis method to fabricate high surface area "Iron (Fe) doped TiO2 materials" via the metal-organic framework (MOF) route for supercapacitor application. Morphological analysis revealed a disc-like shaped pattern for pristine TiO2 (PT), and a cuboid form for Fe-doped TiO2 (FeT). The electrochemical investigation of MOF-derived PT and FeT electrode materials demonstrated the superior performance of FeT. Cyclic Voltammetry revealed enhanced electrochemical properties in FeT. Galvanostatic charge-discharge measurements confirmed FeT's higher energy storage capacity, reaching a maximum specific capacitance of 925 Fg− 1. Long-term cycling tests exhibited excellent stability, with FeT retaining 67% of its initial capacitance after 6000 cycles and showing prolonged self-discharge. Overall, the results underscore the potential of Fe-doped TiO2 for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

We investigated the electrochemical performances of α-MnO2 and β-MnO2 nanorods synthesised via hydrothermal route. The electrochemical properties of α- and β-MnO2 evaluated utilising cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte revealed that the α-MnO2 electrode exhibits a specific capacity of 743 C/g whereas β-MnO2 electrode exhibited a specific capacity of 391 C/g for same current density of 3 A/g. Also, after 5000 cycles, α- MnO2 exhibits a capacity retention of 80%, while β-MnO2 shows 64% retention. The present work reports the enhanced pseudocapacitor electrode performance of α-MnO2 over β-MnO2. For practical application, synthesized α-MnO2 and activated carbon were assembled in Swagelok-type cell to fabricate hybrid supercapacitor. The hybrid supercapacitor exhibits exceptional specific capacitance of 241.25 F g−1, with excellent energy and power density of 85.77 Wh Kg−1 and 1600 W Kg−1 respectively. [ABSTRACT FROM AUTHOR]

Using discarded durian shell (DS), a waste biomass, as the raw material, DS-based activated carbon was prepared. Heteroatom doping with thiourea as the nitrogen and sulfur source was then introduced on the precursor of DS activated carbon to investigate its impact on the material's morphology and electrochemical energy storage performance as a supercapacitor electrode. Characterization techniques such as XPS, XRD, and electrochemical tests were employed to evaluate the relevant properties of the material. The results revealed that when the mass ratio of thiourea to DS activated carbon reached 2:1, the specific surface area of S-DCK-2 peaked at 2394 m2·g−1. Electrochemical testing demonstrated that S-DCK-2 exhibited a remarkable specific capacitance of 370 F·g−1 at 0.5 A·g−1, indicating its superior electrochemical performance. Subsequently, electrodes were assembled into S-DCK-2//S-DCK-2 symmetric supercapacitors in a two-electrode configuration. The results showed that the S-DCK-2//S-DCK-2 device achieved a specific capacitance of 113 F·g−1 in 6 mol·L−1 KOH at a current density of 0.5 A·g−1. The material exhibited an energy density of 15.83 Wh·kg−1 and a power density of 313 W·kg−1. The experiment confirmed that doping with sulfur and nitrogen enhanced the pseudocapacitance capacity, leading to improved electrochemical performance. [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]

Nickel hydroxide (Ni(OH)2) is recognized as a promising material for electrodes in supercapacitors owing to its exceptional theoretical specific capacitance. However, Ni(OH)2 has several drawbacks, including a short cycle life, susceptibility to volume expansion, and poor electrical conductivity. In this work, Ni(OH)2 nanosheets anchored on layered g‐C3N4/C (Ni(OH)2–g–C3N4/C) are designed by biological template induction and a hydrothermal method. Ni(OH)2–g–C3N4/C has unique petal‐like structures, which can provide a vertical charge transport channel to increase reaction potential of the material during the charge–discharge process. The introduction of biomass carbon can solve the problem of the bulk phase accumulation of g‐C3N4 and can also improve the overall conductivity of the composite. Compared to Ni(OH)2 (522 F g−1), g‐C3N4/C (76.2 F g−1), and g‐C3N4 (16 F g−1), the Ni(OH)2–g–C3N4/C‐0.75 (NGC‐0.75) composite exhibits the highest specific capacitance of 1034 F g−1 at 1 A g−1. Furthermore, after 5000 cycles at 5 A g−1, the capacitance of the material is maintained at 85.97%. Meanwhile, the asymmetric supercapacitor based on the NGC‐0.75 shows a high energy density of 18.29 Wh kg−1 at the power density of 400.02 W kg−1 with excellent cyclic stability of 127.45% over 10 000 cycles. [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]

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]

Carbon fiber, with its strong mechanical properties and electrical conductivity, is ideal as a fiber electrode in wearable or structural energy storage devices. However, its energy storage capacity is limited, and coatings like transition metal oxides (TMOs) enhance its electrochemical performance. Metal–organic frameworks (MOFs) are commonly used to grow TMOs on carbon fibers, increasing the surface area for better energy storage. Despite this, TMOs have limited electrical conductivity, so ion exchange is often used to dope them with additional cations, improving both conductivity and energy storage capacity. This study compares different ion-exchange cations in ZIF-L-derived TMO coatings on carbon fiber. Testing both supercapacitor and Li-ion battery applications, Ni-doped samples showed superior results, attributed to their higher exchange ratio with cobalt. As a supercapacitor electrode, the Ni-doped material achieved 13.3 F/g at 50 mA/g—66% higher than undoped samples. For Li-ion battery anodes, it reached a specific capacity of 410.5 mAh/g at 25 mA/g, outperforming undoped samples by 21.4%. [ABSTRACT FROM AUTHOR]