Search

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]

In this paper, we present a continuation of our research on modeling electrolyte solutions within charged pores. We make use of the model developed by Blossey et al. [Phys. Rev. E 95, 060602 (2017)], which takes into account the structural interactions between ions through a bilinear form over the gradients of local ionic concentrations in the grand thermodynamic potential, as well as their steric interactions through the lattice gas model. The structural interactions may describe the effects of the molecular structure of ions at a phenomenological level. For example, these effects include steric effects due to non-spherical shapes of ions, their conformational lability, and solvent effects. In addition, we explore their specific interactions with the pore walls by incorporating external attractive potentials. Our primary focus is on observing the behavior of ionic concentration profiles and the disjoining pressure as the pore width changes. By starting with the local mechanical equilibrium condition, we derive a general expression for the disjoining pressure. Our findings indicate that considering the structural interactions of ions leads to a pronounced minimum on the disjoining pressure profiles at small pore widths. We attribute this minimum to the formation of electric double layers on the electrified surfaces of the pore. In addition, our results demonstrate that the inclusion of the attractive interactions of ions with the pore walls enhances this minimum and shifts it to smaller pore thicknesses. Our theoretical discoveries may be useful for those involved in supercapacitor electrochemical engineering, particularly when working with porous electrodes that have been infused with concentrated electrolyte solutions. [ABSTRACT FROM AUTHOR]

The electronics industry's increasing demand for swift energy storage solutions drives researchers to invest significant resources into enhancing electrode materials. Achieving optimal efficiency throughout the charging process requires meticulous attention to the designing of the morphological, structure and chemical compositions of the electrode materials. Understanding the synergies among elements and structural dynamics is pivotal for maximizing the electrodes' performance. To address these challenges, we propose a groundbreaking approach through a straightforward and cost-effective solid-state reaction method followed by an impregnation technique to design a graphene oxide-wrapped wolframite-type 3D cube-like CuWO 4 (GW-CuWO 4) composite matrix. This design substantially increases the electrode's surface area (5 times greater than pristine CuWO 4 and 12 times greater than sphere-like Na 2 WO 4) and enhances its mesoporous characteristics. We extensively analyzed the physicochemical properties of GW-CuWO 4 and compared them with pristine CuWO 4 and Na 2 WO 4 using various analytical techniques. The electrochemical performance of all electrodes exhibited battery-type characteristics, with the supercapacitive performance thoroughly investigated and compared. The specific capacity of the GW-CuWO 4 composite electrode demonstrated significant results, reaching 520.8 C g−1 at 1.0 A g−1, with outstanding rate capability retaining 93 % capacity even at a high rate of charging current of 10 A g−1. In contrast, the specific capacity and rate capability of pristine CuWO 4 were 392.1 C g−1 and 87 %, respectively, and Na 2 WO 4 showed 295.8 C g−1 and 64 %. Additionally, the GW-CuWO 4 electrode displayed excellent cyclic performance, retaining 95 % capacity at 10 A g−1 compared to CuWO 4 (84 %). The GW-CuWO 4 electrode exhibits enhanced electrochemical performance due to the synergistic interactions between its constituent parts and its distinct 3D mesoporous composite network. High conductivity, rich redox reactions, easy electron transfer, short ion diffusion lengths, quick kinetics, and an abundance of active sites for electrochemical reactions are all made possible by this network. Presenting this cutting-edge electrode design builds a fresh framework for producing effective electrodes suited for the upcoming wave of high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

This paper investigates the enhanced pseudocapacitive properties of cobalt-doped manganese oxide (Co-doped MnO 2) electrode in magnesium sulfate (MgSO 4) electrolyte for supercapacitor applications. Co-doped MnO 2 was synthesized on nickel foam through a controlled hydrothermal process and specific heat treatment parameters. This resulted in the transformation into α-MnO 2 with a 2 × 2 tunnel structure. Morphological investigation illustrates the presence of a hierarchical micro-flower structure with a substantial surface area and mesoporous distribution. The specific surface area of the Co-doped MnO 2 electrode significantly increased to 158 m2 g−1, compared to the pristine (bare MnO 2) electrode (80 m2 g−1). Electrochemical analyses revealed a specific capacitance of 527 F g−1 at 1 A g−1 in MgSO 4 (1 M), showcasing a 1.6 times improvement over Na 2 SO 4 (1 M). The unique structure of the Co-doped MnO 2 , combined with magnesium ions as efficient electron donors, contributes to superior charge-storage, making it a promising candidate for high-performance supercapacitors. Comprehensive characterizations, such as XRD, XPS, BET, SEM, GCD, and EIS, confirm the advantageous electrochemical performance and durability of the Co-doped MnO 2 electrode in MgSO 4 electrolyte. [Display omitted] • One-step hydrothermal synthesis produced α-MnO 2 electrode with a 2 × 2 tunnel structure. • Hierarchical micro-flower morphology provided high surface area and mesoporous distribution. • Bivalent magnesium ions replace univalent sodium, revealing a unique charge-storage mechanism. • Cobalt doping forms a distinct conductive network, boosting electrochemical performance. • Co-doped MnO 2 electrode exhibited exceptional durability, maintaining 93 % capacitance retention. [ABSTRACT FROM AUTHOR]

This investigation is motivated by the surge of interest in materials, combining high spontaneous magnetization and pseudocapacitance at room temperature. Ferrimagnetic MnFe 2 O 4 offers benefits of high magnetization. However, the non-pseudocapacitive behavior, low capacitance and high resistance of MnFe 2 O 4 are limiting factors for its applications in magnetic pseudocapacitive devices. This investigation demonstrates that nearly ideal pseudocapacitive behavior can be achieved for MnFe 2 O 4 electrodes in Na 2 SO 4 electrolyte. High pseudocapacitance is observed in positive and negative potential ranges and two different charging mechanisms are proposed. High capacitance is achieved at a low impedance. The ability to achieve comparable and high areal capacitances in the positive and negative potential ranges facilitates the fabrication of a symmetric pseudocapacitive device, containing ferrimagnetic MnFe 2 O 4 as cathode and anode material for operation in enlarged voltage window of 1.6 V. The symmetric device shows capacitance of 0.92 F cm−2 at a current density of 3 mA cm−2. The individual electrodes and device show good cycling stability. The approach is based on the use of murexide and gallocyanine as redox-active dispersants and charge transfer mediators. The analysis of testing results provides an insight into the influence of chemical structure, charge and redox properties of the dispersants on the capacitive behavior. The ability to fabricate a pseudocapacitive device, containing two ferrimagnetic electrodes is promising for energy storage, water purification and novel applications based on magnetocapacitive effects. [ABSTRACT FROM AUTHOR]

Addressing the slow electrochemical kinetics and electrode pulverization of sodium ion batteries (SIBs) is needed to continuously develop advanced anode materials. Molybdenum telluride (MoTe 2) is considered promising for SIBs anodes due to its wider interlayer distance, faster electronic conductivity, and weaker interlayer force. However, the nanoparticle aggregation and layered structure collapse caused by bond breakage weaken its inherent advantages for excellent sodium storage performance. Herein, hierarchically nanostructured regulation and surface coating of MoTe 2 based SIB anodes are simultaneously achieved by employing Mo-PDA as precursors through a concise and effective method containing chelation, preoxidation and tellurization. The microstructure and morphology of MoTe 2 /C composites can be facilely regulated by controlling the chelation time and tellurization temperature. The as-synthesized MoTe 2 /C-6h-600 electrode exhibits encouraging Na+ storage performance, which delivers discharge capacitances of 290.7 mAh g−1 (0.1 A g−1) and 161.1 mAh g−1 (1.0 A g−1) after hundreds and thousands cycles, respevtively. Furthermore, the assembled full cell of MoTe 2 /C-6h-600//NVP delivers a stable reversible capacitance of 103 mAh g−1, which is promising for future practical applications. [Display omitted] • Hierarchical nanosheet self-assembled MoTe 2 /C are successfully synthesized. • Effects of tellurization temperature and chelation time are systematically investigated. • MoTe 2 /C-6h-600 exhibits excellent Na+ storage performance for half/full cells. • MoTe 2 /C-6h-600 can be successfully applied in an electronic gyroscope. [ABSTRACT FROM AUTHOR]

In this work, the content of lignin, pitch, and PAN as well as the preparation process would be systematically controlled in order to prepare carbon nanofibers (CNFs) with cross‐linked structure, high specific surface area, and good flexibility. The evolution of nanofibers with different lignin contents during stabilization and carbonization were explored, and the properties of the resultant CNFs as supercapacitor self‐supported electrodes were compared. The results indicated that with the increase of lignin content, not only cross‐linked structures were introduced in CNFs, but also the flexibility were obviously improved, accomplishing for supercapacitor self‐supported electrodes. Moreover, CNFs with different content of lignin varied in fiber morphology and microstructure, harvesting developed porous structure in CNFs. PPL3‐CNF prepared with adding lignin at a mass ratio of 3/7 into a concentration of 10 wt.% pitch/PAN solution presented the highest specific surface area of 949 m2 g−1, exhibiting an excellent specific capacitance of 190.7 F g−1 at 0.2 A g−1. [ABSTRACT FROM AUTHOR]

Manganese dioxide is attractive for energy storage but still needs to be combined with highly conductive materials to improve its electrochemical properties. In this paper, δ-MnO2/GNS composites with three-dimensional structures were synthesized by anchoring hydrangea-like δ-MnO2 on graphene substrates. Physicochemical analysis shows that δ-MnO2 is uniformly anchored on the graphene surface, and adjacent hydrangea-like δ-MnO2 self-assembles to build a three-dimensional conductive network, and this special structure not only provides abundant surface active sites but also more fast channels for electron transport during electrochemical reactions. The optimized composite (δ-MnO2/GNS-1.8) exhibited excellent electrochemical performance with a high specific capacitance of 326.6 F g−1 at a current density of 0.2 A g−1 and a cycling performance of 97.1%. Asymmetric supercapacitors assembled with δ-MnO2/GNS and activated carbon (AC) exhibited energy densities up to 42.2 W h kg−1 at a power density of 196.8 W kg−1. Hydrangea-like δ-MnO2 anchored on GNS has great potential for application as a high-performance supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

Carbon-based materials/metal hydroxide composite materials are one type of the most promising electrode materials for improving the performance of supercapacitors. They have the advantages of low cost, controllable morphology, high theoretical capacity, and excellent stability. In this study, nickel hydroxide nanosheets were grown vertically on the surface of carbon nanotubes (Ni(OH)2@CNTs) by a wet chemical method at low temperatures. The unique spatial configuration provides a larger specific surface area and exposes more electrochemically active sites, which is more conducive to improving electrochemical performance. The prominent conductivity of carbon nanotubes can quickly transfer electrons and improve the electrochemical cycling stability of the composite. The Ni(OH)2@CNTs composite exhibits excellent electrochemical performance with a specific capacitance of 1234 F g−1 at a current density of 1 A g−1 under a three-electrode system. In addition, an asymmetric supercapacitor (ASC) assembled using Ni(OH)2@CNTs as a cathode material shows an energy density of 65.63 W h kg−1 at a power density of 752.39 W kg−1 and a capacity retention rate of 85.9% after 10 000 cycles at a current density of 2 A g−1. The results indicate that Ni(OH)2@CNTs has prospects for application as a cathode material in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

A facile hydrothermal method was employed to fabricate tailored NiCo(CO3)(OH) 2 electrodes for high-performance supercapacitors. Ni and Co ions, transition metals with versatile oxidation states, were used, promoting redox reactions. Additionally, a comparative analysis of the characteristics and electrochemical properties between electrodes fabricated with 3D Ni foam substrates and those without substrates was conducted. This comparison emphasizes the critical role of 3D substrate selection in enhancing electro- chemical performance during electrode fabrication. Furthermore, carbonate/hydroxide-based transition metal electrodes have been fabricated. Carbonate-based transition metals can substantially increase the wettability of the electrode surface due to their hydrophilicity, which has proven beneficial in aqueous electrolytes. The NiCo(CO3)(OH)2 electrodes with Ni foam substrates and without Ni foam substrates exhibit impressive specific capacitances of 2576.4 and 1460.2 F g-1, respectively, at 3 A g-1. Furthermore, an asymmetric supercapacitor configuration is introduced, utilizing the NiCo(CO3)(OH)2 electrode with a Ni foam substrate and graphene as positive and negative electrodes, respectively. A remarkable energy density of 35.5 W h kg-1 and a power density of 2555.6 W kg-1 at a current density of 2 A g-1 are exhibited by this configuration. Notably, excellent cycling stability is displayed by the asymmetric supercapacitor, with approximately -71.3% of its capacity retained after 10 000 cycles. These results highlight the promis- ing potential of the fabricated electrodes and asymmetric supercapacitor configuration for practical energy storage applications. [ABSTRACT FROM AUTHOR]

2D transition metal oxides have created revolution in the field of supercapacitors due to their fabulous electrochemical performance and stability. Molybdenum trioxides (MoO3) are one of the most prominent solid-state materials employed in energy storage applications. In this present work, we report a non-laborious physical vapor deposition (PVD) and ultrasonic extraction (USE) followed by vacuum assisted solvothermal treatment (VST) route (DEST), to produce 2D MoO3 nanosheets, without any complex equipment requirements. Phase transition in MoO3 is often achieved at very high temperatures by other reported works. But our well-thought-out, robust approach led to a phase transition from one phase to another phase, for e.g., hexagonal (h-MoO3) to orthorhombic (α-MoO3) structure at very low temperature (90 °C), using a green solvent (H2O) and renewable energy. This was achieved by implementing the concept of oxygen vacancy defects and solvolysis. The synthesized 2D nanomaterials were investigated for electrochemical performance as supercapacitor electrode materials. The α-MoO3 electrode material has shown supreme capacitance (256 Fg−1) than its counterpart h-MoO3 and mixed phases (h and α) of MoO3 (< 50 Fg−1). Thus, this work opens up a new possibility to synthesize electrocapacitive 2D MoO3 nanosheets in an eco-friendly and energy efficient way; hence can contribute in renewable circular economy. [ABSTRACT FROM AUTHOR]

Polyaniline/hydrothermally treated graphite disk (PANI/HT-G disk) with 3D microporous structure and large surface area is suggested as an effective and inexpensive electrode in the supercapacitor application. The PANI/HT-G disk was easily obtained from uniform mixing of commercial and low-cost azodicarboxamide (ADCA-C2H4O2N4) and graphite powders, pressing beneath optimum pressure pursued by treatment at 250 °C to release various gases (NH3, N2, CO) originated from ADCA decomposition (creating porous structure with large surface area) and finally electrodeposition of polyaniline onto the previously HT-G disk. The PANI/HT-G disk demonstrated weak ohmic drop and favorite areal capacitance of 1490 mF cm−2 at 2/0 mA cm−2 in aqueous 1.0 M sulfuric acid electrolyte under the three-electrode system. When PANI/HT-G disk was assembled as symmetric supercapacitor disk device with a PVA/H2SO4 gel, the areal capacitance was 232 mF cm−2 at 2/0 mA cm−2 with high operation voltage. The supercapacitor device had an energy density of 93.17, 83.32, 86, 63.96, 60.2, 48.37, and 44.8 mWh cm−2 in the power density of 2.58, 3.22, 3.87, 4.51, 5.16, 5.8, and 6.45 mW cm−2. It is expected that the strategy introduced in this work could guide designers for scalable fabrication of low-cost supercapacitor disks. [ABSTRACT FROM AUTHOR]

Nickel ferrites have served as electrode materials in energy storage applications such as batteries and supercapacitors in comparison to other metal oxides, they have a higher theoretical capacitance range. Pristine metal oxides are poor candidates as electrode components in electrochemical applications because of their tendency to aggregate and their less specific surface areas. Herein, we reported wet impregnation method to incorporate Nickel Ferrite (NiFe2O4) to multiwalled carbon nanotubes (MWCNTs) for improved electrochemical performance of nickel ferrites (NiFe2O4). The synthesized materials attained good crystallinity confirmed by X-ray diffraction (XRD). NiFe2O4 nanoparticle adhesions on multiwalled carbon nanotubes have been confirmed by scanning electron microscopy (SEM). UV-DRS was used to measure the bandgap for optical studies. Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD), and Electrochemical Impedance Spectroscopy (EIS) investigations for supercapacitor applications revealed that synthesized materials demonstrated good electrochemical potential, but MWCNTs supported NiFe2O4 composite attained exceptionally high specific capacitance (CV: 830 F g−1 at 5 mV s−1, GCD:343 F g−1 at current density of 0.1 A g−1) with capacitance retention of 98% at the current density of 0.8 A g−1 after 3500 stability cycles. [ABSTRACT FROM AUTHOR]

This paper presents a novel binder-free electrochemical synthesis of a porous ternary composite comprising polyaniline/multiwall carbon nanotubes decorated with silver nanoparticles (Ag@PANI/MWCNTs), which serves dual functions as a photocatalyst for methylene blue degradation and as an electrode for high-performance supercapacitors application. Various characterization techniques confirm that the synthesized Ag@PANI/MWCNTs composite exhibits excellent optical, chemical, electrical, structural, morphological, electrochemical and photocatalytic characteristics. The composite exhibits excellent electrochemical and photocatalytic efficacy attributed to its porosity, higher surface area, conductivity and rapid redox properties. Electrochemical tests reveal specific capacitance of 862 F/g, energy density of 65.78 Whkg−1, power density of 444.44 Wkg−1 and cycling stability with 79% capacitance retention even after 10,000 cycles. As a photocatalyst, the composite achieves approximately 95% degradation in 25 min with reusability up to five cycles. It also exhibits high transient photocurrent responses (0.36 mA/cm2) and a high-rate constant (0.13 min−1), confirming excellent photocatalytic activity. The synergistic effect of PANI/MWCNTs and the incorporation of Ag nanoparticles contribute to the outstanding performance of the synthesized nanocomposite. Thus, it is expected that the synthesized Ag@PANI/MWCNT is a promising ternary composite which may prove to be a noble material for photocatalytic and energy storage-related devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optimized hollow ZnO@Co 3 O 4 carbon nanotube composites (CNCs) with a unique morphology were synthesized from dual MOFs using low temperatures. • Fabricated NM-CH/ZnO@Co 3 O 4 CNCs electrode has a remarkable capacitance of 1179 ± 0.10 F/g at 0.5 A g−1 and an excellent rate capability. • NM-CH/ZnO@Co 3 O 4 CNCs solid-state hybrid supercapacitor exhibits excellent energy density (33 ± 0.12 Wh kg−1). • The energy storage hybrid supercapacitor has been enhanced by the synergistic effect of NM-CH and ZnO@Co 3 O 4 CNCs. • Solid-state devices demonstrated excellent long-term cycle stability and good rate capabilities. Electrodes and electroactive materials are crucial components in the development of supercapacitors due to their geometric properties. In this study, bimetal-organic frameworks (Bi-MOFs, ZIF-8@ZIF-67) were utilized as electrode materials for a high-performance hybrid supercapacitor (HSC) by designing a novel synthesis of metallic carbonate hydroxide/oxides. In particular, the Bi-MOFs function as a sacrificial precursor in the synthesis of hollow NiMn(CO 3) 0.5 ·0·.11H 2 O/ZnO@Co 3 O 4 CNCs (NM-CH/ZnO@Co 3 O 4 CNCs) cubic composite materials by a straightforward low-temperature treatment. The NM-CH/ZnO@Co 3 O 4 CNCs exhibited exceptional electrochemical performance with high specific capacity of 196.3 ± 0.08 mAh/g, specific capacitance of 1179 ± 0.10 F g−1 at 0.5 A g−1, and outstanding cycling stability of 98% after 25,000 cycles compared to the other electrode materials. The porous and hollow structure, along with a large surface area, contributed to the enhanced electrochemical properties of the composite material. An HSC was constructed using NM-CH/ZnO@Co 3 O 4 CNCs as the cathode and activated porous carbon (APC) as the anode, resulting in a device with a specific energy of 33 ± 0.12 Wh kg−1 and a power density of 19354 ± 0.07 W kg−1. The use of Bi-MOF electrodes presents new avenues for the development of high-performance energy storage materials, with the potential for industrial energy storage application demonstrated though the successful powering of portable lightbulbs. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal-organic frameworks (MOFs) are highly suitable precursors for supercapacitor electrode materials owing to their high porosity and stable backbone structures that offer several advantages for redox reactions and rapid ion transport. In this study, a carbon-coated Ni 9 S 8 composite (Ni 9 S 8 @C-5) was prepared via sulfuration at 500 ℃ using a spherical Ni-MOF as the sacrificial template. The stable carbon skeleton derived from Ni-MOF and positive structure–activity relationship due to the multinuclear Ni 9 S 8 components resulted in a specific capacity of 278.06 mAh·g−1 at 1 A·g−1. Additionally, the hybrid supercapacitor (HSC) constructed using Ni 9 S 8 @C-5 as the positive electrode and the laboratory-prepared coal pitch-based activated carbon (CTP-AC) as the negative electrode achieved an energy density of 69.32 Wh·kg−1 at a power density of 800.06 W·kg−1, and capacity retention of 83.06 % after 5000 cycles of charging and discharging at 5 A·g−1. The Ni-MOF sacrificial template method proposed in this study effectively addresses the challenges associated with structural collapse and agglomeration of Ni 9 S 8 during electrochemical reactions, thus improving its electrochemical performance. Hence, a simple preparation method is demonstrated, with broad application prospects in supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) MXenes are widely acknowledged as highly adaptable materials for flexible supercapacitors due to their high electronic conductivity, tunable surface chemistry, structural adaptability, and excellent mechanical strength. However, pure MXene nanosheets have a tendency to stack together, which decreases the mechanical and electrochemical properties for flexible devices. Herein, inspired by the structure of modern architecture, MXene/MWCNT/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical-mediated oxidized cellulose nanofibers (TOCNFs) (MMT) composite film (MMT-X, the content of MWCNT and TOCNFs is X% of the total weight of the film) is manufactured using a simple vacuum filtration method. In MMT, two-dimensional (2D) MXene is severed as nanometer "bricks", one-dimensional (1D) TOCNFs is used as a nanometer "mortar" between MWCNTs and MXene based on synergistic electrostatic forces and hydrogen bonding to build a three-dimensional (3D) composite structures with excellent mechanical strength. The flexible MMT-8 film is used as a supercapacitor electrode with specific capacity 856 F cm−3. Furthermore, at a volume power density of 335.5 W L−1, the assembled flexible all-solid-state supercapacitor (ASSC) could provide a volumetric energy density of 11.64 Wh L−1 with good cycle stability. [Display omitted] • A MXene/MWCNT/TOCNF film with structure similar to "modern architecture" was manufactured using vacuum filtration method. • The mechanical properties of MXene/MWCNT/TOCNF films are improved. • The MXene/MWCNT/TOCNF film show excellent electrochemical properties for flexible supercapacitor. [ABSTRACT FROM AUTHOR]

This study reports the preparation of ZnCo 2 O 4 oxide (ZCO) electrode materials with favorable microstructure and porosity arrangement via ultrasonic electrodeposition-calcination. The application of ultrasonic waves at a power of 200 W (using ZCO-2) led to the development of a smooth and flat microstructure, characterized by the presence of numerous micropores. The lattice constant of ZnCo 2 O 4 in the ZCO-2 oxide electrode material was determined to be 0.428 nm via TEM analysis. Furthermore, the XRD analysis of ZCOs demonstrated the effective synthesis of ZnCo 2 O 4 electrode materials. The main lattice diffraction planes of ZCOs were observed at (111), (220), (311), (400), (511), and (440), with corresponding diffraction angles of 29.8°, 36.4°, 42.9°, 45.2°, 62.3°, and 66.5°, respectively. The application of 200 W ultrasonic power during electrochemical experiments significantly improved the electrochemical performance of ZCO-2. The ZCO-2 oxide electrode demonstrated remarkable area capacitance and negligible electrical impedance. At a current density of 3 mA/cm2, the area capacitance was measured to be 1.803 F/cm2. The ZCO-2 oxide electrode showed remarkable capacitance retention of 67.3 % even under high current density conditions. Furthermore, the asymmetric supercapacitor composed of ZCO-2 and AC (ZCO-2/AC ASC) showed outstanding electrochemical performance. The ZCO-2/AC ASC showed a capacitance of 5.721 F/cm3 at a current density of 0.5 mA/cm2. Furthermore, it demonstrated an energy density of 68.2 Wh/kg at a power density of 250 W/kg. The capacitor showed consistent performance and retained 63.8 % of its initial capacitance even after undergoing 24,000 cycles. Furthermore, the findings of this research provide substantial implications for the combination of ultrasonic electrodeposition with capacitors, while also presenting an innovative concept for electrode materials in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Ternary nanocomposites of reduced graphene oxide/multi-walled carbon nanotubes/cobalt oxide nanoparticles (rGO/MWCNT/Co3O4) were synthesized employing a facile hydrolysis method with subsequent heat treatment. The good electrical conductivity and remarkable carrier mobility of rGO and MWCNTs make them a suitable matrix for hybrid supercapacitors, and their composites with metal oxides exhibit enhanced electrochemical properties due to the advantages of the synergistic contribution and the integration of different dimensionalities. The binary counterparts of Co3O4 with GO or MWCNTs were also produced using the same technique to gain additional insight into the characteristics of the individual components. The structural and morphological properties of the composites were analyzed using various analytical techniques. The electrochemical behaviors of the prepared composites were investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4. A platinum electrode modified with the rGO/MWCNT/Co3O4 composite displayed a remarkable specific capacitance of 922 F g−1 at a current density of 1 A g−1 composite with a negligible capacitance drop after 2000 cycles. The symmetric supercapacitor fabricated using the rGO/MWCNT/Co3O4 composite showed an energy density of 32.2 Wh Kg−1 at 1 A g−1, and the corresponding power density was 2000 W Kg−1. The supercapacitor fabricated using the composite displayed 83% capacitance retention after 2000 cycles at 3 A g−1 composite. [ABSTRACT FROM AUTHOR]

In this article, nickel hydroxide nanocrystals are synthesized for the first time by a simple air-plasma electrolysis setup. Aqueous solution of nickel nitrate is used as the electrolyte. Once the electrolysis is started, a green powder is produced at the contact point of the plasma and the solution. Electron microscopy (FESEM and TEM) of the powder indicates that most of the particles are spherical with 25–30 nm size. Elemental analysis, Fourier transform infrared spectroscopy and X-ray diffraction pattern reveal that the powder is nano-crystalline Ni(OH)2⋅0.75H2O with rhombohedral structure (or α-Ni(OH)2). To evaluate the lattice strain and dislocation density, the methods of Scherrer, Williamson–Hall, Williamson–Smallman and also Halder–Wagner are used. Comparisons show that the Halder–Wagner method provides more accurate results. The size of the nano-crystallites is estimated to be about 2.38 nm by this method, and the strain and dislocation density are obtained at 0.3299 and 17.72 line m−2, respectively. The results of this research confirm that the room-temperature atmospheric plasma electrolysis can be a promising and efficient candidate for the synthesis of hydroxide nanocrystals, which may have wide applications in the energy storage systems and supercapacitor industries. [ABSTRACT FROM AUTHOR]

A significant challenge in developing high-performance hybrid supercapacitors (HSCs) is the need to reasonably construct advanced architectures that consist of various components and exhibit superior electrochemical capacitance performance. The FeCoNi-layered double hydroxide (FeCoNi-LDH) porous material has a specific capacitance of 1960 F·g−1 when used as the anode material at 1 A·g−1. The FeCoNi-LDH material exhibits nanoplates with a distinct spindle morphology on their surface. Due to the combined action of the three metals and abundant oxygen vacancies, they exhibit unique rate performance and cycle stability. The electronic structure of LDH and the regulation of oxygen vacancy were confirmed by density functional theory (DFT) calculations. This suggests that the strength of hydroxide can reduce the energy required for oxygen vacancy formation in FeCoNi-LDH nanosheets and enhance ion and charge transfer, as well as electrolyte adsorption on the electrode surface. The FeCoNi-LDH//activated carbon (AC) HSC has an energy density of 53.2 Wh·kg−1 at a power density of 800 W·kg−1, surpassing other devices composed of comparable materials during the same timeframe. This study made significant advances in the design and synthesis of a ternary LDH porous structure with distinct oxygen vacancies, as well as its potential application in electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Binary transition metal chalcogenides and reduced graphene oxide exhibit significant potential for energy storage devices due to their superior electronic conductivity and capacity, surpassing that of single-metal sulfides, owing to their more extensive redox reactions. In this report, we introduce a novel synthesis method for producing a mixed-phase MnSe2/CoSe2 nanocomposite wrapped with reduced graphene oxide (rGO) sheets, designed specifically for supercapacitor applications. The MnSe2/CoSe2 hybrid material was synthesized using an ultrasonic assisted hydrothermal technique, followed by the preparation of the rGO/MnSe2/CoSe2 hybrid composite. The structural characterization was conducted employing x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Raman techniques. Brunauer–Emmett–Teller (BET) analysis demonstrated a significant specific surface area (66.5 m2/g) and a pore size distribution of 28.4 nm in rGO-MnSe2/CoSe2. The interconnected ultrathin rGO nanosheets and conductive carbon layer contributed to the exceptional conductivity and stability achieved by the rGO/MnSe2/CoSe2 composite electrode. The electrochemical performance was assessed using a three-electrode setup in a 3 M KOH solution, with nickel foam as the current collector. The working electrode, consisting of rGO/MnSe2/CoSe2, acetylene black and PVDF in an 80:15:5 weight ratio, demonstrated specific capacitance of 1214 F g−1 and cycling stability of 88% retention after 5000 cycles at 1 A g−1. An asymmetric supercapacitor, constructed using a tailored electrode composition, achieved energy density of 28.6 Wh kg−1 at 2100 W kg−1 and high power density of 888 W kg−1 at 49.7 Wh kg−1. [ABSTRACT FROM AUTHOR]

The rising global energy demand calls for the development of highly efficient energy storage devices, particularly supercapacitors with remarkable power density. Because of its high surface area, activated carbon (AC) is crucial as a supercapacitor electrode material. X-ray irradiation of AC leads to modifications in its surface chemistry by altering the sp2 hybridization of the surface carbons. In the current work, we present x-ray irradiation studies on the supercapacitive properties of AC prepared by adopting an oil wick lamp method using soot derived from waste soybean oil. The activated soot is irradiated at a dose rate of 16 mGy/s under a 60 kV x-ray source and investigated as an electrode active mass for an electric double-layer capacitor (EDLC). The device studies reveal that x-ray irradiation is crucial in determining the sample's physisorption and energy storage properties. The irradiated sample demonstrates high specific power density (135.9 W kg−1) and specific energy density (3.2 Wh kg−1). The energy density of the irradiated AC soot electrode sample is nearly double that of AC, i.e., 3.2 Wh kg−1 versus 1.6 Wh kg−1, respectively, making it a potential candidate for efficient electrodes in EDLC devices. The internal resistance of the supercapacitor shows a reduction from 25.5 Ω to 24.1 Ω after irradiation, thereby increasing the electrode conductivity. The investigations in the current work reveal a significant enhancement of the energy storage capacity of x-ray-irradiated AC for high-performance supercapacitor devices. Moreover, the environmentally friendly methodology adopted to synthesize AC soot can help reduce environmental pollution and contribute to the development of sustainable energy storage devices. [ABSTRACT FROM AUTHOR]

This study intended to synthesize Nickel-doped Cerium oxide (Ni-CeO2 NPs) nanoparticles using Pedalium Murex leaf extract. X-ray diffraction (XRD) was used to investigate the structure of the Ni-CeO2 NPs. The XRD measurements showed that the Ni-CeO2 NPs crystallized into the face-centered cubic system. The Ni(1%)-CeO2 and Ni(3%)-CeO2 NP’s crystallite sizes were between 47nm and 59nm. FTIR and Raman spectral studies were conducted to investigate the sample’s atomic vibrations and chemical bonding. Energy-dispersive X-ray study and field-emission scanning electron microscopy were performed to examine the surface texture and chemical assembly of the Ni-CeO2 NPs. UV–Vis DRS spectrum study was performed to ascertain the reflectance characteristics and bandgap of Ni-CeO2 NPs. The Ni(1%)-CeO2 and Ni(3%)-CeO2 NPs were found to have bandgaps of 2.73eV and 2.82eV, respectively. Electrochemical impedance spectroscopy and cyclic voltammetry were employed to explore the electrochemical nature of Ni-CeO2 NPs and their capacitive properties at various scanning rates. Using the agar well-diffusion technique, the antifungal activities of Ni-CeO2 NPs were assessed. The experimental findings illustrate the utility of Ni-CeO2 NPs for supercapacitor electrode material and healthcare applications. [ABSTRACT FROM AUTHOR]

The utilization of heterostructured electrodes offers an effective approach to boost the energy density of supercapacitors without sacrificing their power density. However, the adoption of such materials is frequently impeded by sluggish reaction kinetics. Herein, an island‐like CoNi2S4@NiCo‐layered double hydroxide/biomass carbon (CoNi2S4@NiCo‐LDH/BC) heterostructure is synthesized by embedding CoNi2S4 in the interlayer of NiCo‐LDH nanosheets on BC through a partial in situ sulfidation process. Theoretical and experimental analyses indicate that this unique structural configuration lowers transport barriers and enhances ion adsorption capacity, leading to a significant improvement in ion/electron reaction kinetics. In addition, the embedded structural design effectively alleviates the significant volume expansion during charge–discharge process, while the robust BC framework prevents electrode degradation, thereby enhancing stability. These advantages enable the developed electrode material to achieve a high specific capacity (1655.75 C g−1 at 1 A g−1) and an extended cycle life (86.82% capacity retention after 10 000 cycles). Significantly, the assembled hybrid supercapacitor CoNi2S4@NiCo‐LDH/BC// activated carbon demonstrates a remarkable energy density of 95.57 Wh kg−1 at 866.61 W kg−1 and exceptional cycling stability, maintaining 95.16% capacity after 10 000 cycles. This research offers an effective strategy to promote ion/charge transfer and adsorption capacity of heterostructure and provides a new approach to the development of advanced supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon-based biomass is considered the most promising functional carbon-based electrode material for energy conversion and storage as a result of its abundant natural resources, multi-heteroatom self-doping and easy of modification. In this study, Ganoderma lucidum spore-derived carbon material (GLSC–2) with oxygen-rich/nitrogen-doped three-dimensional, hierarchically connected porous structure was synthesized by a two-step route of pre-oxidation in air followed by KOH etching. It is worth noting that pre-oxidation in air can not only preserve the natural cage-like structure of spores, but also introduce a significant number of oxygen-containing functional groups with the help of atmospheric oxygen. The synthesized GLSC–2 possessed high O content (14.27%), moderate N content (1.99%) and relatively high specific surface area (1524.73 m2 g−1), along with high-density micropores and narrow mesopore distribution, which were crucial for promoting rapid ion diffusion and improving the electrochemical performance of supercapacitors. Encouragingly, GLSC–2 exhibited an attractive specific capacitance of 261.13 F g−1 at 1 A g−1 and excellent rate capability. Even at a high current density of 10 A g−1, the capacitance retention rate remained at 81.60%. After 10,000 cycles of charge–discharge at 2 A g−1, the capacity retention rate and Coulombic efficiency were maintained at 98.63% and 99.19%, respectively. When assembled into a symmetric supercapacitor (GLSC–2//GLSC–2), the energy density reached 9.03 Wh kg−1, with a power density approaching 500 W kg−1. This study provides a more economical and convenient route for the production of high-performance oxygen-rich/nitrogen-doped electrode materials based on renewable biomass. [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]

Organic potassium salts are the promising green activators for synthesizing porous carbon materials for energy storage. Herein, we report the synthesis of hierarchical porous carbon material derived from the mixture of soluble starch and ethylenediaminetetraacetic acid dipotassium salt dihydrate (EDTA‐2K) via carbonization and activation strategy. The sample is used as supercapacitors electrode, which exhibits superior mass specific capacitance (307.3 F g−1 at 1 A g−1), good rate performance (255.0 F g−1 at 10 A g−1), and excellent stability (retaining 83 % after 15000 cycles). This enhanced electrode performance is mainly due to the high specific surface area, the heteroatom co‐doping providing pseudo‐capacitance and the improved electronic conductivity. In addition, the asymmetric supercapacitor device shows a high energy density of 15 Wh kg−1 at the power density of 800 W kg−1 and capacitance retention of 90 % after 12000 cycles. [ABSTRACT FROM AUTHOR]

The present research work reported the study of nanocomposites of undoped and Mg‐doped ZnO with CNT as electrode materials for supercapacitor application. The undoped ZnO/CNT and Mg‐doped ZnO/CNT nanocomposites (i.e., 10 % Mg‐doped and 20 % Mg‐doped) were synthesized using a cost‐effective blending‐assisted hydrothermal method. The morphological (FESEM & TEM) studies revealed that the diameter of CNT was ~7 nm and the ZnO nanoparticles were spherical in shape with an average particle size of ~5 nm. In addition, it was also found that 10 % Mg‐ZnO and 20 % Mg‐ZnO had a sheet‐like structure. XRD and FTIR studies further confirmed the successful doping of Mg in ZnO and CNT nanocomposites. BET analysis showed that the value of specific capacitance increased with the increase in surface area. Further, the electrochemical performance of these nanocomposites revealed that the higher doping percentage, 20 % Mg‐ZnO/CNT nanocomposite achieved the highest specific capacitance value i.e., 458.5 F/g at 0.1 A/g current density in 3M H2SO4 electrolytic solution, having a retention of 99.8 % after 12,00 long cycles. In addition, the charge storage mechanism revealed that the as‐synthesized nanocomposites showed both the diffusion‐controlled and capacitive‐controlled behaviors. Thus, a higher value of specific capacitance with excellent cyclic stability indicated the higher efficiency of Mg‐doped ZnO/CNT nanocomposite for future supercapacitor applications. [ABSTRACT FROM AUTHOR]

Heterogeneous interface construction is of far-reaching significance to optimize the electrochemical performance of electrodes. Herein, a multi-step alternating electrochemical deposition (MAED) method is proposed to alternately deposit Co0.85Se and Ni3S4 nanosheets on a nickel foam (NF), forming a special alternate layer-by-layer structure with multi-layered heterogeneous interfaces. The creation of the multi-layered heterogeneous interfaces provides a large interfacial area for redox reactions with optimum interstitials facilitating ion diffusion, thus greatly improving the electrochemical energy storage efficiency. With the increase in the layer number, the material exhibits increasingly better energy storage performance, and 8L-Co0.85Se@Ni3S4/NF exhibits the highest specific capacitances of 2508 F g−1 and 1558 F g−1 at a scan rate of 2 mV s−1 and a current density of 1 A g−1. The 8L-Co0.85Se@Ni3S4/NF//polypyrrole (PPy)/NF asymmetric supercapacitor provides a maximum operation potential window of 1.55 V and energy densities of 76.98 and 35.74 W h kg−1 when the power densities are 775.0 and 15 500 W kg−1, respectively, superior to most of the related materials reported. Through MAED, the deposited phase and the layer number can be accurately controlled, thus providing an efficient strategy for interface construction so as to increase the electrochemical activity of the energy storage materials. [ABSTRACT FROM AUTHOR]

Transition metal oxide nanocomposites with heterostructures have gained a lot of attention for use in supercapacitors owing to their low cost, high surface area, fast transport of ions and electrons and high specific capacitance due to efficacious interplay between the electrode and the electrolytes. In this study, we fabricated tri-metallic Cu, Mn, Ni(CMNO), bi-metallic Mn, Ni(MNO) and mono-metallic Ni(NO) oxides through a facile hydrothermal route. All the fabricated materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX), and their electrochemical properties were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD). The CMNO material showed remarkable electrochemical performance with a specific capacitance of 790.63 F g−1 at a current density of 1 A g−1, surpassing the performance of MNO (438.4 F g−1) and NO (290.82 F g−1). Furthermore, CMNO showed high cycling stability with a retention of 96.7% specific capacitance after 8000 cycles. Based on remarkable and unique properties, the CMNO material is regarded as a promising material for new-generation pseudo-capacitor applications. [ABSTRACT FROM AUTHOR]

The advancement of microelectronic devices mandates the development of flexible energy storage systems to enable the fabrication of miniaturized and wearable electronics. Herein, a sustainable approach is demonstrated for tuning the electronic and electrochemical properties of hierarchically porous laser‐induced graphene (LIG) substrates. The methodology entails the electrochemical deposition of polyoxovanadate nanoclusters (K5(CH3CN)3[V12O32Cl] (= K5{V12}) onto the highly porous LIG matrix. The comprehensive characterization is integrated through micro‐Raman spectroscopy and in‐depth X‐ray photoelectron spectroscopy to elucidate the deposition mechanism and electronic properties of the fabricated electrode. The results indicate a significant correlation between the orientation of the deposited clusters and the non‐crystalline regions of the LIG structure. Additionally, the cluster deposition results in a reduction of grain boundary defects in the nano‐graphite lattice of LIG. The optimized electrode exhibits enhanced areal capacitance (CA) of 125 mF cm−2 at a current density of 0.1 mA cm−2, representing a fivefold improvement compared to the undoped LIG substrate. Furthermore, as a proof of concept, a flexible solid‐state symmetrical supercapacitor device, fabricated with a PVA‐H2SO4 gel electrolyte, demonstrates an areal capacitance of 24.92 mF cm−2 at current density of 0.1 mA cm−2 and exhibits exceptional cycling stability, enduring up to 5000 consecutive galvanostatic charge‐discharge cycles. [ABSTRACT FROM AUTHOR]

This study highlights for the first‐time the utilization of nickel foam coated with activated carbon (AC) via the electrophoretic deposition (EPD) method in the fabrication of A7 sized pouch cell supercapacitors. The scale‐up of electrodes via EPD from coin to pouch cells with mass loadings (10 mg cm−2) and thicknesses (>130 μm) that match industrial standards is also reported. Research investigations include: (a) comparison of a two dimensional (2D) aluminum foil current collector's performance with three dimensional (3D) microporous nickel foam current collectors, (b) impact of EPD of AC onto small (10 cm2) and large areas (50 cm2) of nickel foam, and (c) scaling‐up of coin to pouch cells along with a comparison against electrodes prepared via the standard doctor blade coating (or slurry casting) method. We demonstrate practical cell performance, including specific current loading (40 A g−1), hundred thousand of successive charge and discharge operation (150,000 cycles), power (27 kW kg−1) and energy densities (37.7 W h kg−1), capacitance (174 F g−1), capacitance retention (80 %) and coulombic efficiency (close to 100 %). [ABSTRACT FROM AUTHOR]

Wood‐derived carbons demonstrate great potential as self‐standing electrodes in energy storage/conversion applications, including supercapacitors and water‐splitting devices. However, the key challenge remains the rational customization of surface functionalities for optimized performance. This study introduces an innovative approach to self‐standing wood‐derived carbons with tailored nitrogen and metal functionalities. In contrast to traditional impregnation techniques, which offer limited precision in surface modification, this approach entails the intentional attachment of amidoxime groups to the wood substrates. These groups serve as nitrogen sources, and create abundant surface anchoring sites for metal ions due to the chelation between the amidoxime groups and metals. The resulting carbons feature uniform and high dispersion of nitrogen and metal functionalities, along with a distinctive hierarchical porosity combining interconnected open channels with abundant mesopores. As a proof‐of‐concept, different metals are incorporated (i.e., Mn, Co, Ni) into the amidoximated‐wood precursors, and the resulting self‐standing carbons showcase excellent performance in both supercapacitors and water‐splitting applications. Leveraging the specific chelating ability of amidoxime groups toward metal ions, this strategy holds great potential as a generic approach to systematically tailoring the surface functionalities of carbon‐based materials for various electrochemical energy storage/conversion processes. [ABSTRACT FROM AUTHOR]

Here, the hierarchical mesoporous-activated carbon particles obtained by KOH activation from pistachio shell wastes are modified by both the sulfonation process and CuO doping by hydrothermal heating (CuO@S-doped PSAC) for use as a supercapacitor. It is predicted that the electrochemical performance of the porous carbon electrode material obtained by such CuO doping and sulfonation process will be significantly increased with increased Faradaic capacitance. The electrochemical performance of CuO@S doped PSAC composite is systematically investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) in the presence of 1 M H2SO4, 1 M Na2SO4, and 1 M NaOH as electrolytes. The CuO@S doped PSAC-based electrode shows excellent stability with high specific capacitance up to 397.16 F/g at 0.1 A/g and 92.64% retention. Furthermore, FTIR, SEM, XRD, EDS, and nitrogen adsorption/desorption analyses are used for the characterisation of the obtained composites. Based on a significant supercapacitor performance, the synthesis strategy of carbon-based electrode material containing sulfonation and CuO modifications derived from agricultural biomass waste material is predicted to be a valuable example. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected mesoporous nanoflakes of amorphous Ni-Mo-Co trimetallic hydroxides were successfully deposited on a Ni foam (NF) using a facile, environmentally friendly, and scalable electrochemical deposition method. The elemental composition of the nanoflakes, including Ni2+, Mo6+, and Co2+, was characterized by X-ray photoelectron spectroscopy (XPS), while the morphology and particle size of the synthesized nanomaterials were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Ni-Mo-Co trimetallic hydroxides on NF were employed as binder-free electrodes for supercapacitors. The Ni-Mo-Co trimetallic hydroxides with a Ni/Mo/Co ratio of 1/1/0.4 exhibited outstanding long-term cyclability over 5000 cycles, with a high reversible specific capacitance of 2700 F g−1 and a high capacitance retention of 96.63% at 10 A g−1. Furthermore, they demonstrated excellent rate performance, maintaining a capacitance of 2429 F g−1 at a current of 50 A g−1, which corresponds to approximately 80% capacitance retention compared to the capacitance at 2 A g−1. The superior performance of these Ni-Mo-Co trimetallic hydroxides can be attributed to their mesoporous hierarchical architecture, which provides large open spaces between the interconnected nanoflakes, numerous electroactive surface sites, facile electron transmission paths, and the synergistic effects of the trimetallic components. These findings demonstrate that Ni-Mo-Co trimetallic hydroxides are promising electrode materials, offering both high capacitance and long-term cyclability for supercapacitors. [ABSTRACT FROM AUTHOR]

Efficient and sustainable energy storage remains a critical challenge in the advancement of energy technologies. This study presents the fabrication and electrochemical evaluation of a self-supporting electrode material composed of MnO2 nanorods grown directly on a carbon paper and carbon nanotube (CNT) substrate using a hydrothermal method. The resulting CNT/MnO2 electrodes exhibit a unique structural architecture with a high surface area and a three-dimensional hierarchical arrangement, contributing to a substantial electrochemical surface area. Electrochemical testing reveals remarkable performance characteristics, including a specific capacitance of up to 316.5 F/g, which is 11 times greater than that of conventional CP/MnO2 electrodes. Moreover, the CNT/MnO2 electrodes demonstrate outstanding retention capacity, exhibiting a remarkable 165% increase over 10,000 cycles. Symmetric supercapacitor devices utilizing CNT/MnO2 electrodes maintain a large voltage window of 3 V and a specific capacitance as high as 200 F/g. These results underscore the potential of free-standing CNT/MnO2 electrodes to advance the development of high-performance supercapacitors, which can be crucial for efficient and sustainable energy storage solutions in various industrial and manufacturing applications. [ABSTRACT FROM AUTHOR]

Simple and scalable production of micro-supercapacitors (MSCs) is crucial to address the energy requirements of miniature electronics. Although significant advancements have been achieved in fabricating MSCs through solution-based printing techniques, the realization of high-performance MSCs remains a challenge. In this paper, graphene-based MSCs with a high power density were prepared through screen printing of aqueous conductive inks with appropriate rheological properties. High electrical conductivity (2.04 × 104 S∙m−1) and low equivalent series resistance (46.7 Ω) benefiting from the dense conductive network consisting of the mesoporous structure formed by graphene with carbon black dispersed as linkers, as well as the narrow finger width and interspace (200 µm) originating from the excellent printability, prompted the fully printed MSCs to deliver high capacitance (9.15 mF∙cm−2), energy density (1.30 µWh∙cm−2) and ultrahigh power density (89.9 mW∙cm−2). Notably, the resulting MSCs can effectively operate at scan rates up to 200 V∙s−1, which surpasses conventional supercapacitors by two orders of magnitude. In addition, the MSCs demonstrate excellent cycling stability (91.6% capacity retention and ~100% Coulombic efficiency after 10,000 cycles) and extraordinary mechanical properties (92.2% capacity retention after 5000 bending cycles), indicating their broad application prospects in flexible wearable/portable electronic systems. [ABSTRACT FROM AUTHOR]

In the present study, composites incorporating NiO-Co3O4 (NC) and CuO-NiO-Co3O4 (CNC) as active electrode materials were produced through the hydrothermal method and their performance was investigated systematically. The composition, formation, and nanocomposite structure of the fabricated material were characterized by XRD, FTIR, and UV–Vis. The FE-SEM analysis revealed the presence of rod and spherical mixed morphologies. The prepared NC and CNC samples were utilized as supercapacitor electrodes, demonstrating specific capacitances of 262 Fg−1 at a current density of 1 Ag−1. Interestingly, the CNC composite displayed a notable long-term cyclic stability 84.9%, which was observed even after 5000 charge–discharge cycles. The exceptional electrochemical properties observed can be accredited to the harmonious effects of copper oxide addition, the hollow structure, and various metal oxides. This approach holds promise for the development of supercapacitor electrodes. These findings collectively indicate that the hydrothermally synthesized NC and CNC nanocomposites exhibit potential as high-performance electrodes for supercapacitor applications. [ABSTRACT FROM AUTHOR]

A porous electrode material consisting of NiCo2O4/RGO with an approximate diameter of 200 nm has been successfully fabricated. This promising porous material was derived from ZIF-67/RGO (zeolitic imidazolate framework-67 crystals doped with reduced graphene oxide sheets) through an ion exchange and etching process using Ni(NO3)2·6H2O followed by a thermal reaction. The composition was analyzed using spectroscopic and morphological techniques. The obtained porous and hollow structure of NiCo2O4/RGO contains rich active sites. Additionally, its improved performance and stability were demonstrated using potassium ferricyanide (K3[Fe(CN)]6) (PFC) and sodium hydroxide (NaOH) as an electrolyte. NiCo2O4/RGO in NaOH/PFC exhibited a maximum estimated specific capacitance of 212.5 F g−1 at 0.5 A g−1 and demonstrated excellent retention value reaching 91.7% after applying 10,000 cycles at 20 A g−1. This symmetric supercapacitor achieved an outstanding energy density (Ed) of 75.54 Wh kg−1 at a power density (Pd) of 1.6 kW kg−1 at 0.5 A g−1. Surprisingly, there is a 2.5-fold enhancement in Ed (from 32.44 to 75.54 Wh kg−1) of NiCo2O4/RGO through the addition of 0.3 M PFC into 3 M NaOH. The results indicate that the NiCo2O4/RGO electrode could be ideal for supercapacitors. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) are important anode materials in sodium-ion batteries (SIBs) due to their high theoretical capacities, abundant resources, and cost-effectiveness. However, issues such as the low conductivity and large volume variation of TMO bulk materials during the cycling process result in poor electrochemical performance. Nanosizing and compositing with carbon materials are two effective strategies to overcome these issues. In this study, spherical MnFe2O4@xC nanocomposites composed of MnFe2O4 inner cores and tunable carbon shell thicknesses were successfully prepared and utilized as anode materials for SIBs. It was found that the property of the carbon shell plays a crucial role in tuning the electrochemical performance of MnFe2O4@xC nanocomposites and an appropriate carbon shell thickness (content) leads to the optimal battery performance. Thus, compared to MnFe2O4@1C and MnFe2O4@8C, MnFe2O4@4C nanocomposite exhibits optimal electrochemical performance by releasing a reversible specific capacity of around 308 mAh·g−1 at 0.1 A·g−1 with 93% capacity retention after 100 cycles, 250 mAh·g−1 at 1.0 A g−1 with 73% capacity retention after 300 cycles in a half cell, and around 111 mAh·g−1 at 1.0 C when coupled with a Na3V2(PO4)3 (NVP) cathode in a full SIB cell. [ABSTRACT FROM AUTHOR]

How to address the destruction of the porous structure caused by elemental doping in biochar derived from biomass is still challenging. In this work, the in-situ nitrogen-doped porous carbons (ABPCs) were synthesized for supercapacitor electrode applications through pre-carbonization and activation processes using nitrogen-rich pigskin and broccoli. Detailed characterization of ABPCs revealed that the best simple ABPC-4 exhibited a super high specific surface area (3030.2–3147.0 m2 g−1) and plentiful nitrogen (1.35–2.38 wt%) and oxygen content (10.08–15.35 wt%), which provided more active sites and improved the conductivity and electrochemical activity of the material. Remarkably, ABPC-4 showed an outstanding specific capacitance of 473.03 F g−1 at 1 A g−1. After 10,000 cycles, its capacitance retention decreased by only 4.92% at a current density of 10 A g−1 in 6 M KOH. The assembled symmetric supercapacitor ABPC-4//ABPC-4 achieved a power density of 161.85 W kg−1 at the maximum energy density of 17.51 Wh kg−1 and maintained an energy density of 6.71 Wh kg−1 when the power density increased to 3221.13 W kg−1. This study provides a mixed doping approach to achieve multi-element doping, offering a promising way to apply supercapacitors using mixed biomass. [ABSTRACT FROM AUTHOR]

Defect engineering is an effective strategy to improve the electrochemical and electrocatalytic properties of transition metal oxide-based electrode materials. In this work, NH4+ ion intercalated MnO2 nanoflowers (C-A-MnO2) were prepared from hydrothermally synthesized manganese dioxide (MnO2) using a simple temperature-controlled method, in which oxygen vacancies on/inside the C-A-MnO2 nanoflowers were generated by the reduction of Mn4+ species by NH4+ ions. The electrical conductivity and electrochemical properties were improved by modulating the content of oxygen vacancies. In addition, the intercalation of NH4+ ions further enlarged the layer spacing of MnO2, obtaining a larger specific surface area, exposing more active sites, and shortening the electron/ion transport paths. The specific capacitance of the 1 M-A-MnO2 samples exhibited a significant enhancement (from 182.2 F g−1 to 252.2 F g−1 at a current density of 0.5 A g−1). An ASC device (1 M-A-MnO2//La-MoO3/GQD) with an operating voltage of 1.9 V was assembled. The energy density of the device was 66.66 W h kg−1 at a power density of 475 W kg−1. 1 M-A-MnO2 also exhibited excellent cycling stability with 94.3% capacitance retention after 8000 cycles. Meanwhile, it exhibited a low overpotential (361 mV at 10 mA cm−2) and Tafel slope (61 mV dec−1) as the oxygen evolution reaction (OER) electrocatalyst. Thus, this work provides valuable insights for rational intercalation of NH4+ ions for controlled synthesis of supercapacitor electrode materials and OER catalysts. [ABSTRACT FROM AUTHOR]

This manuscript presents a novel method to enhance the electrochemical performance of CaMoO4 for supercapacitors by synthesizing it from a bi-metallic metal–organic framework (MOF). The resulting CaMoO4 nanoparticles retain MOF characteristics, with a high surface area, and demonstrate improved performance over conventionally synthesized CaMoO4. Electrochemical tests showed the MOF-derived CaMoO4 achieved a high capacitance of 377.82 F g−1 at 1 A g−1 and retained 91% of its capacitance after 5000 cycles. The assembled asymmetric supercapacitor also retained 88% of its capacitance after 10 000 cycles, highlighting the potential of this approach for enhancing energy storage devices. [ABSTRACT FROM AUTHOR]

A one-step solvothermal approach was used to integrate nitrogen-doped reduced graphene oxide into vanadium dioxide (VO2) to prepare a V@XN-G (where X = 24, 48 and 96 and is the mass of urea as the nitrogen (N) source) nanocomposite material. After optimization, V@48N-G showed better performance with a specific capacitance of 197.4 F g−1 at 0.5 A g−1 in a wide working potential window of 0.0–0.8 V vs. silver/silver chloride and was adopted as a positive electrode. Thus, cocoa waste-based activated carbon (ACC) was investigated and considered a negative electrode in assembling an asymmetric full-cell V@48N-G//ACC. The device exhibited good specific energy and power of 28.8 W h kg−1 and 425.1 W kg−1, respectively, at a voltage window and specific current of 1.7 V and 0.5 A g−1, respectively. Its cycling stability resulted in a Coulombic efficiency (CE) and capacitance retention (CR) of 99.8% and 73%, respectively, over 10 000 galvanostatic charge/discharge cycles at 10 A g−1. Therefore, the V@48N-G//ACC device shows excellent electrochemical performance and is suitable for energy storage application technology. [ABSTRACT FROM AUTHOR]

[Display omitted] Regarding carbon-based electrodes, simultaneously establishing a well-defined meso -porous architecture, introducing abundant hetero-atoms and improving the graphitization degree can effectively enhance their capacitive performance. However, it remains a significant challenge to achieve a good balance between defects and graphitization degree. In this study, the porous structure and composition of carbon materials are co-optimised through a 'dual-function' strategy. Briefly, K 3 Fe(C 2 O 4) 3 and H 3 BO 3 were hybridised with a gelatin aqueous solution to form a homogeneous composite hydrogel, followed by lyophilisation and carbonisation. Owing to the dual functionality of raw materials, the graphitization, activation and hetero-atom doping processes can occur simultaneously during a one-step high-temperature treatment. The resultant carbon material exhibits a high graphitization degree (I D /I G = 0.9 ± 0.1), high hetero-atom content (N: 9.0 ± 0.3 at.%, B: 6.9 ± 0.5 at.%) and a large specific area (1754 ± 58 m2/g). The as-prepared electrode demonstrates a superior capacitance of 383 ± 1F g−1 at 1 A/g. Interestingly, the cyclic voltammetry (CV) curves exhibit a distinctive pair of broad redox peaks, which is uncommon in KOH electrolyte. Experiment data and density functional theory (DFT) simulation verify that N-5, B co-doping enhances the activity of the faradic reaction of carbon electrodes in KOH electrolyte. Furthermore, the fabricated Zn-ion hybrid supercapacitor (ZHSC) based on this carbon electrode delivers a high-energy density of 140.7 W h kg−1 at a power density of 840 W kg−1. [ABSTRACT FROM AUTHOR]

Extensive research into green technologies is driven by the worldwide push for eco‐friendly materials and energy solutions. The focus is on synergies that prioritize sustainability and environmental benefits. This study explores the potential of abundant, non‐toxic, and sustainable resources such as paper, lignin‐enriched paper, and cork for producing laser‐induced graphene (LIG) supercapacitor electrodes with improved capacitance. A single‐step methodology using a CO2 laser system is developed for fabricating these electrodes under ambient conditions, providing an environmentally friendly alternative to conventional carbon sources. The resulting green micro‐supercapacitors (MSCs) achieve impressive areal capacitance (≈7–10 mF cm−2) and power and energy densities (≈4 μW cm‐2 and ≈0.77 µWh cm−2 at 0.01 mA cm−2). Stability tests conducted over 5000 charge–discharge cycles demonstrate a capacitance retention of ≈80–85%, highlighting the device durability. These LIG‐based devices offer versatility, allowing voltage output adjustment through stacked and sandwich MSCs configurations (parallel or series), suitable for various large‐scale applications. This study demonstrates that it is possible to create high‐quality energy storage devices based on biodegradable materials. This development can lead to progress in renewable energy and off‐grid technology, as well as a reduction in electronic waste. [ABSTRACT FROM AUTHOR]