Ti3C2Tx aerogel with 1D unidirectional channels for high mass loading supercapacitor electrodes

As one of the typical MXenes materials, 2D Ti₃C₂T_x has attracted extensive attention in the field of energy storage. However, due to the restacking problem of Ti₃C₂T_x nanosheets, the electrochemical performance of Ti₃C₂T_x is unsatisfactory. In this paper, a scheme is proposed to obtain 3D aerogel with 1D channels by directional freeze drying of Ti₃C₂T_x. With the help of the unidirectional channels, the 3D Ti₃C₂T_x/Sodium alginate (SA) aerogel can effectively solve the stacking problem of Ti₃C₂T_x nanosheets, and it also accelerates the diffusion of ions. The Ti₃C₂T_x/SA-5 electrode can still reach the mass capacitance of 284.5 F g^?1 and the areal capacitance of 4030.4 mF cm^?2 at 2 mV s^?1 when the loading is 14.2 mg cm^?2 in 1 M H₂SO₄ electrolyte. In addition, the electrode showed good cycling performance without capacitor degradation after 20,000 cycles at 50 mV s^?1. These results suggest that by using the strategy of building special 3D structure of 2D MXene with 1D unidirectional channels, high performance supercapacitor electrodes with high mass loading can be realized.     

Electrochemical method integrating exfoliation and in-situ growth to synthesize MoS2 nanosheets/MnO2 heterojunction for performance-enhanced supercapacitor

Two-dimensional (2D) molybdenum disulfide (MoS₂) nanomaterials have become one of the promising options for constructing excellent supercapacitors. However, the application of MoS₂ materials is limited by low energy density, and the difficulty of large-scale and low-cost preparation seriously hinders its practical application in the field of energy storage. Here, the exfoliation of the MoS₂ nanosheets and the loading of MnO₂ nanoparticles on the MoS₂ nanosheets are realized in one step by electrochemical method. A series of characterization methods have fully confirmed that the electrochemical method has successfully prepared the MoS₂ nanosheet/MnO₂ (MoS₂ NS/MnO₂) heterojunction. The experimental results show that the MoS₂ NS/MnO₂ heterojunction has better electrochemical performance than a single MoS₂ nanosheet. It has a good capacitance even in a neutral solution, and its specific capacitance is 275 F g^?1 at a current density of 2 A g^?1. In addition, a supercapacitor device based on MoS₂ NS/MnO₂ heterojunction was constructed, which not only exhibited excellent capacitive performance, but also exhibited 10,000 charge-discharge cycle stability under 10 A g^?1 conditions. This work provides an experimental basis for the preparation of 2D nanosheets and the large-scale preparation of functionalized 2D material heterojunctions by electrochemical methods.     

Enhanced supercapacitive behavior by CuO@MnO2/carboxymethyl cellulose composites

The exploration of biocompatible materials has received greater significance in the research area of energy storage tools. In the present work, a composite material consisting of carboxymethyl cellulose (CMC) with CuO@MnO₂ is synthesized via thermal reduction protocol. The resulting composite material exhibited unique morphology and excellent electrochemical properties. The electrochemical properties were premeditated by CV, GCD, and spectral impedance analysis. Electrochemical analyses of the composite materials indicated the extraordinary specific capacitance in a three-electrode configuration. The composite displayed the value of ~414 F/g at a current density of 0.5 A g⁻¹ and the electrodes retaining 96.2% capacitance after 5000 cycles. Therefore, our study demonstrated the synergistic effect of CuO@MnO₂ nanoparticles with porous CMC network structures show enhanced electrochemical properties in the presence of 3 M KOH as an electrolyte.     

Enhanced electrochemical performance of hybrid composite microstructure of CuCo2O4 microflowers-NiO nanosheets on 3D Ni foam as positive electrode for stable hybrid supercapacitors

Self-assembled composite porous structures comprising CuCo₂O₄ microflowers and NiO hexagonal nanosheets were synthesized on a conducting 3D Ni foam surface [CCO/NO] using a simple hydrothermal method. This unique composite assembly was further characterized and electrochemically evaluated as a binder-free positive electrode for hybrid supercapacitor application. The study showed that the CCO/NO exhibited a maximum areal capacitance of 1444 mF cm^?2, significantly higher than the parent CuCo₂O₄ and NiO electrodes, with remarkable stability of 88.5% for 10,000 galvanostatic charge-discharge cycles. Key features for the enhanced electrochemical performance of CCO/NO can be related to a lowered diffusion resistance because the hybrid nanocomposite porous assembly generates short diffusion paths for electrolyte ions and more active sites for reversible faradaic transition for charge storage. The hybrid supercapacitor was assembled using activated carbon as a negative electrode and CCO/NO as a positive electrode in alkaline electrolyte, performed at an improved potential of 1.6 V. Device showed a maximum areal capacitance of 122 mF cm^?2, a maximum areal energy density of 43 μWh cm^?2, and a maximum areal power density of 5.1 mW cm^?2. This hybrid supercapacitor showed remarkable cyclic stability up to 98% for 10,000 cycles. This study encourages the development of low-cost, high-performance, durable electrode designs using hybrid composite for next-generation energy storage systems.     

Insight into high areal capacitances of low apparent surface area carbons derived from nitrogen-rich polymers

The energy storage mechanism of N-doped carbons with low apparent specific surface areas (Brunauer–Emmett–Teller specific surface area determined by N₂ adsorption) has puzzled the researchers in the supercapacitor field in recent years. In order to explore this scientific problem, such carbon materials were prepared through pyrolysis of N-rich polymers such as melamine formaldehyde resin and polyaniline. Although these carbons possess low apparent specific surface areas of no more than 60 m² g⁻¹, their areal capacitance could reach up to an abnormally high value of 252 μF cm⁻². The results of systematical materials characterizations and electrochemical measurements show that these carbons contain numerous ultramicropores which could not be detected by the adsorbate of N₂ but are accessible to CO₂ and electrolyte ions. These ultramicropores play dominant roles in the charge storage process for these low apparent surface area carbons, leading to an energy storage mechanism of electric double layer capacitance. The contribution of pseudocapacitance to the total capacitance is calculated to be less than 15%. This finding challenges the widely accepted viewpoint that the high capacitance of N-doped carbon is mainly attributed to the pseudocapacitance generated from the faradic reactions between nitrogen functionalities and electrolyte.     

Nanoengineering of ZnCo2O4@CoMoO4 heterogeneous structures for supercapacitor and water splitting applications

A hybrid ZnCo₂O₄@CoMoO₄ heterogeneous structure deposited onto nickel foam was synthesized via a two-step hydrothermal process. The results demonstrate that the hybrid architecture exhibits excellent electrochemical performance, including the specific capacitance of 1040C g^?1 at 1 A g^?1 for hybrid structures, high energy density of 87.3 Wh kg^?1 at a power density of 2700 W kg^?1 for an as-assembled supercapacitor and excellent cycle stability with a capacity retention of 99% undergoing 8000 charge-discharge for the device. Moreover, it also shows favorable electrocatalytic activity with low overpotentials of 237 mV at 20 mA cm^?2 for oxygen evolution reaction and 114 mV at 10 mA cm^?2 for hydrogen evolution reaction, and low cell voltage of 1.54 V at 10 mA cm^?2 for overall water splitting. In addition, the stability maintains well for the long-term use of 13 h. We believe that this hybrid ZnCo₂O₄@CoMoO₄ heterogeneous structure could be a promising candidate for future energy storage and conversion.     

A Facile Preparation of Zinc Cobaltite (ZnCo2O4) Nanostructures for Promising Supercapacitor Applications

Hybrid nanocomposites have shown their excellent potential in energy storage devices particularly in electrochemical supercapacitors to meet the forthcoming demand in the energy sector applications. Novel hybrid composited displayed the dual nature of electrochemical double layer and pseudocapacitive behaviour, which makes them more advantageous in supercapacitor device fabrication. Zinc cobaltite (ZnCo₂O₄) nanostructures have been prepared by precipitation route and the structural, optical and electrochemical properties of the final product were analyzed. X-ray pattern showed the spinal cubic phase structure with fine nano-crystallites. The FTIR and Raman spectrum confirmed the presence of surface functional groups and confirmed the formation of high-quality ZnCo₂O₄ nanocrystals. XPS and EDX spectrum showed the high purity and good crystallinity nature of the as-prepared ZnCo₂O₄ nanocrystal. FE-SEM and TEM analysis exhibits the bundle like morphology of the final product. Finally, the as-prepared ZnCo₂O₄ nanostructure was investigated by cyclic voltammetry (CV), galvanic charge–discharge analysis (GCD) and electrochemical impedance spectroscopy (EIS) to check its suitability. The electrochemical investigation demonstrated the highest capacitance of 159 F g^?1 at 2 mA cm^?2 in 2 M KOH electrolyte and the long cyclic test showed the 92% initial capacitance retention over 2500 cycles. It reveals/demonstrated that the spinel ZnCo₂O₄ nanostructures own a promising usage in devices for electrochemical energy storage.

     

Enhanced electrochemical performance of graphene aerogels by using combined reducing agents based on mild chemical reduction method

In recent years, 3D assemblies of graphene are developed as promising materials in various applications, such as energy storage devices. In this paper, we have reported a method for the synthesis of Graphene Aerogel (GA) utilizing a novel reducing system to achieve high electrochemical properties. GAs were obtained via chemical reduction of Graphene Oxide (GO) using a combination of l-Ascorbic Acid (L-AA) and sodium bisulfite (NaHSO₃) as the combined reduction media (GASL). However, L-AA exhibited a high level of reduction resulting in a micro/mesoporous structure, but it is incapable of de-epoxidation with high efficiency. Besides, NaHSO₃ enhanced the de-epoxidation step, decreased the shrinkage of the structure, and also increased the size of the pores. The synergistic effect of the combined reducing system led to the proper level of reduction with meso/macroporous structure and lowered shrinkage, which improved the electrochemical performance. The N₂ adsorption analysis with BET formula estimated the specific surface area and the pore volume of 135 m²g^-1 and 2.9 cm³g^-1, respectively. Moreover, FT-IR spectroscopy admitted a high level of reduction for GASL in comparison with single reducing agent samples. The GASL exhibited a high specific capacitance (165 Fg⁻¹ at 1 Ag⁻¹), excellent cycling stability (91% capacitance retention after 1000 cycles) and an adequate capacitive performance (91% capacitance retention by the increase in current density from 1 to 5 Ag⁻¹) with low internal resistance (about 0.005 V). The desired results are due to the high level of reduction and the meso/macroporous structure.     

Freestanding Co3N thin film for high performance supercapacitors

Suitable electrode materials play a decisive role in the performance of supercapacitors. In recent years, transition metal nitrides come into view because of their advantages of superior electrical conductivity exceeding the corresponding metal oxides and higher specific capacitance compared with carbon-based materials. Herein, we have successfully synthesized the binder-free Co₃N thin films for high-efficiency supercapacitor by reactive magnetron sputtering. Remarkedly, the Co₃N thin film electrodes can reach a high specific capacity of 47.5 mC cm^?2 at a current density of 1.0 mA cm^?2 along with reasonable cycling stability (78.1% remaining after 10,000 cycles). These findings have proved that the Co₃N thin films have great potential applications for supercapacitors or other electrochemical energy storage devices.     

In situ synthesis of integrated dodecahedron NiO/NiCo2O4 coupled with N-doped porous hollow carbon capsule for high-performance supercapacitors

NiO and NiCo₂O₄ exhibit excellent synergistic effects and broad application prospects in electrochemical applications. However, the apparent interfacial instability between NiO and NiCo₂O₄ limits ion transport kinetics, charge/ion transfer, and electrochemical stability. In response, we developed and designed an integrated dodecahedron NiO/NiCo₂O₄ by a facile in-situ calcination method. Moreover, by utilizing the porous hollow structure of nitrogen-doped carbon capsules (N-Cc) as a conductive network, the N-Cc_x@NiO/NiCo₂O₄ heterostructures with stable interface structure, excellent electrolyte adsorption, and electron transfer pathways were carefully designed. The N-Cc_1.0@NiO/NiCo₂O₄ heterostructures are found to deliver an outstanding specific capacitance of 658.8 F g⁻¹, and a high energy density of 101.40 Wh kg⁻¹ at a power density of 775.03 W kg⁻¹, along with capacitance retention of more than 93.5% after 8000 cycles. Based on the DFT calculations and electrochemical experimental results, this work provides an effective in situ route for the construction of high-performance metal oxide heterostructure electrode materials for new energy storage devices.     

Preparation of CuMn2O4/Ti3C2 MXene composite electrodes for supercapacitors with high energy density and study on their charge transfer kinetics

In this study, we present a novel electrode material that combines Ti₃C₂ MXene and high-capacity CuMn₂O₄ to increase the energy density of supercapacitors, which are a popular choice for energy storage due to their high-performance potential. The electrode material was synthesized using the hydrothermal method with varying deposition times (3 h, 6 h and 9 h), and the resulting composite materials were characterized using advanced analytical techniques. The CuMn₂O₄/MXene composite electrode synthesized at 3h exhibited exceptional performance, with a specific capacitance of 628 mF/cm² at 4 mA/cm², due to the enhanced electrical conductivity and charge storage properties of CuMn₂O₄ and MXene sheets. We also uncovered an intricate charge transfer mechanism and storage kinetics of CuMn₂O₄/MXene composite on a nickel foam electrode, revealing a diffusion-controlled energy storage mechanism with fast mass transportation. To demonstrate practicality, we constructed an asymmetric coin cell supercapacitor device using CuMn₂O₄/MXene composite synthesized at 3h and activated carbon as the positive and negative electrodes, respectively. The device showed a specific capacitance of 496 mF/cm² at 6 mA/cm² with cyclic stability of 80% for up to 10,000 cycles, and a power density of 1.5 mW/cm² at a higher energy density of 0.073 mWh/cm². Our results demonstrate the potential to significantly advance the development of high-performance supercapacitors by combining Ti₃C₂ MXene and high-capacity oxides, refining the synthesis process, and exploring innovative electrode architectures.     

Enhancing the electrochemical performance of d-Mo2CTx MXene in lithium-ion batteries and supercapacitors by sulfur decoration

With the development of the energy industry, electrochemical energy storage technology is increasingly involved in developing innovations in the field. The materials of the electrode have a significant influence on the performance of energy storage devices. For this purpose, two-dimensional MXene with excellent electrical conductivity, mechanical strength, and a variety of possible surface-active terminations are attracting much attention. In the present work, S-decorated d-Mo₂CT_x (d-Mo₂CT_x--S) is designed. The first-principles calculations reveal that it may possess good energy storage characteristics. Due to the decoration with S, unique morphology and structure are obtained, conferring stability, optimized Li⁺ storage, improved charge transport, and lithium-ion adsorption capabilities. Compared with d-Mo₂CT_x, d-Mo₂CT_x--S exhibits higher discharge capacity (623 mAh g⁻¹ at 1 A g⁻¹) as lithium-ion electrode material and higher specific capacitance (561 F g⁻¹ at 1 A g⁻¹). As a supercapacitor, the material also shows excellent cyclic stability (20,000 charge-discharge cycles). This work may inspire the exploration of other MXene and new surface functionalization methods to improve the performance of MXene as electrode materials for new energy devices.     

Enhanced energy storage performance in bismuth layer-structured BaBi2Me2O9 (Me = Nb and Ta) relaxor ferroelectric ceramics

Bismuth layer-structured BaBi₂Nb₂O₉ (BBN) and BaBi₂Ta₂O₉ (BBT) relaxor ferroelectric ceramics were explored as potential energy storage materials. Remarkable energy storage performances were obtained in both BBN and BBT ceramics, featured by large recoverable energy storage density (~0.84 J/cm³ and ~0.68 J/cm³) and high energy storage efficiency (~90% and ~94%), respectively. Furthermore, both the two ceramics exhibit good thermal and frequency stabilities. Delightedly, both the BBN and BBT ceramics can complete the discharge process within 0.15 μs, resulting in ultrahigh current density of 195 A/cm² and 234 A/cm² and excellent power density of 10.74 MW/cm³ and 12.89 MW/cm³, respectively. The obtained results suggest that BaBi₂Nb₂O₉ and BaBi₂Ta₂O₉ ceramics could have a promising future in energy storage applications. This study also demonstrates that the bismuth layer-structured relaxor ferroelectric ceramic can be considered as a novel potential lead-free energy storage materials, in addition to the widely studied pervoskite-structured relaxor ferroelectric ceramics.     

In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu₂O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu₂O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu₂O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu₂O-CTAB exhibits better lithium storage performance (2.9 mAh cm^?2 at 0.5 mA cm^?2) than bare CuO/Cu₂O (1.8 mAh cm^?2 at 0.5 mA cm^?2).     

Ni@NiCo2O4 core/shells composite as electrode material for supercapacitor

A novel Ni@NiCo₂O₄ core/shells structure consisting of the Ni microspheres skeletons and nanosheet-like NiCo₂O₄ skins was designed and investigated as the electrochemical electrode for supercapacitor. Due to the unique architecture with Ni microspheres as the highly conductive cores improving the electrical conductivity of electrode and external nanosheet-like NiCo₂O₄ shells as the efficient electrochemical active materials facilitating the contact between the electrode and electrolyte, the as-prepared Ni@NiCo₂O₄ exhibited excellent electrochemical performance with high specific capacity of 597 F g⁻¹ (1 A g⁻¹) as well as remarkable capacitance retention of 96% (3000 cycles). These impressive results pave the way to design high-performance electrode materials for energy storage.     

Improvement of electrochemical performance of titania nanowires for supercapacitor electrodes by in-situ growth of polyaniline nanoparticles

Supercapacitors with excellent electrochemical performance are considered the most promising candidates to meet the increasing energy demand. Herein, we developed a novel electrode material for supercapacitors, polyaniline (PANI)-3-aminopropyl triethoxysilane (APTEs)-titania nanowires (TNW), which was synthesized on potassium doped titanium foil via a simple two-step procedure. In the composite, the nano-mesh structure formed by APTEs-coated TNW serves as the framework for the growth of PANI nanoparticles, and PANI nanoparticles act as the electrochemically active part. The specific capacitance of PANI-APTEs-TNW of up to 315.16 mF cm^?2 at 0.2 mA cm^?2 in 1.0 M H₂SO₄ solution is achieved, while that of PANI-TNW is 271.67 mF cm^?2. Meanwhile, the capacitance retention rate of PANI-APTEs-TNW is 86.8% after 1000 cycles under 1.5 mA cm^?2. Compared to PANI-TNW, the better capacitive behavior of PANI-APTEs-TNW is attributed to the anchoring effect of APTEs, which is highly interactive and exhibits compact structures between the TNW and PANI nanoparticles, resulting in a stable structure during the rapid charge-discharge process. This strategy is characterized by its good electrochemical properties, simple equipment, low cost of raw materials, and large-area preparation. Thus, our findings provide an effective method for the design of high-performance supercapacitors and promote their practical applications.     

Hierarchical Co3O4@ZnWO4 core/shell nanostructures on nickel foam: Synthesis and electrochemical performance for supercapacitors

To improve the electrochemical properties of Co₃O₄ for supercapacitors application, a hierarchical Co₃O₄@ZnWO₄ core/shell nanowire arrays (NWAs) material is designed and synthesized successfully via a facile two-step hydrothermal method followed by the heat treatment. Co₃O₄@ZnWO₄ NWAs exhibits excellent electrochemical performances with areal capacitance of 4.1 F cm⁻² (1020.1 F g⁻¹) at a current density of 2 mA cm⁻² and extremely good cycling stability (99.7% of the initial capacitance remained even after 3000 cycles). Compared with pure Co₃O₄ electrodes, the results prove that this unique hierarchical hybrid nanostructure and reasonable assembling of two electrochemical pseudocapacitor materials are more advantageous to enhance the electrochemical performance. Considering these remarkable capacitive behaviors, the hierarchical Co₃O₄@ZnWO₄ core/shell NWAs nanostructure electrode can be revealed promising for high-performance supercapacitors.     

Low-cost and high-performance electrode materials based on BiCoO3 microspheres

Ternary metal oxides have great potential for chemical storage devices because of their outstanding synergistic effects as well as rich redox reactions. However, there are limited reports of 3D structure BiCoO₃ materials and relevant electrochemical properties. Meanwhile, the study of BiCoO₃ is reasonably important for underlying metal oxides researches. In this work, we have successfully developed a 3D urchin-like BiCoO₃ material without using any template and surfactant. For the supercapacitor application, the BiCoO₃ material showed a specific capacitance of 152 F g⁻¹ at the current density of 1 A g ⁻¹, and this value exhibited a rate capability of 82.3% at a high current density of 10 A g ⁻¹. Furthermore, the sample showed the ideal cycling stability (92.7% retention after 5000 times cycles at the current density of 1 A g ⁻¹ and nearly invariable specific capacitance during different current density cycles). These results suggest that the obtained urchin-like BiCoO₃ sample has superb electrochemical performances which suggest its promising applications as renewable and clean energy storage devices electrode materials in the future.     

Hierarchical materials constructed by 1D hollow nickel–cobalt sulfide nanotubes supported on 2D ultrathin MXenes nanosheets for high-performance supercapacitor

To design and prepare novel composites with strong electrode structure and superior electrochemical performances via a facile and convenient synthesis method is a significant challenge to develop the high-performance materials for energy storage and conversion devices. Herein, we fabricated a novel hybridization of two dimensional (2D) Ti₃C₂-MXenes nanosheets and one dimensional (1D) nickel-cobalt sulfide (NiCo₂S₄) hollow nanotubes though the favorable electrostatic interaction between the negatively charged Ti₃C₂ and positively charged NiCo₂S₄ nanotubes. The electrode combined the good metallic conductivity of Ti₃C₂-MXenes and high pseudo-capacitance of NiCo₂S₄ demonstrated the outstanding electrochemical performance for supercapacitors. Herein, 2D Ti₃C₂-MXenes/1D NiCo₂S₄ hybrid electrode achieved an excellent specific capacitance of 1927 F g^-1 at 2 mV s^-1, long cycling stability for 4000 cycles and charming rate performances, which is mainly ascribed to the synergistic effect and interfacial interaction between two components. Particularly, the novel hybrid material with 1D and 2D hierarchical structures can provide additional electrochemical reaction sites, supply shorter paths for ions diffusion and electron transport, and effectively raise the charge transfer kinetics during the electrochemical process, which explores a new strategy aimed to develop 2D Ti₃C₂-MXenes energy storage devices with high electrochemical performance, and is possible potential for expansion into other application fields.     

Hydrothermal synthesis of Polypyrrole/MoS2 intercalation composites for supercapacitor electrodes

As a pseudocapacitive electrode materials for supercapacitor, Polypyrrole (PPy) exhibit excellent theoretical specific capacitance. However, it suffers from a poor cycling stability due to structural instability during charge-discharge process. In this work, a novel and facile hydrothermal method has been developed for the intercalation composites of PPy/MoS₂ with multilayer three-dimensional structure. The report result shows that the as-prepared electrode possess a outstanding electrochemical properties with significantly specific capacitance of 895.6 F g⁻¹ at current density of 1 A g⁻¹, higher energy density (3.774 Wh kg⁻¹) at power density of 252.8 kW kg⁻¹, furthermore, it also achieve remarkable cycling stability (~98% capacitance retention after 10,000 cycles) which is attributed to the synergistic effect of PPy and MoS₂. This synthetic strategy integrates performance enables the multilayer PPy/MoS₂ composites to be a promising electrode for energy storage applications.