The hybrid nanostructure of MnCo2O4.5 nanoneedle/carbon aerogel for symmetric supercapacitors with high energy density

Advances in Mn-Based MOFs and Their Derivatives for High-Performance Supercapacitor

As the most widely used metal material in supercapacitors, manganese (Mn)-based materials possess the merits of high theoretical capacitance, stable structure as well as environmental friendliness. However, due to poor conductivity and easy accumulation, the practical capacitance of Mn-based materials is far lower than that of theoretical value. Therefore, accurate structural adjustment and controllable strategies are urgently needed to optimize the electrochemical properties of Mn-based materials. Metal-organic frameworks (MOFs) are porous materials with high specific surface area (SSA), tunable pore size, and controllable structure. These features make them attractive as precursors or scaffold for the synthesis of metal-based materials and composites, which are important for electrochemical energy storage applications. Therefore, a timely and comprehensive review on the classification, design, preparation and application of Mn-based MOFs and their derivatives for supercapacitors has been given in this paper. The recent advancement of Mn-based MOFs and their derivatives applied in supercapacitor electrodes are particularly highlighted. Finally, the challenges faced by Mn-MOFs and their derivatives for supercapacitors are summarized, and strategies to further improve their performance are proposed. The aspiration is that this review will serve as a beneficial compass, guiding the logical creation of Mn-based MOFs and their derivatives in the future.

High electrochemical performance of nickel cobaltite@biomass carbon composite (NiCoO@BC) derived from the bark of Anacardium occidentale for supercapacitor application

Biomass carbon-based materials are highly promising for supercapacitor (SC) electrodes due to their availability, environment-friendliness, and low cost. Herein, an easy energy-saving hydrothermal process was used to produce NiCo2O4/NiOOH (NiCoO) composites with biomass carbon (BC) derived from the bark of Anacardium occidentale (AO) at different synthesis time durations (2 h, 4 h, 8 h, 16 h). The structural and morphological properties of the samples were analysed using XRD, Raman spectroscopy, XPS, SEM, TEM and BET, and the results exhibit the presence of carbon inserted into the nickel-cobalt hydroxide matrix. The NiCoO@BC composite synthesized in 4 h (NiCoO@BC(4 h)) displays a good specific capacitance of 475 F g-1 at 0.5 A g-1 and a low equivalent series resistance (ESR) value of 0.36 Ω. It shows a good coulombic efficiency of 98% and retains 86% of the capacitance after 4000 cycles. The asymmetric supercapacitor (ASC) device (NiCoO@BC(4 h)//AC) assembled using activated carbon (AC) as a negative electrode displays 20 W h kg-1 energy density and 900 W kg-1 power density at 1 A g-1. The stability test shows a good coulombic efficiency of 99% and 78% capacitance retention after 15 000 cycles. These findings imply that NiCoO@BC composites have outstanding electrochemical properties, making them suitable as SC electrode materials.

Boosting the Electrochemical Storage Properties of Co3O4 Nanowires by the Mn Doping Strategy with Appropriate Mn Doping Concentrations

High specific capacitance, high energy density, and high power density have always been important directions for the improvement of electrode materials for supercapacitors. In this paper, Co3O4 nanowire arrays with various Mn doping concentrations (Mn:Co molar ratio = 1:11, 1:5, 1:2) directly grown on nickel foam (NF) were prepared by a simple hydrothermal method and annealing process. The influence of Mn doping on the morphology, structure, and electrochemical behaviors of Co3O4 was investigated. The results show that partial substitution of Co ions with Mn ions in the spinel structure does not change the nanowire morphology of pure Co3O4 but increases the lattice parameter and decreases the crystallinity of cobalt oxide. Electrochemical measurements showed that Mn doping in Co3O4 could effectively enhance the redox activity, especially Co3O4 with a Mn doping ratio of 1:5, which exhibits the most excellent electrochemical performance, with the maximum specific capacitance of 1210.8 F·g-1 at 1 A·g-1 and a rate capability of 33.0% at 30 A·g-1. The asymmetric supercapacitor (ASC) device assembled with the optimal Mn-Co3O4 (1:5) and activated carbon (AC) electrode performs a high specific capacitance of 105.8 F·g-1, a high energy density of 33 Wh·kg-1 at a power density of 748.1 W·kg-1, and a capacitance retention of 60.2% after 5000 cycles. This work indicates that an appropriate Mn doping concentration in the Co3O4 lattice structure will have great potential in rationalizing the design of spinel oxides for efficient electrochemical performance.

The synthesis of CoS/MnCo2O4-MnO2 nanocomposites for supercapacitors and energy-saving H2 production

In this study, CoS/MnCo₂O₄-MnO₂ (CMM) nanocomposites were synthesized by hydrothermal and then electrochemical deposition. Their electrochemical properties were systematically investigated for supercapacitors and energy-saving H₂ production. As an electrode material for supercapacitor, CMM demonstrates a specific capacitance of 2320F g^-1 at 1 A/g, and maintains a specific capacitance of 1216F g^-1 at 10 A/g. It also shows 72.8 % capacitance retention after 8000 cycles. The aqueous asymmetric supercapacitor exhibited high energy storage capacity (887.86F g^-1 specific capacitance at a current density of 1 A/g), good rate performance and cycling stability. Besides, CMM shows outstanding urea oxidation reaction(UOR) and glycol oxidation reaction (MOR) performances for H₂ production. Compared to oxygen evolution reaction (OER) (1.635 V) at 20 mA cm^-2, the potentials were reduced by 213 mV for UOR and 233 mV for MOR, respectively. Therefore, this study shows the promising practical applications of CMM nanocomposites for energy storage and energy-saving H₂ production.

Nanosheet-assembled porous MnCo2O4.5 microflowers as electrode material for hybrid supercapacitors and lithium-ion batteries

Herein, the MnCo₂O_4.5 microflowers (MFs) assembled by two-dimensional (2D) porous nanosheets were prepared through an initial solvothermal reaction with a subsequent annealing process. In this architecture, many interconnected 2D thin nanosheets were self-assembled together to form a 3D hierarchical MF with plenty of open channels. Such structure endows these MnCo₂O_4.5 MFs with large specific surface area of 156.85 m²/g for energy storage and provides rich ion diffusion pathways for ion transportation, thus the as-prepared MFs can exhibit good overall electrochemical performance in both hybrid supercapacitor (HSC) and lithium-ion battery (LIB). For the utilization in supercapacitor, the MFs deliver a specific capacity of 287.02 C/g at 1 A/g as well as a rate capability with 73.3 % capacity retention at 8 A/g. The energy density of the HSC assembled by MFs and activated carbon can reach up to 30.33 W h kg^-1 at 959.35 W kg^-1. When applied as the anode for Li-ion battery, a specific capacity of 1340.8 mA h g^-1 at 0.1 A/g and cycling performance with low capacity loss of 0.73 mAh/g per cycle after 200 cycles at 0.5 A/g can be achieved. This work uncovers a repeatable and facile synthetic strategy to prepare transition metal oxides with large specific surface area and good overall electrochemical property.

Green preparation of porous hierarchical TiO2(B)/anatase phase junction for effective photocatalytic degradation of antibiotics

In this study, porous hierarchical bronze/anatase phase junction TiO₂ assembled by ultrathin two-dimensional nanosheets was prepared by a novel, green and simple deep eutectic solvent-regulated strategy. Due to its structural features, the TiO₂ sample exhibited enhanced photocatalytic activities for multiple kinds of antibiotics, including ofloxacin, ciprofloxacin and chloramphenicol.

Hierarchical coral-like MnCo2O4.5@Co-Ni LDH composites on Ni foam as promising electrodes for high-performance supercapacitor

Transition metal oxides are generally designed as hybrid nanostructures with high performance for supercapacitors by enjoying the advantages of various electroactive materials. In this paper, a convenient and efficient route had been proposed to prepare hierarchical coral-like MnCo₂O_4.5@Co-Ni LDH composites on Ni foam, in which MnCo₂O_4.5nanowires were enlaced with ultrathin Co-Ni layered double hydroxides nanosheets to achieve high capacity electrodes for supercapacitors. Due to the synergistic effect of shell Co-Ni LDH and core MnCo₂O_4.5, the outstanding electrochemical performance in three-electrode configuration was triggered (high area capacitance of 5.08 F cm^-2at 3 mA cm^-2and excellent rate capability of maintaining 61.69% at 20 mA cm^-2), which is superior to those of MnCo₂O_4.5, Co-Ni LDH and other metal oxides based composites reported. Meanwhile, the as-prepared hierarchical MnCo₂O_4.5@Co-Ni LDH electrode delivered improved electrical conductivity than that of pristine MnCo₂O_4.5. Furthermore, the as-constructed asymmetric supercapacitor using MnCo₂O_4.5@Co-Ni LDH as positive and activated carbon as negative electrode presented a rather high energy density of 220μWh cm^-2at 2400μW cm^-2and extraordinary cycling durability with the 100.0% capacitance retention over 8000 cycles at 20 mA cm^-2, demonstrating the best electrochemical performance compared to other asymmetric supercapacitors using metal oxides based composites as positive electrode material. It can be expected that the obtained MnCo₂O_4.5@Co-Ni LDH could be used as the high performance and cost-effective electrode in supercapacitors.

Uniform MnCo2O4.5 porous nanowires and quasi-cubes for hybrid supercapacitors with excellent electrochemical performances

In this work, uniform MnCo₂O_4.5 nanowires (NWs) on stainless steel foil (SSF) were prepared through a facile, cost-efficient, and eco-friendly hydrothermal method at 120 °C with a post-calcination process in air. The microstructure of MnCo₂O_4.5 samples could be tuned at different hydrothermal temperatures and quasi-cubes (QCs) were obtained in high yield at 150 °C. The MnCo₂O_4.5 NW powder peeled off from the SSF delivered an outstanding capacity of 248.62 C g^-1 at 1 A g^-1 with a capacity preservation of 179.43 C g^-1 at 8 A g^-1, while the QCs exhibited 177.19 and 111.73 C g^-1, respectively. To assess the possibility of its actual applications, a hybrid supercapacitor (HSC) device has been assembled by utilizing these MnCo₂O_4.5 NWs (QCs) and activated carbon (AC) as the cathode and anode, respectively. The MnCo₂O_4.5 NWs//AC HSC delivered a maximum capacity up to 116.95 C g^-1 and extraordinary cycling durability with only 3.56% capacity loss over 5000 cycles. Besides, the MnCo₂O_4.5 NWs//AC HSC achieved a maximum energy density of 25.41 W h kg^-1 at a power density of 782.08 W kg^-1, and for the QC-based HSC, it showed a lower energy density of 20.54 W h kg^-1 at 843.34 W kg^-1. These remarkable electrochemical properties demonstrate that the porous MnCo₂O_4.5 NWs and QCs may serve as promising cathodes for advanced hybrid supercapacitors with superior performance, and the present synthetic methodology may be applied to the preparation of other cobalt-based binary metal oxides with excellent electrochemical properties.

Transition metal dichalcogenide (TMDs) electrodes for supercapacitors: a comprehensive review

As globally, the main focus of the researchers is to develop novel electrode materials that exhibit high energy and power density for efficient performance energy storage devices. This review covers the up-to-date progress achieved in transition metal dichalcogenides (TMDs) (e.g. MoS₂, WS₂, MoSe_2,and WSe₂) as electrode material for supercapacitors (SCs). The TMDs have remarkable properties like large surface area, high electrical conductivity with variable oxidation states. These properties enable the TMDs as the most promising candidates to store electrical energy via hybrid charge storage mechanisms. Consequently, this review article provides a detailed study of TMDs structure, properties, and evolution. The characteristics technique and electrochemical performances of all the efficient TMDs are highlighted meticulously. In brief, the present review article shines a light on the structural and electrochemical properties of TMD electrodes. Furthermore, the latest fabricated TMDs based symmetric/asymmetric SCs have also been reported.

Biomass-Derived Porous Carbons Derived from Soybean Residues for High Performance Solid State Supercapacitors

A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m2 g-1 and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g-1 at 1 A g-1 in 6 M LiNO3 aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g-1 at 1 A g-1 and a high energy density of 68.2 Wh kg-1 at a power density of 1 kW kg-1 with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g-1 (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.

Development of vertically aligned trimetallic Mg-Ni-Co oxide grass-like nanostructure for high-performance energy storage applications

Direct growth of nanostructured trimetallic oxide on substrate is considered as one of the promising electrode fabrication for high-performance hybrid supercapacitors. Herein, binder-free one-dimensional grass-like nanostructure was constructed on nickel foam by using electrodeposition approach. The admirable enhancement in rate capability was observed by the substitution of Mg and Ni in cobalt oxide crystallite. The prepared nickel cobalt oxide (NCO) and cobalt oxide (CO) electrode exhibited a rate capability of 57% and 58% (2 to 10 A g^-1) respectively. Interestingly, the rate capability was increased to 87% by the substitution of Mg and Ni simultaneously. The novel vertically aligned trimetallic Mg-Ni-Co oxide (MNCO) grass-like nanostructure electrode exhibited a high specific capacity of 846 C g^-1 at 2 A g^-1_, retained 97.3% specific capacity and showed an outstanding coulombic efficiency of 99% after 10,000 charge-discharge cycles. Moreover, we assembled hybrid supercapacitor (HSC) device for practical applications by using MNCO and activated carbon (AC) as the positive and negative electrode materials, respectively. HSC device exhibited a high specific capacity of 144 C g^-1 at 0.5 A g^-1. The high energy density of 31.5 Wh kg^-1 and the power density of 7.99 kW kg^-1 were achieved. All these interesting and attractive results demonstrate the significance of the vertically aligned electrode material towards practical applications.

Cobalt-tungsten diselenide-supported nickel foam as a battery-type positive electrode for an asymmetric supercapacitor device: comparison with various MWSe2 (M = Ni, Cu, Zn, and Mn) on the structural and capacitance characteristics

New exploration in nanomaterial research has been greatly encouraged so as to discover active electrode materials with extraordinary properties and performances. In this report, we demonstrated the synthesis of different transition metal-incorporated MWSe2 (M = Co, Ni, Cu, Zn, and Mn) and studied them using various characterization techniques. Subsequently, the proposed bimetallic chalcogenides were successfully applied as the active electrode materials for pseudocapacitor applications. The results of the electrochemical studies showed that CoWSe2 exhibited a higher specific capacitance of 3309.58 F g-1 at a constant applied current density of 1.35 A g-1, which is 1.07, 1.76, 2.04, 8.7, and 12.28-fold higher than that of NiWSe2, CuWSe2, ZnWSe2, MnWSe2, and pristine WSe2, respectively. The interconnected nanosheet structure with voids facilitates rich active sites for efficient electrolyte uptake and superior charge transfer during the faradaic redox reaction. In addition, the cycle stability of CoWSe2/NF was studied and the retention capacitance of about 82.1% was recorded, which is higher than that of NiWSe2 (60.4%), CuWSe2 (50.12%), ZnWSe2 (46.44%), MnWSe2 (40.12%), and pristine WSe2 (31.2%). Owing to the higher specific capacitance and cycle stability, CoWSe2 was proposed as a battery-type electrode material for the fabrication of an asymmetric device. The fabricated CoWSe2//AC device provided excellent energy density and power density of 182.54 W h kg-1 and 2810.81 W kg-1, respectively, at 3.51 A g-1. Based on these properties, the proposed research and studies can provide a way for the profound development of 2D-layered metal chalcogenides for energy storage applications.

Hierarchical Porous Carbon with Interconnected Ordered Pores from Biowaste for High-Performance Supercapacitor Electrodes

Using biowastes as precursors for the preparation of value-added nanomaterials is critical to the sustainable development of devices. Lignosulphonates are the by-products of pulp and paper-making industries and usually discarded as wastes. In the present study, lignosulphonate is used as the precursor to prepare hierarchical ordered porous carbon with interconnected pores for the electrochemical energy storage application. The unique molecular structure and properties of lignosulphonate ensure the acquisition of high-quality porous carbon with a controllable pore structure and improved physical properties. As a result, the as-prepared hierarchical order porous carbon show excellent energy storage performance when used to assemble the symmetric supercapacitor, which exhibits high-specific capacitance of 289 F g-1 at a current density of 0.5 A g-1, with the energy density of 40 Wh kg-1 at the power density of 900 W kg-1. The present study provides a promising strategy for the fabrication of high-performance energy storage devices at low cost.

Achieving Ultrahigh Capacity with Self-Assembled Ni(OH)2 Nanosheet-Decorated Hierarchical Flower-like MnCo2O4.5 Nanoneedles as Advanced Electrodes of Battery-Supercapacitor Hybrid Devices

Self-assembled Ni(OH)₂ nanosheet-decorated hierarchical flower-like MnCo₂O_4.5 nanoneedles were synthesized via a cost-effective and facile hydrothermal strategy, aiming to realize a high-capacity advanced electrode of a battery-supercapacitor hybrid (BSH) device. It is demonstrated that the as-synthesized hierarchical flower-like MnCo₂O_4.5@Ni(OH)₂-nanosheet electrode exhibits a high specific capacity of 318 mAh g^-1 at a current density of 3 A g^-1 and still maintains a capacity of 263.5 mAh g^-1 at a higher current density of 20 A g^-1, with an extremely long cycle lifespan of 87.7% capacity retention after 5000 cycles. Moreover, using the unique core-shell structure as the cathode and hollow Fe₂O₃ nanoparticles/reduced graphene oxide as the anode, the BSH device delivers a high energy density of 56.53 Wh kg^-1 when the power density reaches 1.9 kW kg^-1, and there is an extraordinarily good cycling stability with the capacity retention rate of 90.4% after 3000 cycles. It is believed that the superior properties originate from desirable core-shell structures alleviating the impact of volume changes as well as the existence of two-dimensional Ni(OH)₂ nanosheets with more active sites, thereby improving the cycle stability and achieving ultrahigh capacity. These results will provide more access to the rational material design of diverse nanostructures toward high-performance energy storage devices.

3D flower-like binary nickel cobalt oxide decorated coiled carbon nanotubes directly grown on nickel nanocones and binder-free hydrothermal carbons for advanced asymmetric supercapacitors

The development of high performance supercapacitors with high energy densities without sacrificing power densities has always been at the leading edge of the emerging field of renewable energy. Herein, the design and fabrication of innovative high performance binder-free electrodes consisting of coiled carbon nanotubes (CNTs) and biomass-derived hydrothermal carbon spheres (HTCSs) as, respectively, positive and negative electrodes is reported. High performance asymmetric supercapacitors (ASCs) were developed using novel 3D core/shell-like binary Ni-Co oxide (NCO) decorated coiled CNTs directly grown on Ni nano-cone arrays (NCAs) and HTCSs directly deposited on NCAs. Novel 3D structures of NCAs were synthesized via a facile and scalable cathodic electrodeposition route and coiled CNTs were directly grown on them by catalytic chemical vapour deposition (CVD) followed by a facile hydrothermal method to integrally decorate the coiled CNTs/NCAs by 3D flower-like NCO. A one-pot hydrothermal method is also used to direct the synthesis of biomass-derived HTCSs on NCAs to fabricate a novel binder-free negative electrode. The ASC based on NCO@coiled CNTs/NCAs//HTCSs/NCAs not only exhibits superior energy density (72.5 W h kg-1) at a reasonable power density of 1.4 kW kg-1, but also represents remarkable cycling durability (retaining almost over 85% of its initial capacitance after 5000 charge-discharge cycles). The fabricated ASC, therefore, seems to be a potent candidate for practical applications in future high performance energy storage systems.

Facile Synthesis of Manganese Cobalt Oxide/Nickel Cobalt Oxide Composites for High-Performance Supercapacitors

Transition metal oxides (TMOs) with spinel structures have a promising potential as the electrode materials for supercapacitors application owning to its outstanding theoretical capacity, good redox activity, and eco-friendly feature. In this work, MnCo₂O_4.5@NiCo₂O₄ nanowire composites for supercapacitors has been successfully fabricated by using a mild hydrothermal approach without any surfactant. The morphology and physicochemical properties of the prepared products can be well-controlled by adjusting experimental parameters of preparation. The double spinel composite exhibits a high specific capacitance of 325 F g⁻¹ (146 C g⁻¹) and 70.5% capacitance retention after 3,000 cycling tests at 1 A g⁻¹.

Graphene/transition metal dichalcogenides hybrid supercapacitor electrode: status, challenges, and perspectives

Supercapacitors, based on fast ion transportation, are among the most promising energy storage solutions that can deliver fast charging-discharging within seconds and exhibit excellent cycling stability. The development of a good electrode material is one of the key factors in enhancing supercapacitor performance. Graphene (G), an allotrope of carbon that consists of a single layer of carbon atoms arranged in a hexagonal lattice, elicits research attention among scientists in the field of energy storage due to its remarkable properties, such as outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior. Furthermore, numerous studies focus on 2D materials that are analogous to graphene as electrode supercapacitors, including transition metal dichalcogenides (TMDs). Recently, scientists and researchers are exploring TMDs because of the distinct features that make 2D TMDs highly attractive for capacitive energy storage. This study provides an overview of the structure, properties, synthesis methods, and electrochemical performance of G/TMD supercapacitors. Furthermore, the combination of G and TMDs to develop a hybrid structure may increase their energy density by introducing an asymmetric supercapacitor system. We will also discuss the future prospect of this system in the energy field.

Self-Sacrificial Salt Templating: Simple Auxiliary Control over the Nanoporous Structure of Porous Carbon Monoliths Prepared through the Solvothermal Route

The conventional sol-gel method for preparing porous carbons is tedious and high-cost to prepare porous carbons and the control over the nanoporous architecture by solvents and carbonization is restricted. A simple and novel self-sacrificial salt templating method was first presented to adjust the microporous structure of porous carbon monoliths synthesized via the solvothermal method. Apart from good monolithic appearance, the solvothermal route allowed for ambient drying because it made sure that the polymerization reaction was completed quickly and thoroughly. The intact and crack-free porous carbon monoliths were investigated by scanning electron microscopy (SEM), thermogravimetric differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and nitrogen sorption measurements. It was proven that the self-sacrificial salts NH₄SCN had been removed during pyrolyzing and so, porous carbon monoliths could be directly obtained after carbonization without the need of washing removal of salts. Most importantly, the microporous specific surface area of the resultant porous carbon monoliths was dramatically increased up to 770 m²/g and the Brunauer–Emmett–Teller (BET) specific surface area was up to 1131 m²/g. That was because the salts NH₄SCN as self-sacrificial templating helped to form more around 0.6 nm, 0.72 nm and 1.1 nm micropores. The self-sacrificial salt templating is also a suitable and feasible method for controlling the nanoporous structure of other porous materials.

Hybrid nanowires and nanoparticles of WO3 in a carbon aerogel for supercapacitor applications

In the field of electrochemical energy storage, incorporation of metal oxides into porous carbon has attracted significant attention. Since each advantage of nanoparticles and nanowires of metal oxide has been distinguished for supercapacitor applications, a combination of the advantages of both structures together can meet a capacitive synergy. In this study, WO₃ nanowires and nanoparticles were first incorporated into a carbon aerogel (CA) simultaneously via a facile and one-pot route. A comparative study on the capacitive properties of this novel hybrid structure and single nanoparticles in CA was conducted. The introduction of WO₃ nanowires with diameter <40 nm provided an additional pair of redox peaks and improved the specific capacitance by 50% and the rate capacity by 61%. The composite within the hybrid nanowires and nanoparticles exhibits an excellent cycling stability of only 2% decay in specific capacitance detected at 50 mV s^-1 for 1000 cycles. The individual contribution of nanowires and nanoparticles to the enhanced capacitance has been discussed, and the enhanced capacitive properties can be ascribed to the hybrid structure better for charge transport during the electrochemical process. More importantly, this route can be extended to incorporate nanowires of other metal oxides into mesoporous carbon, and enhanced capacitive properties can be expected.

Graphene/Ruthenium Active Species Aerogel as Electrode for Supercapacitor Applications

Ruthenium active species containing Ruthenium Sulphide (RuS₂) is synthesized together with a self-assembled reduced graphene oxide (RGO) aerogel by a one-pot hydrothermal synthesis. Ruthenium Chloride and L-Cysteine are used as reactants. The hydrothermal synthesis of the innovative hybrid material occurs at 180 °C for 12 h, by using water as solvent. The structure and morphology of the hybrid material are fully characterized by Raman, XRD, XPS, FESEM and TEM. The XRD and diffraction pattern obtained by TEM display an amorphous nanostructure of RuS₂ on RGO crystallized flakes. The specific capacitance measured in planar configuration in 1 M NaCl electrolyte at 5 mV s-1 is 238 F g-1. This supercapacitor electrode also exhibits perfect cyclic stability without loss of the specific capacitance after 15,000 cycles. In summary, the RGO/Ruthenium active species hybrid material demonstrates remarkable properties for use as active material for supercapacitor applications.

Pore structure improvement of carbon aerogel and investigation of the supercapacitive behavior of a Co3O4 nanoball/carbon aerogel composite

In the present study, hybrid nanostructures of porous Co₃O₄ nanoball/carbon aerogel were prepared via the in situ growth of Co₃O₄ nanoballs with nanosized uniform structures within the pores of a pre-synthesized atmospheric pressure-dried highly mesoporous carbon aerogel.

1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability

The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo₂S₄ nanotube array/carbon aerogel and NiCo₂O₄ nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo₂S₄ nanotube array/carbon aerogel and NiCo₂O₄ nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg^-1 and 47.5 Wh kg^-1 at a power density of 400 W kg^-1, respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

A Porous Perchlorate-Doped Polypyrrole Nanocoating on Nickel Nanotube Arrays for Stable Wide-Potential-Window Supercapacitors

A bottom-up synthetic strategy is developed to fabricate a highly porous wave-superposed perchlorate-doped polypyrrole nanocoating on nickel nanotube arrays. The delicate nanostructure and the unique surface chemistry synergistically endow the obtained electrode with revealable pseudocapacitance, large operating potential window, and excellent cycling stability, which are highly promising for both asymmetric and symmetric supercapacitors.