Facile synthesis of nickel cobalt sulfide nano flowers for high performance supercapacitor applications

A facile synthesis of nickel cobalt sulfide (NCS) nanoflowers have been deposited successfully onto binder free 3D nickel foam electrodes using simple successive ionic layer adsorption and reaction (SILAR) method for supercapacitor applications. The obtained NCS nanoflowers manifest ultrahigh specific capacitance of 1899 F g^?1 at a scan rate of 5 mV s^?1. The NCS nanoflowers exhibit a prominent energy density of 55.16 Wh kg^?1 at power density of 495 W kg^?1 and superior cyclic stability of 94% after 10000 cycles. In addition, the asymmetric supercapacitor (ASC) device is fabricated using NCS nanoflower as positive and reduced graphene oxide (rGO) as negative electrodes, respectively. The ASC (NCS//rGO) delivered good capacity with excellent energy and power densities within 1.6 V wider potential window. Hence, NCS nanoflowers are an outstanding material for energy storage applications in near future.     

Electrochemical capacitance of nickel oxide nanotubes synthesized in anodic aluminum oxide templates

Nickel oxide (NiO) nanotubes for supercapacitors were synthesized by chemically depositing nickel hydroxide in anodic aluminum oxide templates and thermally annealing at 360 °C. The synthesized nanotubes have been characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The capacitive behavior of the NiO nanotubes was investigated by cyclic voltammetry, galvanostatic charge–discharge experiment, and electrochemical impedance spectroscopy in 6 M KOH. The electrochemical data demonstrate that the NiO nanotubes display good capacitive behavior with a specific capacitance of 266 F g⁻¹ at a current density of 0.1 A g⁻¹ and excellent specific capacitance retention of ca. 93% after 1,000 continuous charge–discharge cycles, indicating that the NiO nanotubes can become promising electroactive materials for supercapacitor.     

In situ polymerization and reduction to fabricate gold nanoparticle‐incorporated polyaniline as supercapacitor electrode materials

Nanocomposites of gold nanoparticles and polyaniline are synthesized by using HAuCl₄ and ammonium peroxydisulfate as the co‐oxidant involving in situ polymerization of aniline and in situ reduction of HAuCl₄. Through these in situ methods, the synthesized Au nanoparticles of ca. 20 nm embedded tightly and dispersed uniformly in polyaniline backbone. With the Au content in composite increasing from 4.20 to 24.72 wt.%, the specific capacitance of the materials first increased from 334 to 392 F g⁻¹ and then decreased to 298 F g⁻¹. Based on the real content of PANI in composite material, the highest specific capacitance is calculated to be 485 F g⁻¹ at the Au amount of 19.15 wt.%, which remains 55.6% after 5000 cycles at the current density of 2 A g⁻¹. Finally, the asymmetric supercapacitor of AuNP/PANI||AC and the symmetric supercapacitor of AuNP/PANI||AuNP/PANI are assembled. The asymmetric supercapacitor device shows a better electrochemical performance, which delivers the maximum energy density of 7.71 Wh kg⁻¹ with power density of 125 W kg⁻¹ and maximum power density of 2500 W kg⁻¹ with the energy density of 5.35 Wh kg⁻¹.     

Synthesis of Ni-poor NiO nanoparticles for p-DSSC applications

To improve the performances of p-Dye Sensitized Solar Cell (p-DSSC) for the future, the synthesis of modified p-type nickel oxide semiconductor, commonly used as photocathode in such devices, was initiated with Ni₃O₂(OH)₄ as precursor. This specific nickel oxyhydroxide was first characterized by X-ray photo-electron spectroscopy and magnetic susceptibility measurements. Then its thermal decomposition was thoroughly studied in order to control the particles size of the as-prepared NiO nanopowders. Low temperature decomposition in air of this precursor allows the formation of Ni_1−xO nanoparticles with a large amount of Ni vacancies and specific surface areas up to 250 m² g⁻¹. Its ammonolysis at 250 °C leads to nanostructured N-doped NiO (NiO:N) materials.     

A High-Performance Asymmetric Supercapacitor Based on Tungsten Oxide Nanoplates and Highly Reduced Graphene Oxide Electrodes

Tungsten oxide/graphene hybrid materials are attractive semiconductors for energy-related applications. Herein, we report an asymmetric supercapacitor (ASC, HRG//m-WO₃ ASC), fabricated from monoclinic tungsten oxide (m-WO₃) nanoplates as a negative electrode and highly reduced graphene oxide (HRG) as a positive electrode material. The supercapacitor performance of the prepared electrodes was evaluated in an aqueous electrolyte (1 m H₂SO₄) using three- and two-electrode systems. The HRG//m-WO₃ ASC exhibits a maximum specific capacitance of 389 F g⁻¹ at a current density of 0.5 A g⁻¹, with an associated high energy density of 93 Wh kg⁻¹ at a power density of 500 W kg⁻¹ in a wide 1.6 V operating potential window. In addition, the HRG//m-WO₃ ASC displays long-term cycling stability, maintaining 92 % of the original specific capacitance after 5000 galvanostatic charge–discharge cycles. The m-WO₃ nanoplates were prepared hydrothermally while HRG was synthesized by a modified Hummers method.     

A facile synthesis of hierarchical porous carbon derived from renewable lignin for high-performance supercapacitor

In this work, we proposed a facile one-pot pyrolysis method to conveniently manufacture lignin-derived carbon materials with graded porous construction for use in supercapacitors. The renewable lignin was selected as precursor, while the potassium citrate was used as a pore-forming agent. The properties of the prepared lignin-derived carbon (LAC) and the performance for supercapacitor application were thoroughly evaluated. The LAC at optimal preparation conditions shows a layered porous structure with a large specific surface area of 3174 cm² g⁻¹ and pore volume of 2.796 cm³ g⁻¹, where the specific capacitance reach to 241 F g⁻¹ at 1 A g⁻¹ scan rate in 6 M KOH electrolyte solution. At the same time, the specific capacitance remains at 220 F g⁻¹ even at an excessive scan velocity of 20 A g⁻¹, while the capacitance retention is still close to 91.3%. The capacitance retention rate is stable above 95% after 10,000 charge/discharge cycles, which shows the desired long-time stability. All these results demonstrate the outstanding properties of the new prepared LAC material and the considerable application potential in the field of electrical energy storage.     

Enhanced Supercapacitor Performance Using a Co3O4@Co3S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co₃O₄ and Co₃S₄ on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co₃O₄@Co₃S₄ nanocomposite, the nanostructure of Co₃S₄ was fabricated from Co₃O₄ nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm⁻² (5651.24 F g⁻¹) at a current density of 6 mA cm⁻² compared to the Co₃O₄/rGO/NF electrode with a capacitance of 3.06 F cm⁻² (1230.77 F g⁻¹) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg⁻¹, specific power density of 6048.03 W kg⁻¹ and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s⁻¹). Finally, by using Co₃O₄ @Co₃S₄/rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm⁻² at the applied current density of 1 mA cm⁻², and delivered an energy density of 0.143 Wh kg⁻¹ at the power density of 5.42 W kg⁻¹.     

Coordination polymer template synthesis of hierarchical MnCo2O4.5 and MnNi6O8 nanoparticles for electrochemical capacitors electrode

Two types of ternary metal oxides, MnCo₂O_4.5 and MnNi₆O₈ nanoparticles have been separately synthesized through chemical transformation from the corresponding bimetallic coordination polymer particles precursor under high-heating conditions. Series of electrochemical measurements are performed to examine the MnCo₂O_4.5 and MnNi₆O₈ electrodes, and the result shows that MnCo₂O_4.5 structure, especially for Mn/Co-600, has much higher capacitance than that of MnNi₆O₈ nanoparticles, indicating MnCo₂O_4.5 electrode is more suitable for applying in neutral electrolyte system. The Mn/Co-600 electrode exhibits a specific capacitance of 158 F g⁻¹ at 5 mV s⁻¹, good rate capability of 53.8% with a 20 times current density increase, good cycle performance (92.9% capacitance retention after 1000 cycles) and high power density (a specific power of 5760 W kg⁻¹ at 4.0 A g⁻¹) with low charge transfer resistance value of 1.8 Ω.     

Impact of polypyrrole incorporation on nickel oxide@multi walled carbon nanotube composite for application in supercapacitors

In this article we report the synthesis of polypyrrole incorporated nickel oxide multi walled carbon nanotube (NiO@NMWCNT/PPy) composites by thermal reduction protocol for supercapacitor applications. The structural and morphological properties of the composites were confirmed by the aid of X-ray diffraction (XRD), Field-emission scanning electron microscope (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Field-emission transmission electron microscopy (FE-TEM) analysis indicating the hexagonal crystal structure of NiO decorated on NMWCNT/Ppy. The electrochemical characteristics of the NiO@MWCNT/PPy composite were analyzed in the presence of 2 M KOH as an electrolyte. The NiO@NMWCNT/PPy nanostructured composite produced a plenty of active sites for ion migration reactions that facilitate the energy storage mechanism. As a proof of concept demonstration, the NiO@NMWCNT/PPy composite was explored as an electrode materials in supercapacitor and exhibited specific capacitance of 395 F g⁻¹ and cyclic stability up to 5000 cycles at 0.5 A g⁻¹. Enhanced performance of composite is attributed to the incorporation of polypyrrole in NiO@NMWCNT. The improved capacitance and cyclic stability demonstrated by the composite indicates the NiO@NMWCNT/PPy to be a promising candidate for supercapacitor applications.     

Preparation and characterization of form-stable tetradecanol–palmitic acid expanded perlite composites containing carbon fiber for thermal energy storage

In this study, tetradecanol–palmitic acid/expanded perlite composites containing carbon fiber (TD-PA/EP-CF CPCMs) were prepared by a vacuum impregnation method. Binary eutectic mixtures of PA and TD were utilized as thermal energy storage material in the composites, where EP behaved as supporting material. X-ray diffraction demonstrated that crystal structures of PA, TD, EP, and CF remained unchanged, confirming no chemical interactions among raw materials besides physical combinations. The microstructures indicated that TD-PA was sufficiently absorbed into EP porous structure, forming no leakage even in molten state. Differential scanning calorimetry estimated the melting temperature of TD-PA/EP-CF CPCM to 33.6 °C, with high phase change latent heat (PCLH) of 138.3 kJ kg⁻¹. Also, the freezing temperature was estimated at 29.7 °C, with PCLH of 137.5 kJ kg⁻¹. The thermal cycling measurements showed that PCM composite had adequate stability even after 200 melting/freezing cycles. Moreover, the thermal conductivity enhanced from 0.48 to 1.081 W m⁻¹ K⁻¹ in the presence of CF. Overall, the proposed CPCMs look promising materials for future applications due to their appropriate phase change temperature, elevated PCLH, and better thermal stability.

     

Nickel oxide coated on ultrasonically pretreated carbon nanotubes for supercapacitor

Nickel oxide/carbon nanotubes (NiO/CNTs) composite materials for supercapacitor are prepared by chemically depositing nickel hydroxide onto carbon nanotubes pretreated by ultrasonication and followed by thermal annealing at 300 °C. A series of NiO/CNTs composites with different weight ratios of nickel oxide versus carbon nanotubes are synthesized via the same route. The high-resolution TEM and SEM results show that a lot of nicks, which favored the nucleation of the nickel hydroxide formed on the outer walls of carbon nanotubes due to ultrasonic cavitations, and then nickel oxide coated uniformly on the outer surface of the individual carbon nanotubes. The NiO/CNTs electrode presents a maximum specific capacitance of 523 F/g as well as a good cycle life during 1,000 cycles in 6 M KOH electrolyte. The good electrochemical characteristics of NiO/CNTs composite can be attributed to the three-dimensionally interconnected nanotubular structure with a thin film of electroactive materials.     

Rational Design of Porous Structured Nickel Manganese Sulfides Hexagonal Sheets-in-Cage Structures as an Advanced Electrode Material for High-Performance Electrochemical Capacitors

The design of hierarchical electrodes comprising multiple components with a high electrical conductivity and a large specific surface area has been recognized as a feasible strategy to remarkably boost pseudocapacitors. Herein, we delineate hexagonal sheets-in-cage shaped nickel–manganese sulfides (Ni-Mn-S) with nanosized open spaces for supercapacitor applications to realize faster redox reactions and a lower charge-transfer resistance with a markedly enhanced specific capacitance. The hybrid was facilely prepared through a two-step hydrothermal method. Benefiting from the synergistic effect between Ni and Mn active sites with the improvement of both ionic and electric conductivity, the resulting Ni-Mn-S hybrid displays a high specific capacitance of 1664 F g⁻¹ at a current density of 1 A g⁻¹ and a capacitance of 785 F g⁻¹ is maintained at a current density of 50 A g⁻¹, revealing an outstanding capacity and rate performance. The asymmetric supercapacitor device assembled with the Ni-Mn-S hexagonal sheets-in-cage as the positive electrode delivers a maximum energy density of 40.4 Wh kg⁻¹ at a power density of 750 W kg⁻¹. Impressively, the cycling retention of the as-fabricated device after 10 000 cycles at a current density of 10 A g⁻¹ reaches 85.5 %. Thus, this hybrid with superior capacitive performance holds great potential as an effective charge-storage material.     

Fabrication of porous Co/NiO core/shell nanowire arrays for electrochemical capacitor application

We report self-supported porous Co/NiO core/shell nanowire arrays via the combination of hydrogen reduction and chemical bath deposition methods. The Co nanowire acts as the backbone for the growth of NiO nanoflake shell forming hierarchically porous Co/NiO core/shell nanowire arrays. As electrode materials for pseudo-capacitors, the Co/NiO core/shell nanowire arrays exhibit a specific capacitance of 956 F g^− 1 at 2 Å g^− 1 and 737 F g^− 1 at 40 Å g^− 1, and good cycling stability, which is mainly due to the metal nanowire based core/shell nanowire architecture which provides good conductive network as well as fast ion/electron transfer and sufficient contact between active materials and electrolyte.     

介孔氧化镍的合成、表征和在电化学电容器中的应用

以十二烷基硫酸钠为模板剂, 采用尿素为沉淀剂, 用均匀沉淀法, 适当控制尿素的水解速度, 制备具有介孔结构的氢氧化镍胶体, 在不同温度下焙烧处理得到孔分布集中的氧化镍介孔分子筛. 结果表明, 在523 K下焙烧得到的氧化镍BET比表面达到477.7 m²•g^－1. 结构表征还显示, 介孔氧化镍的孔壁为多晶结构, 其孔结构形成机理应为准反胶束模板机理. 循环伏安法表明用NiO介孔分子筛制备的电极有很好的电容性能. 与浸渍法和阴极沉淀法制得的NiO相比, 这种介孔结构的NiO能够大量用来制作电化学电容器电极, 并且保持较高的比电容量和良好的电容性能.     

A high performance solid-state asymmetric supercapacitor based on Anderson-type polyoxometalate-doped graphene aerogel

The manufacture of single-atom transition metal-doping carbon nanocomposites as electrode materials is crucial for electrochemical energy storage with high energy and power density. However, the simple strategy for preparation of such active materials with controlled structure remains a great challenge. Here, cobalt-doped carbon nanocomposites (Co-POM/rGO) were synthesized successfully by deposition of Anderson-type polyoxometalate (POM) on the surface of reduced graphene oxide (rGO) aerogel via one-pot hydrothermal treatment. The resulting Co-POM/rGO possesses three-dimensional graphene-based frameworks with hierarchical porous structure, high surface area and uniform single-atom metal doping. These intriguing features render Co-POM/rGO to be a promising electrode for applications in electrochemical energy storage. As an electrode material of a supercapacitor, Co-POM/rGO shows high-performance electrochemical energy storage (211.3 F g^?1 at 0.5 A g^?1). Furthermore, the solid-state asymmetric supercapacitor (ASC) device, using Co-POM/rGO as a positive electrode, exhibits the outstanding energy density of 37.6 Wh kg^?1 at a power density of 500 W kg^?1, and high capacitance retention of 95.2% after 5000 charge–discharge cycles. These results indicate that the proposed strategy for rational design of single-atom-metal doped carbon nanocomposites for flexible ASC devices with excellent capacitive properties.

     

线状全固态CNTF@ZnCo-OH//CNTF@RGO超级电容器的制备与电化学性能

采用电化学沉积在碳纳米管纤维上复合锌钴氢氧化物纳米片（CNTF@ZnCo-OH）,并研究其电化学性能。实验结果表明CNTF@ZnCo-OH电极在2 A·g^-1的电流密度下比电容为748 F·g^-1,在10 A·g^-1的电流密度下循环2 000圈以后,比电容保持率高达110.4%。该优异循环性能得益于碳纳米管纤维基底的网络结构和ZnCo-OH的纳米片状结构。以CNTF@RGO（石墨烯）为负极、CNTF@ZnCo-OH为正极,组装线状全固态非对称CNTF@ZnCo-OH//CNTF@RGO超级电容器。该器件在0.5 A·g^-1电流密度下比电容为70 F·g^-1,2 000次循环后电容保持率为79.6%,并且在不同的弯曲状态下保持电化学性能不变,具有优良的机械稳定性。该非对称线状器件可以在0.8~1.4 V之间工作,其能量密度高达19.1 Wh·kg^-1,对应的功率密度为1 400.3 W·kg^-1。2个30 mm长的线状器件可持续点亮LED灯10 s。     

Influence of addition of cobalt oxide on microstructure and electrochemical capacitive performance of nickel oxide

Ni–Co oxide nanocomposite was prepared by thermal decomposition of the precursor obtained via a new method—coordination homogeneous coprecipitation method. The synthesized sample was characterized physically by X-ray diffraction, scanning electron microcopy, energy dispersive spectrum, transmission electron microscope, and Brunauer–Emmett–Teller surface area measurement, respectively. Electrochemical characterization of Ni–Co oxide electrode was examined by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance measurements in 6-mol L⁻¹ KOH aqueous solution electrolyte. The results indicated that the addition of cobalt oxide not only changed the morphology of NiO but also enhance its electrochemical capacitance value. A specific capacitance value of 306 F g⁻¹ of Ni–Co oxide nanocomposite with n _Co = 0.5 (n _Co is the mole fraction of Co with respect to the sum of Co and Ni) was measured at the current density of 0.2 A g⁻¹, nearly 1.5 times greater than that of pure NiO electrode. Lower resistance and better rate capability can also be observed.     

Significantly enhanced rate capability in supercapacitors using carbide-derived carbons electrode with superior microstructure

Mesoporous carbide-derived carbons (CDC) with hierarchical pore structure were fabricated by chlorine etching of mesoporous titanium carbides. Their capacitive behaviors for electrochemical capacitor were investigated in comparison to those of purely microporous CDC. The as-prepared mesoporous CDC exhibited not only uniform micropores formed by leaching out titanium atoms but a 3-D mesoporous network inherited from their parent carbides. These mesoporous CDC could deliver a high specific capacitance of 120 F g⁻¹ in 1 M tetraethylammonium tetrafluoroborate dissolved in propylene carbonate. Moreover, they owned excellent frequency response and superior rate capability with capacitance retention ratio of 91% at current density of 10 A g⁻¹. A high energy density of 16.3 Wh kg⁻¹ was obtained even though power density was raised up to 4,300 W kg⁻¹. The distinctive capacitive performance of mesoporous CDC would be attributed to their superior microstructure, in which the uniform micropores contributed to high charge storage while the 3-D mesoporous network and nanometer-scaled dimension of particles facilitated ions transfer as well as shortened electrolyte diffusion distance.     

A renewable bamboo carbon/polyaniline composite for a high-performance supercapacitor electrode material

A high-performance conducting polymer-activated carbon composite electrode material was prepared by potentiostatic deposition of aniline on a hierarchically porous carbon, which was carbonized from the natural bamboo. The obtained composite combined the contribution of the unique properties of the activated carbon and pseudocapacitance of the deposited polyaniline layer. This active material possessed excellent rate capability and good cycle performance, over 92% of the original capacitance is retained after 1,000 cycles. The energy density of the composite can reach 47.5 W h kg⁻¹ calculated only by active mass. It can be a good candidate for high-performance supercapacitor.     

Carbon Electrode Material with High Densities of Energy and Power

Activated carbon (AC) samples as electrode materials were prepared by means of simultaneous physical-chemical activation using walnut shells as precursors. The porosity and surface chemistry of the resultant AC samples were studied by the nitrogen adsorption at 77 K, and FTIR spectrum. The testing supercapacitors were assembled with resultant carbon electrode and electrolyte of 6 mol·L⁻¹ KOH solution. Their electrochemical properties were investigated by charge-discharge of constant current, cyclic voltammogram, impedance spectrum and so on. The results showed that the capacitor had low inner resistance, low leakage current, high stability, and capacitance retainability. The specific capacitance of AC increased with increasing BET specific surface area. The specific capacitance of the AC sample with a specific area of 1197 m²·g⁻¹ could be as high as 292 F·g⁻¹. At a discharge current of 80 mA, the corresponding specific energy density, power density, and maximum power of the supercapacitor are 7.3 Wh·kg⁻¹, 770 W·kg⁻¹, and 5.1 W·g⁻¹, respectively.