聚吡咯/氧化石墨烯层状复合材料的制备及其在超级电容器中的应用(英文)

通过将吡咯单体在低温下与氧化石墨烯进行原位聚合,获得聚吡咯/石墨烯(Ppy/CRGO)复合材料.采用场发射电子显微镜(FESEM)、红外(FT-IR)和热重分析(TGA)对复合物的表面形貌、结构进行表征.FESEM结果表明,通过控制氧化石墨烯(GO)和吡咯单体的质量比例,可以对复合物的层状和厚度进行调控.FT-IR和TGA结果表明,聚吡咯(Ppy)是通过化学键合的方式与氧化石墨烯复合在一起.通过机械冷压法将粉末状Ppy/CRGO复合物压成圆片电极,并探讨了石墨烯和聚吡咯复合比例、反应时间、烘干温度和孔隙率等因素对Ppy/CRGO复合物电极的电学和电化学性能的影响.结果表明,Ppy与CRGO质量比为10∶1所制得的Ppy/CRGO复合物的电容量为421 F·g-1,通过在电极中引入孔隙,电容量能进一步提升为509 F·g-1.     

Nanosized Fe3O4-modified activated carbon for supercapacitor electrodes

Nanosized Fe₃O₄-modified activated carbon composites for supercapacitor electrodes have been investigated. Structural and morphological characterizations of activated materials are carried out using X-ray diffraction and scanning electron microscopy, respectively. The electrochemical performances of the composite electrodes are evaluated by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The experimental results show that the specific capacitances of the 10 wt % Fe₃O₄-modified activated carbon composite electrode (154.3 F g^?1) is highly improved compared with that of Fe₃O₄ (78.5 F g^?1) and AC (79.2 F g^?1) at the current density of 5 mA cm^?2, respectively. The charge/discharge tests show that it could retain 79.6% of its initial capacitance over 1000 cycles, suggesting its potential application for the fabrication of high-quality supercapacitors.     

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.     

Functional Porous Carbon/Nickel Oxide Nanocomposites as Binder‐Free Electrodes for Supercapacitors

High‐surface‐area, guava‐leaf‐derived, heteroatom‐containing activated carbon (GHAC) materials were synthesized by means of a facile chemical activation method with KOH as activating agent and exploited as catalyst supports to disperse nickel oxide (NiO) nanocrystals (average size (2.0±0.1) nm) through a hydrothermal process. The textural and structural properties of these GHAC/NiO nanocomposites were characterized by various physicochemical techniques, namely, field‐emission SEM, high‐resolution TEM, elemental analysis, X‐ray diffraction, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The as‐synthesized GHAC/NiO nanocomposites were employed as binder‐free electrodes, which exhibited high specific capacitance (up to 461 F g^?1 at a current density of 2.3 A g^?1) and remarkable cycling stability, which may be attributed to the unique properties of GHAC and excellent electrochemical activity of the highly dispersed NiO nanocrystals.     

Preparation and Characterization of Carbon Nano‐Onion/PEDOT:PSS Composites

Composites of unmodified or oxidized carbon nano‐onions (CNOs/ox‐CNOs) with poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are prepared with different compositions. By varying the ratio of PEDOT:PSS relative to CNOs, CNO/PEDOT:PSS composites with various PEDOT:PSS loadings are obtained and the corresponding film properties are studied as a function of the polymer. X‐ray photoelectron spectroscopy characterization is performed for pristine and ox‐CNO samples. The composites are characterized by scanning and transmission electron microscopy and differential scanning calorimetry studies. The electrochemical properties of the nanocomposites are determined and compared. Doping the composites with carbon nanostructures significantly increases their mechanical and electrochemical stabilities. A comparison of the results shows that CNOs dispersed in the polymer matrices increase the capacitance of the CNO/PEDOT:PSS and ox‐CNO/PEDOT:PSS composites.     

Thiourea aldehyde resin-based carbon/graphene composites for high-performance supercapacitors

Thiourea aldehyde resin-based heteroatom doping carbon and graphene composites (RHDC/GN) were prepared by an in situ polymerization and carbonization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that thiourea aldehyde resin deposited on lamellar GO flakes during the polymerization and RHDC/GN composites had a hierarchical structure. The specific capacitance of the RHDC/GN composites was high up to 355 F g^?1, much higher than that of the pure thiourea aldehyde resin-based heteroatom doping carbon (RHDC) with specific capacitance of 135 F g^?1 at a current density of 1.0 A g^?1 in 6-M KOH electrolyte. And the hetroatoms in RHDC/GN composites increase the specific capacitance, and GN enhances the conductivity of the electrodes which is beneficial to improving electrochemical cycling stability of the electrode significantly. The specific capacitance retains 90.97% after 5000 charge-discharge processes at 10 A g^?1, which provides potential as supercapacitors.     

Core‐Shell Structured Cobalt Sulfide/Cobalt Aluminum Hydroxide Nanosheet Arrays for Pseudocapacitor Application

The direct synthesis of nanostructured electrode materials on three‐dimensional substrates is important for their practical application in electrochemical cells without requiring the use of organic additives or binders. In this study, we present a simple two‐step process to synthesize a stable core–shell structured cobalt sulfide/cobalt aluminum hydroxide nanosheet (LDH‐S) for pseudocapacitor electrode application. The cobalt aluminum layered double hydroxide (CoAl‐LDH) nanoplates were synthesized in basic aqueous solution with a kinetically‐controlled thickness. Owing to the facile diffusion of electrolytes through the nanoplates, thin CoAl‐LDH nanoplates have higher specific capacitance values than thick nanoplates. The as‐grown CoAl‐LDH nanoplates were transformed into core–shell structured LDH‐S nanosheets by a surface modification process in Na₂S aqueous solution. The chemically robust cobalt sulfide (CoS) shell increased the electrochemical stability compared to the sulfide‐free CoAl‐LDH electrodes. The LDH‐S electrodes exhibited high electrochemical performance in terms of specific capacitance and rate capability with a galvanostatic discharge of 1503 F g^?1 at a current density of 2 A g^?1 and a specific capacitance of 91 % at 50 A g^?1.     

基于含锌有机配位聚合物的微孔碳的合成及其电化学性能

报道了一种基于含锌(II)有机配位聚合物制备微孔碳的新方法. 通过锌离子和酒石酸之间的配位作用获得含锌有机配位化合物, 并通过氢键作用将其引入到间苯二酚/甲醛低聚物溶胶的开放网络结构中. 使含锌有机配位化合物和酚醛低聚物溶胶体系发生共聚反应得到酚醛和含锌有机配位共聚物, 在950℃下热处理分解以及锌蒸气蒸发后制得微孔碳. 微孔碳材料典型样品具有相对较大以及比较规则的微孔, 其比表面积可以达到1260 m²·g^-1, 孔体积为0.63 cm³·g^-1. 所得微孔碳作为超级电容器电极材料的等效串联电阻为0.46 Ω, 其循环伏安曲线展示出较好的矩形性. 恒流充放电分析结果表明, 当电流密度为1 A·g^-1时, 微孔碳电极的比电容为196 F·g^-1; 在10 A·g^-1的大电流密度下, 比电容仍然达到137 F·g^-1. 该电极具有优良的循环稳定性, 1000次循环后比电容保持率达到98%. 这一研究结果表明, 所得微孔碳在超级电容器电极材料方面具有重要的应用前景.     

Capacitive Properties of the Binder‐Free Electrode Prepared from Carbon Derived from Cotton and Reduced Graphene Oxide

The binder‐free composite films of reduced graphene oxide (rGO ) and activated carbon derived from cotton (aCFC ) have been fabricated and used as electrodes for electrochemical capacitors (ECs ) to avoid the decrease of capacitive performance in traditional process caused by the additional binder. The optimal aCFC is prepared at 850 °C when the mass ratio of carbon and potassium hydroxide is 1 to 4. The optimal composite film prepared from the mass ratio of aCFC /GO =2/1 exhibits porous structure, and has a specific surface area of 849.6 m²•g⁻¹ and a total pore volume of 0.61 mL •g⁻¹. Based on the two‐electrode system testing in 6.0 mol/L KOH electrolyte, the optimal composite has specific capacitance of about 202 F•g⁻¹, 374 mF •cm⁻² and 116 F•cm⁻³ in terms of mass, area and volume, and shows excellent rate capability and good cyclic stability (91.7% retention of the initial capacitance after 5000 cycles). Furthermore, the assembled solid‐state ECs by using KOH /polyvinyl alcohol as electrolyte show good mechanical stability and capacitive performances after repeated bending cycles. It is proved that this method is effective to fabricate binder‐free electrodes for ECs and will open up a novel route for the reuse of waste cotton.     

Multi-stage Ordered Mesoporous Carbon-graphene Aerogel-Ni3S2/Co4S3 for Supercapacitor Electrode

Transition metal sulfides have emerged as promising materials in supercapacitor. In this work, we firstly developed an interface-induced superassembly approach to fabricate NiS_x and CoS_x nanoparticles, which based on ordered mesoporous carbon-graphene aerogel composites for supercapacitor electrodes. The obtained multi-component superassembled nanoparticles-carbon matrix composites have controllable 3D porous structure of multi-stage composite. The two-dimensional graphene interlaced to form a 3D framework with large sponge-like pores, and then the graphene surface was loaded with mesoporous carbon with mesoporous pore size and vertical orientation. The composites display high specific capacitance of 958.1 F g⁻¹ at 0.1 A g⁻¹. The capacitance retains about 97.3 % after 3000 charging-discharging cycles at 2 A g⁻¹. These results indicate that the obtained OMC−GA−Ni₃S₂/Co₄S₃ is a promising material for electrochemical capacitors, which providing new technical methods and ideas for the research of new energy and analytical sensor materials in the fields of energy storage, photocatalysis, point-of-care testing devices and other fields.     

Ultrasonic-assisted synthesis of magnetite/carbon nanocomposite for electrochemical supercapacitor

Iron oxides are considered as the promising pseudocapacitive materials for high-performance supercapacitors due to their high theoretical specific capacitance, low cost, environmental benignity, and natural abundance. In this work, we study capacitive behavior of different magnetite (Fe₃O₄) nanoparticles/carbon black (CB) composites ratios. These composites are synthesized by the coprecipitation method in the presence of ultrasonic waves. The structural and morphological characteristics of the magnetite/CB composites are investigated by X-ray diffraction and scanning electron microscopy, respectively. The electrochemical performance of magnetite/CB composite electrodes is tested by cyclic voltammetry and galvanostatic charge/discharge in a Na₂SO₄ electrolyte. The results indicate that the magnetite/CB electrodes show typical pseudo-capacitive behavior in Na₂SO₄ solution. Moreover, in comparison to the pure Fe₃O₄ (37 F g^?1) and carbon black (23 F g^?1), the as-prepared 45 % magnetite/CB nanocomposite electrode shows a higher specific capacitance (300 F g^?1). Additionally, the supercapacitor device of the magnetite/CB nanocomposite exhibits excellent long cycle life along with 98.5 % specific capacitance retained after 10,000 cycle tests.     

Hierarchically Designed Three‐Dimensional Macro/Mesoporous Carbon Frameworks for Advanced Electrochemical Capacitance Storage

Mesoporous carbon (m‐C) has potential applications as porous electrodes for electrochemical energy storage, but its applications have been severely limited by the inherent fragility and low electrical conductivity. A rational strategy is presented to construct m‐C into hierarchical porous structures with high flexibility by using a carbon nanotube (CNT) sponge as a three‐dimensional template, and grafting Pt nanoparticles at the m‐C surface. This method involves several controllable steps including solution deposition of a mesoporous silica (m‐SiO₂) layer onto CNTs, chemical vapor deposition of acetylene, and etching of m‐SiO₂, resulting in a CNT@m‐C core–shell or a CNT@m‐C@Pt core–shell hybrid structure after Pt adsorption. The underlying CNT network provides a robust yet flexible support and a high electrical conductivity, whereas the m‐C provides large surface area, and the Pt nanoparticles improves interfacial electron and ion diffusion. Consequently, specific capacitances of 203 and 311 F g^?1 have been achieved in these CNT@m‐C and CNT@m‐C@Pt sponges as supercapacitor electrodes, respectively, which can retain 96 % of original capacitance under large degree compression.     

Hierarchically Porous Carbons Derived from Metal–Organic Framework/Chitosan Composites for High‐Performance Supercapacitors

Hierarchically porous carbon materials with high surface areas are promising candidates for energy storage and conversion. Herein, the facile synthesis of hierarchically porous carbons through the calcination of metal–organic framework (MOF)/chitosan composites is reported. The effects of the chitosan (CS) additive on the pore structure of the resultant carbons are discussed. The corresponding MOF/chitosan precursors could be readily converted into hierarchically porous carbons (NPC‐V, V=1, 2, 4, and 6) with much higher ratios of meso‐/macropore volume to micropore volume (V_meso‐macro/V_micro). The derived carbon NPC‐2 with the high ratio of V_meso‐macro/V_micro=1.47 demonstrates a high specific surface area of 2375 m² g^?1, and a high pore volume of 2.49 cm³ g^?1, as well as a high graphitization degree, in comparison to its counterpart (NPC) without chitosan addition. These excellent features are favorable for rapid ion diffusion/transport, endowing NPC‐2 with enhanced electrochemical behavior as supercapacitor electrodes in a symmetric electrode system, corresponding to a high specific capacitance of 199.9 F g^?1 in the aqueous electrolyte and good rate capability. Good cycling stability is also observed after 10 000 cycles.     

Electrochemical capacitance of the composite of poly (3,4-ethylenedioxythiophene) and functionalized single-walled carbon nanotubes

The homogenous coating of poly (3,4-ethylenedioxythiophene) (PEDOT) on carbon nanotubes was realized by using functionalization of single-walled carbon nanotubes (SWNTs) in this study. Consequently, the PEDOT/functionalized SWNTs (PEDOT/F-SWNTs) composites, with size of around 100nm, which is much smaller than that of PEDOT, were prepared by the electrochemical method. Its small granule increased the active/nonactive mass ratio and reduced the ions diffusion length. Therefore, its specific capacitance of the composite was up to 200F g^?1, which was remarkably greater than that of PEDOT. Furthermore, the PEDOT/F-SWNTs composites had very rapid charge/discharge ability with specific capacitance of 180F g^?1 at scanning rate of 200mV s^?1 and 170F g^?1 at frequency of 1Hz, which is an important practical advantage. In addition, such composite had a good cycling performance and a wide potential window.     

Self-sustaining hybrid electrode prepared from polyaniline,carbon nanotubes,and carbon fibers: morphological,structural, and electrochemical analyses

The self-sustaining hybrid electrode was prepared via chemical polymerization of aniline in acid medium containing dispersed carbon nanotubes (CNT), using carbon fiber (CF) as conducting substrate. The ternary composites called PAni/CNT/CF were characterized in order to evaluate their morphologies, structures, and thermal properties. The influence of the polyaniline (PAni) layer in the ternary composite properties was studied considering different deposition times on CF samples (30, 60, and 90 min). The ternary composite morphologies were observed by scanning electron microscopy while thermal structural analyses were obtained using thermogravimetric measurements. The structural features were analyzed by Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). The possible interactions between PAni and CNT were discussed on the basis of Raman and FTIR spectra. These spectroscopic analyses also confirmed that the PAni present in the composite is in the emeraldine (ES) salt form. Furthermore, the ternary composites were also evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) techniques. The results showed good charge storage capacity for ternary composites, in particular, for PAni/CNT/CF obtained with 90 min of deposition time, which exhibited specific capacitance of around 500 F g^?1. Therefore, this electrode was selected to build a prototype of type I supercapacitor. This device presented specific capacitance of around 143 F g^?1 after 3200 charge/discharge cycles.     

The rods-like manganese dioxide films grown on nickel foam for electrochemical capacitor applications

MnO₂ films grown on nickel foam (NF) with a desirable 3D structure are investigated as electrochemical pseudocapacitor materials for potential energy storage applications. The prepared MnO₂ films are characterized by X-ray diffraction, FT-IR and scanning electron microscopy. Results indicate that the products are typical hexagonal ?-MnO₂ with a uniform nanorod structure. The electrochemical measurements showed that the MnO₂ films with rods-like morphology have excellent electrochemical performances and its specific capacitance value as single electrode is up to 664 F g^?1 at a discharge current density of 5.5 A g^?1, which is higher than that of most reported corresponding materials. The specific capacitance retention ratio is 76.7% at the current density range from 5.5 to 30 A g^?1. Furthermore, we found that the deposition conditions such as deposition potential and deposition mass have a pronounced effect on their electrochemical activities.     

Heteroatom‐Doped Porous Carbon Nanosheets: General Preparation and Enhanced Capacitive Properties

High‐performance electrical double‐layer capacitors (EDLCs) require carbon electrode materials with high specific surface area, short ion‐diffusion pathways, and outstanding electrical conductivity. Herein, a general approach combing the molten‐salt method and chemical activation to prepare N‐doped carbon nanosheets with high surface area (654 m² g^?1) and adjustable porous structure is presented. Owing to their structural features, the N‐doped carbon nanosheets exhibited superior capacitive performance, demonstrated by a maximum capacitance of 243 F g^?1 (area‐normalized capacitance up to 37 μF cm^?2) at a current density of 0.5 A g^?1 in aqueous electrolyte, high rate capability (179 F g^?1 at 20 A g^?1), and excellent cycle stability. This method provides a new route to prepare porous and heteroatom‐doped carbon nanosheets for high‐performance EDLCs, which could also be extended to other polymer precursors and even waste biomass.     

Core–Shell Carbon‐Coated CuO Nanocomposites: A Highly Stable Electrode Material for Supercapacitors and Lithium‐Ion Batteries

Herein we present a simple method for fabricating core–shell mesostructured CuO@C nanocomposites by utilizing humic acid (HA) as a biomass carbon source. The electrochemical performances of CuO@C nanocomposites were evaluated as an electrode material for supercapacitors and lithium‐ion batteries. CuO@C exhibits an excellent capacitance of 207.2 F g^?1 at a current density of 1 A g^?1 within a potential window of 0–0.46 V in 6 M KOH solution. Significantly, CuO electrode materials achieve remarkable capacitance retentions of approximately 205.8 F g^?1 after 1000 cycles of charge/discharge testing. The CuO@C was further applied as an anode material for lithium‐ion batteries, and a high initial capacity of 1143.7 mA h g^?1 was achieved at a current density of 0.1 C. This work provides a facile and general approach to synthesize carbon‐based materials for application in large‐scale energy‐storage systems.     

MnO2 Nanosheets Grown on Nitrogen‐Doped Hollow Carbon Shells as a High‐Performance Electrode for Asymmetric Supercapacitors

A hierarchical hollow hybrid composite, namely, MnO₂ nanosheets grown on nitrogen‐doped hollow carbon shells (NHCSs@MnO₂), was synthesized by a facile in situ growth process followed by calcination. The composite has a high surface area (251 m²g^?1) and mesopores (4.5 nm in diameter), which can efficiently facilitate transport during electrochemical cycling. Owing to the synergistic effect of NHCSs and MnO₂, the composite shows a high specific capacitance of 306 F g^?1, good rate capability, and an excellent cycling stability of 95.2 % after 5000 cycles at a high current density of 8 A g^?1. More importantly, an asymmetric supercapacitor (ASC) assembled by using NHCSs@MnO₂ and activated carbon as the positive and negative electrodes exhibits high specific capacitance (105.5 F g^?1 at 0.5 A g^?1 and 78.5 F g^?1 at 10 A g^?1) with excellent rate capability, achieves a maximum energy density of 43.9 Wh kg^?1 at a power density of 408 W kg^?1, and has high stability, whereby the ASC retains 81.4 % of its initial capacitance at a current density of 5 A g^?1 after 4000 cycles. Therefore, the NHCSs@MnO₂ electrode material is a promising candidate for future energy‐storage systems.     

Non‐Covalent Functionalization of Graphene with Bisphenol A for High‐Performance Supercapacitors

The reduced graphene oxide (RGO)/bisphenol A (BPA) composites were prepared by an adsorption‐reduction method. The composites are characterized by X‐ray diffraction (XRD), UV‐vis, thermogravimetric (TG) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results confirm that BPA is adsorbed on the basal plane of RGO by π‐π stacking interaction. Furthermore, the electrochemical behaviors were evaluated by cyclic voltammetry, galvanostatic charge/discharge techniques and electrochemical impedance spectroscopy (EIS). The results show that the RGO/BPA nanocomposites exhibit ultrahigh specific capacitance of 466 F·g^?1 at a current density of 1 A·g^?1, excellent rate capability (more than 81% retention at 10 A·g^?1 relative to 1 A·g^?1) and superior cycling stability (90% capacitance decay after 4000 cycles). Consequently, the RGO/BPA nanocomposites can be regarded as promising electrode materials for supercapacitor applications.