Highly specific capacitance materials constructed via in situ synthesis of polyaniline in a cellulose matrix for supercapacitors

On the basis of the requirements for both biobased economy and energy storage materials, we are interested in using cellulose-based microporous film as a template for in situ synthesis of polyaniline (PANI). Multifunctional carbon nanotube (CNT)/cellulose composite films were also prepared from a CNT/cellulose suspension in a NaOH/urea aqueous system. Subsequently, PANI was synthesized in situ in the pores of cellulose and CNT/cellulose substrates to construct PANI/cellulose (PC) films and PANI/CNT/cellulose (PCC) films, respectively. Both PC and PCC films were flexible and exhibited a highly specific capacitance and good cycle stability. With the addition of CNTs, the specific capacitance of the PCC films as supercapacitor materials was significantly improved. Moreover, a homogeneous structure intertwined with the cellulose, CNTs and PANI appeared in the composite films, indicating good miscibility. This work has provided a new approach to the fabrication of flexible, lightweight, highly effective, and low-cost energy storage materials, broadening the applications of cellulose.     

Carbon Nanotube Fibers Decorated with MnO2 for Wire-Shaped Supercapacitor

Fibers made from CNTs (CNT fibers) have the potential to form high-strength, lightweight materials with superior electrical conductivity. CNT fibers have attracted great attention in relation to various applications, in particular as conductive electrodes in energy applications, such as capacitors, lithium-ion batteries, and solar cells. Among these, wire-shaped supercapacitors demonstrate various advantages for use in lightweight and wearable electronics. However, making electrodes with uniform structures and desirable electrochemical performances still remains a challenge. In this study, dry-spun CNT fibers from CNT carpets were homogeneously loaded with MnO₂ nanoflakes through the treatment of KMnO₄. These functionalized fibers were systematically characterized in terms of their morphology, surface and mechanical properties, and electrochemical performance. The resulting MnO₂–CNT fiber electrode showed high specific capacitance (231.3 F/g) in a Na₂SO₄ electrolyte, 23 times higher than the specific capacitance of the bare CNT fibers. The symmetric wire-shaped supercapacitor composed of CNT–MnO₂ fiber electrodes and a PVA/H₃PO₄ electrolyte possesses an energy density of 86 nWh/cm and good cycling performance. Combined with its light weight and high flexibility, this CNT-based wire-shaped supercapacitor shows promise for applications in flexible and wearable energy storage devices.     

Fabrication of 3D ordered needle-like polyaniline@hollow carbon nanofibers composites for flexible supercapacitors

Carbon nanofiber-based supercapacitors have broad prospects in powering wearable electronics owing to their high specific capacity,fast charge/discharge process,along with long-cycling life.Herein,a poly(ac rylo n it rile-co-β-methyl hydrogen itaconate) copolymer was prepared and used to synthesize flexible hollow carbon nanofibers(HCNFs) via an electrospinning method without breaking after multiple bending.Subsequently,the inner and outer surfaces of HCNFs were evenly covered with ordered needlelike polyaniline(PANI) through in-situ polymerization methods to obtain three-dimensional flexible HCNFs/PANI composites,which exhibited a high capacity 1196.7 F/g at 1 A/g and good cycling stability(90.1% retention at 5 A/g after 3000 cycles).The symmetrical supercapacitor based on the HCNFs/PANI composites also delive red an outsta nding electrochemical performance with high energy/power density(60.28 Wh/kg at 1000 W/kg) and superior cycling durability(90% capacitance retention after at 5 A/g3000 cycles),which confirmed that the HCNFs/PANI composites had a wide application potential in flexible energy storage devices.     

碳纳米管薄膜的制备及其在柔性电子器件中的应用

近年来,柔性电子器件的发展日新月异。以碳纳米管为代表的碳纳米材料,尤其是其组装成的宏观结构碳纳米管薄膜具有良好的柔性和优异的导电性,且具有化学稳定、热稳定、光学透明性等优点,在柔性电子领域展现了极大的应用潜力。本文简要综述了近年来碳纳米管薄膜在柔性电子器件领域的研究进展。首先详细介绍了碳纳米管薄膜的两类主要制备方法,分别为干法制备和湿法制备;继而介绍了碳纳米管薄膜在多种柔性电子器件的组装、性能与应用方面的最新研究进展;最后总结了碳纳米管薄膜基柔性电子领域的发展现状,并讨论了该领域所面临的挑战及其未来前景。     

Effects of Precursors and Carbon Nanotubes on Electrochemical Properties of Electrospun Nickel Oxide Nanofibers-Based Supercapacitors

Supercapacitors have been considered as one of the main energy storage devices. Recently, electrospun nanofibers have served as promising supercapacitor electrodes because of their high surface area, high porosity, flexibility, and resistance to aggregation. Here, we investigate the effects of electrospinning parameters and nickel precursors on the nanostructure of electrospun nickel oxide (NiO), as well as on their electrochemical performance as supercapacitor electrodes. In contrast to the case of using nickel nitrate, increasing the nickel acetate molar concentration maintains the flexible fibrous sheet morphology of the as-spun sample during the polycondensation and calcination of NiO. As a result, our flexible electrode of NiO nanofibers derived from nickel acetate (NiO-A) exhibits much better electrochemical performance values than that of nickel nitrate-derived NiO. To further improve the electrochemical storage performance, we combined NiO-A nanofibers with single-walled carbon nanotubes (CNTs) as a hybrid electrode. In both half-cell and full-cell configurations, the hybrid electrode displayed a higher and steadier areal capacitance than the NiO-A nanofibers because of the synergetic effect between the NiO-A nanofibers and CNTs. Altogether, this work demonstrates the potency of the hybrid electrodes combined with the electrospun NiO-A nanofibers and CNTs for supercapacitor applications.     

碳材料在电化学储能中的应用

电化学储能材料是电化学储能器件发展及性能提高的关键之一. 碳材料在各种电化学储能体系中都起到了极为重要的作用,特别是近期出现的各类新型碳材料为电化学储能的发展带来了新动力,并展现了广阔的应用前景. 本文综述了碳材料,特别是以碳纳米管和石墨烯为代表的纳米碳材料,在典型电化学储能器件（锂离子/钠离子电池、超级电容器和锂硫电池等）、柔性电化学储能和电化学催化等领域的研究进展,并对碳材料在这些领域的应用前景进行了展望.     

Facile preparation of highly conductive,flexible, and strong carbon nanotube/polyaniline composite films

In general, the high electrical conductivity (EC) comes into conflict with the good flexibility and high strength of carbon nanotube (CNT)/polyaniline (PANI) composites. In other words, a high CNT content will bring about a high EC but lead to a low flexibility and strength due to the CNT‐constrained matrix deformation and CNT aggregation. In this work, a highly conductive, flexible and strong CNT/PANI composite film prepared via a facile solvent‐evaporation method is readily obtained by a cold stretching. The cold stretching is conducted at room temperature for the CNT/PANI film. It is observed that the cold stretching process leads to an unexpectedly enhanced EC. The as‐obtained EC of 231 S/cm is much higher than that (2 – 50 S/cm) of the previously reported CNT/PANI composite films. Meanwhile, the strength is obviously improved over that of the pure PANI film and the good flexibility is maintained to a high degree by the introduction of a proper CNT content. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1575–1585     

三元复合材料PANI／Ag／MWNT的电化学行为和比电容

通过原位聚合的方式在银纳米粒子/多壁碳纳米管（Ag/MWCNT）复合材料的表面成功聚合苯胺单体制备了聚苯胺/银纳米粒子/多壁碳纳米管（PANI/Ag/MWCNT）三元复合材料苯．通过对三元复合材料的结构以及表面形貌进行分析,表明聚苯胺层完全包覆了Ag/MWCNT复合材料,形成了核壳式结构．同时银纳米粒子则以单质晶体的形态存在于多壁碳纳米管与聚苯胺层之间．三元复合材料电极在1 mol/L的KOH溶液中具有极低的阻抗,而与聚苯胺电极相比,这些复合材料电极则表现出更低的电阻、更高的电化学活性和更好的循环稳定性．尤其是当苯胺和Ag：MWCNTs质量比为5：5时,该复合材料电极在0.25 A/g的电流密度下表现出最大的比电容值为160 F/g．     

Recent developments in MoS2-based flexible supercapacitors

In the modern world, miniaturization of electronic devices for various applications is becoming more common. In particular, the development of flexible energy storage devices have received much attention since they have a superior role in the development of newer technologies such as in public wearables, portable electronic devices, and electronic skin proceeds. Considering the high power density, long cycle life, and shelf life as well as outstanding mechanical strength, flexible supercapacitors are one of the integral parts of these new technologies. In the recent past, researchers have developed innumerable nanomaterials to develop supercapacitors. Among these, MoS₂ has received much attention due to its several physical and chemical properties, which are more favorable for energy storage applications. Their sheet-like structure, high surface-to-volume ratio, ease of synthesis, flexibility, high mechanical strength, and pseudocapacitive storage mechanism make them potential candidates for flexible storage applications similar to graphene. This review provides recent applications and scope of MoS₂ in flexible supercapacitors in both composite forms with other carbon nanomaterials, metal oxides, and polymers as well as MoS₂ itself. Also, we will discuss some MoS₂-based self-standing devices, which can generate and store energy in a single device.     

Challenges and prospects of metal sulfide materials for supercapacitors

Worldwide, the research on advanced materials for energy storage devices has drawn greater attention. Numerous works on different energy storage materials has been reported and still continuing. Among the energy storage devices, electrochemical supercapacitors (ESs) are one of the most investigated topics. The globalization and increasing demand of smart and flexible devices has forced the current research to develop low-cost, high-energy density and stable ESs. In this regard, metal sulfides (MSs)–based materials have been envisioned for ESs applications owing to their unique and promising properties. Recently, several research articles have been published on MSs-based electrodes for ESs with enhanced performances. This review presents a brief survey on such recent developments towards synthesis of MSs and their use as an efficient electrode material in ESs. The challenges and future aspect involved with MSs to develop and establish it as a promising energy storage material are also discussed.     

Lignin in storage and renewable energy applications:A review

Lignin is a cheap, abundant and non-toxic group of complex phenolic polymers obtained in large amounts from the papermaking and cellulosic biofuel industries. Although the application of lignin has been explored in these and several more industries, there are limited applications of lignin in the energy industry.However, numerous research revealed a great interest in the exploration of this renewable biopolymer in storage energy devices. Some of these applications include the use of lignin as an expander for lead-acid batteries, electrodes for primary and rechargeable batteries, electrodes for electronic double layer capacitors and electrochemical pseudocapacitors, and to feed different types of fuel cells. The use of lignin in energy storage devices improves not only the performance of these devices but also decreases the price and toxicity, contributing to obtaining greener energy devices. Based on the above, this review provides an overview of the main research work related to the use of lignin as a renewable component, suitable to replace some synthetic and toxic compounds used in the fabrication of energy storage devices with particular emphasis on batteries, advanced supercapacitors, and solar and fuel cells.     

Carbon‐Nanotube Based Electrochemical Biosensors: A Review

This review addresses recent advances in carbon‐nanotubes (CNT) based electrochemical biosensors. The unique chemical and physical properties of CNT have paved the way to new and improved sensing devices, in general, and electrochemical biosensors, in particular. CNT‐based electrochemical transducers offer substantial improvements in the performance of amperometric enzyme electrodes, immunosensors and nucleic‐acid sensing devices. The greatly enhanced electrochemical reactivity of hydrogen peroxide and NADH at CNT‐modified electrodes makes these nanomaterials extremely attractive for numerous oxidase‐ and dehydrogenase‐based amperometric biosensors. Aligned CNT “forests” can act as molecular wires to allow efficient electron transfer between the underlying electrode and the redox centers of enzymes. Bioaffinity devices utilizing enzyme tags can greatly benefit from the enhanced response of the biocatalytic‐reaction product at the CNT transducer and from CNT amplification platforms carrying multiple tags. Common designs of CNT‐based biosensors are discussed, along with practical examples of such devices. The successful realization of CNT‐based biosensors requires proper control of their chemical and physical properties, as well as their functionalization and surface immobilization.     

Printing polyaniline for sensor applications

In recent years, much research has focused on the development of low-cost, printed electrochemical sensor platforms for environmental monitoring and clinical diagnostics. Much effort in this area has been based on utilising the redox properties of conducting polymers, particularly polyaniline (PANI). In tackling the inherent lack of processability exhibited by these materials, several groups have examined various mass-amenable fabrication approaches to obtain suitable thin films of PANI for sensing applications. Specifically, the approaches investigated over the years include the in situ chemical synthesis of PANI, the use of sulphonated derivatives of PANI and the synthesis of aqueousbased nano-dispersions of PANI. Nano-dispersions have shown a great deal of promise for sensing applications, given that they are inkjet-printable, facilitating the patterning of conducting polymer directly to the substrate. We have shown that inkjet-printed films of PANI can be finely controlled in terms of their two-dimensional pattern, thickness, and conductivity, highlighting the level of precision achievable by inkjet printing. Utilising these nanomaterials as inkjet-printable inks opens novel, facile, and economical possibilities for conducting polymer-printed electronic applications in areas of sensing, but also many other application areas such as energy storage, displays, organic light-emitting diodes. Given that inkjet-printing is a scalable manufacturing technique, it renders possible the large-scale production of devices such as sensors for a range of applications. Several successes have emerged from our work and from the work of others in the area of applying PANI in low-cost sensor applications, which is the focus of this review.     

Optimized carbon nanotube fiber microelectrodes as potential analytical tools

The preparation and interesting electrochemical properties of carbon nanotube (CNT) fiber microelectrodes are reported. By combining the advantages of CNT with those of fiber electrodes, this type of microelectrode differs from CNT-modified or CNT-containing composite electrodes, because they are made solely of CNT without other components, for example additives or binders. The performance of these electrodes has been characterized with regard to, among others, the electrocatalytic oxidation of analytes via dehydrogenase-mediated reactions. In this context the reversible regeneration of the coenzyme NAD(+) using a mediator is a key step in the development of new amperometric sensor devices and we have successfully immobilized mediator molecules that are very efficient for this purpose on the surface of the CNT fiber electrode. The microelectrodes thus obtained have been compared with classic carbon microelectrodes and have promising behavior in biosensing applications, especially after specific pretreatments such as CNT alignment inside the fiber or expansion of the specific surface by chemically induced swelling.     

基于阵列电极的新型混合电容器

混合电容器由于兼具电池高能量密度和超级电容器高功率密度的优势,成为当前储能领域的研究热点。然而,电池电极和电容电极之间容量和功率的不平衡严重限制了混合电容器的实际性能。因此,如何实现二者的有效匹配,优化器件性能是混合电容器实用化的关键。阵列电极的使用打破传统粉末电极中不导电粘结剂对电化学动力学的限制,其独特的结构为正负极的匹配提供了新策略。此专论结合新型储能器件的研究现状以及本课题组在混合电容器方面的探索,简单探讨了混合电容器的储能机理和阵列结构作为电极材料的优势,着重介绍了本课题组近年来在混合电容器领域的研究工作,针对存在的科学问题提出了相应的解决方案,阐明了阵列电极混合电容器在柔性/可穿戴电子器件等领域的应用前景,并展望了混合电容器在未来的发展方向和挑战。     

Removal of toxic metal ions using chitosan coated carbon nanotube composites for supercapacitors

Environmental pollution and energy crisis are two major global challenges to human beings.Recovering energy from wastewater is considered to be one of the effective approaches to address these two issues synchronously.As the main pollutants in wastewater,toxic heavy metal ions are the potential candidates for energy storage devices with pseudocapacitive behaviors.In this study,toxic metal ions of Cr(VI)and Cu(II)are removed efficiently by chitosan coated oxygen-containing functional carbon nanotubes,and the corresponding equilibrium adsorption capacity is 142.1 and 123.7 mg g~(-1).Followed by carbonization of metal ions-adsorbed adsorbents,Cu-and Cr N-loaded carbon composites can be obtained.Electrochemical measurements show that the supercapacitor electrodes based on Cu-and Cr N-loaded carbon composites have specific capacitance of 144.9 and 114.9 F g~(-1)at2 m V s~(-1),with superior electrochemical properties to pure chitosan coated carbon nanotubes after carbonization.This work demonstrates a new strategy for the resource-utilization of other heavy metal ions for energy devices,and also provides a new way to turn environmental pollutants into clean energy.     

氧化石墨烯诱导的Ni-Co氢氧化物整体电极的制备及电储能特性

超级电容器作为一种新型储能装置,由于其能量密度、功率密度高和良好的循环稳定性,而在实际工业应用中(新能源汽车、航天航空业、电子通信系统、可穿戴设备等)显示出巨大的潜力.但目前面临的最大挑战是构造柔性、轻薄可变形的储能设备.在本项研究工作中,利用溶剂热法和真空抽滤法开发了一种碳基/层状金属氢氧化物的复合材料.设计将氧化石...     

Electrochemical Energy Storage Electrodes via Citrus Fruits Derived Carbon: A Minireview

This review investigates the synthesis and electrochemical performance of the electrode of the electrochemical energy storage (EES) devices obtained from peels and scraps of the citrus fruits. The EES devices include batteries, supercapacitors, and hybrid systems that have considerable value and various applications. The electrode is considered as the most important part of all EES devices. Tremendous efforts have been done to enhance the electrochemical energy storage electrode (EESE). The citrus fruits abundance leads to a decrease in their price and makes possible to use them as ingredients to fabricate EESE. Also, the electrochemical analyses determined that citrus fruits have considerable potential to use as the EESE. Using citrus fruits peels and scraps as biomass substances to prepare EESE leads to the electrodes which have low cost, environmentally friendly and appropriate electrochemical applications.     

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.     

Magnetic loading of carbon nanotube/nano-Fe3O4 composite for electrochemical sensing

An electrochemical sensing platform was developed based on the magnetic loading of carbon nanotube (CNT)/nano-Fe₃O₄ composite on electrodes. To demonstrate the concept, nano-Fe₃O₄ was deposited by the chemical coprecipitation of Fe²⁺ and Fe³⁺ in the presence of CNTs in an alkaline solution. The resulting magnetic nanocomposite brings new capabilities for electrochemical devices by combining the advantages of CNT and nano-Fe₃O₄ and provides an alternative way for loading CNT on electrodes. The fabrication and the performances of the magnetic nanocomposite modified electrodes have been described. Cyclic voltammetry (CV) and constant potential measurement indicated that the incorporated CNT exhibited higher electrocatalytic activity toward the redox processes of hydrogen peroxide. In addition, chitosan (CTS) has also been introduced into the bulk of the CNT/nano-Fe₃O₄ composite by coprecipitation to immobilize glucose oxidase (GOx) for sensing glucose. The marked electrocatalytic activity toward hydrogen peroxide permits effective low-potential amperometric biosensing of glucose, in connection with the incorporation of GOx into CNT/Fe₃O₄/CTS composite. The accelerated electron transfer is coupled with surface renewability. TEM images and XRDs offer insights into the nature of the magnetic composites. The concept of the magnetic loading of CNT nanocomposites indicates great promise for creating CNT-based biosensing devices and expands the scope of CNT-based electrochemical devices.