g-C3N4基超级电容器用电极材料的研究进展

超级电容器由于具有功率密度大、储放电速度快、循环寿命长等优点受到储能领域的极大关注，电极材料是其性能优劣的关键所在。而具有较高含氮量、活性位点多且形貌与稳定性良好的g-C₃N₄作为一种优秀的超级电容器电极材料受到研究者的青睐。本文综述了g-C₃N₄基超级电容器的结构特征以及储能机理，重点阐述了g-C₃N₄基复合材料的性能提升策略，最后梳理了g-C₃N₄基超级电容器电极材料的性能提升研究进展，明确了g-C₃N₄基复合材料具有优秀的超级电容器电极材料应用前景。     

三维筋撑石墨烯负载氧化锰的超级电容器

石墨烯基超级电容器,其功率密度较高,但能量密度受限。开发以三维石墨烯材料为载体的复合型赝电容多孔电极,是解决方案之一。本文采用铵盐辅助化学发泡法,制备了三维筋撑石墨烯泡沫体(SG);以SG为载体,采用水热还原法在其表面生长二氧化锰(MnO₂)纳米棒阵列,从而构建了MnO₂/SG自支撑多孔材料。利用MnO₂/SG复合电极,组装了超级电容器,在0.5 A·g^-1的电流密度下,比电容达343.6 F·g^-1;经5000次循环,其容量保持率为83.8%;在500 W·kg^-1的功率密度下,其能量密度达11.93 W·h·kg^-1。因此,MnO₂/SG复合电极是一种性能优异的赝电容材料,在电化学储能领域有良好的应用前景。     

橡胶木纤维素纳米纤丝/二氧化锰/碳纳米管柔性电极材料的制备及表征

以橡胶木为原料,通过化学处理得到橡胶木纯化纤维素(PCF),在此基础上通过高速剪切结合超声波处理制备得到纤维素纳米纤丝(CNF)。通过单相合成法制备二氧化锰(MnO₂)纳米片。以CNF为结构支撑体,MnO₂纳米片和碳纳米管(CNTs)作为活性电极物质,通过真空抽滤的方式制备CNF/MnO₂/CNTs柔性电极材料。采用多种手段对CNF、MnO₂以及电极材料的结构性能进行表征,并测试了电极材料的电化学性能。结构性能表征结果表明：CNF的直径为3~10 nm,具有大的长径比,是很好的结构支撑体,CNF为纤维素Ⅰ型结构;MnO₂纳米片为片层花瓣状结构,晶型为δ型。电化学性能测试结果表明：在扫描速率为50 mV/s时电极材料的比电容值为78.45 F/g,在电流密度为0.1 A/g时的电极材料比电容值为97.02 F/g,在低频区时,交流阻抗(EIS)曲线的直线部分斜率较大,表明电极材料具有良好的电容特性,在200次充放电循环测试过程中,电极材料的电容保留率始终维持在99%左右,表明该电极材料具有良好的电化学性能并且具有一定的柔性变形能力,可用作超级电容器的电极材料。     

石墨烯基材料在超级电容器中的研究进展

超级电容器作为一种新型的储能器件,具有广泛的应用前景。石墨烯基材料表现出优异的电化学性能,在超级电容器电极材料方面具有潜在的应用价值。文章简单对石墨烯/碳,石墨烯/金属氧化物,石墨烯/导电聚合物等三类石墨烯基超级电容器电极材料进行简单论述。     

二氧化锰基纳米复合材料电极在超级电容器应用中的研究进展

超级电容器是一种具有高的功率密度、良好的循环稳定性和快的充放电速率的储能器件。与传统的电容器相比,由于受到较高的成本和较低能量密度的限制,超级电容器目前仍很难替代传统能源。在此前提条件下,寻求一种电化学储能能力更强、成本更低的电极材料是目前超级电容器电极材料的研究重点。二氧化锰由于其价格低廉、来源广泛和能量密度高的优点成为当前研究最为广泛的电极材料之一。该文以二氧化锰基的纳米复合材料为研究对象,从二氧化锰的制备与改性方法的角度出发,总结了当前二氧化锰基的纳米复合材料在超级电容器方面的应用研究进展,并对未来的发展趋势提出了展望。     

表面化学反应控制制备多级结构电极材料及性能

超级电容器和锂离子电池等储能设备的研究和开发日益受到人们的关注。对于超级电容器和锂离子电池等储能设备,其电化学性能主要取决于电极材料,因此高效储能材料的制备成为开发高效储能设备的关键。本文主要介绍了多级结构过渡金属氧化物基电极材料的制备及性能,重点阐述了本实验室近年来在研制高性能超级电容器和锂离子电池方面的相关工作:基于表面化学反应控制制备多级结构金属氧化物、金属氢氧化物/碳嵌入式纳米杂化物以及多种三维结构的多元复合电极材料,表现出优异的电化学性能。     

高导电三明治状MnO2/CNTs/MnO2介孔材料的制备及其赝电容性能

MnO₂具有低成本、无毒性、高天然丰度和优异的理论比电容等优点,被认为是一种极具前景的超级电容器(SC)电极材料。赝电容电极材料MnO₂仍然存在导电性差以及充放电过程中易剥落的问题。本文利用恒电流沉积的方法在硝酸预氧化处理的碳纸表面制备了一种MnO₂/CNTs/MnO₂复合电极材料。X射线衍射(XRD)、扫描电子显微镜(SEM)和氮吸附测试证明,所制备的复合材料具有一种三明治状的夹层结构,同时富含5 nm左右的介孔,介孔结构能够保证电解液离子的高效传输。采用三维立体的碳纸能够为MnO₂提供丰富的附着位点,而电沉积法合成的α-MnO₂生长在有效的导电位点上,具有蓬松多孔的形貌,在MnO₂发生膨胀/收缩过程中,这种海绵状形貌可以有效降低材料受到的膨胀应力。中间层碳纳米管(CNTs)相互搭接于内外两层MnO₂之间,作为一种导电中继,提高了复合材料的导电性。该复合材料具有优异的电化学性能：在0.1 A·g^-1的电流密度下,能够获得428.8 F·g^-1的可逆比电容,并在5 A·g^-1的高电流密度下仍能具有80%的电容保持率。同时,电极表现出优异的循环稳定性,在1 A·g^-1循环6000次之后比电容仅衰减5%。     

免黏结剂V2O5和Fe2O3柔性电极的构建及在超级电容器中的应用

近年来,越来越多的研究致力于开发新型、超高能量密度、高法拉第反应活性的电极材料,尤其将其应用于新一代超级电容器储能系统。通过水热法直接在柔性基质碳布上生长海胆状V₂O₅纳米球和十四面体Fe₂O₃纳米盒子。V₂O₅微观结构和储能性能可通过改变水热时间进行调控。海胆状V₂O₅纳米球正极材料具有最高比容量535 F·g^-1。以十四面体Fe₂O₃纳米盒子作为负极材料组装的新型结构V₂O₅-CC//Fe₂O₃-CC柔性超级电容器,在功率密度为699.49 W·kg^-1时,能量密度可达46.06 W·h·kg^-1。而且具有良好的机械柔韧性,在180°弯曲循环测试5000次,比容量保持率仍高达83.4%。研究为开发下一代超高能量密度、柔性电子器件提供了一种通用而有效的策略。     

MnO2纳米空心球的制备及其电化学性能

采用水热法通过添加Ce离子制备了MnO₂纳米空心球电极材料。Ce离子对MnO₂的形貌和结晶程度有很大的影响,添加Ce离子后生成由纳米棒组成的中空球,中空球比表面积(BET)达到315.2 m²·g^-1。MnO₂电极电化学测试结果表明:当铈锰摩尔比为0.2时电极材料具有较好的电化学性能,其比电容达到178.6 F·g^-1,与未加Ce离子相比其比电容提高了2.6倍,而且经过1000次循环稳定性测试后比电容仍保留了90.5%。这些结果表明添加Ce离子有利于形成中空结构,并提高了MnO₂电极的比电容。     

一维有序聚苯胺纳米阵列在超级电容器中的研究进展

从聚苯胺（polyaniline, PANI）的结构特征和导电机理出发,详细叙述了一维有序PANI纳米阵列的优点及各种制备方法,指出了PANI纳米阵列作为超级电容器电极材料的优势。根据电极材料分类,重点综述了PANI阵列结构基与导电高分子材料、碳材料、金属氧化物复合作为超级电容器电极材料的应用情况;讨论了这些电极材料的结构特点、制备方法、提高电化学储能性的机理及上述研究中存在的问题;最后根据存在的问题,提出进一步优化PANI阵列结构基电极材料电化学性能的制备方法与策略,并对未来PANI阵列结构基电极材料在超级电容器的发展前景进行了展望。     

A novel LiTi2(PO4)3/MnO2 hybrid supercapacitor in lithium sulfate aqueous electrolyte

In this work, carbon-coated lithium-ion intercalated compound LiTi₂(PO₄)₃ and MnO₂ have been synthesized and they deliver a capacity of 90 and 60 mAh/g in 1 M Li₂SO₄ neutral aqueous electrolyte within safe potentials without O₂ and H₂ evolution, respectively. The novel hybrid supercapacitor in which MnO₂ was used as a positive electrode and carbon-coated LiTi₂(PO₄)₃ as a negative electrode was assembled and the LiTi₂(PO₄)₃/MnO₂ hybrid supercapacitor showed a sloping voltage profile from 0.7 to 1.9 V, at an average voltage near 1.3 V, and delivers a capacity of 36 mAh/g and an energy density of 47 Wh/kg based on the total weight of the active electrode materials. It exhibits a desirable profile and maintains over 80% of its initial energy density after 1000 cycles. The hybrid supercapacitor also exhibit an excellent rate capability, even at a power density of 1000 W/kg, it has a specific energy 25 Wh/kg compared with 43 Wh/kg at the power density about 200 W/kg.     

Ni(OH)2与不同碳质材料复合制备超级电容器电极材料研究进展

超级电容器具有功率密度大、寿命长、生产成本低等优点,被认为是最有发展前途的储能系统之一。然而,超级电容器的低能量密度阻碍了其实际应用。由于存储的能量与CV2成正比,可以通过增加材料的电容"C"或操作电压窗口"V"或两者同时增加来提高超级电容器的能量密度。然而具有宽电位窗口的有机电解质离子往往电导率差,成本高,容易引起环境问题。因此为改善能量密度,应采用高比电容的电极材料,故而设计出具有高比电容的适合电极材料就成为研究热点。Ni(OH)2作为超级电容器电极材料,具有理论容量大、成本低、天然丰富、易于合成等优点,近年来备受关注。但由于Ni(OH)2导电率低、比表面积小,其容量劣化严重。碳质材料作为双电层超级电容器的电极材料,其能量存储机制取决于电极表面的电解质离子吸附和解离,具有导电率好、原料丰富、成本较低、电化学稳定性高等优点而应用广泛。因此,有必要将高导电碳质材料引入Ni(OH)2组成复合材料以提高电容性能。笔者综述了Ni(OH)2基材料的合成方法,特别是与碳质材料复合来提高Ni(OH)2基材料的循环稳定性和倍率性能方面的研究新进展。     

Bi2O3 modified cobalt hydroxide as an electrode for alkaline batteries

Manganese dioxide electrode shows reversible charge storage capacity, if the charge-discharge process is limited to 0.3e⁻ exchange. Addition of small amount of Bi₂O₃ to manganese dioxide induces reversibility with an exchange of 2e⁻/Mn. Nickel hydroxide is known to reversibly exchange 1e⁻. In spite of isostructural relationship between the cobalt hydroxide, nickel hydroxide and manganese dioxide, cobalt hydroxide does not show any electrochemical activity. Bi₂O₃ modified cobalt hydroxide electrodes exchanges 0.3-0.5e⁻/Co during the charge discharge process. The oxidation-reduction process in cobalt hydroxide and Bi₂O₃ modified cobalt hydroxide electrodes were monitored using the PXRD patterns.     

Studies of electrodeposition from Mn(II) species of thin layers of birnessite onto transparent semiconductor

This paper describes successful electrodeposition of very homogeneous, adherent and well-crystallized thin layers of birnessite on a cheap transparent semiconductor substrate, SnO₂, in neutral sulphate solutions. Birnessite, a layered manganese oxide, plays an important role in environmental chemistry due to its large surface area. A coupled approach based on electrochemical measurements and pH measurements allowed us to give information about electrodeposition mechanism of birnessite. An intermediary Mn(III) compound, α-MnOOH (groutite), is formed in deaerated solutions leading to mixed thin layers of birnessite and groutite. But, thin layers of pure birnessite can be efficiently electrodeposited in aerated solutions due to the oxidation of groutite by dissolved oxygen in such solutions. Thin layers of pure birnessite are well suitable for studies devoted to environmental applications as hazardous waste remediation or chemical sensors but also as electrode material for energy storage.     

Microwave-hydrothermal synthesis of Fe-based materials for lithium-ion batteries and supercapacitors

Fe-based materials, Fe₂O₃, Fe₃O₄, and FeOOH, were synthesized by the microwave–hydrothermal process in the temperature range of 100–200 °C and under very short reaction times of 15 min to 2 h. Under microwave-controlled hydrolysis and redox reactions, cube-like Fe₂O₃ was crystallized using FeCl₃, Fe₃O₄ particles were crystallized from FeCl₂ and FeOOH nanorods were crystallized using FeCl₃. The Fe-based materials were fabricated to make anodes and cathodes of lithium-ion battery and supercapacitor electrode materials to study their potential electrochemical applications. The electrochemical results showed that FeOOH had better anode capacity as lithium-ion batteries than those of Fe₂O₃ and Fe₃O₄. The present results suggest that the microwave–hydrothermally synthesized Fe-based materials are promising lithium-ion battery anode materials.     

Oxidative energy storage behavior of a porous nanostructured TiO2–Ni(OH)2 bilayer photocatalysis system

TiO₂–Ni(OH)₂ bilayer electrodes were prepared by the cathodic electrodeposition of Ni(OH)₂ layer on a TiO₂/ITO substrate. The porous Ni(OH)₂ layers were obtained at relatively high current densities (≥1.0 mA cm⁻²), and the particle size increased with increasing the deposition current density. A porous nanostructured TiO₂–Ni(OH)₂ bilayer was obtained at a current density of 1.0 mA cm⁻². The effects of OH⁻ concentration in the electrolyte and surface structure in the Ni(OH)₂ layer on storage of the oxidative energy of TiO₂ were investigated. In our experimental conditions the oxidative energy storage of an UV-irradiated TiO₂ photocatalyst in Ni(OH)₂ was obviously enhanced in the electrolyte with 1.0 M OH⁻. The porous nanostructured TiO₂–Ni(OH)₂ bilayer electrode showed the notably improved oxidative energy storage performance, resulting from its porous structure and nanostructured Ni(OH)₂ particles. The TiO₂–Ni(OH)₂ bilayer electrode during UV irradiation exhibited much higher potentials and larger photocurrent than the TiO₂/ITO electrode. The transition from Ni(OH)₂ to NiOOH under UV irradiation proceeded in the potential range of −0.5 to −0.2 V, much more negative than the Ni(OH)₂/NiOOH redox potential. A possible mechanism on the oxidative energy storage of an UV-irradiated TiO₂ photocatalyst in Ni(OH)₂ was proposed, and the related experimental results were discussed in terms of the suggested model.     

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

Conductive and porous nitrogen-rich materials have great potential as supercapacitor electrode materials. The exceptional efficiency of such compounds, however, is dependent on their larger surface area and the level of nitrogen doping. To address these issues, we synthesized a porous covalent triazine framework (An-CTFs) based on 9,10-dicyanoanthracene (An-CN) units through an ionothermal reaction in the presence of different molar ratios of molten zinc chloride (ZnCl₂) at 400 and 500 °C, yielding An-CTF-10-400, An-CTF-20-400, An-CTF-10-500, and An-CTF-20-500 microporous materials. According to N₂ adsorption–desorption analyses (BET), these An-CTFs produced exceptionally high specific surface areas ranging from 406–751 m²·g⁻¹. Furthermore, An-CTF-10-500 had a capacitance of 589 F·g⁻¹, remarkable cycle stability up to 5000 cycles, up to 95% capacity retention, and strong CO₂ adsorption capacity up to 5.65 mmol·g⁻¹ at 273 K. As a result, our An-CTFs are a good alternative for both electrochemical energy storage and CO₂ uptake.     

Meldola blue immobilized on a new SiO2/TiO2/graphite composite for electrocatalytic oxidation of NADH

Meldola blue immobilized on a new SiO₂/TiO₂/graphite composite was applied in the electrocatalytic oxidation of NADH. The materials were prepared by the sol-gel processing method and characterized by several techniques including scanning electronic microscopy coupled to energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electronic microscopy (HRTEM). Si and Ti mapping profiles on the surface showed a homogeneous distribution of the components. Ti2p binding energy peaks indicate that the formation of Si-O-Ti linkage is presumably the responsible for the high rigidity of the matrices. The good electrical conductivity presented by the composites (5 and 11 S cm⁻¹) can be related to a homogeneous distribution of graphite particles observed by TEM. After the materials characterization, a SiO₂/TiO₂/graphite electrode was prepared and some chemical modifications were performed on its surface to promote the adsorption of meldola blue. The resulting system presented electrocatalytic properties toward the oxidation of NADH, decreasing the oxidation potential to −120 mV. The proposed sensor showed a wide linear response range from 0.018 to 7.29 mmol l⁻¹ and limit of detection of 0.008 mmol l⁻¹. SiO₂/TiO₂/graphite has shown to be a promising material to be used as a suitable support in the construction of new electrochemical sensors.     

Electrochemical performances of poly(3,4-ethylenedioxythiophene)-NiFe2O4 nanocomposite as electrode for supercapacitor

Poly 3,4-ethylenedioxythiophene (PEDOT)-based NiFe₂O₄ conducting nanocomposites were synthesized and their electrochemical properties were studied in order to find out their suitability as electrode materials for supercapacitor. Nanocrystalline nickel ferrites (5-20 nm) have been synthesized by sol-gel method. Reverse microemulsion polymerization in n-hexane medium for PEDOT nanotube and aqueous miceller dispersion polymerization for bulk PEDOT formation using different surfactants have been adopted. Structural morphology and characterization were studied using XRD, SEM, TEM and IR spectroscopy. Electrochemical performances of these electrode materials were carried out using cyclic voltammetry at different scan rates (2-20 mV/s) and galvanostatic charge-discharge at different constant current densities (0.5-10 mA/cm²) in acetonitrile solvent containing 1 M LiClO₄ electrolyte. Nanocomposite electrode material shows high specific capacitance (251 F/g) in comparison to its constituents viz NiFe₂O₄ (127 F/g) and PEDOT (156 F/g) where morphology of the pore structure plays a significant role over the total surface area. Contribution of pseudocapacitance (C_FS) arising from the redox reactions over the electrical double layer capacitance (C_DL) in the composite materials have also been investigated through the measurement of AC impedance in the frequency range 10 kHz-10 mHz with a potential amplitude of 5 mV. The small attenuation (∼16%) in capacitance of PEDOT-NiFe₂O₄ composite over 500 continuous charging/discharging cycles suggests its excellent electrochemical stability.     

Electrochemically Activated CNT Sheet as a Cathode for Zn-CO2 Batteries

High demand for electrochemical storage devices is increasing the need for high-performance batteries. A Zn-CO₂ battery offers a promising solution for CO₂ reduction as well as energy storage applications. For this study, a Zn-CO₂ battery was fabricated using a Carbon Nanotube (CNT) sheet as a cathode and a Zn plate as an anode. The electrochemical activation technique was used to increase the surface area of the CNT electrode by roughly 4.5 times. Copper (Cu) as a catalyst was then deposited onto the activated CNT electrode using electrodeposition method and different Cu loadings were investigated to optimize CO₂ reduction. The final assembled Zn-CO₂ battery has a 1.6 V output voltage at a current density of 0.063 mA/cm², which is higher than most devices reported in the literature. This study demonstrates the importance of activation process which enabled more catalyst loading on the cathode resulted in additional active sites for electroreduction process. This paper presents the activated CNT sheet as a promising cathode material for Zn-CO₂ batteries.