MnO2/carbon nanotube free-standing electrode recycled from spent manganese-oxygen battery as high-performance supercapacitor material

Journal of Materials Science - Metal–oxygen batteries have been growing rapidly as an energy storage technology in light of their high specific energy density. However, waste...     

Fabrication horizontal aligned MoO2/single-walled carbon nanotube nanowires for electrochemical supercapacitor

The horizontally aligned MoO₂/single-walled carbon nanotube (MoO₂/SWNT) composite has been prepared by electrochemically induced deposition method which utilizes the good electronic conductivity of SWNTs as supporting material to deposit MoO₂. The morphology and crystal structure of the composite were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The capacitive properties of the MoO₂/SWNT composites have been investigated by cyclic voltammetry (CV). A specific capacitance (based on MoO₂) as high as 597 F g^− 1 is obtained at a scan rate of 10 mV s^− 1 in 0.1 M Na₂SO₄ aqueous solution. Additionally, the MoO₂/SWNT composites electrode shows excellent long-term cycle stability (only 2.5% decrease of the specific capacitance is observed after 600 CV cycles).     

Three-dimensional heterostructured MnO2/graphene/carbon nanotube composite on Ni foam for binder-free supercapacitor electrode

In this article, three-dimensional (3D) heterostructured of MnO₂/graphene/carbon nanotube (CNT) composites were synthesized by electrochemical deposition (ELD)-electrophoretic deposition (EPD) and subsequently chemical vapour deposition (CVD) methods. MnO₂/graphene/CNT composites were directly used as binder-free electrodes to investigate the electrochemical performance. To design a novel electrode material with high specific area and excellent electrochemical property, the Ni foam was chosen as the substrate, which could provide a 3D skeleton extremely enhancing the specific surface area and limiting the huge volume change of the active materials. The experimental results indicated that the specific capacitance of MnO₂/graphene/CNT composite was up to 377.1 F g^?1 at the scan speed of 200 mV s^?1 with a measured energy density of 75.4 Wh kg^?1. The 3D hybrid structures also exhibited superior long cycling life with close to 90% specific capacitance retained after 500 cycles.     

Integrating carbon nanotube into activated carbon matrix for improving the performance of supercapacitor

A method of in situ integrating carbon nanotubes (CNTs) into activated carbon (AC) matrix was developed to improve the performance of AC as a supercapacitor electrode. Glucose solution containing pre-dispersed CNTs was hydrothermally carbonized to be a char-like intermediate product, and finally converted into a “tube-in-AC” structure by the chemical activation using KOH. The “tube-in-AC” composite had oxygen content of 12.98 wt%, specific surface area of 1626 m²/g and 90% of 1–2 nm micropores. It exhibited capacitance of 378 F/g in the aqueous KOH electrolyte and excellent cyclibility under high current, that is, the capacitance only decreased 4.6% after 2000 cycles at scanning rate of 100 mV/s. These performances of “tube-in-AC” electrode are better than those of commercial AC electrodes, post-mixed with CNTs or carbon black.     

琼脂隔膜 MnO2/C超级电容器的研究

通过液相法制备了α相和γ相组成的纤维状：MnO2电极材料,并以琼脂为基体,通过聚丙烯酰胺(PAM)改性,制备了新型超级电容器隔膜材料。当PAM含量达到800ppm时,改性琼脂膜的吸液率与保液率分别为400．1％和335．1％,且隔膜韧性也得到改善。应用此隔膜的：MnO2／C超级电容器放电比容量可达23．4F／cm^3,比琼脂膜提高了49％,此时ESR仅为54mΩ,同时千次循环容量衰减幅度仅为10％。     

Activated carbon–carbon nanotube composite porous film for supercapacitor applications

Activated carbon/carbon nanotube composite electrodes have been assembled and tested in organic electrolyte (NEt₄BF₄ 1.5 M in acetonitrile). The performances of such cells have been compared with pure activated carbon-based electrodes. CNTs content of 15 wt.% seems to be a good compromise between power and energy, with a cell series resistance of 0.6 Ω cm² and an active material capacitance as high as 88 F g⁻¹.     

Morphology-controlled synthesis of MnO2 grown on carbon fiber paper for high-rate supercapacitor electrode

Journal of Materials Science: Materials in Electronics - Nanostructured MnO2 with different morphologies based on carbon fiber paper (CFP) had been successfully synthesized via a hydrothermal...     

Silicide-induced multi-wall carbon nanotube growth on silicon nanowires

A novel multi-walled carbon nanotube (MWNT) growth process is reported based on carbon incorporation in a nickel catalyst layer deposited via plasma-enhanced atomic layer deposition (PEALD) on silicon nanowires and silicon wafer substrates. As-deposited PEALD Ni films containing relatively high amounts of carbon (>18?at.%) were observed to promote the growth of MWNTs upon post-deposition rapid thermal annealing. For these films the carbon originated from the ALD precursor ligand and MWNT growth occurred in the absence of a vapor-phase carbon feedstock. MWNT growth relied on the formation of nickel silicide at the PEALD Ni/Si interface which increased the local carbon concentration in the Ni film sufficiently to promote carbon saturation/precipitation at Ni catalyst grains and nucleate MWNT growth. Similar MWNT growth from annealed PEALD Ni films was not observed on SiO(2)-coated Si wafer substrates, consistent with the role of silicidation in the observed Ni-catalyzed MWNT growth on Si. This MWNT growth mode requires neither the catalytic decomposition of a gaseous hydrocarbon source nor the high-temperature pyrolysis of metallocene materials and purposely avoids a catalyst diffusion barrier at the Si substrate, commonly used in MWNT growth processes on Si.     

无定型氧化锰超级电容器电极材料

采用化学共沉淀法制备超级电容器用氧化锰电极材料,借助X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)和BET比表面积分析手段对样品进行表征。结果表明,产物为无定型结构,粒径分布较均匀,约在40～50nm,BET比表面积达到160．5m^2／g。在0．5mol／LK2SO4水溶液中,电位窗口为0～0．8V(vs.SCE)内,通过循环伏安和恒流充放电测试,显示该材料制备的电极具有良好的电容行为和功率特性。在扫描速度为4mV／s时,单电极的比容量达到140F／g。     

Dielectrophoretically trapping semiconductive carbon nanotube networks

The construction of carbon nanotube field effect transistors (CNT-FETs) can be accomplished by techniques such as spin coating, dielectrophoresis (DEP), and chemical vapor deposition, among which DEP has advantages in terms of the ease of manufacturability and the potential of scalability. In this study, we improved on DEP trapping of CNTs by demonstrating that CNT-FETs of CNT networks with highly semiconductive characteristics are formed with proper tuning of DEP parameters. By investigating the factors that are significant in forming these networks, we rationalize guidelines for effectively fabricating highly semiconductive CNT-FETs with mixtures of metallic and semiconductive multi-walled carbon nanotubes.     

DNA-directed synthesis of zinc oxide nanowires on carbon nanotube tips

This paper describes a class of three component hybrid nanowires templated by DNA directed self-assembly. Through the modification of carbon nanotube (CNT) termini with synthetic DNA oligonucleotides, gold nanoparticles are delivered, via DNA hybridization, to CNT tips that then serve as growth sites for zinc oxide (ZnO) nanowires. The structures we have generated using DNA templating represent an advance toward building higher order sequenced one dimensional nanostructures with rational control.     

Growth of ZnO nanowires on modified well-aligned carbon nanotube arrays

Single-crystal ZnO nanowires were successfully grown on modified well-aligned carbon nanotube (CNT) arrays by a hydrothermal process. The pre-deposited ZnO grains on the CNTs served as the nucleation sites for the growth of ZnO nanowires. The attached growth of ZnO nanowires on the well-aligned CNT arrays formed a 3D configuration. The 3D hybrid nanostructured material could find application in sensors and other electronic or optoelectronic devices.     

Novel electrode design of three-dimensional carbon foam modified with MnO2 nanosheet arrays for high-performance quasi-solid supercapacitor

Journal of Materials Science: Materials in Electronics - In recent years, as a flexible electrode material, melamine foam has attracted more and more attention from researchers in the field of...     

超级电容器用MnO2纳米棒的水热法合成和表征

采用水热法制备了超级电容器用MnO2纳米棒。运用SEM、XRD和N2吸附对实验制备的MnO2进行了形貌和结构分析。通过循环伏安和恒流充放电测试研究了MnO2的电化学性能。结果表明,实验制备的MnO2纳米棒为α型结构,直径为50～70nm,比表面积为105.2m2/g。在-0.5～0.4V(vs.SCE)的电位范围内表现出典型的赝电容行为和良好的功率特性,电流密度为10mA/cm2时,其比容达到413F/g。     

Multilayer super-short carbon nanotube/nickel hydroxide nanoflakes for enhanced supercapacitor properties

Multilayer super-short carbon nanotubes (SSCNTs) could be synthesized by tailoring the raw multiwalled carbon nanotubes with a simple ultrasonic oxidation-cut method. Nanostructured layered nickel hydroxide and SSCNTs have been successfully assembled to form Ni(OH)₂/SSCNTs composite by electrostatic force. Compared with pure Ni(OH)₂ (665 F g^?1), the Ni(OH)₂/SSCNTs composite exhibits the much better electrochemical performance with a specific capacitance of 1887 F g^?1 at 1 A g^?1, and demonstrates a good rate capability and excellent long-term cyclic stability (92 % capacity retention after 3000 cycles). It is the reason that the SSCNTs can form a conductive network onto the surface of Ni(OH)₂ nanoflakes, and their excellent electric conductivity is advantaged to the charge transport on the electrode in discharge process and charge process. Therefore, the greatly enhanced capacitive performance of Ni(OH)₂/SSCNTs can be attributed to a synergetic effect of Ni(OH)₂ and SSCNTs.     

Facile synthesis and characterization of potassium-doped MnO2 nanowires

A new type of potassium doped manganese oxide nanowires were synthesized using a simple hydrothermal route. The reduction of MnO4- in the presence of acetate species led to the formation of the Multi-filamentous nanowire structure. Detailed TEM and chemical characterizations indicated that potassium ions were homogeneously distributed in the nanowires. XPS results show a clear binding energy shift (1 eV) for K(2p) peak in nanowires compared with its starting material of KMnO4. Detailed synthetic condition investigation indicated that the presence of acetate ions played an important role in the formation of such a type of nanowires other than layered structures.     

Wafer-level assembly of carbon nanotube networks using dielectrophoresis

We use dielectrophoresis (DEP) to controllably and simultaneously assemble multiple carbon nanotube (CNT) networks at the wafer level. By an appropriate choice of electrode dimensions and geometry, an electric field is generated that captures CNTs from a sizable volume of suspension, resulting in good CNT network uniformity and alignment. During the DEP process, the electrical characteristics of the CNT network are measured and correlated with the network morphology. These experiments give novel insight into the physics of DEP assembly of CNT networks, and demonstrate the scalability of DEP for future device applications.