Hierarchical activated mesoporous phenolic-resin-based carbons for supercapacitors.

PubMed

Wang, Zhao; Zhou, Min; Chen, Hao; Jiang, Jingui; Guan, Shiyou

2014-10-01

A series of hierarchical activated mesoporous carbons (AMCs) were prepared by the activation of highly ordered, body-centered cubic mesoporous phenolic-resin-based carbon with KOH. The effect of the KOH/carbon-weight ratio on the textural properties and capacitive performance of the AMCs was investigated in detail. An AMC prepared with a KOH/carbon-weight ratio of 6:1 possessed the largest specific surface area (1118 m(2) g(-1)), with retention of the ordered mesoporous structure, and exhibited the highest specific capacitance of 260 F g(-1) at a current density of 0.1 A g(-1) in 1 M H2 SO4 aqueous electrolyte. This material also showed excellent rate capability (163 F g(-1) retained at 20 A g(-1)) and good long-term electrochemical stability. This superior capacitive performance could be attributed to a large specific surface area and an optimized micro-mesopore structure, which not only increased the effective specific surface area for charge storage but also provided a favorable pathway for efficient ion transport. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of CO{sub 2} activation on electrochemical performance of microporous carbons derived from poly(vinylidene fluoride)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Seul-Yi; Park, Soo-Jin, E-mail: sjpark@inha.ac.kr

In this work, we have prepared microporous carbons (MPCs) derived from poly(vinylidene fluoride) (PVDF), and the physical activation of MPCs using CO{sub 2} gas is subsequently carried out with various activation temperatures to investigate the electrochemical performance. PVDF is successfully converted into MPCs with a high specific surface area and well-developed micropores. After CO{sub 2} activation, the specific surface areas of MPCs (CA-MPCs) are enhanced by 12% compared with non-activated MPCs. With increasing activation temperature, the micropore size distributions of A-MPCs also become narrower and shift to larger pore size. It is also confirmed that the CO{sub 2} activation hadmore » developed the micropores and introduced the oxygen-containing groups to MPCs′ surfaces. From the results, the specific capacitances of the electrodes in electric double layer capacitors (EDLCs) based on CA-MPCs are distinctly improved through CO{sub 2} activation. The highest specific capacitance of the A-MPCs activated at 700 °C is about 125 F/g, an enhancement of 74% in comparison with NA-MPCs, at a discharge current of 2 A/g in a 6 M KOH electrolyte solution. We also found that micropore size of 0.67 nm has a specific impact on the capacitance behaviors, besides the specific surface area of the electrode samples. - Graphical abstract: The A-MPC samples with high specific surface area (ranging from 1030 to 1082 m{sup 2}/g), corresponding to micropore sizes of 0.67 and 0.72 nm, and with the amount of oxygen-containing groups ranging from 3.2% to 4.4% have been evaluated as electrodes for EDLC applications. . Display Omitted - Highlights: • Microporous carbons (MPCs) were synthesized without activation process. • Next, we carried out the CO{sub 2} activation of MPCs with activation temperatures. • It had developed the micropores and introduced the O-functional groups to MPCs. • The highest specific capacitance: 125 F/g, an increase of 74% compared to MPCs.« less

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: an excellent structure for high-performance flexible solid-state supercapacitors

PubMed Central

Hu, Nantao; Zhang, Liling; Yang, Chao; Zhao, Jian; Yang, Zhi; Wei, Hao; Liao, Hanbin; Feng, Zhenxing; Fisher, Adrian; Zhang, Yafei; Xu, Zhichuan J.

2016-01-01

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance of 391 F/cm3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm2, and a competitive volumetric capacitance of 25.6 F/cm3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. This structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices. PMID:26795067

Hybrid MnO2/carbon nanotube-VN/carbon nanotube supercapacitors

NASA Astrophysics Data System (ADS)

Su, Y.; Zhitomirsky, I.

2014-12-01

Composite materials, containing fibrous VN nanoparticles and multiwalled carbon nanotubes (MWCNT) are prepared by a chemical method for application in electrochemical supercapacitors. We demonstrate for the first time that VN-MWCNT electrodes exhibit good capacitive behavior in 0.5 M Na2SO4 electrolyte in a negative voltage window of 0.9 V. Quartz crystal microbalance studies provide an insight into the mechanism of charge storage. Composite VN-MWCNT materials show significant improvement in capacitance, compared to individual VN and MWCNT materials. Testing results indicate that VN-MWCNT electrodes exhibit high specific capacitance at high mass loadings in the range of 10-30 mg cm-2, good capacitance retention at scan rates in the range of 2-200 mV s-1 and good cycling stability. The highest specific capacitance of 160 F g-1 is achieved at a scan rate of 2 mV s-1. The new findings open a new and promising strategy in the fabrication of hybrid devices based on VN. The proof-of-principle is demonstrated by the fabrication of hybrid supercapacitor devices based on VN-MWCNT negative electrodes and MnO2 -MWCNT positive electrodes with voltage window of 1.8 V in aqueous 0.5 M Na2SO4 electrolyte. The hybrid VN-MWCNT/MnO2-MWCNT supercapacitor cells show promising capacitive and power-energy characteristics.

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: An excellent structure for high-performance flexible solid-state supercapacitors

DOE PAGES

Hu, Nantao; Zhang, Liling; Yang, Chao; ...

2016-01-22

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance ofmore » 391 F/cm 3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm 2, and a competitive volumetric capacitance of 25.6 F/cm 3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. Lastly, this structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices.« less

Vertically aligned cobalt hydroxide nano-flake coated electro-etched carbon fiber cloth electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Cheng, Qian; Tang, Jie; Zhang, Han; Qin, Lu-Chang

2014-11-01

We describe preparation and characterization of nanostructured electrodes using Co(OH)2 nano-flakes and carbon fiber cloth for supercapacitors. Nanostructured Co(OH)2 flakes are produced by electrodeposition and they are coated onto the electro-etched carbon fiber cloth. A highest specific capacitance of 3404.8 F g-1 and an area-normalized specific capacitance of 3.3 F cm-2 have been obtained from such electrodes. Morphology and structure of the nanostructured electrodes have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties have been studied by cyclic voltammetry (CV), constant-current charge and discharge, electrochemical impedance spectroscopy (EIS), and long-time cycling.

Design of 3D Graphene-Oxide Spheres and Their Derived Hierarchical Porous Structures for High Performance Supercapacitors.

PubMed

Li, Zhuangnan; Gadipelli, Srinivas; Yang, Yuchen; Guo, Zhengxiao

2017-11-01

Graphene-oxide (GO) based porous structures are highly desirable for supercapacitors, as the charge storage and transfer can be enhanced by advancement in the synthesis. An effective route is presented of, first, synthesis of three-dimensional (3D) assembly of GO sheets in a spherical architecture (GOS) by flash-freezing of GO dispersion, and then development of hierarchical porous graphene (HPG) networks by facile thermal-shock reduction of GOS. This leads to a superior gravimetric specific capacitance of ≈306 F g -1 at 1.0 A g -1 , with a capacitance retention of 93% after 10 000 cycles. The values represent a significant capacitance enhancement by 30-50% compared with the GO powder equivalent, and are among the highest reported for GO-based structures from different chemical reduction routes. Furthermore, a solid-state flexible supercapacitor is fabricated by constructing the HPG with polymer gel electrolyte, exhibiting an excellent areal specific capacitance of ≈220 mF cm -2 at 1.0 mA cm -2 with exceptional cyclic stability. The work reveals a facile but efficient synthesis approach of GO-based materials to enhance the capacitive energy storage. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile Synthesis of Hierarchical Mesoporous Honeycomb-like NiO for Aqueous Asymmetric Supercapacitors.

PubMed

Ren, Xiaochuan; Guo, Chunli; Xu, Liqiang; Li, Taotao; Hou, Lifeng; Wei, Yinghui

2015-09-16

Three-dimensional (3D) hierarchical nanostructures have been demonstrated as one of the most ideal electrode materials in energy storage systems due to the synergistic combination of the advantages of both nanostructures and microstructures. In this study, the honeycomb-like mesoporous NiO microspheres as promising cathode materials for supercapacitors have been achieved using a hydrothermal reaction, followed by an annealing process. The electrochemical tests demonstrate the highest specific capacitance of 1250 F g(-1) at 1 A g(-1). Even at 5 A g(-1), a specific capacitance of 945 F g(-1) with 88.4% retention after 3500 cycles was obtained. In addition, the 3D porous graphene (reduced graphene oxide, rGO) has been prepared as an anode material for supercapacitors, which displays a good capacitance performance of 302 F g(-1) at 1 A g(-1). An asymmetric supercapacitor has been successfully fabricated based on the honeycomb-like NiO and rGO. The asymmetric supercapacitor achieves a remarkable performance with a specific capacitance of 74.4 F g(-1), an energy density of 23.25 Wh kg(-1), and a power density of 9.3 kW kg(-1), which is able to light up a light-emitting diode.

MnO2 ultrathin films deposited by means of magnetron sputtering: Relationships between process conditions, structural properties and performance in transparent supercapacitors

NASA Astrophysics Data System (ADS)

Borysiewicz, Michał A.; Wzorek, Marek; Myśliwiec, Marcin; Kaczmarski, Jakub; Ekielski, Marek

2016-12-01

This study focuses on the relationships between the process parameters during magnetron sputter deposition of MnO2 and the resulting film properties. Three MnO2 phases were identified - γ, β and λ and the dependence of MnO2 phase presence on the oxygen content in the sputtering atmosphere was found. Selected MnO2 phases were subsequently applied as ultrathin coatings on top of nanostructured ZnO electrodes for transparent supercapacitors with LiCl-based gel electrolyte. The films containing λ-MnO2 exhibited both the highest optical transparency of 62% at 550 nm as well as the highest specific capacitance in the supercapacitor structure, equal to 73.1 μF/cm2. Initially lower, the capacitance was elevated by charge-discharge conditioning.

The composite capacitive behaviors of the N and S dual doped ordered mesoporous carbon with ultrahigh doping level

NASA Astrophysics Data System (ADS)

Zhang, Deyi; Lei, Longyan; Shang, Yonghua; Wang, Kunjie; Wang, Yi

2016-01-01

Heteroatoms doping provides a promising strategy for improving the energy density of supercapacitors based on the carbon electrodes. In this paper, we present a N and S dual doped ordered mesoporous carbon with ultrahigh doping level using dimethylglyoxime as pristine precursor. The N doping content of the reported materials varies from 6.6 to 15.6 at.% dependent on the carbonization temperature, and the S doping content varies from 0.46 to 1.01 at.%. Due to the ultrahigh heteroatoms doping content, the reported materials exhibit pronounced pseudo-capacitance. Meanwhile, the reported materials exhibit high surface areas (640⿿869 m2 g⿿1), large pore volume (0.71⿿1.08 cm2 g⿿1) and ordered pore structure. The outstanding textual properties endow the reported materials excellent electrical double-layer capacitance (EDLC). By effectively combining the pseudo-capacitance with EDLC, the reported materials exhibit a surprising energy storage/relax capacity with the highest specific capacitance of 565 F g⿿1, which value is 3.3 times higher than that of pristine CMK-3, and can compete against some conventional pseudo-capacitance materials.

Versatile NiO/mesoporous carbon nanodisks: controlled synthesis from hexagon shaped heterobimetallic metal-organic frameworks.

PubMed

Zeng, Dehong; Yang, Ying; Yang, Feng; Guo, Fangmin; Yang, Senjie; Liu, Baijun; Hao, Shijie; Ren, Yang

2017-08-24

Hexagonal NiO/mesoporous carbon nanodisks (NiO/MCN) are facilely and controllably synthesized via constructing nickel-zinc trimesic acid heterobimetallic metal-organic framework (HMOF) disks before pyrolysis at 910 °C. Tailoring the Ni/(Zn + Ni) feed ratio and the reaction time during the HMOF synthesis creates a well-defined hexagonal carbon nanodisk with properly populated NiO nanocrystals while maintaining high porosity and conductivity. Such an elaborately fabricated NiO/MCN is highly stable, and exhibits the largest specific capacitance of 261 F g -1 and the highest specific activity factor of 1.93 s -1 g -1 of any composite nanodisk during the capacitive test and 4-nitrophenol reduction, respectively.

Hydrothermal synthesis of Mn-doped ZnCo2O4 electrode material for high-performance supercapacitor

NASA Astrophysics Data System (ADS)

Mary, A. Juliet Christina; Bose, A. Chandra

2017-12-01

Mn-doped ZnCo2O4 nanoparticle has been synthesized by hydrothermal method without adding any surfactants. Structural, morphological and electrochemical performances have been studied for the pure and various concentration of Mn-doped ZnCo2O4 nanoparticles. XRD and Raman studies demonstrate the crystalline structure of the material. Specific capacitance of the 10 wt% Mn doped ZnCo2O4 nanomaterial is analysed using the three-electrode system. 10 wt% Mn-doped ZnCo2O4 has a maximum capacitance of 707.4 F g-1 at a current density of 0.5 A g-1. Coulombic efficiency of the material is 96.3% for 500 cycles in the KOH electrolyte medium. A two-electrode device using 10 wt% Mn-doped ZnCo2O4 exhibits the highest specific capacitance of 6.5 F g-1 at a current density of 0.03 A g-1 which is the suitable material for supercapacitor application.

Vertically Aligned Niobium Nanowire Arrays for Fast-Charging Micro-Supercapacitors.

PubMed

Mirvakili, Seyed M; Hunter, Ian W

2017-07-01

Planar micro-supercapacitors are attractive for system on chip technologies and surface mount devices due to their large areal capacitance and energy/power density compared to the traditional oxide-based capacitors. In the present work, a novel material, niobium nanowires, in form of vertically aligned electrodes for application in high performance planar micro-supercapacitors is introduced. Specific capacitance of up to 1 kF m -2 (100 mF cm -2 ) with peak energy and power density of 2 kJ m -2 (6.2 MJ m -3 or 1.7 mWh cm -3 ) and 150 kW m -2 (480 MW m -3 or 480 W cm -3 ), respectively, is achieved. This remarkable power density, originating from the extremely low equivalent series resistance value of 0.27 Ω (2.49 µΩ m 2 or 24.9 mΩ cm 2 ) and large specific capacitance, is among the highest for planar micro-supercapacitors electrodes made of nanomaterials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Fe doping on the electrochemical capacitor behavior of MnO2 nanocrystals

NASA Astrophysics Data System (ADS)

Poonguzhali, R.; Shanmugam, N.; Gobi, R.; Senthilkumar, A.; Viruthagiri, G.; Kannadasan, N.

2015-10-01

In this work, the influence of Fe doping on the capacitance behavior of MnO2 nanoparticles synthesized by chemical precipitation was investigated. During the doping process the concentration of Fe was increased from 0.025 M to 0.125 M in steps of 0.025 M. The products obtained were characterized by X-ray diffraction, Fourier infrared spectroscopy, scanning electron microscopy and N2 adsorption-desorption isotherms. To demonstrate the suitability of Fe-doped MnO2 for capacitor applications, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance were recorded. Among the different levels of doping, the specific capacitance of 912 F/g was delivered by 0.075 M of Fe-doped MnO2 at a scan rate of 10 mV/s, which is almost more than fourfold that of the bare MnO2 electrode (210 F/g). Moreover, for the same concentration the charge, discharge studies revealed the highest specific capacitance of 1084 F/g at a current density of 10 A/g.

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Shi, C.; Zhitomirsky, I.

2010-03-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Electrodeposition and capacitive behavior of films for electrodes of electrochemical supercapacitors.

PubMed

Shi, C; Zhitomirsky, I

2010-01-08

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

PubMed Central

2010-01-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0–3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g−1 was observed for the sample with a specific mass of 89 μg cm−2 at a scan rate of 2 mV s−1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES). PMID:20672082

A high-capacity carbon prepared from renewable chicken feather biopolymer for supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Qiang; Cao, Qi; Wang, Xianyou; Jing, Bo; Kuang, Hao; Zhou, Ling

2013-03-01

Micropopous chicken feather carbon (CFC) severing as electrode materials for the first time is prepared via the activation with KOH agent to different extents. The structure and electrochemical properties of CFC materials are characterized with N2 adsorption/desorption measurements, X-ray diffraction (XRD), transmission electron microscope (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). The obtained results show that CFC activated by KOH with KOH/CFC weight ratio of 4/1 (CFCA4) possesses the specific surface area of 1839 m2 g-1, average micropore diameter of 1.863 nm, and exhibits the highest initial specific capacitance of 302 F g-1 at current density of 1 A g-1 in 1 M H2SO4, and that even after 5000 cycles, CFCA4 specific capacitance is still as high as 253 F g-1. Furthermore, CFCA4 also delivers specific capacitance of 181 F g-1 at current density of 5 A g-1 and 168 F g-1 at current density of 10 A g-1. Accordingly, the microporous activated carbon material derived from chicken feather provides favorable prospect in electrode materials application in supercapacitors.

Enhanced electrochemical performance of in situ reduced graphene oxide-polyaniline nanotubes hybrid nanocomposites using redox-additive aqueous electrolyte

NASA Astrophysics Data System (ADS)

Devi, Madhabi; Kumar, A.

2018-02-01

Reduced graphene oxide (RGO)-polyaniline nanotubes (PAniNTs) nanocomposites have been synthesized by in situ reduction of GO. The morphology and structure of the nanocomposites are characterized by HRTEM, XRD and micro-Raman spectroscopy. The electrical and electrochemical performances of the nanocomposites are investigated for different RGO concentrations by conductivity measurements, cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy. Highest gravimetric specific capacitance of 448.71 F g-1 is obtained for 40 wt.% of RGO-PAniNTs nanocomposite as compared to 194.92 F g-1 for pure PAniNTs in 1 M KCl electrolyte. To further improve the electrochemical performance of the nanocomposite electrode, KI is used as redox-additive with 1 M KCl electrolyte. Highest gravimetric specific capacitance of 876.43 F g-1 and an improved cyclic stability of 91% as compared to 79% without KI after 5000 cycles is achieved for an optimized 0.1 M KI concentration. This is attributed to the presence of different ionic species of I- ions that give rise to a number of possible redox reactions improving the pseudocapacitance of the electrode. This improved capacitive performance is compared with that of catechol redox-additive in 1 M KCl electrolyte, and that of KI and catechol redox-additives added to 1 M H2SO4 electrolyte.

Enhanced electrochemical performances with a copper/xylose-based carbon composite electrode

NASA Astrophysics Data System (ADS)

Sirisomboonchai, Suchada; Kongparakul, Suwadee; Nueangnoraj, Khanin; Zhang, Haibo; Wei, Lu; Reubroycharoen, Prasert; Guan, Guoqing; Samart, Chanatip

2018-04-01

Copper/carbon (Cu/C) composites were prepared through the simple and environmentally benign hydrothermal carbonization of xylose in the presence of Cu2+ ions. The morphology, specific surface area, phase structure and chemical composition were investigated. Using a three-electrode system in 0.1 M H2SO4 aqueous electrolyte, the Cu/C composite (10 wt% Cu) heat-treated at 600 °C gave the highest specific capacitance (316.2 and 350.1 F g-1 at 0.5 A g-1 and 20 mV s-1, respectively). The addition of Cu was the major factor in improving the electrochemical performance, enhancing the specific capacitance more than 30 times that of the C without Cu. Therefore, the Cu/C composite presented promising results in improving biomass-based C electrodes for supercapacitors.

Wet-spun, porous, orientational graphene hydrogel films for high-performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Kou, Liang; Liu, Zheng; Huang, Tieqi; Zheng, Bingna; Tian, Zhanyuan; Deng, Zengshe; Gao, Chao

2015-02-01

Supercapacitors with porous electrodes of graphene macroscopic assembly are supposed to have high energy storage capacity. However, a great number of ``close pores'' in porous graphene electrodes are invalid because electrolyte ions cannot infiltrate. A quick method to prepare porous graphene electrodes with reduced ``close pores'' is essential for higher energy storage. Here we propose a wet-spinning assembly approach based on the liquid crystal behavior of graphene oxide to continuously spin orientational graphene hydrogel films with ``open pores'', which are used directly as binder-free supercapacitor electrodes. The resulting supercapacitor electrodes show better electrochemical performance than those with disordered graphene sheets. Furthermore, three reduction methods including hydrothermal treatment, hydrazine and hydroiodic acid reduction are used to evaluate the specific capacitances of the graphene hydrogel film. Hydrazine-reduced graphene hydrogel film shows the highest capacitance of 203 F g-1 at 1 A g-1 and maintains 67.1% specific capacitance (140 F g-1) at 50 A g-1. The combination of scalable wet-spinning technology and orientational structure makes graphene hydrogel films an ideal electrode material for supercapacitors.Supercapacitors with porous electrodes of graphene macroscopic assembly are supposed to have high energy storage capacity. However, a great number of ``close pores'' in porous graphene electrodes are invalid because electrolyte ions cannot infiltrate. A quick method to prepare porous graphene electrodes with reduced ``close pores'' is essential for higher energy storage. Here we propose a wet-spinning assembly approach based on the liquid crystal behavior of graphene oxide to continuously spin orientational graphene hydrogel films with ``open pores'', which are used directly as binder-free supercapacitor electrodes. The resulting supercapacitor electrodes show better electrochemical performance than those with disordered graphene sheets. Furthermore, three reduction methods including hydrothermal treatment, hydrazine and hydroiodic acid reduction are used to evaluate the specific capacitances of the graphene hydrogel film. Hydrazine-reduced graphene hydrogel film shows the highest capacitance of 203 F g-1 at 1 A g-1 and maintains 67.1% specific capacitance (140 F g-1) at 50 A g-1. The combination of scalable wet-spinning technology and orientational structure makes graphene hydrogel films an ideal electrode material for supercapacitors. Electronic supplementary information (ESI) available: The schematic diagram for fabricating graphene oxide hydrogel films, stress-strain curves and TGA curves of three GHFs, a digital photo of the test device for the two-electrode system, and comparison of the electrochemical performance of our GHF-HZ supercapacitors. See DOI: 10.1039/c4nr07038k

Percoll gradient-centrifuged capacitated mouse sperm have increased fertilizing ability and higher contents of sulfogalactosylglycerolipid and docosahexaenoic acid-containing phosphatidylcholine compared to washed capacitated mouse sperm.

PubMed

Furimsky, Anna; Vuong, Ngoc; Xu, Hongbin; Kumarathasan, Premkumari; Xu, Min; Weerachatyanukul, Wattana; Bou Khalil, Maroun; Kates, Morris; Tanphaichitr, Nongnuj

2005-03-01

Although Percoll gradient centrifugation has been used routinely to prepare motile human sperm, its use in preparing motile mouse sperm has been limited. Here, we showed that Percoll gradient-centrifuged (PGC) capacitated mouse sperm had markedly higher fertilizing ability (sperm-zona pellucida [ZP] binding and in vitro fertilization) than washed capacitated mouse sperm. We also showed that the lipid profiles of PGC capacitated sperm and washed capacitated sperm differed significantly. The PGC sperm had much lower contents of cholesterol and phospholipids. This resulted in relative enrichment of male germ cell-specific sulfogalactosylglycerolipid (SGG), a ZP-binding ligand, in PGC capacitated sperm, and this would explain, in part, their increased ZP-binding ability compared with that of washed capacitated sperm. Analyses of phospholipid fatty acyl chains revealed that PGC capacitated sperm were enriched in phosphatidylcholine (PC) molecular species containing highly unsaturated fatty acids (HUFAs), with docosahexaenoic acid (DHA; C22: 6n-3) being the predominant HUFA (42% of total hydrocarbon chains of PC). In contrast, the level of PC-HUFAs comprising arachidonic acid (20:4n-6), docosapentaenoic acid (C22:5n-6), and DHA in washed capacitated sperm was only 27%. Having the highest unsaturation degree among all HUFAs in PC, DHA would enhance membrane fluidity to the uppermost. Therefore, membranes of PGC capacitated sperm would undergo fertilization-related fusion events at higher rates than washed capacitated sperm. These results suggested that PGC mouse sperm should be used in fertilization experiments and that SGG and DHA should be considered to be important biomarkers for sperm fertilizing ability.

Outstanding supercapacitive properties of Mn-doped TiO2 micro/nanostructure porous film prepared by anodization method

PubMed Central

Ning, Xuewen; Wang, Xixin; Yu, Xiaofei; Zhao, Jianling; Wang, Mingli; Li, Haoran; Yang, Yang

2016-01-01

Mn-doped TiO2 micro/nanostructure porous film was prepared by anodizing a Ti-Mn alloy. The film annealed at 300 °C yields the highest areal capacitance of 1451.3 mF/cm2 at a current density of 3 mA/cm2 when used as a high-performance supercapacitor electrode. Areal capacitance retention is 63.7% when the current density increases from 3 to 20 mA/cm2, and the capacitance retention is 88.1% after 5,000 cycles. The superior areal capacitance of the porous film is derived from the brush-like metal substrate, which could greatly increase the contact area, improve the charge transport ability at the oxide layer/metal substrate interface, and thereby significantly enhance the electrochemical activities toward high performance energy storage. Additionally, the effects of manganese content and specific surface area of the porous film on the supercapacitive performance were also investigated in this work. PMID:26940546

Biowaste-Derived Hierarchical Porous Carbon Nanosheets for Ultrahigh Power Density Supercapacitors.

PubMed

Yu, Dengfeng; Chen, Chong; Zhao, Gongyuan; Sun, Lei; Du, Baosheng; Zhang, Hong; Li, Zhuo; Sun, Ye; Besenbacher, Flemming; Yu, Miao

2018-03-05

Low-cost activated carbons with high capacitive properties remain desirable for supercapacitor applications. Herein, a three-dimensional scaffolding framework of porous carbon nanosheets (PCNSs) has been produced from a typical biowaste, namely, ground cherry calyces, the specific composition and natural structures of which have contributed to the PCNSs having a very large specific surface area of 1612 m 2  g -1 , a hierarchical pore size distribution, a turbostratic carbon structure with a high degree graphitization, and about 10 % oxygen and nitrogen heteroatoms. A high specific capacitance of 350 F g -1 at 0.1 A g -1 has been achieved in a two-electrode system with 6 m KOH; this value is among the highest specific capacitance of biomass-derived carbon materials. More inspiringly, a high energy density of 22.8 Wh kg -1 at a power density of 198.8 W kg -1 can be obtained with 1 m aqueous solution of Li 2 SO 4 , and an ultrahigh energy density of 81.4 Wh kg -1 at a power density of 446.3 W kg -1 is realized with 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Supercapacitor electrode materials with hierarchically structured pores from carbonization of MWCNTs and ZIF-8 composites.

PubMed

Li, Xueqin; Hao, Changlong; Tang, Bochong; Wang, Yue; Liu, Mei; Wang, Yuanwei; Zhu, Yihua; Lu, Chenguang; Tang, Zhiyong

2017-02-09

Due to their high specific surface area and good electric conductivity, nitrogen-doped porous carbons (NPCs) and carbon nanotubes (CNTs) have attracted much attention for electrochemical energy storage applications. In the present work, we firstly prepared MWCNT/ZIF-8 composites by decoration of zeolitic imidazolate frameworks (ZIF-8) onto the surface of multi-walled CNTs (MWCNTs), then obtained MWCNT/NPCs by the direct carbonization of MWCNT/ZIF-8. By controlling the reaction conditions, MWCNT/ZIF-8 with three different particle sizes were synthesized. The effect of NPCs size on capacitance performance has been evaluated in detail. The MWCNT/NPC with large-sized NPC (MWCNT/NPC-L) displayed the highest specific capacitance of 293.4 F g -1 at the scan rate of 5 mV s -1 and only lost 4.2% of capacitance after 10 000 cyclic voltammetry cycles, which was attributed to the hierarchically structured pores, N-doping and high electrical conductivity. The studies of symmetric two-electrode supercapacitor cells also confirmed MWCNT/NPC-L as efficient electrode materials that have good electrochemical performance, especially for high-rate applications.

Monodisperse Carbon Nanospheres with Hierarchical Porous Structure as Electrode Material for Supercapacitor

NASA Astrophysics Data System (ADS)

Yang, Xiutao; Xia, Hui; Liang, Zhongguan; Li, Haiyan; Yu, Hongwen

2017-09-01

Carbon nanospheres with distinguishable microstructure were prepared by carbonization and subsequent KOH activation of F108/resorcinol-formaldehyde composites. The dosage of triblock copolymer Pluronic F108 is crucial to the microstructure differences. With the adding of F108, the polydisperse carbon nanospheres (PCNS) with microporous structure, monodisperse carbon nanospheres (MCNS) with hierarchical porous structure, and agglomerated carbon nanospheres (ACNS) were obtained. Their microstructure and capacitance properties were carefully compared. As a result of the synergetic effect of mono-dispersion spheres and hierarchical porous structures, the MCNS sample shows improved electrochemical performance, i.e., the highest specific capacitance of 224 F g-1 (0.2 A g-1), the best rate capability (73% retention at 20 A g-1), and the most excellent capacitance retention of 93% over 10,000 cycles, making it to be the promising electrode material for high-performance supercapacitors.

Three-dimensional structures of graphene/polyaniline hybrid films constructed by steamed water for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Liling; Huang, Da; Hu, Nantao; Yang, Chao; Li, Ming; Wei, Hao; Yang, Zhi; Su, Yanjie; Zhang, Yafei

2017-02-01

A novel three-dimensional (3D) structure of reduced graphene oxide/polyaniline (rGO/PANI) hybrid films has been demonstrated for high-performance supercapacitors. Steamed water in closed vessels with high pressure and moderately high temperature is applied to facilely construct this structure. The as-designed rGO/PANI hybrid films exhibit a highest gravimetric specific capacitance of 1182 F g-1 at 1 A g-1 in the three-electrode test. The assembled symmetric device based on this structure shows both a high capacitance of 808 F g-1 at 1 A g-1 and a high gravimetric energy density (28.06 Wh kg-1 at a power density of 0.25 kW kg-1). Above all, this novel 3D structure constructed by steamed water regulation techniques shows excellent capacitance performance and holds a great promise for high-performance energy storage applications.

Graphene/Poly(aniline-co-pyrrole) Nanocomposite: Potential Candidate for Supercapacitor and Microwave Absorbing Applications.

PubMed

Sahoo, Sumanta; Bhattacharya, Pallab; Dhibar, Saptarshi; Hatui, Goutam; Das, Tanya; Das, Chapal Kumar

2015-09-01

A simple and cost-effective in-situ chemical route to prepare the nanocomposites based on graphene and Poly(aniline-co-pyrrole) [PPP] has been proposed. Introduction of graphene changes the morphology of copolymer from spherical to fiber like. Graphene/Poly(aniline-co-pyrrole) [GPPP] nanocomposite achieved highest specific capacitance of 351 F/g and energy density of 124.8 Wh/Kg at 10 mV/s scan rate. The composite also obtained moderate specific capacitance retention of 66% after 500 cycles, which establish its potentiality as supercapacitor electrode materials. The composite also exhibited high electrical conductivity and superior microwave absorbing properties (maximum reflection loss is -29.97 dB). The absorption range corresponding to ≥ 90% absorption (or -10 dB) is 2.72 GHz which is excellent for the microwave absorbing applications.

Three-dimensional hierarchical NiCo2O4 nanowire@Ni3S2 nanosheet core/shell arrays for flexible asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Bo; Kong, Dezhi; Huang, Zhi Xiang; Mo, Runwei; Wang, Ye; Han, Zhaojun; Cheng, Chuanwei; Yang, Hui Ying

2016-05-01

Three-dimensional (3D) hierarchical NiCo2O4@Ni3S2 core/shell arrays on Ni foam were synthesized by a facile, stepwise synthesis approach. The 3D heterogeneous NiCo2O4 nanostructure forms an interconnected web-like scaffold and serves as the core for the Ni3S2 shell. The as-prepared NiCo2O4@Ni3S2 nanowire array (NWA) electrodes exhibited excellent electrochemical performance, such as high specific areal capacitance and excellent cycling stability. The specific areal capacitance of 3.0 F cm-2 at a current density of 5 mA cm-2 is among the highest values and the only 6.7% capacitance decay after 10 000 cycles demonstrates the excellent cycling stability. A flexible asymmetric supercapacitor (ASC) was fabricated with activated carbon (AC) as the anode and the obtained NiCo2O4@Ni3S2 NWAs as the cathode. The ASC device exhibited a high energy density of 1.89 mW h cm-3 at 5.81 W cm-3 and a high power density of 56.33 W cm-3 at 0.94 mW h cm-3. As a result, the hybrid nanoarchitecture opens a new way to design high performance electrodes for electrochemical energy storage applications.Three-dimensional (3D) hierarchical NiCo2O4@Ni3S2 core/shell arrays on Ni foam were synthesized by a facile, stepwise synthesis approach. The 3D heterogeneous NiCo2O4 nanostructure forms an interconnected web-like scaffold and serves as the core for the Ni3S2 shell. The as-prepared NiCo2O4@Ni3S2 nanowire array (NWA) electrodes exhibited excellent electrochemical performance, such as high specific areal capacitance and excellent cycling stability. The specific areal capacitance of 3.0 F cm-2 at a current density of 5 mA cm-2 is among the highest values and the only 6.7% capacitance decay after 10 000 cycles demonstrates the excellent cycling stability. A flexible asymmetric supercapacitor (ASC) was fabricated with activated carbon (AC) as the anode and the obtained NiCo2O4@Ni3S2 NWAs as the cathode. The ASC device exhibited a high energy density of 1.89 mW h cm-3 at 5.81 W cm-3 and a high power density of 56.33 W cm-3 at 0.94 mW h cm-3. As a result, the hybrid nanoarchitecture opens a new way to design high performance electrodes for electrochemical energy storage applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02600a

Fast fabrication of NiO@graphene composites for supercapacitor electrodes: Combination of reduction and deposition.

PubMed

Hui, Xu; Qian, Luming; Harris, Gary; Wang, Tongxin; Che, Jianfei

2016-11-05

Graphene-based inorganic composites have been attracting more and more attention since the attachment of inorganic nanoparticles instead of conducting polymeric materials to graphene sheets turns out higher capacitances and good capacity retention. Here we report a fast fabrication method to prepare NiO@graphene composite modified electrodes for supercapacitors. By this method, preparation of electrochemical active materials of NiO/graphene and modification of the electrode can be simultaneously performed, which is achieved separately by traditional method. Moreover, the problem of poor adhesion of active materials on the surface of the electrode can be well solved. The NiO particles introduced to the films exhibit pseudocapacitive behavior arising from the reversible Faradaic transitions of Ni(II)/Ni(III) and greatly improve the capacitance of the electrodes. With the increase in NiO content, highly reduced graphene can be obtained during cyclic voltammetry sweeping, leading to the increase in the electrode capacitance. The highest specific capacitance of the constructed electrodes can reach 1258 F/g at a current density of 5 A/g.

Synthesis of iron oxides nanoparticles with very high saturation magnetization form TEA-Fe(III) complex via electrochemical deposition for supercapacitor applications

NASA Astrophysics Data System (ADS)

Elrouby, Mahmoud; Abdel-Mawgoud, A. M.; El-Rahman, Rehab Abd

2017-11-01

This work is devoted to the synthesis of magnetic iron oxides nanoparticles with very high saturation magnetization to be qualified for supercapacitor applications using, a simple electrodeposition technique. It is found that the electrochemical reduction process depends on concentration, temperature, deposition potential and the scan rate of potential. The nature of electrodeposition process has been characterized via voltammetric and chronoamperometric techniques. The morphology of the electrodeposits has been investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and phase content of these investigated electrodeposits have been examined and calculated. The obtained iron oxides show a high saturation magnetization (Ms) of about 229 emu g-1. The data exhibited a relation between Ms of electrodeposited iron oxide and specific capacitance. This relation exhibits that the highest Ms value of electrodeposited iron oxides gives also highest specific capacitance of about 725 Fg-1. Moreover, the electrodeposited iron oxides exhibit a very good stability. The new characteristics of the electro synthesized iron oxides at our optimized conditions, strongly qualify them as a valuable material for high-performance supercapacitor applications.

Simple synthesis of amorphous NiWO4 nanostructure and its application as a novel cathode material for asymmetric supercapacitors.

PubMed

Niu, Lengyuan; Li, Zhangpeng; Xu, Ye; Sun, Jinfeng; Hong, Wei; Liu, Xiaohong; Wang, Jinqing; Yang, Shengrong

2013-08-28

This study reports a simple synthesis of amorphous nickel tungstate (NiWO4) nanostructure and its application as a novel cathode material for supercapacitors. The effect of reaction temperature on the electrochemical properties of the NiWO4 electrode was studied, and results demonstrate that the material synthesized at 70 °C (NiW-70) has shown the highest specific capacitance of 586.2 F g(-1) at 0.5 A g(-1) in a three-electrode system. To achieve a high energy density, a NiW-70//activated carbon asymmetric supercapacitor is successfully assembled by use of NiW-70 and activated carbon as the cathode and anode, respectively, and then, its electrochemical performance is characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The results show that the assembled asymmetric supercapacitor can be cycled reversibly between 0 and 1.6 V with a high specific capacitance of 71.1 F g(-1) at 0.25 A g(-1), which can deliver a maximum energy density of 25.3 Wh kg(-1) at a power density of 200 W kg(-1). Furthermore, this asymmetric supercapacitor also presented an excellent, long cycle life along with 91.4% specific capacitance being retained after 5000 consecutive times of cycling.

A core–shell structured nanocomposite of NiO with carbon nanotubes as positive electrode material of high capacitance for supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Z.B., E-mail: zbwen@jxnu.edu.cn; Yu, F.; College of Energy, Nanjing Tech University, Nanjing 211816, Jiangsu Province

2016-02-15

Highlights: • A core–shell structured NiO@CNTs nanocomposite is synthesized by a simple hydrothermal method. • The CNTs core effectively improves the capacitance, rate and cycling performance of NiO. • A supercapacitor is assembled when activated carbon is used as the negative electrode. • The supercapacitor presents an energy density up to 52.6 Wh kg{sup −1}. - Abstract: A nanocomposite of carbon nanotubes coated with nickel oxide was prepared by a simple hydrothermal method. The structure, morphology and electrochemical performance of the nanocomposite were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, electrochemical tests including cyclic voltammogram, galvanostaticmore » charge–discharge and electrochemical impedance spectroscopy, respectively. It presents the highest specific capacitance of 1844 F g{sup −1} at 1 A g{sup −1} and 1145 F g{sup −1} at current density of 10 A g{sup −1} with 88.9% (at 1 A g{sup −1}) capacitance retention after 1000 cycles. The specific capacitance of the nanocomposite is almost double of that of the virginal NiO (972 F g{sup −1} at 1 A g{sup −1}). Its cycling behavior is also very good. When combined with activated carbon as the negative electrode, the energy density can be up to 52.6 Wh kg{sup −1}. Such good electrochemical behavior indicates that the nanocomposite is a promising electrode material for supercapacitors.« less

Electrochemical performance of PVA stabilized nickel ferrite nanoparticles via microwave route

NASA Astrophysics Data System (ADS)

William, J. Johnson; Babu, I. Manohara; Muralidharan, G.

2017-05-01

Nanosized nickel ferrite nanoparticles were effectively synthesized through microwave route.PVA is used as a stabilizer. The cubic inverse spinel crystal structure was identified from the X-ray diffraction pattern. FTIR spectrum identified the octahedral site vibrations of the Ni2+ ions and tetrahedral sites vibrations of Fe3+ ions, which additionally confirms the existence of nickel ferrite nanoparticles. Nano-granular morphology was observed from scanning electron microscope. The tuning of morphology was clearly seen in SEM images. Electrochemical performance of nickel ferrite nanoparticles was studied using cyclic voltammetry and chronopotentiometry. Highest specific capacitance of 459 F g-1 was achieved through cyclic voltammetry at 2 mV s-1 for NF10. Also, non-linearity was observed in chronopotentiometry which confirms the pseudocapacitance nature of nickel ferrite nanoparticles. The estimated specific capacitance was 341 F g-1 at 2.5 A g-1.

Growth of highly mesoporous CuCo2O4@C core-shell arrays as advanced electrodes for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Yan, Hailong; Lu, Yang; Zhu, Kejia; Peng, Tao; Liu, Xianming; Liu, Yunxin; Luo, Yongsong

2018-05-01

A series of CuCo2O4 nanostructures with different morphologies were prepared by a hydrothermal method in combination with thermal treatment. The morphology, structure and composition were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. As the electrode materials for supercapacitors, CuCo2O4 nanoneedles delivered the highest specific capacitance compared with other CuCo2O4 nanostructures. Electrochemical performance measurements demonstrate that the carbon layer can improve the electrochemical stability of CuCo2O4 nanoneedles. The CuCo2O4@C electrode exhibits a high specific capacitance of 1432.4 F g-1 at a current density of 1 A g-1, with capacitance retention of 98.2% after 3000 circles. These characteristics of CuCo2O4@C composite are mainly due to the unique one dimensional needle-liked architecture and the conducting carbon, which provide a faster ion/electron transfer rate. These excellent performances of the CuCo2O4@C electrode confirmed the material as a positive electrode for hybrid supercapacitor application.

Facile synthesis of nickel-based metal organic framework [Ni3(HCOO)6] by microwave method and application for supercapacitor

NASA Astrophysics Data System (ADS)

Luo, Jujie; Yang, Xing; Wang, Shumin; Bi, Yuhong; Nautiyal, Amit; Zhang, Xinyu

The metal organic framework (MOF) [Ni3(HCOO)6] was synthesized via the simple and fast microwave method, and the effect of irradiation power on crystallinity of synthesized Ni-based MOF was studied. The samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The synthesized Ni-based MOF was electrochemically characterized by using galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. The synthesized MOF showed the highest specific capacitance of 1196.2F/g at 1A/g with excellent cyclability (86.04% capacitance retention after 2,000 cycles), thereby demonstrating its potential application in supercapacitors.

B-Site Cation-Ordered Double-Perovskite Oxide as an Outstanding Electrode Material for Supercapacitive Energy Storage Based on the Anion Intercalation Mechanism.

PubMed

Xu, Zhenye; Liu, Yu; Zhou, Wei; Tade, Moses O; Shao, Zongping

2018-03-21

Perovskite oxides are highly promising electrodes for oxygen-ion-intercalation-type supercapacitors owing to their high oxygen vacancy concentration, oxygen diffusion rate, and tap density. Based on the anion intercalation mechanism, the capacitance is contributed by surface redox reactions and oxygen ion intercalation in the bulk materials. A high concentration of oxygen vacancies is needed because it is the main charge carrier. In this study, we propose a B-site cation-ordered Ba 2 Bi 0.1 Sc 0.2 Co 1.7 O 6-δ as an electrode material with an extremely high oxygen vacancy concentration and oxygen diffusion rate. A maximum capacitance of 1050 F g -1 was achieved, and a high capacitance of 780 F g -1 was maintained even after 3000 charge-discharge cycles at a current density of 1 A g -1 with an aqueous alkaline solution (6 M KOH) electrolyte, indicating an excellent cycling stability. In addition, the specific volumetric capacitance of Ba 2 Bi 0.1 Sc 0.2 Co 1.7 O 6-δ reaches up to 2549.4 F cm -3 based on the dense construction and high tap density (3.2 g cm -3 ). In addition, an asymmetric supercapacitor was constructed using activated carbon as a negative electrode, and it displayed the highest specific energy density of 70 Wh kg -1 at the power density of 787 W kg -1 in this study.

Determination of specific capacitance of modified candlenut shell based carbon as electrode material for supercapacitor

NASA Astrophysics Data System (ADS)

Zakir, M.; Budi, P.; Raya, I.; Karim, A.; Wulandari, R.; Sobrido, A. B. J.

2018-03-01

Surface modification of candlenut shell carbon (CSC) using three chemicals: nitric acid (HNO3), hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) has been carried out. Activation of CSC was performed using H3PO4 solution with different ratio between CSC and activator. Carbon surface area was determined by methylene blue adsorption method. Surface characterization was performed using FTIR spectroscopy and Boehm titration method. Specific capacitance of electrode prepared from CSAC (candlenuts shell activated carbon) materials was quantified by Cyclic Voltammetry (CV) measurement. The surface area before and after activation are 105,127 m2/g, 112,488 m2/g, 124,190 m2/g, and 135,167 m2/g, respectively. Surface modification of CSAC showed the improvement in the chemical functionality of CSAC surface. Analyses using FTIR spectroscopy and Boehm titration showed that modifications with HNO3, H2SO4 and H2O2 on the surface of the CSAC increased the number of oxygen functional groups. As a consequence, the specific capacitance of CSAC modified with 65% HNO3 attained the highest value (127 μF/g). There is an incredible increase by a factor of 298% from electrode which was constructed with un-modified CSAC material. This increase correlates to the largest number of oxygen functional groups of CSAC modified with nitric acid (HNO3).

Porous carbons prepared by direct carbonization of MOFs for supercapacitors

NASA Astrophysics Data System (ADS)

Yan, Xinlong; Li, Xuejin; Yan, Zifeng; Komarneni, Sridhar

2014-07-01

Three porous carbons were prepared by direct carbonization of HKUST-1, MOF-5 and Al-PCP without additional carbon precursors. The carbon samples obtained by carbonization at 1073 K were characterized by XRD, TEM and N2 physisorption techniques followed by testing for electrochemical performance. The BET surface areas of the three carbons were in the range of 50-1103 m2/g. As electrode materials for supercapacitor, the MOF-5 and Al-PCP derived carbons displayed the ideal capacitor behavior, whereas the HKUST-1 derived carbon showed poor capacitive behavior at various sweep rates and current densities. Among those carbon samples, Al-PCP derived carbons exhibited highest specific capacitance (232.8 F/g) in 30% KOH solution at the current density of 100 mA/g.

Preparation of porous carbon sphere from waste sugar solution for electric double-layer capacitor

NASA Astrophysics Data System (ADS)

Hao, Zhi-Qiang; Cao, Jing-Pei; Wu, Yan; Zhao, Xiao-Yan; Zhuang, Qi-Qi; Wang, Xing-Yong; Wei, Xian-Yong

2017-09-01

Waste sugar solution (WSS), which contains abundant 2-keto-L-gulonic acid, is harmful to the environment if discharged directly. For value-added utilization of the waste resource, a novel process is developed for preparation of porous carbon spheres by hydrothermal carbonization (HTC) of WSS followed by KOH activation. Additionally, the possible preparation mechanism of carbon spheres is proposed. The effects of hydrothermal and activation parameters on the properties of the carbon sphere are also investigated. The carbon sphere is applied to electric double-layer capacitor and its electrochemical performance is studied. These results show that the carbon sphere obtained by HTC at 180 °C for 12 h with the WSS/deionized water volume ratio of 2/3 possess the highest specific capacitance under identical activation conditions. The specific capacitance of the carbon spheres can reach 296.1 F g-1 at a current density of 40 mA g-1. Besides, excellent cycle life and good capacitance retention (89.6%) are observed at 1.5 A g-1 after 5000 cycles. This study not only provides a facile and potential method for the WSS treatment, but also achieves the high value-added recycling of WSS for the preparation of porous carbon spheres with superior electrochemical properties.

Facile preparation of novel dandelion-like Fe-doped NiCo2O4 microspheres@nanomeshes for excellent capacitive property in asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Li; Zhang, Huijuan; Fang, Ling; Mu, Yanping; Wang, Yu

2016-09-01

In this work, we successfully synthesized the dandelion-like Fe-doped NiCo2O4 microspheres@nanomeshes (Fe-NCO-M@N-1h) using a facile hydrothermal method, followed by calcinations. In the unique structure, numerous nanoneedles radially grow on the surface of microsphere and some porous nanomeshes orderly develop in the inside of microsphere, therefore dandelion-like Fe-NCO-M@N-1h displays large specific surface area (101.15 m2 g-1) and more active sites. Electrochemical properties of the Fe-NCO-M@N-1h have been tested for symmetric supercapacitors (SCs) and asymmetric supercapacitors (ASCs). Benefiting from the structural advantages, Fe-NCO-M@N-1h electrode exhibits outstanding capacitive behaviors, such as the desirable specific capacitance and eminent rate performance (2237 and 1810 F g-1 at the current densities of 1 and 20 A g-1, respectively) and remarkable cycling performance (95.8% retention after 4500 cycles). Besides, a Fe-NCO-M@N-1h//AC-ASCs device has been constructed successfully, presenting the highest energy density of 46.68 Wh kg-1. The results indicate that the Fe-NCO-M@N-1h is a potential material for SCs.

In situ electrochemical polymerization of a nanorod-PANI-Graphene composite in a reverse micelle electrolyte and its application in a supercapacitor.

PubMed

Hu, Liwen; Tu, Jiguo; Jiao, Shuqiang; Hou, Jungang; Zhu, Hongmin; Fray, Derek J

2012-12-05

Highly porous nanorod-PANI-Graphene composite films were prepared by in situ electrochemical polymerization onto an ITO substrate in a reverse micelle electrolyte. The morphology and microstructure of the composite films were analyzed by using a field emission scanning electron microscope. It was observed that the films were highly porous and the nanorod PANI films were inserted by graphene nanosheets. This indicated that a good conductive network between PANI nanorods and graphene sheets was formed. Further electrochemical tests involved cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in 1 mol L(-1) HClO(4) solution. The results showed that the composite film had a favorable capacitance with a high electron transfer rate and low resistance. The highest specific capacitance that could be achieved was as high as 878.57 F g(-1) with the charge loading of 500 mC at a current density of 1 A g(-1). The GCD at different charge loadings showed good cycle stability with a low fading rate of specific capacitance after 1000 cycles. The results demonstrated that the nanorod-PANI-Graphene composite was proved to be of great potential as an electrode material for supercapacitors.

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

NASA Astrophysics Data System (ADS)

Jiang, Baojiang; Tian, Chungui; Wang, Lei; Sun, Li; Chen, Chen; Nong, Xiaozhen; Qiao, Yingjie; Fu, Honggang

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 °C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Facile Co-Electrodeposition Method for High-Performance Supercapacitor Based on Reduced Graphene Oxide/Polypyrrole Composite Film.

PubMed

Chen, Junchen; Wang, Yaming; Cao, Jianyun; Liu, Yan; Zhou, Yu; Ouyang, Jia-Hu; Jia, Dechang

2017-06-14

A facile co-electrodeposition method has been developed to fabricate reduced graphene oxide/polypyrrole (rGO/PPy) composite films, with sodium dodecyl benzene sulfonate as both a surfactant and supporting electrolyte in the precursor solution. The introduction of rGO into the PPy films forms porous structure and enhances the conductivity across the film, leading to superior electrochemical performance. By controlling the deposition time and rGO concentration, the highest area capacitance can reach 411 mF/cm 2 (0.2 mA/cm 2 ) for rGO/PPy films, whereas optimized specific capacitance is as high as 361 F/g (0.2 mA/cm 2 ). All of the composite films exhibit excellent rate capability (at least 175 F/g at the current density of 12 mA/cm 2 ) compared with pure PPy film (only 12 F/g at the current density of 12 mA/cm 2 ). The rGO/PPy composite exhibits excellent cycling stability that maintains 104% of its initial capacitance after cycling for 2000 cycles and 80% for 5000 cycles. The two-electrode solid-state supercapacitor (SC) based on rGO/PPy composite electrodes demonstrates good rate performance, excellent cycling stability, as well as a high area capacitance of 222 mF/cm 2 . The solid-state planar SC based on the rGO/PPy composite exhibits an area capacitance of 9.4 mF/cm 2 , demonstrating great potential for fabrication of microsupercapacitors.

A novel and facile synthesis approach for a porous carbon/graphene composite for high-performance supercapacitors.

PubMed

Liu, Ting; Zhang, Xuesha; Liu, Kang; Liu, Yanyan; Liu, Mengjie; Wu, Wenyu; Gu, Yu; Zhang, Ruijun

2018-03-02

We propose a novel and facile synthesis approach to a porous carbon/graphene composite. Graphene is obtained from room-temperature expanded graphite (RTEG), not involving the use of graphite oxide (GO). Porous carbon is acquired by carbonization and KOH-activation of polyvinylpyrrolidone (PVP), which is used to exfoliate RTEG into graphene and inhibit the restacking of the resultant graphene in the present work. The prepared porous carbon/graphene composite has a high specific surface area (SSA) (3008 m 2 g -1 ) and a hierarchical micro- and meso- pore structure (dominant pores in the range of 1-5 nm). Electrochemical measurement demonstrates that the as-prepared porous carbon/graphene composite can deliver an outstanding specific capacitance of up to 340 F g -1 at 5 mV s -1 in 6 M KOH electrolyte. This specific capacitance is among the highest reported so far for porous carbon/graphene materials. Moreover, the prepared composite as an electrode material also exhibits excellent cycling stability (94.4% capacitance retention over 10 000 cycles). The as-fabricated symmetrical supercapacitor exhibits a high energy density of 10.9 W h kg -1 (based on total mass of electrode materials) and an outstanding energy density retention, even at high power density. Compared with conventional preparation routes for porous carbon/graphene composites, the present approach is significantly simple, convenient and cost-effective, which will make it more competent in the development of electrode materials for high-performance supercapacitors.

Vertically aligned BCN nanotubes with high capacitance.

PubMed

Iyyamperumal, Eswaramoorthi; Wang, Shuangyin; Dai, Liming

2012-06-26

Using a chemical vapor deposition method, we have synthesized vertically aligned BCN nanotubes (VA-BCNs) on a Ni-Fe-coated SiO(2)/Si substrate from a melamine diborate precursor. The effects of pyrolysis conditions on the morphology and thermal property of grown nanotubes, as well as the nanostructure and composition of an individual BCN nanotube, were systematically studied. It was found that nitrogen atoms are bonded to carbons in both graphitic and pyridinic forms and that the resultant VA-BCNs grown at 1000 °C show the highest specific capacitance (321.0 F/g) with an excellent rate capability and high durability with respect to nonaligned BCN (167.3 F/g) and undoped multiwalled carbon nanotubes (117.3 F/g) due to synergetic effects arising from the combined co-doping of B and N in CNTs and the well-aligned nanotube structure.

MnO2-Graphene Oxide-PEDOT:PSS Nanocomposite for an Electrochemical Supercapacitor

NASA Astrophysics Data System (ADS)

Patil, Dipali S.; Pawar, Sachin A.; Shin, Jae Cheol; Kim, Hyo Jin

2018-04-01

A ternary nanocomposite with poly (3,4 ethylene dioxythiophene:poly(styrene sulfonate) (PEDOT:PSS)-MnO2 nanowires-graphene oxide (PMn-GO) was synthesized by using simple chemical route. The formation of the nanocomposite was analyzed by using X-ray diffraction and X-ray photoelectron spectroscopy. Field-emission scanning microscopy (FESEM) revealed the formation of MnO2 nanowires and graphene oxide nanosheets. The highest specific capacitance (areal capacitance) of 841 Fg -1 (177 mFcm -2) at 10 mVs -1 and energy density of 0.593 kWhkg -1 at 0.5 mA were observed for PMn-GO, indicating a constructive synergistic effect of PEDOT:PSS, MnO2 nanowires and graphene oxide. The achieved promising electrochemical characteristics showed that this ternary nanocomposite is a good alternative as an electrode material for supercapacitor.

All-solid state symmetric supercapacitors based on compressible and flexible free-standing 3D carbon nanotubes (CNTs)/poly(3,4-ethylenedioxythiophene) (PEDOT) sponge electrodes

NASA Astrophysics Data System (ADS)

He, Xin; Yang, Wenyao; Mao, Xiling; Xu, Lu; Zhou, Yujiu; Chen, Yan; Zhao, Yuetao; Yang, Yajie; Xu, Jianhua

2018-02-01

Flexible supercapacitors that maintain electrochemical performance under deformation have attracted much attention for the potential application in the flexible electronics market. A compressible and flexible free-standing electrodes sponge and all-solid-state symmetric supercapacitors based on as-prepared electrodes are presented. The carbon nanotubes (CNTs) framework is synthesized by chemical vapor deposition (CVD) method, and then composited with poly (3,4-ethylenedioxythiophene) PEDOT by the electrodeposition. This CNTs/PEDOT sponge electrode shows highest mass-specific capacitance of 147 Fg-1 at 0.5 A g-1, tuned by the PEDOT mass loading, and exhibits good cyclic stability with the evidence that more than 95% of capacitance is remained after 3000 cycles. Furthermore, the symmetric supercapacitor shows the highest energy density of 12.6 Wh kg-1 under the power density of 1 kW kg-1 and highest power density of 10.2 kW kg-1 with energy density of 8 Wh kg-1, which exhibits both high energy density and power density. The electrochemical performance of composite electrode also indicates that the operate voltage of device could be extend to 1.4 V by the n-doping and p-doping process in different potential of PEDOT component. This flexible supercapacitor maintains stable electrochemical performance working on different bending condition, which shows promising prospect for wearable energy storage applications.

Activated carbons from KOH-activation of argan (Argania spinosa) seed shells as supercapacitor electrodes.

PubMed

Elmouwahidi, Abdelhakim; Zapata-Benabithe, Zulamita; Carrasco-Marín, Francisco; Moreno-Castilla, Carlos

2012-05-01

Activated carbons were prepared by KOH-activation of argan seed shells (ASS). The activated carbon with the largest surface area and most developed porosity was superficially treated to introduce oxygen and nitrogen functionalities. Activated carbons with a surface area of around 2100 m(2)/g were obtained. Electrochemical measurements were carried out with a three-electrode cell using 1M H(2)SO(4) as electrolyte and Ag/AgCl as reference electrode. The O-rich activated carbon showed the lowest capacitance (259 F/g at 125 mA/g) and the lowest capacity retention (52% at 1A/g), due to surface carboxyl groups hindering electrolyte diffusion into the pores. Conversely, the N-rich activated carbon showed the highest capacitance (355 F/g at 125 mA/g) with the highest retention (93% at 1A/g), due to its well-developed micro-mesoporosity and the pseudocapacitance effects of N functionalities. This capacitance performance was among the highest reported for other activated carbons from a large variety of biomass precursors. Copyright © 2012 Elsevier Ltd. All rights reserved.

Manufacturing conductive polyaniline/graphite nanocomposites with spent battery powder (SBP) for energy storage: A potential approach for sustainable waste management.

PubMed

Duan, Xiaojuan; Deng, Jinxing; Wang, Xue; Guo, Jinshan; Liu, Peng

2016-07-15

A potential approach for sustainable waste management of the spent battery material (SBM) is established for manufacturing conductive polyaniline (PANI) nanocomposites as electrode materials for supercapacitors, following the principle of "What comes from the power should be used for the power". The ternary nanocomposites (G/MnO2/PANI) containing PANI, graphite powder (G) and remanent MnO2 nanoparticles and the binary nanocomposites of polyaniline and graphite powder (G/PANI) are synthesized by the chemical oxidative polymerization of aniline in hydrochloric aqueous solution with the MnO2 nanoparticles in the spent battery powder (SBP) as oxidant. The G/PANI sample, which was prepared with MnO2/aniline mole ratio of 1:1 with 1.0mL aniline in 50mL of 1.0molL(-1) HCl, exhibits the electrical conductivity of 22.22Scm(-1), the highest specific capacitance up to 317Fg(-1) and the highest energy density of 31.0 Wh kg(-1), with retention of as high as 84.6% of its initial capacitance after 1000 cycles, indicating good cyclic stability. Copyright © 2016 Elsevier B.V. All rights reserved.

Composite electrodes for electrochemical supercapacitors.

PubMed

Li, Jun; Yang, Quanmin; Zhitomirsky, Igor

2010-01-07

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4-6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7-15 mg cm-2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g-1 was obtained at a scan rate of 2 mV s-1 for mass loading of 7 mg cm-2. The SC decreased with increasing scan rate and increasing electrode mass.

Composite Electrodes for Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Li, Jun; Yang, Quan Min; Zhitomirsky, Igor

2010-03-01

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4-6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7-15 mg cm-2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g-1 was obtained at a scan rate of 2 mV s-1 for mass loading of 7 mg cm-2. The SC decreased with increasing scan rate and increasing electrode mass.

Composite Electrodes for Electrochemical Supercapacitors

PubMed Central

2010-01-01

Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT) into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm−2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC). The highest SC of 185 F g−1 was obtained at a scan rate of 2 mV s−1 for mass loading of 7 mg cm−2. The SC decreased with increasing scan rate and increasing electrode mass. PMID:20672101

MnFe2O4: Synthesis, morphology and electrochemical properties

NASA Astrophysics Data System (ADS)

Kulkarni, Shrikant; Thombare, Balu; Patil, Shankar

2017-05-01

MnFe2O4 has been synthesized by simple ammonia assisted co-precipitation method to obtain nanocrystalline powder. X-ray diffraction studies confirmed its crystallinity and phase purity. The MnFe2O4 calcined at 1000°C for 4 h has spinel crystal structure with Fd3m space group and lattice constant 8.511 Å. The electrode was prepared by dip coating method on stainless steel substrate and fired at 600°C for 2 h. Random shape grains of 0.2 to 1.5 micron with pores of 1-2 micron dimensions were observed in SEM images. The electrochemical studies of MnFe2O4 were carried out with 1 mole Na2SO4 electrolyte. The MnFe2O4 electrode shows highest specific capacitance of 27.53 F.g-1 and interfacial capacitance of 0.83 F.cm-2.

Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density.

PubMed

Zhang, Qichong; Wang, Xiaona; Pan, Zhenghui; Sun, Juan; Zhao, Jingxin; Zhang, Jun; Zhang, Cuixia; Tang, Lei; Luo, Jie; Song, Bin; Zhang, Zengxing; Lu, Weibang; Li, Qingwen; Zhang, Yuegang; Yao, Yagang

2017-04-12

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm 2 in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na 2 SO 4 poly(vinyl alcohol) (PVA) as the solid electrolyte, and MnO 2 /conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm 2 and an exceptional energy density of 96.07 μWh/cm 2 , the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices.

Dendritic Ni(Cu)-polypyrrole hybrid films for a pseudo-capacitor.

PubMed

Choi, Bit Na; Chun, Woo Won; Qian, Aniu; Lee, So Jeong; Chung, Chan-Hwa

2015-11-28

Dendritic Ni(Cu)-polypyrrole hybrid films are fabricated for a pseudo-capacitor in a unique morphology using two simple methods: electro-deposition and electrochemical de-alloying. Three-dimensional structures of porous dendrites are prepared by electro-deposition within the hydrogen evolution reaction (HER) at a high cathodic potential; the high-surface-area structure provides sufficient redox reactions between the electrodes and the electrolyte. The dependence of the active-layer thickness on the super-capacitor performance is also investigated, and the 60 μm-thick Ni(Cu)PPy hybrid electrode presents the highest performance of 659.52 F g(-1) at the scan rate of 5 mV s(-1). In the thicker layers, the specific capacitance became smaller due to the diffusion limitation of the ions in an electrolyte. The polypyrrole-hybridization on the porous dendritic Ni(Cu) electrode provides superior specific capacitance and excellent cycling stability due to the improvement in electric conductivity by the addition of conducting polypyrrole in the matrices of the dendritic nano-porous Ni(Cu) layer and the synergistic effect of composite materials.

Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors.

PubMed

Hou, Jianhua; Jiang, Kun; Wei, Rui; Tahir, Muhammad; Wu, Xiaoge; Shen, Ming; Wang, Xiaozhi; Cao, Chuanbao

2017-09-13

Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (S BET : 3301 m 2 g -1 ), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g -1 at 90 A g -1 for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg -1 or 53 Wh L -1 has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

Highly Uniform Anodically Deposited Film of MnO2 Nanoflakes on Carbon Fibers for Flexible and Wearable Fiber-Shaped Supercapacitors.

PubMed

Rafique, Amjid; Massa, Andrea; Fontana, Marco; Bianco, Stefano; Chiodoni, Angelica; Pirri, Candido F; Hernández, Simelys; Lamberti, Andrea

2017-08-30

A highly uniform porous film of MnO 2 was deposited on carbon fiber by anodic electrodeposition for the fabrication of high-performance electrodes in wearable supercapacitors (SCs) application. The effects of potentiostatic and galvanostatic electrodeposition and the deposition time were investigated. The morphology, crystalline structure, and chemical composition of the obtained fiber-shaped samples were analyzed by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The charge storage performance of the carbon fibers@MnO 2 composite electrode coupled to a gel-like polymeric electrolyte was investigated by cyclic voltammetry and galvanostatic charge-discharge measurements. The specific capacitance of the optimized carbon fiber@MnO 2 composite electrodes could reach up to 62 F g -1 corresponding to 23 mF cm -1 in PVA/NaCl gel-polymer electrolyte, i.e., the highest capacitance value ever reported for fiber-shaped SCs. Finally, the stability and the flexibility of the device were studied, and the results indicate exceptional capacitance retention and superior stability of the device subjected to bending even at high angles up to 150°.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying; Yang, Feng; Lee, Sungsik

Facile fabrication of manganese oxide (MnO x, 0 < x < 2) and nitrogen (N) co-doped carbon microspheres (MnO x-N-CS) has been firstly developed by one-pot construction of Mn-functionalized melamine-formaldehyde (Mn-MF) resin spheres before pyrolysis. The resulting hybrids bear evenly dispersed MnO x and N moieties in situ anchored on hierarchically porous carbon microspheres formed simultaneously. The capacitive performance is greatly tailored by varying the Mn/melamine molar ratio in the synthetic mixture and pyrolysis temperature. It is found that the MnO x-N-CS hybrid (0.008 wt% Mn, pyrolyzed at 800 °C) exhibits the highest specific capacitance up to 258 F gmore » –1 at a scan rate of 1 mV s –1 (in 6 M KOH), and keeps a high capacitance retention ratio of 98% after 5000 cycles. The synergism between MnO x, N moieties and carbon spheres proves to be responsible for the remarkably improved performance, as compared to the pure carbon sphere and MnO x (N)-doped carbon sphere. Lastly, the well-developed MnO x-N-CS hybrids highlight the great potentials for widespread supercapacitor applications.« less

High-performance flexible supercapacitors based on electrochemically tailored three-dimensional reduced graphene oxide networks.

PubMed

Purkait, Taniya; Singh, Guneet; Kumar, Dinesh; Singh, Mandeep; Dey, Ramendra Sundar

2018-01-12

A simple approach for growing porous electrochemically reduced graphene oxide (pErGO) networks on copper wire, modified with galvanostatically deposited copper foam is demonstrated. The as-prepared pErGO networks on the copper wire are directly used to fabricate solid-state supercapacitor. The pErGO-based supercapacitor can deliver a specific capacitance (C sp ) as high as 81±3 F g -1 at 0.5 A g -1 with polyvinyl alcohol/H 3 PO 4 gel electrolyte. The C sp per unit length and area are calculated as 40.5 mF cm -1 and 283.5 mF cm -2 , respectively. The shape of the voltammogram retained up to high scan rate of 100 V s -1 . The pErGO-based supercapacitor device exhibits noticeably high charge-discharge cycling stability, with 94.5% C sp retained even after 5000 cycles at 5 A g -1 . Nominal change in the specific capacitance, as well as the shape of the voltammogram, is observed at different bending angles of the device even after 5000 cycles. The highest energy density of 11.25 W h kg -1 and the highest power density of 5 kW kg -1 are also achieved with this device. The wire-based supercapacitor is scalable and highly flexible, which can be assembled with/without a flexible substrate in different geometries and bending angles for illustrating promising use in smart textile and wearable device.

High Performance and Economic Supercapacitors for Energy Storage Based on Carbon Nanomaterials

NASA Astrophysics Data System (ADS)

Samuilov, Vladimir; Farshid, Behzad; Frenkel, Alexander; Sensor CAT at Stony Brook Team

2015-03-01

We designed and manufactured very inexpensive prototypes of supercapacitors for energy storage based on carbon nanomaterials comprised of: reduced graphene oxide (RGOs) and carbon nanotubes (CNTs) as electrodes filled with polymer gel electrolytes. The electrochemical properties of supercapacitors made using these materials were compared and analyzed. A significant tradeoff between the energy density and the power density was determined; RGO electrodes demonstrated the highest energy density, while composite RGO/CNT electrodes showed the highest power density. The thickness of the RGO electrode was varied to determine its effect on the power density of the supercapacitor and results showed that with decreasing electrode thickness power density would increase. The specific capacitances of over 600 F/g were observed.

Density Functional Theory Calculations of the Quantum Capacitance of Graphene Oxide as a Supercapacitor Electrode.

PubMed

Song, Ce; Wang, Jinyan; Meng, Zhaoliang; Hu, Fangyuan; Jian, Xigao

2018-03-31

Graphene oxide has become an attractive electrode-material candidate for supercapacitors thanks to its higher specific capacitance compared to graphene. The quantum capacitance makes relative contributions to the specific capacitance, which is considered as the major limitation of graphene electrodes, while the quantum capacitance of graphene oxide is rarely concerned. This study explores the quantum capacitance of graphene oxide, which bears epoxy and hydroxyl groups on its basal plane, by employing density functional theory (DFT) calculations. The results demonstrate that the total density of states near the Fermi level is significantly enhanced by introducing oxygen-containing groups, which is beneficial for the improvement of the quantum capacitance. Moreover, the quantum capacitances of the graphene oxide with different concentrations of these two oxygen-containing groups are compared, revealing that more epoxy and hydroxyl groups result in a higher quantum capacitance. Notably, the hydroxyl concentration has a considerable effect on the capacitive behavior. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A high performance flexible all solid state supercapacitor based on the MnO2 sphere coated macro/mesoporous Ni/C electrode and ionic conducting electrolyte

NASA Astrophysics Data System (ADS)

Zhi, Jian; Reiser, Oliver; Wang, Youfu; Hu, Aiguo

2016-06-01

A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm-3, which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L-1 and 549 W L-1, based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices.A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm-3, which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L-1 and 549 W L-1, based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02215d

Defect states and their energetic position and distribution in organic molecular semiconductors

NASA Astrophysics Data System (ADS)

Sharma, Akanksha; Yadav, Sarita; Kumar, Pramod; Ray Chaudhuri, Sumita; Ghosh, Subhasis

2013-04-01

Energetic position and distribution of defect states due to structural disorder in pentacene and copper phthalocyanine have been obtained by capacitance based spectroscopic techniques. It has been shown that capacitance-frequency and capacitance-voltage characteristics exhibit Gaussian distribution of traps with an energetic position at around 0.5 eV above the highest occupied molecular orbital level of the pentacene and CuPc. These traps have been created by varying growth conditions and almost identical trap parameters in pentacene and copper phthalocyanine indicate that similar structural disorder is responsible for these traps.

Synergistic interaction between pseudocapacitive Fe3O4 nanoparticles and highly porous silicon carbide for high-performance electrodes as electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Kim, Myeongjin; Kim, Jooheon

2017-05-01

Composites of micro- and mesoporous SiC flakes (SiCF) and ferroferric oxide (Fe3O4), SiCF/Fe3O4, were prepared via the chemical deposition of Fe3O4 on SiCF by the chemical reduction of an Fe precursor. The SiCF/Fe3O4 electrodes were fabricated at different Fe3O4 feeding ratios to determine the optimal Fe3O4 content that can maintain a high total surface area of SiCF/Fe3O4 composites as well as cause a vigorous redox reaction, thereby maximizing the synergistic effect between the electric double-layer capacitive effects of SiCF and the pseudo-capacitive effects of Fe3O4. The SiCF/Fe3O4 electrode fabricated with a Fe3O4/SiCF feeding ratio of 1.5:1 (SiCF/Fe3O4(1.5)) exhibited the highest charge storage capacity, showing a specific capacitance of 423.2 F g-1 at a scan rate of 5 mV s-1 with a rate performance of 81.8% from 5 to 500 mV s-1 in an aqueous 1 M KOH electrolyte. The outstanding capacitive performance of the SiCF/Fe3O4(1.5) electrode could be attributed to the harmonious synergistic effect between the electric double-layer capacitive contribution of the SiCF and the pseudocapacitive contribution of the Fe3O4 nanoparticles introduced on the SiCF surface. These encouraging results demonstrate that the SiCF/Fe3O4(1.5) electrode is a promising high-performance electrode material for use in supercapacitors.

Synergistic interaction between pseudocapacitive Fe3O4 nanoparticles and highly porous silicon carbide for high-performance electrodes as electrochemical supercapacitors.

PubMed

Kim, Myeongjin; Kim, Jooheon

2017-05-12

Composites of micro- and mesoporous SiC flakes (SiCF) and ferroferric oxide (Fe 3 O 4 ), SiCF/Fe 3 O 4 , were prepared via the chemical deposition of Fe 3 O 4 on SiCF by the chemical reduction of an Fe precursor. The SiCF/Fe 3 O 4 electrodes were fabricated at different Fe 3 O 4 feeding ratios to determine the optimal Fe 3 O 4 content that can maintain a high total surface area of SiCF/Fe 3 O 4 composites as well as cause a vigorous redox reaction, thereby maximizing the synergistic effect between the electric double-layer capacitive effects of SiCF and the pseudo-capacitive effects of Fe 3 O 4 . The SiCF/Fe 3 O 4 electrode fabricated with a Fe 3 O 4 /SiCF feeding ratio of 1.5:1 (SiCF/Fe 3 O 4 (1.5)) exhibited the highest charge storage capacity, showing a specific capacitance of 423.2 F g -1 at a scan rate of 5 mV s -1 with a rate performance of 81.8% from 5 to 500 mV s -1 in an aqueous 1 M KOH electrolyte. The outstanding capacitive performance of the SiCF/Fe 3 O 4 (1.5) electrode could be attributed to the harmonious synergistic effect between the electric double-layer capacitive contribution of the SiCF and the pseudocapacitive contribution of the Fe 3 O 4 nanoparticles introduced on the SiCF surface. These encouraging results demonstrate that the SiCF/Fe 3 O 4 (1.5) electrode is a promising high-performance electrode material for use in supercapacitors.

Engineering hierarchical ultrathin CuCo2O4 nanosheets array on Ni foam by rapid electrodeposition method toward high-performance binder-free supercapacitors

NASA Astrophysics Data System (ADS)

Abbasi, Laleh; Arvand, Majid

2018-07-01

In the present work, we engineer hierarchical ultrathin CuCo2O4 nanosheets arrays on Ni foam through a facile, controllable and low-cost electrodeposition method by controlling deposition time and adjusting precursor's type, as a binder-free electrode for high performance supercapacitors. The effects of deposition time and types of precursors on the morphology of the as-prepared electrodes were investigated by X-ray diffraction, energy dispersive X-ray analysis, field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. As a results, the CuCo2O4 electrode prepared by nitrate salts at the deposition time of 10 min, includes the most uniform and ultrathin nanosheet arrays and exhibits the highest capacitance performance, such as ultrahigh specific capacitance of 1330 F g-1 at 2 A g-1 with 70% capacitance retention (938 F g-1) at ultrahigh current density of 60 A g-1, excellent cycling stability of 93.6% capacitance retention after 5000CD cycles and the maximum energy density of 29.55 Wh kg-1 at the power density of 0.4 kW kg-1. These superior electrochemical performances have been attributed to its unique structures with direct connected ultrathin nanosheets on the surface of Ni foam and abundant pores provide large electroactive sites for electrochemical reactions, as well as facile electron, ion transport and high electrical conductivity.

Predicting ion specific capacitances of supercapacitors due to quantum ionic interactions.

PubMed

Parsons, Drew F

2014-08-01

A new theoretical framework is now available to help explain ion specific (Hofmeister) effects. All measurements in physical chemistry show ion specificity, inexplicable by classical electrostatic theories. These ignore ionic dispersion forces that change ionic adsorption. We explored ion specificity in supercapacitors using a modified Poisson-Boltzmann approach that includes ionic dispersion energies. We have applied ab initio quantum chemical methods to determine required ion sizes and ion polarisabilities. Our model represents graphite electrodes through their optical dielectric spectra. The electrolyte was 1.2 M Li salt in propylene carbonate, using the common battery anions, PF6(-), BF4(-) and ClO4(-). We also investigated the perhalate series with BrO4(-) and IO4(-). The capacitance C=dσ/dψ was calculated from the predicted electrode surface charge σ of each electrode with potential ψ between electrodes. Compared to the purely electrostatic calculation, the capacitance of a positively charged graphite electrode was enhanced by more than 15%, with PF6(-) showing >50% increase in capacitance. IO4(-) provided minimal enhancement. The enhancement is due to adsorption of both anions and cations, driven by ionic dispersion forces. The Hofmeister series in the single-electrode capacitance was PF6(-)>BF4(-)>ClO4(-)>BrO4(-)>IO4(-) . When the graphite electrode was negatively charged, the perhalates provided almost no enhancement of capacitance, while PF6(-) and BF4(-) decreased capacitance by about 15%. Due to the asymmetric impact of nonelectrostatic ion interactions, the capacitances of positive and negative electrodes are not equal. The capacitance of a supercapacitor should therefore be reported as two values rather than one, similar to the matrix of mutual capacitances used in multielectrode devices. Copyright © 2014 Elsevier Inc. All rights reserved.

Flexible capacitive behavior of hybrid carbon materials prepared from graphene sheets

NASA Astrophysics Data System (ADS)

Ding, Y.-H.; Xie, W.; Zhang, P.; Jiang, Y.

2016-06-01

High frequency ultrasonication was employed to reduce the aggregation of graphene by constructing hybrid carbon materials (HCMs), which are endowed with a large electrochemical reaction area and high energy density. HCMs exhibited a specific capacitance of 168.5 F · g-1 with ˜100% capacitance retention over 500 cycles. Flexible supercapacitors fabricated from HCMs also showed an excellent capacitive behavior even under tough conditions. These outstanding electrochemical properties were ascribed to the increased specific surface area and open structure of HCMs.

A comparative study of Ni-Mn layered double hydroxide/carbon composites with different morphologies for supercapacitors.

PubMed

Li, M; Liu, F; Zhang, X B; Cheng, J P

2016-11-02

A variety of carbon materials varying from 0D to 2D, i.e. 0D nanoparticles, 1D carbon nanotubes (CNTs) and 2D reduced graphene oxide (rGO) are selected to in situ combine with Ni-Mn layered double hydroxide (LDH) to prepare electrode materials for supercapacitors. Through a simple solution method, hierarchical Ni-Mn LDH/carbon composites can be easily fabricated. A comparative study is carried out on the sandwich-like LDH/rGO, flower-like LDH/carbon black, turbostratic-structured LDH/CNTs and ternary LDH/CNTs/rGO for their structure, morphology, porous properties and electrochemical performances. The results show that the ternary Ni-Mn LDH/CNTs/rGO composite yields the highest specific capacitance of 1268 F g -1 in 2 M KOH electrolyte and a long lifespan, exhibiting great potential for supercapacitor applications. Meanwhile, investigation on the influence of the cation species of MOH (M = Li + , Na + or K + ) and the alkali concentration of the KOH electrolyte illustrates that increasing the concentration of the KOH electrolyte can benefit the capacitive performance of the electrode and that NaOH shows great advantages as an electrolyte for the Ni-Mn LDH/CNTs/rGO electrode due to its high capacitance and small resistance.

Biobased Nano Porous Active Carbon Fibers for High-Performance Supercapacitors.

PubMed

Huang, Yuxiang; Peng, Lele; Liu, Yue; Zhao, Guangjie; Chen, Jonathan Y; Yu, Guihua

2016-06-22

Activated carbon fibers (ACFs) with different pore structure have been prepared from wood sawdust using the KOH activation method. A study was conducted to examine the influence of the activation parameters (temperature, alkali/carbon ratio, and time) on the morphology and structure of the as-prepared ACFs developed in the process of pore generation and evolution. Activation temperature was very essential for the formation of utramicropores (<0.6 nm), which greatly contributed to the electric double layer capacitance. The significance of metallic potassium vapor evolved when the temperature was above 800 °C, since the generation of 0.8- and 1.1 nm micropores cannot be ignored. When the the KOH/fiber ratio was increased and the activation time was prolonged, to some extent, the micropores were enlarged to small mesopores within 2-5 nm. The sample with the optimal condition exhibited the highest specific capacitance (225 F g(-1) at a current density of 0.5 A g(-1)). Its ability to retain capacitance corresponding to 10 A g(-1) and 6 M KOH was 85.3%, demonstrating a good rate capability. With 10 000 charge-discharge cycles at 3 A g(-1), the supercapacitor kept 94.2% capacity, showing outstanding electrochemical performance as promising electrode material.

Facile fabrication of MnO x and N co-doped hierarchically porous carbon microspheres for high-performance supercapacitors

DOE PAGES

Yang, Ying; Yang, Feng; Lee, Sungsik; ...

2016-01-16

Facile fabrication of manganese oxide (MnO x, 0 < x < 2) and nitrogen (N) co-doped carbon microspheres (MnO x-N-CS) has been firstly developed by one-pot construction of Mn-functionalized melamine-formaldehyde (Mn-MF) resin spheres before pyrolysis. The resulting hybrids bear evenly dispersed MnO x and N moieties in situ anchored on hierarchically porous carbon microspheres formed simultaneously. The capacitive performance is greatly tailored by varying the Mn/melamine molar ratio in the synthetic mixture and pyrolysis temperature. It is found that the MnO x-N-CS hybrid (0.008 wt% Mn, pyrolyzed at 800 °C) exhibits the highest specific capacitance up to 258 F gmore » –1 at a scan rate of 1 mV s –1 (in 6 M KOH), and keeps a high capacitance retention ratio of 98% after 5000 cycles. The synergism between MnO x, N moieties and carbon spheres proves to be responsible for the remarkably improved performance, as compared to the pure carbon sphere and MnO x (N)-doped carbon sphere. Lastly, the well-developed MnO x-N-CS hybrids highlight the great potentials for widespread supercapacitor applications.« less

Enhancing the performance of green solid-state electric double-layer capacitor incorporated with fumed silica nanoparticles

NASA Astrophysics Data System (ADS)

Chong, Mee Yoke; Numan, Arshid; Liew, Chiam-Wen; Ng, H. M.; Ramesh, K.; Ramesh, S.

2018-06-01

Solid polymer electrolyte (SPE) based on fumed silica nanoparticles as nanofillers, hydroxylethyl cellulose (HEC) as host polymer, magnesium trifluoromethanesulfonate salt and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid is prepared by solution casting technique. The ionic conductivity, interactions of adsorbed ions on the host polymer, structural crystallinity and thermal stability are evaluated by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Ionic conductivity studies at room temperature reveals that the SPE with 2 wt. % of fumed silica nanoparticles gives the highest conductivity compared to its counterpart. The XRD and FTIR studies confirm the dissolution of salt, ionic liquid and successful incorporation of fumed silica nanoparticles with host polymer. In order to examine the performance of SPEs, electric double-layer capacitor (EDLC) are fabricated by using activated carbon electrodes. EDLC studies demonstrate that SPE incorporated with 2 wt. % fumed silica nanoparticles gives high specific capacitance (25.0 F/g) at a scan rate of 5 mV/s compared to SPE without fumed silica. Additionally, it is able to withstand 71.3% of capacitance from its initial capacitance value over 1600 cycles at a current density of 0.4 A/g.

Surfactant-treated graphene covered polyaniline nanowires for supercapacitor electrode

NASA Astrophysics Data System (ADS)

Rajagopalan, Balasubramaniyan; Hur, Seung Hyun; Chung, Jin Suk

2015-04-01

Surfactant-treated graphene/polyaniline (G/PANI) nanocomposites were prepared by the MnO2 template-aided oxidative polymerization of aniline (ANI) on the surfactant-treated graphene sheets. The electrochemical performances of the G/PANI nanocomposites in a three-electrode system using an aqueous sulfuric acid as an electrolyte exhibited a specific capacitance of 436 F g-1 at 1 A g-1, which is much higher than the specific capacitance of pure PANI (367 F g-1). Such a higher specific capacitance of the G/PANI nanocomposite inferred an excellent synergistic effect of respective pseudocapacitance and electrical double-layer capacitance of PANI and graphene.

In-situ conversion of rGO/Ni2P composite from GO/Ni-MOF precursor with enhanced electrochemical property

NASA Astrophysics Data System (ADS)

Lv, Zijian; Zhong, Qin; Bu, Yunfei

2018-05-01

Owing to the metalloid characteristic and superior electrical conductivity, the metal phosphides have received increasing interests in energy storage systems. Here, xrGO/Ni2P composites are successfully synthesized via an In-situ phosphorization process with GO/Ni-MOF as precursors. Compared to pure Ni2P, the xrGO/Ni2P composites appear enhanced electrochemical properties in terms of the specific capacitance and cycling performance as electrodes for supercapacitors. Especially, the 2rGO/Ni2P electrode shows a highest specific capacitance of 890 F g-1 at 1 A g-1 among the obtained composites. The enhancement can be attributed to the inherited structure from Ni-MOF and the well assembled of rGO and Ni2P through the In-situ conversion process. Moreover, when applied as positive electrode in a hybrid supercapacitor, an energy density of 35.9 W h kg-1 at a power density of 752 W kg-1 has been achieved. This work provides an In-situ conversion strategy for the synthesis of rGO/Ni2P composite which might be a promising electrode material for SCs.

Evaluation on carbon nanocapsules for supercapacitors using a titanium cavity electrode

NASA Astrophysics Data System (ADS)

Wu, Cheng-Yeou; Wu, Pu-Wei; Lin, Pang

We synthesize carbon nanocapsules (CNCs) by a flame combustion method and evaluate their potential as the electrode material for electrochemical double layer capacitor using a titanium cavity electrode (TCE). Identical process is conducted on commercially available carbonaceous materials such as Vulcan XC72R, Black Pearl 2000 (BP2000), multi-walled carbon nanotubes (MWCNTs), and active carbon (AC1100) for comparison purposes. Images from Scanning electron microscope and Transmission electron microscope on the CNCs demonstrate irregular-shaped particles in average size of 10-20 nm with graphene layers on perimeter compassing a hollow core. Electrochemical characterizations including cyclic voltammetry (CV), current reversal chronopotentiometry (CRC), and impedance spectroscopy are carried out in 1N H 2SO 4 to determine the specific capacitance and cycle life time. Among these samples, the BP2000 still delivers the highest specific capacitance in F g -1 but the CNCs demonstrate the largest value in μF cm 2. In addition, the CNCs exhibit impressive life time for 5000 cycles without notable degradation. Consistent results are obtained by CV, CRC, and impedance measurements, validating the TCE as a facile tool to perform reliable electrochemical evaluations.

The effect of CO2 activation temperature on the physical and electrochemical properties of activated carbon monolith from banana stem waste

NASA Astrophysics Data System (ADS)

Taer, E.; Susanti, Y.; Awitdrus, Sugianto, Taslim, R.; Setiadi, R. N.; Bahri, S.; Agustino, Dewi, P.; Kurniasih, B.

2018-02-01

The effect of CO2 activation on the synthesis of activated carbon monolith from banana stem waste has been studied. Physical characteristics such as density, degree of crystallinity, surface morphology and elemental content has been analyzed, supporting the finding of an excellent electrochemical properties for the supercapacitor. The synthesis of activated carbon electrode began with pre-carbonization process at temperature of 250°C for 2.5 h. Then the process was continued by chemical activation using KOH as activating agent with a concentration of 0.4 M. The pellets were formed with 8 ton hydrolic pressure. All the samples were carbonized at a temperature of 600°C, followed by physical activation using CO2 gas at a various temperatures ranging from 800°C, 850°C, 900°C and 950°C for 2 h. The carbon content was increased with increasing temperature and the optimum temperature was 900°C. The specific capacitance depends on the activation temperature with the highest specific capacitance of 104.2 F/g at the activation temperature of 900°C.

Functionalization of Graphene Oxide and its Composite with Poly(3,4-ethylenedioxythiophene) as Electrode Material for Supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Minchao; Jamal, Ruxangul; Wang, Yujie; Yang, Lei; Liu, Fangfang; Abdiryim, Tursun

2015-09-01

In this study, poly(3,4-ethylenedioxythiophene)/thiophene-grafted graphene oxide (PEDOT/Th-GO) composites from covalently linking of Th-GO with PEDOT chains were prepared via in situ chemical polymerization with different weight percentage of Th-GO ranging between 40 and 70 % in reaction medium. The resulting composite materials were characterized using a various analytical techniques. The structural analysis showed that the composites displayed a higher degree of conjugation and thermal stability than pure PEDOT, and the weight percentage of Th-GO could affect the doping level, amount of undesired conjugated segments, and porous structure of composites. Electrochemical analysis suggested that the highest specific capacitance of 320 F g-1 at a current density of 1 A g-1 with good cycling stability (capacitance retention of 80 % at 1 A g-1 after 1000 cycles) was achieved for the composite prepared from 50 wt% Th-GO content in reaction medium.

Facile synthesis of CuFe2O4-Fe2O3 composite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Khan, Rashid; Habib, Muhammad; Gondal, Mohammed A.; Khalil, Adnan; Rehman, Zia Ur; Muhammad, Zahir; Haleem, Yasir A.; Wang, Changda; Wu, Chuan Qiang; Song, Li

2017-10-01

We report the synthesis of CuFe2O4-Fe2O3 composite material for efficient and highly stable supercapacitor electrode by using eco-friendly low-temperature co-precipitation method. The CuFe2O4-Fe2O3 composite demonstrated the highest specific capacitance of 638.24 F g-1 and excellent stability up to 2000 charge/discharge cycles. The achieved capacitance value is 16 times higher than that of pure CuFe2O4. The results revealed the extraordinary performance of CuFe2O4-Fe2O3 composite as supercapacitor electrode with excellent retention in comparison to CuFe2O4. The enhanced electrochemical activity of CuFe2O4-Fe2O3 composite is attributed to the synergistic effect which is responsible for redox coupling between Cu2+ and Fe3+ that has never been achieved by single component before.

Functionalization of Graphene Oxide and its Composite with Poly(3,4-ethylenedioxythiophene) as Electrode Material for Supercapacitors.

PubMed

Wang, Minchao; Jamal, Ruxangul; Wang, Yujie; Yang, Lei; Liu, Fangfang; Abdiryim, Tursun

2015-12-01

In this study, poly(3,4-ethylenedioxythiophene)/thiophene-grafted graphene oxide (PEDOT/Th-GO) composites from covalently linking of Th-GO with PEDOT chains were prepared via in situ chemical polymerization with different weight percentage of Th-GO ranging between 40 and 70 % in reaction medium. The resulting composite materials were characterized using a various analytical techniques. The structural analysis showed that the composites displayed a higher degree of conjugation and thermal stability than pure PEDOT, and the weight percentage of Th-GO could affect the doping level, amount of undesired conjugated segments, and porous structure of composites. Electrochemical analysis suggested that the highest specific capacitance of 320 F g(-1) at a current density of 1 A g(-1) with good cycling stability (capacitance retention of 80 % at 1 A g(-1) after 1000 cycles) was achieved for the composite prepared from 50 wt% Th-GO content in reaction medium.

Controlled synthesis of nanostructured molybdenum oxide electrodes for high performance supercapacitor devices

NASA Astrophysics Data System (ADS)

Maheswari, Nallappan; Muralidharan, Gopalan

2017-09-01

Well defined crystallographic and one dimensional morphological structure of molybdenum oxide were successfully synthesized by adjusting the duration of hydrothermal treatment. The prepared molybdenum oxide was examined through XRD, SEM, FTIR, TEM, BET and electrochemical studies. The XRD patterns illustrate that MoOx prepared by variying the hydrothermal reaction time are in different crystallographic structure of MoyOx (Mo8O23 and MoO3). SEM studies reveal the different morphological structures ranging from flake like morphology to nanorods. TEM images confirm the excellent nanorod structure. The nanorod structure ensures good cyclic behaviour with maximum capacitance of 1080 F g-1 at a current density of 2 A g-1. This large capacity of the MoO3 nanostructures enabled fabrication of symmetric and asymmertic supercapacitor devices. The asymmertic device exhibits a maximum specific capacitance of 145 F g-1 at 2 mV s-1 with highest energy density of 38.6 W h kg-1 at 374.7 W kg-1 power density.

A facile one-step synthesis of Mn{sub 3}O{sub 4} nanoparticles-decorated TiO{sub 2} nanotube arrays as high performance electrode for supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jianfang; Wang, Yan; Key Laboratory of Advance Functional Materials and Devices of Anhui Province, Hefei 230009

Via a facile one-step chemical bath deposition route, homogeneously dispersed Mn{sub 3}O{sub 4} nanoparticles have been successfully deposited onto the inner surface of TiO{sub 2} nanotube arrays (TNAs). The content and size of Mn{sub 3}O{sub 4} can be controlled by changing the deposition time. Field emission scanning electron microscopy and transmission electron microscopy analysis reveal the morphologies structures of Mn{sub 3}O{sub 4}/TNAs composites. The crystal-line structures are characterized by the X-ray diffraction patterns and Raman spectra. X-ray photoelectron spectroscopy further confirms the valence states of the sample elements. The electrochemical properties of Mn{sub 3}O{sub 4}/TNAs electrodes are systematically investigated bymore » the combine use of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The resulting Mn{sub 3}O{sub 4}/TNAs electrode prepared by deposition time of 3 h shows the highest specific capacitance of 570 F g{sup −1} at a current density of 1 A g{sup −1}. And it also shows an excellent long-term cycling stability at a current density of 5 A g{sup −1}, which remaining 91.8% of the initial capacitance after 2000 cycles. Thus this kind of Mn{sub 3}O{sub 4} nanoparticles decorated TNAs may be considered as an alternative promising candidate for high performance supercapacitor electrodes. - Graphical abstract: Mn{sub 3}O{sub 4} nanoparticles have been uniformly deposited onto the inner surfaces of TiO{sub 2} nanotube arrays through a facile one-step chemical bath deposition method. As electrodes for supercapacitors, they exhibit a relatively high specific capacity and excellent cycling stability. - Highlights: • Mn{sub 3}O{sub 4} nanoparticles have been deposited onto TiO{sub 2} nanotube arrays by chemical bath deposition. • The Mn{sub 3}O{sub 4}/TNAs exhibits a highest specific capacitance of 570 F g{sup –1} at a current density of 1 A g{sup –1}. • The Mn{sub 3}O{sub 4}/TNAs electrode shows an excellent cycling stability of 91.8% after 2000 cycles.« less

Facile fabrication of cobalt oxalate nanostructures with superior specific capacitance and super-long cycling stability

NASA Astrophysics Data System (ADS)

Cheng, Guanhua; Si, Conghui; Zhang, Jie; Wang, Ying; Yang, Wanfeng; Dong, Chaoqun; Zhang, Zhonghua

2016-04-01

Transition metal oxalate materials have shown huge competitive advantages for applications in supercapacitors. Herein, nanostructured cobalt oxalate supported on cobalt foils has been facilely fabricated by anodization, and could directly serve as additive/binder-free electrodes for supercapacitors. The as-prepared cobalt oxalate electrodes present superior specific capacitance of 1269 F g-1 at the current density of 6 A g-1 in the galvanostatic charge/discharge test. Moreover, the retained capacitance is as high as 87.2% as the current density increases from 6 A g-1 to 30 A g-1. More importantly, the specific capacitance of cobalt oxalate retains 91.9% even after super-long cycling of 100,000 cycles. In addition, an asymmetric supercapacitor assembled with cobalt oxalate (positive electrode) and activated carbon (negative electrode) demonstrates excellent capacitive performance with high energy density and power density.

Synthesis and Microstructural Characterization of Manganese Oxide Electrodes for Application as Electrochemical Supercapacitors

NASA Astrophysics Data System (ADS)

Babakhani, Banafsheh

The aim of this thesis work was to synthesize Mn-based oxide electrodes with high surface area structures by anodic electrodeposition for application as electrochemical capacitors. Rod-like structures provide large surface areas leading to high specific capacitances. Since templated electrosynthesis of rods is not easy to use in practical applications, it is more desirable to form rod-like structures without using any templates. In this work, Mn oxide electrodes with rod-like structures (˜1.5 µm in diameter) were synthesized from a solution of 0.01 M Mn acetate under galvanostatic control without any templates, on Au coated Si substrates. The electrochemical properties of the synthesized nanocrystalline electrodes were investigated to determine the effect of morphology, chemistry and crystal structure on the corresponding electrochemical behavior of Mn oxide electrodes. Mn oxides prepared at different current densities showed a defective antifluoritetype crystal structure. The rod-like Mn oxide electrodes synthesized at low current densities (5 mAcm.2) exhibited a high specific capacitance due to their large surface areas. Also, specific capacity retention after 250 cycles in an aqueous solution of 0.5 M Na2SO4 at 100 mVs -1 was about 78% of the initial capacity (203 Fg-1 ). To improve the electrochemical capacitive behavior of Mn oxide electrodes, a sequential approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 µm long and less than 1.5 µm in diameter) were first synthesized, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected by the composition and pH of the electrolyte, temperature, current density and polymer deposition time. Mn oxide/PEDOT coaxial core/shell rods consisted of MnO2 with an antifluorite-type structure coated with amorphous PEDOT. The Mn oxide/PEDOT coaxial core/shell electrodes prepared by the sequential method showed significantly better specific capacity and redox performance properties relative to both uncoated Mn oxide rods and co- electrodeposited Mn oxide/PEDOT electrodes. The best specific capacitance for Mn oxide/PEDOT rods produced sequentially was ˜295 F g-1 with ˜92% retention after 250 cycles in 0.5 M Na2SO4 at 100 mV s-1. To further improve the electrochemical capacitive behavior of Mn oxide electrodes, Co-doped and Fe-doped Mn oxide electrodes with a rod-like morphology and antifluorite-type crystal structure were synthesized by anodic electrodeposition, on Au coated Si substrates, from dilute solutions of Mn acetate and Co sulphate and Mn acetate and Fe chloride. Also, Mn-Co oxide/PEDOT coaxial core/shell rods were synthesized by applying a shell of PEDOT on Mn-Co oxide electrodes. Mn-Co oxide/PEDOT electrodes consisted of MnO2, with partial Co 2+ and Co3+ ion substitution for Mn4+, and amorphous PEDOT. Mn-Fe oxide electrodes consisted of MnO2, with partial Fe2+ and Fe3+ ion substitution for Mn4+. Electrochemical analysis showed that the capacitance values for all deposits increased with increasing scan rate to 100 mVs -1, and then decreased after 100 mVs-1. The Mn-Co oxide/PEDOT electrodes showed improved specific capacity and electrochemical cyclability relative to uncoated Mn-Co oxides and Mn-Fe oxides. Mn-Co oxide/PEDOT electrodes with rod-like structures had high capacitances (up to 310 Fg -1) at a scan rate of 100 mVs-1 and maintained their capacitance after 500 cycles in 0.5 M Na2SO4 (91% retention). Capacitance reduction for the deposits was mainly due to the loss of Mn ions by dissolution in the electrolyte solution. To better understand the nucleation and growth mechanisms of Mn oxide electrodes, the effects of supersaturation ratio on the morphology and crystal structure of electrodeposited Mn oxide were studied. By changing deposition parameters, including deposition current density, electrolyte composition, pH and temperature, a series of nanocrystalline Mn oxide electrodes with various morphologies (continuous coatings, rod-like structures, aggregated rods and thin sheets) and an antifluorite-type crystal structure was obtained. Mn oxide thin sheets showed instantaneous nucleation and single crystalline growth; rods had a mix of instantaneous/progressive nucleation and polycrystalline growth and continuous coatings formed by progressive nucleation and polycrystalline growth. Electrochemical analysis revealed the best capacitance behaviour obtained for Mn oxide thin sheets followed by Mn oxide rods, with dimensions on the microscale, and then continuous coatings. The highest specific capacitance (˜230 Fg-1) and capacitance retention rates (˜88%) were obtained for Mn oxide thin sheets after 250 cycles in 0.5 M Na2 SO4 at 20 mVs-1.

Electropolymerized polyazulene as active material in flexible supercapacitors

NASA Astrophysics Data System (ADS)

Suominen, Milla; Lehtimäki, Suvi; Yewale, Rahul; Damlin, Pia; Tuukkanen, Sampo; Kvarnström, Carita

2017-07-01

We report the capacitive behavior of electrochemically polymerized polyazulene films in different ionic liquids. The ionic liquids in this study represent conventional imidazolium based ionic liquids with tetrafluoroborate and bis(trifluoromethylsulfonyl)imide anions as well as an unconventional choline based ionic liquid. The effect of different ionic liquids on the polymerization and capacitive performance of polyazulene films is demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy in a 3-electrode cell configuration. The films exhibit the highest capacitances in the lowest viscosity ionic liquid (92 mF cm-2), while synthesis in high viscosity ionic liquid shortens the conjugation length and results in lower electroactivity (25 mF cm-2). The obtained films also show good cycling stabilities retaining over 90% of their initial capacitance over 1200 p-doping cycles. We also demonstrate, for the first time, flexible polyazulene supercapacitors of symmetric and asymmetric configurations using the choline based ionic liquid as electrolyte. In asymmetric configuration, capacitance of 55 mF (27 mF cm-2) with an equivalent series resistance of 19 Ω is obtained at operating voltage of 1.5 V. Upon increasing the operating voltage up to 2.4 V, the capacitance increases to 72 mF (36 mF cm-2).

Specific methodology for capacitance imaging by atomic force microscopy: A breakthrough towards an elimination of parasitic effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Estevez, Ivan; Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis; Chrétien, Pascal

2014-02-24

On the basis of a home-made nanoscale impedance measurement device associated with a commercial atomic force microscope, a specific operating process is proposed in order to improve absolute (in sense of “nonrelative”) capacitance imaging by drastically reducing the parasitic effects due to stray capacitance, surface topography, and sample tilt. The method, combining a two-pass image acquisition with the exploitation of approach curves, has been validated on sets of calibration samples consisting in square parallel plate capacitors for which theoretical capacitance values were numerically calculated.

Three Dimensional Nitrogen-Doped and Nitrogen, Sulfur-Codoped Graphene Hydrogels for Electrode Materials in Supercapacitors.

PubMed

Yuan, Zhao; Qiao, Fei; Wang, Guiqiang; Zhou, Jin; Cui, Hongyou; Zhuo, Shuping; Xing, Ling-Bao

2018-08-01

In present work, reduced graphene oxide hydrogels (RGOHs) with three-dimensional (3D) porous structure are prepared through chemical reduction method by using aminourea (NRGOHs) and aminothiourea (NSRGOHs) as reductants. The as-prepared RGOHs are considered not only as promising electrode materials for supercapacitors, but also the doping of nitrogen (aminourea, NRGOHs) or nitrogen/sulfur (aminothiourea, NSRGOHs) can improve electrochemical performance through faradaic pseudocapacitance. The optimized samples have been prepared by controlling the mass ratios of graphene oxide (GO) to aminourea or aminothiourea to be 1:1, 1:2 and 1:5, respectively. With adding different amounts of aminourea or aminothiourea, the obtained RGOHs exhibited different electrochemical performance in supercapacitors. With increasing the dosage of the reductants, the RGOHs revealed better specific capacitances. Moreover, NSRGOHs with nitrogen, sulfur-codoping exhibited better capacitance performance than that of NRGOHs with only nitrogen-doping. NSRGOHs showed excellent capacitive performance with a very high specific capacitance up to 232.2, 323.3 and 345.6 F g-1 at 0.2 A g-1, while NRGOHs showed capacitive performance with specific capacitance up to 220.6, 306.5 and 332.7 F g-1 at 0.2 A g-1. This provides a strategy to improve the capacitive properties of RGOHs significantly by controlling different doping the materials.

Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

NASA Astrophysics Data System (ADS)

Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

2015-12-01

Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

Mesoporous silica wrapped with graphene oxide-conducting PANI nanowires as a novel hybrid electrode for supercapacitor

NASA Astrophysics Data System (ADS)

Javed, Mohsin; Abbas, Syed Mustansar; Siddiq, Mohammad; Han, Dongxue; Niu, Li

2018-02-01

A high charge-carrier transport is an important aim in the synthesis of nanostructures for an effective supercapacitor. This article describes a methodology to prepare mesoporous silica nanoparticles (MSNs) wrapped with graphene oxide (GO) together with conducting polyaniline (PANI) wires. The morphology and chemical structure of the prepared samples have been tested by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD), whereas the stability and electrostatic interaction of the structures have been verified by thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The supercapacitive behaviour of these nanocomposites has been analysed by cyclic voltammetry (CV), charge-discharge tests, and electrochemical impedance spectroscopy (EIS). Compared with pristine MSNs and PANI, the 20%-GO@MSNs/PANI nanocomposite had the highest specific capacitance, reaching 412 F g-1. The nanocomposite structure maximizes the synergy between mesoporous metal oxide, conducting PANI, and GO, yielding a significantly enhanced specific capacitance, rapid charge-discharge rates, and good cycling stability of the resulting device. The wrapping with GO prevents the structural breakdown and acts as a highly conductive pathway by bridging the individual particles, whereas the MSNs nanoparticles greatly enlarge the specific surface area to facilitate ion transport and charge transfer throughout the cycling performance of supercapacitor. The approach adopted in this article can be applied for preparing similar novel functional materials in future for electrochemical applications.

Carbon-polyaniline nanocomposites as supercapacitor materials

NASA Astrophysics Data System (ADS)

Sathish Kumar, M.; Yamini Yasoda, K.; Batabyal, Sudip Kumar; Kothurkar, Nikhil K.

2018-04-01

Polyaniline-based nanocomposites containing carbon nanotubes (CNT), reduced graphene oxide (rGO) and mixture of CNTs and rGO were synthesized. UV-visible spectroscopy and FT-IR spectroscopy confirmed the presence of polyaniline (PANi) and carbon nanomaterials. Scanning electron microscopy revealed that the neat PANi had a granular morphology, which can lead to increased electrical resistance to high interfacial resistance between domains of PANi. Cyclic voltammetry of PANi, PANi/CNT, PANi/rGO and PANi/CNT/rGO showed that in general, specific capacitance reduces with increasing scan rate within the range (10–100 mV s‑1). Also the specific capacitance values at any given scan rate within the above range, for PANi, PANi/CNT, PANi/rGO and PANi/CNT/rGO were found to be in increasing order. The specific capacitance of the PANi/CNT/rGO nanocomposite as measured by galvanostatic charge-discharge measurements, was found to be 312.5 F g‑1. The introduction of the carbon nanomaterials (CNTs, rGO) in PANi in general leads to improved specific capacitance, while the addition of CNTs and rGO together leads to synergistic improvement in the specific capacitance, owing to a combination of factors.

Electrochemical synthesis of three-dimensional porous networks of nickel with different micro-nano structures for the fabrication of Ni/MnOx nanocomposites with enhanced supercapacitive performance

NASA Astrophysics Data System (ADS)

Ashassi-Sorkhabi, H.; La'le Badakhshan, P.

2017-10-01

We have electrochemically synthesized 3D-porous Ni/MnOx nanocomposites for supercapacitor applications. 3D porous micro-nanostructured networks of nickel were prepared using hydrogen bubbles as a dynamic template at different deposition potentials and times. The prepared nickel films were used then as 3D-porous substrates for anodic deposition of manganese oxide nanostructures. The effects of deposition potential and time on the structure of the prepared nickel scaffolds and especially on the capacitive behavior of the subsequently fabricated 3D-porous Ni/MnOx nanocomposites were investigated. The results show that the areal capacitance and especially the rate capability of prepared Ni/MnOx nanocomposites have improved with increasing the deposition potential or optimizing the deposition time of nickel films in the nanocomposites. The prepared 3D-porous Ni/MnOx nanocomposite, in which the nickel scaffold has been deposited at the potential of -6 V and duration of 90s, show almost the highest capacitive performance among all other prepared nanocomposites. This prepared nanocomposite, with the loading mass of 1.65 mg cm-2, showed the high areal capacitance of 654 mF cm-2 (396.4 F g-1) at the current density of 0.5 mA cm-2 (0.3 A g-1) in 0.5 M Na2SO4 solution. This nanocomposite also revealed the highest rate capability; the capacitance retention is about 63% (412 mF cm-2) with increasing the discharge rate from 0.5 to 20 mA cm-2, which is almost twice the observed amount of retention when the deposition potential of Ni films was -2 V (31%) or their deposition time was 45 s (34%). In addition, the prepared nanocomposite exhibited an outstanding cycling stability. The capacitance retention was about 98.91% after performing 2000 charge-discharge cycles.

Biredox ionic liquids: new opportunities toward high performance supercapacitors.

PubMed

Bodin, C; Mourad, E; Zigah, D; Le Vot, S; Freunberger, S A; Favier, F; Fontaine, O

2018-01-01

Nowadays commercial supercapacitors are based on purely capacitive storage at the porous carbons that are used for the electrodes. However, the limits that capacitive storage imposes on energy density calls to investigate new materials to improve the capacitance of the device. This new type of electrodes (e.g., RuO 2 , MnO 2 …) involves pseudo-capacitive faradaic redox processes with the solid material. Ion exchange with solid materials is, however, much slower than the adsorption process in capacitive storage and inevitably leads to significant loss of power. Faradaic process in the liquid state, in contrast can be similarly fast as capacitive processes due to the fast ion transport. Designing new devices with liquid like dynamics and improved specific capacitance is challenging. We present a new approach to increase the specific capacitance using biredox ionic liquids, where redox moieties are tethered to the electrolyte ions, allowing high redox concentrations and significant pseudo-capacitive storage in the liquid state. Anions and cations are functionalized with anthraquinone (AQ) and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) moieties, respectively. Glassy carbon, carbon-onion, and commercial activated carbon electrodes that exhibit different double layer structures and thus different diffusion dynamics were used to simultaneously study the electrochemical response of biredox ionic liquids at the positive and negative electrode.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-10-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g-1 present high specific capacities of the 308 and 200 F g-1 in KOH electrolyte at current densities of 0.1 and 10 A g-1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g-1 at 0.1 A g-1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors.

PubMed

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-10-16

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m(2) g(-1) present high specific capacities of the 308 and 200 F g(-1) in KOH electrolyte at current densities of 0.1 and 10 A g(-1), respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g(-1) at 0.1 A g(-1) and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry.

A droplet-based passive force sensor for remote tactile sensing applications

NASA Astrophysics Data System (ADS)

Nie, Baoqing; Yao, Ting; Zhang, Yiqiu; Liu, Jian; Chen, Xinjian

2018-01-01

A droplet-based flexible wireless force sensor has been developed for remote tactile-sensing applications. By integration of a droplet-based capacitive sensing unit and two circular planar coils, this inductor-capacitor (LC) passive sensor offers a platform for the mechanical force detection in a wireless transmitting mode. Under external loads, the membrane surface of the sensor deforms the underlying elastic droplet uniformly, introducing a capacitance response in tens of picofarads. The LC circuit transduces the applied force into corresponding variations of its resonance frequency, which is detected by an external electromagnetic coupling coil. Specifically, the liquid droplet features a mechanosensitive plasticity, which results in an increased device sensitivity as high as 2.72 MHz N-1. The high dielectric property of the droplet endows our sensor with high tolerance for noise and large capacitance values (20-40 pF), the highest value in the literature for the LC passive devices in comparable dimensions. It achieves excellent reproducibility under periodical loads ranging from 0 to 1.56 N and temperature fluctuations ranging from 10 °C to 55 °C. As an interesting conceptual demonstration, the flexible device has been configured into a fingertip-amounted setting in a highly compact package (of 11 mm × 11 mm × 0.25 mm) for remote contact force sensing in the table tennis game.

High nitrogen-containing cotton derived 3D porous carbon frameworks for high-performance supercapacitors

PubMed Central

Fan, Li-Zhen; Chen, Tian-Tian; Song, Wei-Li; Li, Xiaogang; Zhang, Shichao

2015-01-01

Supercapacitors fabricated by 3D porous carbon frameworks, such as graphene- and carbon nanotube (CNT)-based aerogels, have been highly attractive due to their various advantages. However, their high cost along with insufficient yield has inhibited their large-scale applications. Here we have demonstrated a facile and easily scalable approach for large-scale preparing novel 3D nitrogen-containing porous carbon frameworks using ultralow-cost commercial cotton. Electrochemical performance suggests that the optimal nitrogen-containing cotton-derived carbon frameworks with a high nitrogen content (12.1 mol%) along with low surface area 285 m2 g−1 present high specific capacities of the 308 and 200 F g−1 in KOH electrolyte at current densities of 0.1 and 10 A g−1, respectively, with very limited capacitance loss upon 10,000 cycles in both aqueous and gel electrolytes. Moreover, the electrode exhibits the highest capacitance up to 220 F g−1 at 0.1 A g−1 and excellent flexibility (with negligible capacitance loss under different bending angles) in the polyvinyl alcohol/KOH gel electrolyte. The observed excellent performance competes well with that found in the electrodes of similar 3D frameworks formed by graphene or CNTs. Therefore, the ultralow-cost and simply strategy here demonstrates great potential for scalable producing high-performance carbon-based supercapacitors in the industry. PMID:26472144

Pre-selection by double layer density gradient centrifugation improves the fertilising capacity of frozen-thawed, capacitated stallion sperm.

PubMed

Morató, Roser; Soares, Juleide M De Souza; Orero, Guifré; Mogas, Teresa; Miró, Jordi

2013-06-01

The effect of combining double layer density gradient centrifugation (DL-DGC) with different capacitation treatments on the fertilising capacity of frozen-thawed stallion sperm was examined via a heterologous assay involving in vitro-matured, zona pellucida-free bovine oocytes. In a first experiment, aliquots of frozen-thawed stallion sperm were subjected to one of five capacitation treatments without DL-DGC - ionomycin at 1.0μM, 0.1μM, 0.05μM or 0.01μM, or caffeine at 200μg/mL. The fertilising capacity of the semen was then assessed at 18h by staining the above oocytes with 4,6-diamidino-2-phenylindole (DAPI) and examining for sperm penetration, the number of penetrated spermatozoa per oocyte, and male pronucleus formation. In a second experiment, aliquots of frozen-thawed stallion sperm were subjected to DL-DGC selection - or not - and then further subjected to the two best capacitation treatments (0.1μM and 0.05μM ionomycin). The fertilising capacity of the semen was then determined as above. The DL-DGC/capacitated sperm samples showed the highest mean penetration rates: 24.16% following capacitation with 0.1μM ionomycin, and 12.21% following capacitation with 0.05μM ionomycin. The capacitated but non-DL-DGC-selected sperm returned significantly lower values: 6.26% and 7.02% for the same ionomycin treatments respectively. These findings suggest that combining DL-DGC selection with ionomycin capacitation improves the fertilising capacity of frozen-thawed stallion sperm. Copyright © 2013 Elsevier B.V. All rights reserved.

Measurement of n-type Dry Thermally Oxidized 6H-SiC Metal-oxide Semiconductor Diodes by Quasistatic and High-Frequency Capacitance Versus Voltage and Capacitance Transient Techniques

NASA Technical Reports Server (NTRS)

Neudeck, P.; Kang, S.; Petit, J.; Tabib-Azar, M.

1994-01-01

Dry-oxidized n-type 6H-SiC metal-oxide-semiconductor capacitors are investigated using quasistatic capacitance versus voltage (C-V), high-frequency C-V, and pulsed high-frequency capacitance transient (C-t) analysis over the temperature range from 297 to 573 K. The quasistatic C - V characteristics presented are the first reported for 6H-SiC MOS capacitors, and exhibit startling nonidealities due to nonequilibrium conditions that arise from the fact that the recombination/generation process in 6H-SiC is extraordinarily slow even at the highest measurement temperature employed. The high-frequency dark C-V characteristics all showed deep depletion with no observable hysteresis. The recovery of the high-frequency capacitance from deep depletion to inversion was used to characterize the minority-carrier generation process as a function of temperature. Zerbst analysis conducted on the resulting C-t transients, which were longer than 1000 s at 573 K, showed a generation lifetime thermal activation energy of 0.49 eV.

High energy density supercapacitors from lignin derived submicron activated carbon fibers in aqueous electrolytes

NASA Astrophysics Data System (ADS)

Hu, Sixiao; Zhang, Sanliang; Pan, Ning; Hsieh, You-Lo

2014-12-01

Highly porous submicron activated carbon fibers (ACFs) were robustly generated from low sulfonated alkali lignin and fabricated into supercapacitors for capacitive energy storage. The hydrophilic and high specific surface ACFs exhibited large-size nanographites and good electrical conductivity to demonstrate outstanding electrochemical performance. ACFs from KOH activation, in particular, showed very high 344 F g-1 specific capacitance at low 1.8 mg cm-2 mass loading and 10 mV s-1 scan rate in aqueous electrolytes. Even at relatively high scan rate of 50 mV s-1 and mass loading of 10 mg cm-2, a decent specific capacitance of 196 F g-1 and a remarkable areal capacitance of 0.55 F cm-2 was obtained, leading to high energy density of 8.1 Wh kg-1 based on averaged electrodes mass. Furthermore, over 96% capacitance retention rates were achieved after 5000 charge/discharge cycles. Such excellent performance demonstrated great potential of lignin derived carbons for electrical energy storage.

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors.

PubMed

Dang, Yong-Qiang; Ren, Shao-Zhao; Liu, Guoyang; Cai, Jiangtao; Zhang, Yating; Qiu, Jieshan

2016-11-14

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H₂SO₄. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

Oxygen- and Nitrogen-Enriched 3D Porous Carbon for Supercapacitors of High Volumetric Capacity.

PubMed

Li, Jia; Liu, Kang; Gao, Xiang; Yao, Bin; Huo, Kaifu; Cheng, Yongliang; Cheng, Xiaofeng; Chen, Dongchang; Wang, Bo; Sun, Wanmei; Ding, Dong; Liu, Meilin; Huang, Liang

2015-11-11

Efficient utilization and broader commercialization of alternative energies (e.g., solar, wind, and geothermal) hinges on the performance and cost of energy storage and conversion systems. For now and in the foreseeable future, the combination of rechargeable batteries and electrochemical capacitors remains the most promising option for many energy storage applications. Porous carbonaceous materials have been widely used as an electrode for batteries and supercapacitors. To date, however, the highest specific capacitance of an electrochemical double layer capacitor is only ∼200 F/g, although a wide variety of synthetic approaches have been explored in creating optimized porous structures. Here, we report our findings in the synthesis of porous carbon through a simple, one-step process: direct carbonization of kelp in an NH3 atmosphere at 700 °C. The resulting oxygen- and nitrogen-enriched carbon has a three-dimensional structure with specific surface area greater than 1000 m(2)/g. When evaluated as an electrode for electrochemical double layer capacitors, the porous carbon structure demonstrated excellent volumetric capacitance (>360 F/cm(3)) with excellent cycling stability. This simple approach to low-cost carbonaceous materials with unique architecture and functionality could be a promising alternative to fabrication of porous carbon structures for many practical applications, including batteries and fuel cells.

Synthesis and Electrochemical Analyses of Manganese Oxides for Super-Capacitors.

PubMed

Kim, Taewoo; Hwang, Hyein; Jang, Jaeyong; Park, Inyeong; Shim, Sang Eun; Baeck, Sung-Hyeon

2015-11-01

δ-Phase and α-phase manganese oxides were prepared using a hydrothermal method and their electrochemical properties were characterized. The influence of calcination temperature on the properties of manganese oxides was studied. Crystallinities were studied by X-ray diffraction, and scanning and transmission electron microscopy were utilized to examine morphologies. Average pore sizes and specific surface areas of samples were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. After calcination in the range 300 degrees C to 600 degrees C, changes in morphology and crystallinity were observed. The flower-like shape of as synthesized samples became nanorod-like and the δ-phase changed to the α-phase. These changes may have been due to the removal of water during calcination. Furthermore, a transition stage in which the two phases coexisted was observed. Synthesized manganese oxides were mixed with carbon by sonification, to increase electric conductivity and to induce a synergistic effect between pseudo-capacitor and electric double layer capacitor (EDLC). Specific capacitances and rate durability of each composite were investigated by cyclic voltammetry in 1 M Na2SO4 electrolyte at different scan rates. MnO2 calcined at 400 degrees C exhibited the highest capacitance, probably due to its high surface area and more porous structure.

Engineering the electrochemical capacitive properties of graphene sheets in ionic-liquid electrolytes by correct selection of anions.

PubMed

Shi, Minjie; Kou, Shengzhong; Yan, Xingbin

2014-11-01

Graphene sheet (GS)-ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS-aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM(+)) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM-dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF4(-)) has the best electrochemical stability, the GS-[EMIM][BF4] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS-IL supercapacitors to meet different needs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of reactivation on the electrochemical performances of activated carbon based on coconut shell.

PubMed

Geng, Xin; Li, Lixiang; Zhang, Meiling; An, Baigang; Zhu, Xiaoming

2013-12-01

Coconut shell-based activated carbon (AC) were prepared by CO2 activation, and then the ACs with higher mesopore ratio were obtained by steam activation and by impregnating iron catalyst followed by steam activation, respectively. The AC with the highest mesopore ratio (AChmr) shows superior capacitive behavior, power output and high-frequency performance in supercapacitors. The results should attribute to the connection of its wide micropores and mesopores larger than 3 nm, which is more favorable for fast ionic transportation. The pore size distribution exhibits that the mesopore ratios of the ACs are significantly increased by reactivation of steam or catalyst up to 75% and 78%, respectively. As evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic measurements, the AChmr shows superior capacitive behaviors, conductivity and performance of electrolytic ionic transportation. The response current densities are evidently enhanced through the cyclic voltammery test at 50 mV/sec scan rate. The electrochemical impedance spectroscopy demonstrates that the conductivity and ion transport performance of the ACs are improved. The specific capacitances of the ACs were increased from 140 to 240 F/g at 500 mA/g current density. The AChmr can provide much higher power density while still maintaining good energy density, and demonstrate excellent high-frequency performances. The pore structure and conductivity of the AChmr also improve the cycleability and self-discharge of supercapacitors. Such AChmr exhibits a great potential in supercapacitors, particularly for applications where high power output and good high-frequency capacitive performances are required. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors

PubMed Central

Andres, Britta; Engström, Ann-Christine; Blomquist, Nicklas; Forsberg, Sven; Dahlström, Christina; Olin, Håkan

2016-01-01

Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC’s specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes— Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)—and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost. PMID:27658253

Direct in situ measurement of specific capacitance, monolayer tension, and bilayer tension in a droplet interface bilayer

DOE PAGES

Taylor, Graham J.; Venkatesan, Guru A.; Collier, C. Patrick; ...

2015-08-05

In this study, thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow formore » determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance.« less

Polypyrrole/titanium oxide nanotube arrays composites as an active material for supercapacitors.

PubMed

Kim, Min Seok; Park, Jong Hyeok

2011-05-01

The authors present the first reported use of vertically oriented titanium oxide nanotube/polypyrrole (PPy) nanocomposites to increase the specific capacitance of TiO2 based energy storage devices. To increase their electrical storage capacity, titanium oxide nanotubes were coated with PPy and their morphologies were characterized. The incorporation of PPy increased the specific capacitance of the titanium oxide nanotube based supercapacitor system, due to their increased surface area and additional pseudo-capacitance.

Porous hollow Co3O4 with rhombic dodecahedral structures for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-01

Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04782f

Highly conductive and porous activated reduced graphene oxide films for high-power supercapacitors.

PubMed

Zhang, Li Li; Zhao, Xin; Stoller, Meryl D; Zhu, Yanwu; Ji, Hengxing; Murali, Shanthi; Wu, Yaping; Perales, Stephen; Clevenger, Brandon; Ruoff, Rodney S

2012-04-11

We present a novel method to prepare highly conductive, free-standing, and flexible porous carbon thin films by chemical activation of reduced graphene oxide paper. These flexible carbon thin films possess a very high specific surface area of 2400 m(2) g(-1) with a high in-plane electrical conductivity of 5880 S m(-1). This is the highest specific surface area for a free-standing carbon film reported to date. A two-electrode supercapacitor using these carbon films as electrodes demonstrated an excellent high-frequency response, an extremely low equivalent series resistance on the order of 0.1 ohm, and a high-power delivery of about 500 kW kg(-1). While higher frequency and power values for graphene materials have been reported, these are the highest values achieved while simultaneously maintaining excellent specific capacitances and energy densities of 120 F g(-1) and 26 W h kg(-1), respectively. In addition, these free-standing thin films provide a route to simplify the electrode-manufacturing process by eliminating conducting additives and binders. The synthetic process is also compatible with existing industrial level KOH activation processes and roll-to-roll thin-film fabrication technologies. © 2012 American Chemical Society

Electronic Structure Control of Tungsten Oxide Activated by Ni for Ultrahigh-Performance Supercapacitors.

PubMed

Meng, Tian; Kou, Zongkui; Amiinu, Ibrahim Saana; Hong, Xufeng; Li, Qingwei; Tang, Yongfu; Zhao, Yufeng; Liu, Shaojun; Mai, Liqiang; Mu, Shichun

2018-04-17

Tuning the electron structure is of vital importance for designing high active electrode materials. Here, for boosting the capacitive performance of tungsten oxide, an atomic scale engineering approach to optimize the electronic structure of tungsten oxide by Ni doping is reported. Density functional theory calculations disclose that through Ni doping, the density of state at Fermi level for tungsten oxide can be enhanced, thus promoting its electron transfer. When used as electrode of supercapacitors, the obtained Ni-doped tungsten oxide with 4.21 at% Ni exhibits an ultrahigh mass-specific capacitance of 557 F g -1 at the current density of 1 A g -1 and preferable durability in a long-term cycle test. To the best of knowledge, this is the highest supercapacitor performance reported so far in tungsten oxide and its composites. The present strategy demonstrates the validity of the electronic structure control in tungsten oxide via introducing Ni atoms for pseudocapacitors, which can be extended to other related fields as well. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Electrodeposition Mode and Deposition Cycle on the Electrochemical Performance of MnO2-NiO Composite Electrodes for High-Energy-Density Supercapacitors.

PubMed

Rusi; Majid, S R

2016-01-01

Nanostructured network-like MnO2-NiO composite electrodes were electrodeposited onto stainless steel substrates via different electrodeposition modes, such as chronopotentiometry, chronoamperometry, and cyclic voltammetry, and then subjected to heat treatment at 300°C for metal oxide conversion. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to study the crystalline natures and morphologies of the deposited films. The electrochemical properties were investigated using cyclic voltammetry and charge/discharge tests. The results revealed that the electrochemical performance of the as-obtained composite electrodes depended on the electrodeposition mode. The electrochemical properties of MnO2-NiO composite electrodes prepared using cyclic voltammetry exhibited the highest capacitance values and were most influenced by the deposition cycle number. The optimum specific capacitance was 3509 Fg-1 with energy and power densities of 1322 Wh kg-1 and 110.5 kW kg-1, respectively, at a current density of 20 Ag-1 in a mixed KOH/K3Fe(CN)6 electrolyte.

Centrifugal spinning: A novel approach to fabricate porous carbon fibers as binder-free electrodes for electric double-layer capacitors

NASA Astrophysics Data System (ADS)

Lu, Yao; Fu, Kun; Zhang, Shu; Li, Ying; Chen, Chen; Zhu, Jiadeng; Yanilmaz, Meltem; Dirican, Mahmut; Zhang, Xiangwu

2015-01-01

Carbon nanofibers (CNFs), among various carbonaceous candidates for electric double-layer capacitor (EDLC) electrodes, draw extensive attention because their one-dimensional architecture offers both shortened electron pathways and high ion-accessible sites. Creating porous structures on CNFs yields larger surface area and enhanced capacitive performance. Herein, porous carbon nanofibers (PCNFs) were synthesized via centrifugal spinning of polyacrylonitrile (PAN)/poly(methyl methacrylate) (PMMA) solutions combined with thermal treatment and were used as binder-free EDLC electrodes. Three precursor fibers with PAN/PMMA weight ratios of 9/1, 7/3 and 5/5 were prepared and carbonized at 700, 800, and 900 °C, respectively. The highest specific capacitance obtained was 144 F g-1 at 0.1 A g-1 with a rate capability of 74% from 0.1 to 2 A g-1 by PCNFs prepared with PAN/PMMA weight ratio of 7/3 at 900 °C. These PCNFs also showed stable cycling performance. The present work demonstrates that PCNFs are promising EDLC electrode candidate and centrifugal spinning offers a simple, cost-effective strategy to produce PCNFs.

Spray pyrolysed Ru:TiO2 thin film electrodes prepared for electrochemical supercapacitor

NASA Astrophysics Data System (ADS)

Fugare, B. Y.; Thakur, A. V.; Kore, R. M.; Lokhande, B. J.

2018-04-01

Ru doped TiO2 thin films are prepared by using 0.06 M aqueous solution of potassium titanium oxalate (pto), and 0.005 M aqueous solution of ruthenium tri chloride (RuCl3) precursors. The deposition was carried on stainless steel (SS) by using well known ultrasonic spray pyrolysis technique (USPT) at 723° K by maintaining the spray rate 12 cc/min and compressed air flow rate 10 Lmin-1. Prepared Ru:TiO2 thin films were characterized by structurally, morphologically and electrochemically. Deposited RuO2 shows amorphous structure and TiO2 shows tetragonal crystal structure with rutile as prominent phase at very low decomposition temperature. SEM micrographs of RuO2 exhibits porous, interconnected, spherical grains type morphology and TiO2 shows porous, nanorods and nanoplates like morphology and also Ru doped TiO2 shows porous, spherical, granular and nanorods type morphology. The electrochemical cyclic voltammetery shows mixed capacitive behavior. The achieved highest value of specific capacitance 2692 F/g was Ru doped TiO2 electrode in 0.5 M H2SO4.

Synthesis of Fluorinated Graphene/CoAl-Layered Double Hydroxide Composites as Electrode Materials for Supercapacitors.

PubMed

Peng, Weijun; Li, Hongqiang; Song, Shaoxian

2017-02-15

CoAl-layered double hydroxide/fluorinated graphene (CoAl-LDH/FGN) composites were fabricated via a two-step hydrothermal method. The synthesized CoAl-LDH/FGN composites have been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and electrochemical measurements. The results indicated that the fluorinated carbon with various configuration forms were grafted onto the framework of graphene, and the C-F bond configuration and fluorine content could be tuned by the fluorination time. Most of semi-ionic C-F bonds were formed at an appropriate fluorination time and, then, converted into fluorine rich surface groups (such as CF 2 , CF 3 , etc.) which were electrochemically inactive as the fluorination time prolonged. Moreover, the CoAl-LDH/FGN composites prepared at the optimal fluorination time exhibited the highest specific capacitance (1222 F/g at 1 A/g), the best rate capability, and the most stable capacitance retention, which offered great promise as electrode materials for supercapacitors.

Effects of Electrodeposition Mode and Deposition Cycle on the Electrochemical Performance of MnO2-NiO Composite Electrodes for High-Energy-Density Supercapacitors

PubMed Central

Rusi; Majid, S. R.

2016-01-01

Nanostructured network-like MnO2-NiO composite electrodes were electrodeposited onto stainless steel substrates via different electrodeposition modes, such as chronopotentiometry, chronoamperometry, and cyclic voltammetry, and then subjected to heat treatment at 300°C for metal oxide conversion. X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to study the crystalline natures and morphologies of the deposited films. The electrochemical properties were investigated using cyclic voltammetry and charge/discharge tests. The results revealed that the electrochemical performance of the as-obtained composite electrodes depended on the electrodeposition mode. The electrochemical properties of MnO2-NiO composite electrodes prepared using cyclic voltammetry exhibited the highest capacitance values and were most influenced by the deposition cycle number. The optimum specific capacitance was 3509 Fg−1 with energy and power densities of 1322 Wh kg−1 and 110.5 kW kg−1, respectively, at a current density of 20 Ag−1 in a mixed KOH/K3Fe(CN)6 electrolyte. PMID:27182595

Hydrothermally grown β-V₂O₅ electrode at 95°C.

PubMed

Vernardou, D; Apostolopoulou, M; Louloudakis, D; Katsarakis, N; Koudoumas, E

2014-06-15

The hydrothermal growth of crystalline β-V2O5 microstructures was performed on fluorine doped tin dioxide glass substrates using oxalic acid to adjust the pH of the solution for various deposition periods. It was observed that the sample grown for 48 h at pH 2 exhibited the best electrochemical response in terms of the highest specific charge and capacitance, being 772 C g(-1) and 386 F g(-1) respectively. The importance of achieving high crystalline quality samples and increased surface area toward the improvement of the electrochemical performance of β-V2O5 is highlighted. Copyright © 2014 Elsevier Inc. All rights reserved.

Preparation and electrochemical characterization of polyaniline/activated carbon composites as an electrode material for supercapacitors.

PubMed

Oh, Misoon; Kim, Seok

2012-01-01

Polyaniline (PANI)/activated carbon (AC) composites were prepared by a chemical oxidation polymerization. To find an optimum ratio between PANI and AC which shows superior electrochemical properties, the preparation was carried out in changing the amount of added aniline monomers. The morphology of prepared composites was investigated by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The structural and thermal properties were investigated by Fourier transform infrared spectra (FT-IR) and thermal gravimetric analysis (TGA), respectively. The electrochemical properties were characterized by cyclic voltammetry (CV). Composites showed a summation of capacitances that consisted of two origins. One is double-layer capacitance by ACs and the other is faradic capacitance by redox reaction of PANI. Fiber-like PANIs are coated on the surface of ACs and they contribute to the large surface for redox reaction. The vacancy among fibers provided the better diffusion and accessibility of ion. High capacitances of composites were originated from the network structure having vacancy made by PANI fibers. It was found that the composite prepared with 5 ml of aniline monomer and 0.25 g of AC showed the highest capacitance. Capacitance of 771 F/g was obtained at a scan rate of 5 mV/s.

Constructing Ultrahigh-Capacity Zinc-Nickel-Cobalt Oxide@Ni(OH)2 Core-Shell Nanowire Arrays for High-Performance Coaxial Fiber-Shaped Asymmetric Supercapacitors.

PubMed

Zhang, Qichong; Xu, Weiwei; Sun, Juan; Pan, Zhenghui; Zhao, Jingxin; Wang, Xiaona; Zhang, Jun; Man, Ping; Guo, Jiabin; Zhou, Zhenyu; He, Bing; Zhang, Zengxing; Li, Qingwen; Zhang, Yuegang; Xu, Lai; Yao, Yagang

2017-12-13

Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc-nickel-cobalt oxide (ZNCO)@Ni(OH) 2 nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm 3 (10.678 F/cm 2 ) at a current density of 1 mA/cm 2 , These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm 2 ) and four times higher than Ni(OH) 2 /CNTF electrodes (2.55 F/cm 2 ). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni(OH) 2 NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm 3 (573.75 mF/cm 2 ) and an exceptional energy density of 33.66 mWh/cm 3 (204.02 μWh/cm 2 ) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices.

Effect of reducing system on capacitive behavior of reduced graphene oxide film: Application for supercapacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akbi, Hamdane; Yu, Lei; Wang, Bin

2015-01-15

To determine the best chemical reduction of graphene oxide film with hydriodic acid that gives maximum energy and power density, we studied the effect of two reducing systems, hydriodic acid/water and hydriodic acid/acetic acid, on the morphology and electrochemical features of reduced graphene oxide film. Using acetic acid as solvent results in high electrical conductivity (5195 S m{sup −1}), excellent specific capacitance (384 F g{sup −1}) and good cyclic stability (about 98% of its initial response after 4000 cycles). Using water as a solvent, results in an ideal capacitive behavior and excellent cyclic stability (about 6% increase of its initialmore » response after 2100 cycles). - Graphical abstract: The choice of reducing system determines the morphology and structure of the chemically reduced graphene film and, as a result, affects largely the capacitive behavior. - Highlights: • The structure of the graphene film has a pronounced effect on capacitive behavior. • The use of water/HI as reducing system results in an ideal capacitive behavior. • The use of acetic acid/HI as reducing system results in a high specific capacitance.« less

Electrostatic Self-Assembly of Sandwich-Like CoAl-LDH/Polypyrrole/Graphene Nanocomposites with Enhanced Capacitive Performance.

PubMed

Zhang, Yu; Du, Dongfeng; Li, Xuejin; Sun, Hongman; Li, Li; Bai, Peng; Xing, Wei; Xue, Qingzhong; Yan, Zifeng

2017-09-20

A novel sandwich-like composite with ultrathin CoAl-layered double hydroxide (LDH) nanoplates electrostatically assembled on both sides of two-dimensional polypyrrole/graphene (PG) substrate has been successfully fabricated using facile hydrothermal techniques. The PG not only serves as an excellent conductive and structural scaffold to enhance the transmission of electrons and prevent aggregation of CoAl-LDH nanoplates but also contributes to the enhancement of the specific capacitance. Owing to the homogeneous dispersion of CoAl-LDH nanoplates and its intimate interaction with PG substrate, the resulting CoAl-LDH/PG nanocomposite material exhibits excellent capacitive performance, for example, enhanced gravimetric specific capacitance (864 F g -1 at 1 A g -1 ), high rate performance (75% retention at 20 A g -1 ), and excellent cycle life (almost no degradation in supercapacitor performance after 5000 cycles) in aqueous KOH solution. Furthermore, the assembled asymmetric capacitor is able to deliver a superhigh energy density of 46.8 Wh kg -1 at 1.2 kW kg -1 and maintain 90.1% of its initial capacitance after 10 000 cycles. These results indicate a rational assembly strategy toward a high-performance pseudocapacitive electrode material with excellent rate performance, high specific capacitance, and outstanding cycle stability.

CMOS micromachined capacitive cantilevers for mass sensing

NASA Astrophysics Data System (ADS)

Li, Ying-Chung; Ho, Meng-Han; Hung, Shi-Jie; Chen, Meng-Huei; S-C Lu, Michael

2006-12-01

In this paper, we present the design, fabrication and characterization of the CMOS micromachined cantilevers for mass sensing in the femtogram range. The cantilevers consisting of multiple metal and dielectric layers are fabricated after completion of a conventional CMOS process by dry etching steps. The cantilevers are electrostatically actuated to resonance by in-plane electrodes. The mechanical resonant frequency is detected capacitively with on-chip circuitry, where the modulation technique is applied to eliminate capacitive feedthrough from the driving port and to lessen the effect of flicker noise. The highest resonant frequency of the cantilevers is measured at 396.46 kHz with a quality factor of 2600 at 10 mTorr. The resonant frequency shift after deposition of a 0.1 µm SiO2 layer is 140 Hz, averaging 353 fg Hz-1.

Facile preparation of 3D hierarchical coaxial-cable-like Ni-CNTs@beta-(Ni, Co) binary hydroxides for supercapacitors with ultrahigh specific capacitance.

PubMed

Zhang, Manyu; Ma, Xiaowei; Bi, Han; Zhao, Xuebing; Wang, Chao; Zhang, Jie; Li, Yuesheng; Che, Renchao

2017-09-15

A facile chemical method for Co doping Ni-CNTs@α-Ni(OH) 2 combining with an in situ phase transformation process is successfully proposed and employed to synthesize three-dimensional (3D) hierarchical Ni-CNTs@β-(Ni, Co) binary hydroxides. This strategy can effectively maintain the coaxial-cable-like structure of Ni-CNTs@α-Ni(OH) 2 and meanwhile increase the content of Co as much as possible. Eventually, the specific capacitances and electrical conductivity of the composites are remarkably enhanced. The optimized composite exhibits high specific capacitances of 2861.8F g -1 at 1A g -1 (39.48F cm -2 at 15mAcm -2 ), good rate capabilities of 1221.8F g -1 at 20A g -1 and cycling stabilities (87.6% of capacitance retention after 5000cycles at 5A g -1 ). The asymmetric supercapacitor (ASC) constructed with the as-synthesized composite and activated carbon as positive and negative electrode delivers a high specific capacitance of 287.7F g -1 at 1A g -1 . The device demonstrates remarkable energy density (96Whkg -1 ) and high power density (15829.4Wkg -1 ). The retention of capacitance remains 83.5% at the current density of 5A g -1 after 5000cycles. The charged and discharged samples are further studied by ex situ electron energy loss spectroscopy (EELS) analysis, XRD and SEM to figure out the reasons of capacitance fading. Overall, it is believable that this facile synthetic strategy can be applied to prepare various nanostructured metal hydroxide/CNT composites for high performance supercapacitor electrode materials. Copyright © 2017. Published by Elsevier Inc.

Effects of pore structure and electrolyte on the capacitive characteristics of steam- and KOH-activated carbons for supercapacitors

NASA Astrophysics Data System (ADS)

Wu, Feng-Chin; Tseng, Ru-Ling; Hu, Chi-Chang; Wang, Chen-Ching

Four kinds of activated carbons (denoted as ACs) with specific surface area of ca. 1050 m 2 g -1 were fabricated from fir wood and pistachio shell by means of steam activation or chemical activation with KOH. Pore structures of ACs were characterized by a t-plot method based on N 2 adsorption isotherms. The amount of mesopores within KOH-activated carbons ranged from 9.2 to 15.3% while 33.3-49.5% of mesopores were obtained for the steam-activated carbons. The pore structure, surface functional groups, and raw materials of ACs, as well as pH and the supporting electrolyte were also found to be significant factors determining the capacitive characteristics of ACs. The excellent capacitive characteristics in both acidic and neutral media and the weak dependence of the specific capacitance on the scan rate of cyclic voltammetry (CV) for the ACs derived from the pistachio shell with steam activation (denoted as P-H 2O-AC) revealed their promising potential in the application of supercapacitors. The ACs derived from fir wood with KOH activation (denoted as F-KOH-AC), on the other hand, showed the best capacitive performance in H 2SO 4 due to excellent reversibility and high specific capacitance (180 F g -1 measured at 10 mV s -1), which is obviously larger than 100 F g -1 (a typical value of activated carbons with specific surface areas equal to/above 1000 m 2 g -1).

Enhanced capacitance and rate capability of graphene/polypyrrole composite as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Zhang, Dacheng; Zhang, Xiong; Chen, Yao; Yu, Peng; Wang, Changhui; Ma, Yanwei

Graphene and polypyrrole composite (PPy/GNS) is synthesized via in situ polymerization of pyrrole monomer in the presence of graphene under acid conditions. The structure and morphology of the composite are characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), X-rays photoelectron spectroscopy (XPS) and transmission electron microscope (TEM). It is found that a uniform composite is formed with polypyrrole being homogeneously surrounded by graphene nanosheets (GNS). The composite is a promising candidate for supercapacitors to have higher specific capacitance, better rate capability and cycling stability than those of pure polypyrrole. The specific capacitance of PPy/GNS composite based on the three-electrode cell configuration is as high as 482 F g -1 at a current density of 0.5 A g -1. After 1000 cycles, the attenuation of the specific capacitance is less than 5%, indicating that composite has excellent cycling performance.

In situ fabrication of nickel aluminum-layered double hydroxide nanosheets/hollow carbon nanofibers composite as a novel electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

He, Fang; Hu, Zhibiao; Liu, Kaiyu; Zhang, Shuirong; Liu, Hongtao; Sang, Shangbin

2014-12-01

This paper introduces a new design route to fabricate nickel aluminum-layered double hydroxide (NiAl-LDH) nanosheets/hollow carbon nanofibers (CNFs) composite through an in situ growth method. The NiAl-LDH thin layers which grow on hollow carbon nanofibers have an average thickness of 13.6 nm. The galvanostatic charge-discharge test of the NiAl-LDH/CNFs composite yields an impressive specific capacitance of 1613 F g-1 at 1 A g-1 in 6 M KOH solution, the composite shows a remarkable specific capacitance of 1110 F g-1 even at a high current density of 10 A g-1. Furthermore, the composite remains a specific capacitance of 1406 F g-1 after 1000 cycles at 2 A g-1, indicating the composite has excellent high-current capacitive behavior and good cycle stability in compared to pristine NiAl-LDH.

Low-temperature direct synthesis of mesoporous vanadium nitrides for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Lee, Hae-Min; Jeong, Gyoung Hwa; Kim, Sang-Wook; Kim, Chang-Koo

2017-04-01

Mesoporous vanadium nitrides are directly synthesized by a one-step chemical precipitation method at a low temperature (70 °C). Structural and morphological analyses reveal that vanadium nitride consist of long and slender nanowhiskers, and mesopores with diameters of 2-5 nm. Compositional analysis confirms the presence of vanadium in the VN structure, along with oxidized vanadium. The cyclic voltammetry and charge-discharge tests indicate that the obtained material stores charges via a combination of electric double-layer capacitance and pseudocapacitance mechanisms. The vanadium nitride electrode exhibits a specific capacitance of 598 F/g at a current density of 4 A/g. After 5000 charge-discharge cycles, the electrode has an equivalent series resistance of 1.42 Ω and retains 83% of its initial specific capacitance. This direct low-temperature synthesis of mesoporous vanadium nitrides is a simple and promising method to achieve high specific capacitance and low equivalent series resistance for electrochemical capacitor applications.

Hydrogenated TiO2 nanotube arrays for supercapacitors.

PubMed

Lu, Xihong; Wang, Gongming; Zhai, Teng; Yu, Minghao; Gan, Jiayong; Tong, Yexiang; Li, Yat

2012-03-14

We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors. © 2012 American Chemical Society

Whole-tree water transport scales with sapwood capacitance in tropical forest canopy trees.

Treesearch

F.C. Meinzer; S.A. James; G. Goldstein; D. Woodruff

2003-01-01

The present study examines the manner in which several whole-tree water transport properties scale with species specific variation in sapwood water storage capacity. The hypothesis that constraints on relationships between sapwood capacitance and other water relations characteristics lead to predictable scaling relationships between intrinsic capacitance and whole-tree...

Graphene/Polyaniline Aerogel with Superelasticity and High Capacitance as Highly Compression-Tolerant Supercapacitor Electrode

NASA Astrophysics Data System (ADS)

Lv, Peng; Tang, Xun; Zheng, Ruilin; Ma, Xiaobo; Yu, Kehan; Wei, Wei

2017-12-01

Superelastic graphene aerogel with ultra-high compressibility shows promising potential for compression-tolerant supercapacitor electrode. However, its specific capacitance is too low to meet the practical application. Herein, we deposited polyaniline (PANI) into the superelastic graphene aerogel to improve the capacitance while maintaining the superelasticity. Graphene/PANI aerogel with optimized PANI mass content of 63 wt% shows the improved specific capacitance of 713 F g-1 in the three-electrode system. And the graphene/PANI aerogel presents a high recoverable compressive strain of 90% due to the strong interaction between PANI and graphene. The all-solid-state supercapacitors were assembled to demonstrate the compression-tolerant ability of graphene/PANI electrodes. The gravimetric capacitance of graphene/PANI electrodes reaches 424 F g-1 and retains 96% even at 90% compressive strain. And a volumetric capacitance of 65.5 F cm-3 is achieved, which is much higher than that of other compressible composite electrodes. Furthermore, several compressible supercapacitors can be integrated and connected in series to enhance the overall output voltage, suggesting the potential to meet the practical application.

Graphene/Polyaniline Aerogel with Superelasticity and High Capacitance as Highly Compression-Tolerant Supercapacitor Electrode.

PubMed

Lv, Peng; Tang, Xun; Zheng, Ruilin; Ma, Xiaobo; Yu, Kehan; Wei, Wei

2017-12-19

Superelastic graphene aerogel with ultra-high compressibility shows promising potential for compression-tolerant supercapacitor electrode. However, its specific capacitance is too low to meet the practical application. Herein, we deposited polyaniline (PANI) into the superelastic graphene aerogel to improve the capacitance while maintaining the superelasticity. Graphene/PANI aerogel with optimized PANI mass content of 63 wt% shows the improved specific capacitance of 713 F g -1 in the three-electrode system. And the graphene/PANI aerogel presents a high recoverable compressive strain of 90% due to the strong interaction between PANI and graphene. The all-solid-state supercapacitors were assembled to demonstrate the compression-tolerant ability of graphene/PANI electrodes. The gravimetric capacitance of graphene/PANI electrodes reaches 424 F g -1 and retains 96% even at 90% compressive strain. And a volumetric capacitance of 65.5 F cm -3 is achieved, which is much higher than that of other compressible composite electrodes. Furthermore, several compressible supercapacitors can be integrated and connected in series to enhance the overall output voltage, suggesting the potential to meet the practical application.

Nitrogen-doped two-dimensional porous carbon sheets derived from clover biomass for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Cunjing; Wu, Dapeng; Wang, Hongju; Gao, Zhiyong; Xu, Fang; Jiang, Kai

2017-09-01

Highly porous carbon sheets were prepared from fresh clover stems under air atmosphere via a facile potassium chloride salt-sealing technique, which not only avoids using the high cost inert gas protection but also spontaneously introduce multi-level porosity into the carbon structure taking advantage of the trace of oxygen in the molten salt system. The as-obtained porous carbon sheets possess high specific surface area of 2244 m2 g-1 and interconnected hierarchical pore structures from micro-to macro-scale, which provide abundant storage active sites and fast ion diffusion channels. In addition, the spontaneously formed N (2.55 at%) and O (6.94 at%) doping sites not only improve the electron conductivity of the electrode but also enhance the specific capacitance by introducing pseudocapacitance. When employed as supercapacitor electrodes, a high specific capacitance of 436 F g-1 at 1 A g-1 and an excellent rate capacity with capacitance remaining 290 F g-1 at 50 A g-1 are demonstrated. Furthermore, the assembled symmetric supercapacitor delivers a high specific capacitance of 420 F g-1 at 0.5 A g-1, excellent energy density of 58.4 Wh kg-1 and good cycling stability which retains 99.4% of the initial capacitance at 5 A g-1 after 30,000 cycles.

Symmetric redox supercapacitor based on micro-fabrication with three-dimensional polypyrrole electrodes

NASA Astrophysics Data System (ADS)

Sun, Wei; Zheng, Ruilin; Chen, Xuyuan

To achieve higher energy density and power density, we have designed and fabricated a symmetric redox supercapacitor based on microelectromechanical system (MEMS) technologies. The supercapacitor consists of a three-dimensional (3D) microstructure on silicon substrate micromachined by high-aspect-ratio deep reactive ion etching (DRIE) method, two sputtered Ti current collectors and two electrochemical polymerized polypyrrole (PPy) films as electrodes. Electrochemical tests, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatical charge/discharge methods have been carried out on the single PPy electrodes and the symmetric supercapacitor in different electrolytes. The specific capacitance (capacitance per unit footprint area) and specific power (power per unit footprint area) of the PPy electrodes and symmetric supercapacitor can be calculated from the electrochemical test data. It is found that NaCl solution is a good electrolyte for the polymerized PPy electrodes. In NaCl electrolyte, single PPy electrodes exhibit 0.128 F cm -2 specific capacitance and 1.28 mW cm -2 specific power at 20 mV s -1 scan rate. The symmetric supercapacitor presents 0.056 F cm -2 specific capacitance and 0.56 mW cm -2 specific power at 20 mV s -1 scan rate.

A high performance flexible all solid state supercapacitor based on the MnO2 sphere coated macro/mesoporous Ni/C electrode and ionic conducting electrolyte.

PubMed

Zhi, Jian; Reiser, Oliver; Wang, Youfu; Hu, Aiguo

2016-06-09

A high contact resistance between the active materials and the current collector, a low ionic conductivity of the gel electrolyte, and an impenetrable electrode structure are the three major barriers which greatly limit the capacitance of MnO2 in solid state supercapacitors. As a potential solution to these problems, in this work we report a novel electrode for solid state supercapacitors, based on a ternary system composed of hierarchical MnO2 spheres as the active material, macroporous Ni foam as gel penetrable skeletons and an ordered mesoporous carbon (OMC) membrane as the charge-transport accelerating layer. By employing butyl-3-methylimidazolium chloride (BMIMCl) modified gels as the ionic conducting electrolyte, the utilization efficiency of MnO2 on the specific capacitance was enhanced up to 88% of the theoretical value, delivering a volumetric capacitance of 81 F cm(-3), which is the highest value among MnO2 based solid state supercapacitors. Moreover, such a flexible device exhibits exceptional volumetric energy and power density (6.6 Wh L(-1) and 549 W L(-1), based on the whole device volume) combined with a small capacity loss of 8.5% after 6000 cycles under twisting. These encouraging findings unambiguously overcome the energy bottleneck of MnO2 in solid state supercapacitors, and open up a new application of macro/mesoporous materials in flexible devices.

Asymmetric Supercapacitors Using 3D Nanoporous Carbon and Cobalt Oxide Electrodes Synthesized from a Single Metal-Organic Framework.

PubMed

Salunkhe, Rahul R; Tang, Jing; Kamachi, Yuichiro; Nakato, Teruyuki; Kim, Jung Ho; Yamauchi, Yusuke

2015-06-23

Nanoporous carbon and nanoporous cobalt oxide (Co3O4) materials have been selectively prepared from a single metal-organic framework (MOF) (zeolitic imidazolate framework, ZIF-67) by optimizing the annealing conditions. The resulting ZIF-derived carbon possesses highly graphitic walls and a high specific surface area of 350 m(2)·g(-1), while the resulting ZIF-derived nanoporous Co3O4 possesses a high specific surface area of 148 m(2)·g(-1) with much less carbon content (1.7 at%). When nanoporous carbon and nanoporous Co3O4 were tested as electrode materials for supercapacitor application, they showed high capacitance values (272 and 504 F·g(-1), respectively, at a scan rate of 5 mV·s(-1)). To further demonstrate the advantages of our ZIF-derived nanoporous materials, symmetric (SSCs) and asymmetric supercapacitors (ASCs) were also fabricated using nanoporous carbon and nanoporous Co3O4 electrodes. Improved capacitance performance was successfully realized for the ASC (Co3O4//carbon), better than those of the SSCs based on nanoporous carbon and nanoporous Co3O4 materials (i.e., carbon//carbon and Co3O4//Co3O4). The developed ASC with an optimal mass loading can be operated within a wide potential window of 0.0-1.6 V, which leads to a high specific energy of 36 W·h·kg(-1). More interestingly, this ASC also exhibits excellent rate capability (with the highest specific power of 8000 W·kg(-1) at a specific energy of 15 W·h·kg(-1)) combined with long-term stability up to 2000 cycles.

Fabrication and electrochemical properties of activated CNF/Cu x Mn1- x Fe2O4 composite nanostructures

NASA Astrophysics Data System (ADS)

Nilmoung, Sukanya; Sonsupap, Somchai; Sawangphruk, Montree; Maensiri, Santi

2018-06-01

This work reports the fabrication and electrochemical properties of activated carbon nanofibers composited with copper manganese ferrite (ACNF/Cu x Mn1- x Fe2O4: x = 0.0, 0.2, 0.4, 0.6, 0.8) nanostructures. The obtained samples were characterized by means of X-ray diffraction, field emission scanning electron microscopy, Brunauer-Emmett-Teller analyzer, thermal gravimetric analysis, X-ray photoemission spectroscopy, and X-ray absorption spectroscopy. The supercapacitive behavior of the electrodes is tested using cyclic voltammetery, galvanostatic charge-discharge and electrochemical impedance spectroscopy. By varying ` x', the highest specific capacitance of 384 F/g at 2 mV/s using CV and 314 F/g at 2 A/g using GCD are obtained for the x = 0.2 electrode. The second one of 235 F/g at 2 mV/s using CV and 172 F/g at 2 A/g using GCD are observed for x = 0.8 electrode. The corresponding energy densities are 74 and 41 Wh/kg, respectively. It is observed that the cyclic stability of the prepared samples strongly depend on the amount of carbon, while the specific capacitance was enhanced by the sample with nearly proportional amount between carbon and CuMnFe2O4. Such results may arise from the synergetic effect between CuMnFe2O4 and ACNF.

Structural design of high-performance capacitive accelerometers using parametric optimization with uncertainties

NASA Astrophysics Data System (ADS)

Teves, André da Costa; Lima, Cícero Ribeiro de; Passaro, Angelo; Silva, Emílio Carlos Nelli

2017-03-01

Electrostatic or capacitive accelerometers are among the highest volume microelectromechanical systems (MEMS) products nowadays. The design of such devices is a complex task, since they depend on many performance requirements, which are often conflicting. Therefore, optimization techniques are often used in the design stage of these MEMS devices. Because of problems with reliability, the technology of MEMS is not yet well established. Thus, in this work, size optimization is combined with the reliability-based design optimization (RBDO) method to improve the performance of accelerometers. To account for uncertainties in the dimensions and material properties of these devices, the first order reliability method is applied to calculate the probabilities involved in the RBDO formulation. Practical examples of bulk-type capacitive accelerometer designs are presented and discussed to evaluate the potential of the implemented RBDO solver.

In situ fabrication of nickel based oxide on nitrogen-doped graphene for high electrochemical performance supercapacitors

NASA Astrophysics Data System (ADS)

Pan, Denghui; Zhang, Mingmei; Wang, Ying; Yan, Zaoxue; Jing, Junjie; Xie, Jimin

2017-10-01

In this article, we synthesize Ni(OH)2 homogeneous grown on nitrogen-doped graphene (Ni(OH)2/NG), subsequently, small and uniform nickel oxide nanoparticle (NiO/NG) is also successfully obtained through tube furnace calcination method. The high specific capacitance of the NiO/NG electrode can reach to 1314.1 F/g at a charge and discharge current density of 2 A/g, meanwhile the specific capacitance of Ni(OH)2/NG electrode is also 1350 F/g. The capacitance of NiO/NG can remain 93.7% of the maximum value after 1000 cycles, while the Ni(OH)2/NG electrode losses 16.9% of the initial capacitance after 1000 cycles. It can be attributed to nickel hydroxide instability during charge-discharge cycles.

Size-dependent capacitance of NiO nanoparticles synthesized with cathodic contact glow discharge electrolysis

NASA Astrophysics Data System (ADS)

Allagui, Anis; Alami, Abdul Hai; Baranova, Elena A.; Wüthrich, Rolf

2014-09-01

NiO nanoparticles of 70, 91 and 107 nm average diameter are synthesized by cathodic contact glow discharge electrolysis at 30, 36 and 42 VDC respectively, in 2 M H2SO4 + 0.5 M ethanol + 2.5 mg ml-1 of PVP, and are investigated for electrochemical energy storage. From the cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M KOH, it was found that a maximum specific capacitance of 218 F g-1 is achieved with the 70 nm NiO nanoparticles at 2.7 A g-1. Larger nanoparticles of 91 and 107 nm diameter exhibit specific capacitances of 106 and 63 F g-1, respectively, suggesting a size-dependent capacitive performance enhanced with decreasing particles size.

Facile and environmentally friendly synthesis of ultrathin nickel hydroxide nanosheets with excellent supercapacitor performances

NASA Astrophysics Data System (ADS)

Hu, Xiaowei; Liu, Sheng; Li, Chenghui; Huang, Jiahao; Luv, Jixing; Xu, Pan; Liu, Jian; You, Xiao-Zeng

2016-06-01

In this article, we report a facile and environmentally friendly glutamic acid-assisted hydrothermal strategy for the preparation of ultrathin two-dimensional (2D) β-Ni(OH)2 nanosheets with a thickness of about 2 nm, which exhibit a maximum specific capacitance of 2537.4 F g-1 at a current density of 1 A g-1, even at 10 A g-1, the specific capacitance is still maintained at 2290.0 F g-1 with 77.6% retention after 3000 cycles.In this article, we report a facile and environmentally friendly glutamic acid-assisted hydrothermal strategy for the preparation of ultrathin two-dimensional (2D) β-Ni(OH)2 nanosheets with a thickness of about 2 nm, which exhibit a maximum specific capacitance of 2537.4 F g-1 at a current density of 1 A g-1, even at 10 A g-1, the specific capacitance is still maintained at 2290.0 F g-1 with 77.6% retention after 3000 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02912d

Effect of ion concentration, solution and membrane permittivity on electric energy storage and capacitance.

PubMed

Tajparast, Mohammad; Glavinović, Mladen I

2018-06-06

Bio-membranes as capacitors store electric energy, but their permittivity is low whereas the permittivity of surrounding solution is high. To evaluate the effective capacitance of the membrane/solution system and determine the electric energy stored within the membrane and in the solution, we estimated their electric variables using Poisson-Nernst-Planck simulations. We calculated membrane and solution capacitances from stored electric energy. The effective capacitance was calculated by fitting a six-capacitance model to charges (fixed and ion) and associated potentials, because it cannot be considered as a result of membrane and solution capacitance in series. The electric energy stored within the membrane (typically much smaller than that in the solution), depends on the membrane permittivity, but also on the external electric field, surface charge density, water permittivity and ion concentration. The effect on capacitances is more specific. Solution capacitance rises with greater solution permittivity or ion concentration, but the membrane capacitance (much smaller than solution capacitance) is only influenced by its permittivity. Interestingly, the effective capacitance is independent of membrane or solution permittivity, but rises as the ion concentration increases and surface charge becomes positive. Experimental estimates of membrane capacitance are thus not necessarily a reliable index of its surface area. Copyright © 2018. Published by Elsevier B.V.

Tuning the porosity of mesoporous NiO through calcining isostructural Ni-MOFs toward supercapacitor applications

NASA Astrophysics Data System (ADS)

Hou, Xiang-Yang; Yan, Xiao-Li; Wang, Xiao; Zhai, Quan-Guo

2018-07-01

NiO has an unusually high theoretical specific capacitance and possess relatively high electrical conductivity compared to other metal oxides. However, the reported specific capacitance of the NiO-based electrodes is far below the theoretical value up to now. In this paper, three porous NiO materials with different specific surface area were synthesized simply by calcining iso-structural Ni-based MOFs templates. The formation mechanism of NiO was discussed by taking into account the thermal behavior and intrinsic structural features of the Ni-MOFs. Taking advantages of the Ni-MOFs precursors, all prepared NiO compounds are mesoporous and their porosity can be tuned by the structure of MOFs. Specially, due to the high porosity, three NiO exhibited an improved electrochemical performance and the specific discharge capacitances are of 102, 105, and 116 F g-1 at the current density of 1 A g-1, respectively. The specific capacitance of 1-NiO-450 is approximately 93.2% of its maximum value after 3000 cycles, which obviously superior to most of the previously reported NiO electrode materials and suggests their promising applications in supercapacitors.

Three-Dimensional Hierarchical NixCo1-xO/NiyCo2-yP@C Hybrids on Nickel Foam for Excellent Supercapacitors.

PubMed

Shao, Yubo; Zhao, Yongqing; Li, Hua; Xu, Cailing

2016-12-28

Active materials and special structures of the electrode have decisive influence on the electrochemical properties of supercapacitors. Herein, three-dimensional (3D) hierarchical Ni x Co 1-x O/Ni y Co 2-y P@C (denoted as NiCoOP@C) hybrids have been successfully prepared by a phosphorization treatment of hierarchical Ni x Co 1-x O@C grown on nickel foam. The resulting NiCoOP@C hybrids exhibit an outstanding specific capacitance and cycle performance because they couple the merits of the superior cycling stability of Ni x Co 1-x O, the high specific capacitance of Ni y Co 2-y P, the mechanical stability of carbon layer, and the 3D hierarchical structure. The specific capacitance of 2638 F g -1 can be obtained at the current density of 1 A g -1 , and even at the current density of 20 A g -1 , the NiCoOP@C electrode still possesses a specific capacitance of 1144 F g -1 . After 3000 cycles at 10 A g -1 , 84% of the initial specific capacitance is still remained. In addition, an asymmetric ultracapacitor (ASC) is assembled through using NiCoOP@C hybrids as anode and activated carbon as cathode. The as-prepared ASC obtains a maximum energy density of 39.4 Wh kg -1 at a power density of 394 W kg -1 and still holds 21 Wh kg -1 at 7500 W kg -1 .

Nano ZnO-activated carbon composite electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Selvakumar, M.; Krishna Bhat, D.; Manish Aggarwal, A.; Prahladh Iyer, S.; Sravani, G.

2010-05-01

A symmetrical (p/p) supercapacitor has been fabricated by making use of nanostructured zinc oxide (ZnO)-activated carbon (AC) composite electrodes for the first time. The composites have been characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction analysis (XRD). Electrochemical properties of the prepared nanocomposite electrodes and the supercapacitor have been studied using cyclic voltammetry (CV) and AC impedance spectroscopy in 0.1 M Na 2SO 4 as electrolyte. The ZnO-AC nanocomposite electrode showed a specific capacitance of 160 F/g for 1:1 composition. The specific capacitance of the electrodes decreased with increase in zinc oxide content. Galvanostatic charge-discharge measurements have been done at various current densities, namely 2, 4, 6 and 7 mA/cm 2. It has been found that the cells have excellent electrochemical reversibility and capacitive characteristics in 0.1 M Na 2SO 4 electrolyte. It has also been observed that the specific capacitance is constant up to 500 cycles at all current densities.

Humic acids-based hierarchical porous carbons as high-rate performance electrodes for symmetric supercapacitors.

PubMed

Qiao, Zhi-jun; Chen, Ming-ming; Wang, Cheng-yang; Yuan, Yun-cai

2014-07-01

Two kinds of hierarchical porous carbons (HPCs) with specific surface areas of 2000 m(2)g(-1) were synthesized using leonardite humic acids (LHA) or biotechnology humic acids (BHA) precursors via a KOH activation process. Humic acids have a high content of oxygen-containing groups which enabled them to dissolve in aqueous KOH and facilitated the homogeneous KOH activation. The LHA-based HPC is made up of abundant micro-, meso-, and macropores and in 6M KOH it has a specific capacitance of 178 F g(-1) at 100 Ag(-1) and its capacitance retention on going from 0.05 to 100 A g(-1) is 64%. In contrast, the BHA-based HPC exhibits a lower capacitance retention of 54% and a specific capacitance of 157 F g(-1) at 100 A g(-1) which is due to the excessive micropores in the BHA-HPC. Moreover, LHA-HPC is produced in a higher yield than BHA-HPC (51 vs. 17 wt%). Copyright © 2014 Elsevier Ltd. All rights reserved.

Flexible solid-state supercapacitors based on three-dimensional graphene hydrogel films.

PubMed

Xu, Yuxi; Lin, Zhaoyang; Huang, Xiaoqing; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

2013-05-28

Flexible solid-state supercapacitors are of considerable interest as mobile power supply for future flexible electronics. Graphene or carbon nanotubes based thin films have been used to fabricate flexible solid-state supercapacitors with high gravimetric specific capacitances (80-200 F/g), but usually with a rather low overall or areal specific capacitance (3-50 mF/cm(2)) due to the ultrasmall electrode thickness (typically a few micrometers) and ultralow mass loading, which is not desirable for practical applications. Here we report the exploration of a three-dimensional (3D) graphene hydrogel for the fabrication of high-performance solid-state flexible supercapacitors. With a highly interconnected 3D network structure, graphene hydrogel exhibits exceptional electrical conductivity and mechanical robustness to make it an excellent material for flexible energy storage devices. Our studies demonstrate that flexible supercapacitors with a 120 μm thick graphene hydrogel thin film can exhibit excellent capacitive characteristics, including a high gravimetric specific capacitance of 186 F/g (up to 196 F/g for a 42 μm thick electrode), an unprecedented areal specific capacitance of 372 mF/cm(2) (up to 402 mF/cm(2) for a 185 μm thick electrode), low leakage current (10.6 μA), excellent cycling stability, and extraordinary mechanical flexibility. This study demonstrates the exciting potential of 3D graphene macrostructures for high-performance flexible energy storage devices.

Microbial fuel cell as a biocapacitor by using pseudo-capacitive anode materials

NASA Astrophysics Data System (ADS)

Lv, Zhisheng; Xie, Daohai; Li, Fusheng; Hu, Yun; Wei, Chaohai; Feng, Chunhua

2014-01-01

Here, we report that the microbial fuel cell (MFC) containing pseudo-capacitive anode materials such as polypyrrole (PPy)/9,10-anthraquinone-2-sulfonic acid sodium salt (AQS) composite films and RuO2 nanoparticles can function as a biocapacitor, able to store bioelectrons generated from microbial oxidation of substrate and release the accumulated charge upon requirement. Influences of the specific capacitance of the PPy/AQS- and RuO2-modified carbon felt anodes on the extent of accumulated charge are examined. Results show that increasing anode capacitance is responsible for the increases in the amount of electrons stored and released, and thereby leading to more energy stored and average power dissipated. The long-term charging-discharging tests indicate that the RuO2-modified biocapacitor with a specific capacitance of 3.74 F cm-2 exhibits 6% loss in the amount of released charge over 10 cycles for one-month operation, and 40% loss over 60 cycles for six-month operation. Our findings suggest that the MFC anode incorporating pseudo-capacitive materials shows potential for storing energy from waste organic matter and releasing in a short time of high power to the electronic device.

Important parameters affecting the cell voltage of aqueous electrical double-layer capacitors

NASA Astrophysics Data System (ADS)

Wu, Tzu-Ho; Hsu, Chun-Tsung; Hu, Chi-Chang; Hardwick, Laurence J.

2013-11-01

This study discusses and demonstrates how the open-circuit potential and charges stored in the working potential window on positive and negative electrodes affect the cell voltage of carbon-based electrical double-layer capacitors (EDLCs) in aqueous electrolytes. An EDLC consisting of two activated carbon electrodes is employed as the model system for identifying these key parameters although the potential window of water decomposition can be simply determined by voltammetric methods. First, the capacitive performances of an EDLC with the same charge on positive and negative electrodes are evaluated by cyclic voltammetric, charge-discharge, electrochemical impedance spectroscopic (EIS) analyses, and inductance-capacitance-resistance meter (LCR meter). The principles for obtaining the highest acceptable cell voltage of such symmetric ECs with excellent reversibility and capacitor-like behaviour are proposed. Aqueous charge-balanced EDLCs can be operated as high as 2.0 V with high energy efficiency (about 90%) and only 4% capacitance loss after the 600-cycle stability checking. The necessity of charge balance (but not capacitance balance) for positive and negative electrodes is substantiated from the lower acceptable cell voltage of charge-unbalanced EDLCs.

Heavy Metal-Free Tannin from Bark for Sustainable Energy Storage.

PubMed

Mukhopadhyay, Alolika; Jiao, Yucong; Katahira, Rui; Ciesielski, Peter N; Himmel, Michael; Zhu, Hongli

2017-12-13

A novel renewable cathode made from earth abundant, low-cost materials can contribute to the intermittent storage needs of renewable energy-based society. In this work, we report for the first-time tannin from Nature as a cathode material. Our approach exploits the charge storage mechanism of the redox active quinone moiety. Tannins extracted from tree bark using environmental friendly aqueous solvents have the highest phenol content (5.56 mol g -1 ) among all the natural phenolic biopolymers, 5000 times higher than lignin. Tannins coupled with a conductive polymer polypyrrole acquire high specific capacitance values of 370 F g -1 at 0.5 A g -1 as well as excellent rate performance of 196 F g -1 at 25 A g -1 . Additionally, we employed carbonized wood as an electrode substrate to produce a sustainable electrochemical device with dramatically improved performance compared to conventional devices. The high surface area provided by the well-aligned, cellular porosity of wood-derived substrate combined with the high mobility of ions and electrons in the carbonized cell walls and deposited tannin can achieve an areal capacitance of 4.6 F cm -2 at 1 mA cm -2 , which is 1.5 times higher than activated wood carbon.

Ionic Liquid Catalyzed Electrolyte for Electrochemical Polyaniline Supercapacitors

NASA Astrophysics Data System (ADS)

Inamdar, A. I.; Im, Hyunsik; Jung, Woong; Kim, Hyungsang; Kim, Byungchul; Yu, Kook-Hyun; Kim, Jin-Sang; Hwang, Sung-Min

2013-05-01

The effect of different wt.% of ionic liquid "1,6-bis (trimethylammonium-1-yl) hexane tetrafluoroborate" in 0.5 M LiClO4+PC electrolyte on the supercapacitor properties of polyaniline (PANI) thin film are investigated. The PANI film is synthesized using electropolymerization of aniline in the presence of sulfuric acid. The electrochemical properties of the PANI thin film are studied by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) measurements. The optimum amount of the ionic liquid is found to be 2 wt.% which provides better ionic conductivity of the electrolyte. The highest specific capacitance of 259 F/g is obtained using the 2 wt.% electrolyte. This capacitance remains at up to 208 F/g (80% capacity retention) after 1000 charge-discharge cycles at a current density of 0.5 mA/g. The PANI film in the 2 wt.% ionic liquid catalyzed 0.5 M LiClO4+PC electrolyte shows small electrochemical resistance, better rate performance and higher cyclability. The increased ionic conductivity of the 2 wt.% ionic liquid catalyzed electrolyte causes a reduction in resistance at the electrode/electrolyte interface, which can be useful in electrochemically-preferred power devices for better applicability.

Two-Dimensional Titanium Carbide/RGO Composite for High-Performance Supercapacitors.

PubMed

Zhao, Chongjun; Wang, Qian; Zhang, Huang; Passerini, Stefano; Qian, Xiuzhen

2016-06-22

Ti3C2Tx, a 2D titanium carbide in the MXenes family, is obtained from Ti3AlC2 through selective etching of the Al layer. Due to its good conductivity and high volumetric capacitance, Ti3C2Tx is regarded as a promising candidate for supercapacitors. In this paper, the fabrication of Ti3C2Tx/RGO composites with different proportions of Ti3C2Tx and RGO is reported, in which RGO acts as a conductive "bridge" to connect different Ti3C2Tx blocks and a matrix to alleviate the volume change during charge/discharge process. In addition, RGO nanosheets can serve as a second nanoscale current collector and support as well for the electrode. The electrochemical performance of the as-fabricated Ti3C2Tx/RGO electrodes, characterized by CV, GCD, and EIS, are also reported. A highest specific capacitance (Cs) of 154.3 F/g at 2 A/g is obtained at the Ti3C2Tx: RGO weight ratio of 7:1 combined with an outstanding capacity retention (124.7 F/g) after 6000 cycles at 4 A/g.

Comparative study of CO2 and H2O activation in the synthesis of carbon electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Taer, E.; Apriwandi, Yusriwandi, Mustika, W. S.; Zulkifli, Taslim, R.; Sugianto, Kurniasih, B.; Agustino, Dewi, P.

2018-02-01

The physical activation for the comparative study of carbon electrode synthesized for supercapacitor applications made from rubber wood sawdust has been performed successfully. Comparison of physical activation used in this research is based on the different gas activation such as CO2 and H2O. The CO2 and H2O activation are made by using an integrated carbonization and activation system. The carbonization process is performed in N2 atmosphere followed by CO2 and H2O activation process. The carbonization process at temperature of 600°C, the CO2 and H2O activation process at a temperature of 900°C and maintained at this condition for 2 h and 3 h. The electrochemical properties were analyzed using cyclic voltammetric (CV) method. The CV results show that the carbon electrode with CO2 activation has better capacitive properties than H2O, the highest specific capacitance obtained is 93.22 F/g for 3 h of activation time. In addition, the analysis of physical properties such as surface morphology and degree of crystallinity was also performed.

Effect of porosity variation on the electrochemical behavior of vertically aligned multi-walled carbon nanotubes.

PubMed

Raut, Akshay S; Parker, Charles B; Stoner, Brian R; Glass, Jeffrey T

2012-06-01

Electrochemical charge storage characteristics of vertically aligned multi-walled carbon nanotubes (MWCNTs) as a function of varying diameter and spacing are reported. It was observed that the specific capacitance of the MWCNTs increased as both diameter and inter-tube spacing decreased. The MWCNT films with 229 nm inter-MWCNT spacing exhibited specific capacitance of 228 F/g versus 70 F/g for 506 nm spacing, when tested in a non-aqueous electrolyte. Further, a trend in specific capacitance versus pore size is proposed. Coupled with previously reported trends observed in the sub-10 nm pore size regime, this is expected to offer better understanding of electrochemical behavior of porous carbon materials over a wide range of pore sizes.

Freestanding polyaniline nanorods grown on graphene for highly capacitive energy storage

NASA Astrophysics Data System (ADS)

Li, Zijiong; Qin, Zhen; Yang, Baocheng; Guo, Jian; Wang, Haiyan; Zhang, Weiyang; Lv, Xiaowei; Stack, Alison

2015-02-01

Freestanding polyaniline (PANI) nanorods grown in situ on microwave-expanded graphene oxide (MEGO) sheets were prepared through a facile solution method. The morphological characterization indicates that large quantity of free-standing PANI nanorods with average diameter of 50 nm were uniformly deposited onto the double sides of the MEGO nanosheets to form a sandwich structure. The hybrid of PANI/MEGO (GPANI) exhibit high specific surface area and high electrical conductivity, compared with pristine PANI nanorods. When evaluated as electrodes for supercapacitors, the GPANI demonstrate high specific capacitance of 628 F g-1 at a current density of 1.1 A g-1, high-rate performance, and excellent cycle stability compared to individual component. Such excellent electrochemical performance should be attributed to the combined double-layer capacitance and pseudo -capacitance mechanisms from the MEGO sheets and PANI nanorods.

Architecture engineering of supercapacitor electrode materials

NASA Astrophysics Data System (ADS)

Chen, Kunfeng; Li, Gong; Xue, Dongfeng

2016-02-01

The biggest challenge for today’s supercapacitor systems readily possessing high power density is their low energy density. Their electrode materials with controllable structure, specific surface area, electronic conductivity, and oxidation state, have long been highlighted. Architecture engineering of functional electrode materials toward powerful supercapacitor systems is becoming a big fashion in the community. The construction of ion-accessible tunnel structures can microscopically increase the specific capacitance and materials utilization; stiff 3D structures with high specific surface area can macroscopically assure high specific capacitance. Many exciting findings in electrode materials mainly focus on the construction of ice-folded graphene paper, in situ functionalized graphene, in situ crystallizing colloidal ionic particles and polymorphic metal oxides. This feature paper highlights some recent architecture engineering strategies toward high-energy supercapacitor electrode systems, including electric double-layer capacitance (EDLC) and pseudocapacitance.

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors

NASA Astrophysics Data System (ADS)

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-10-01

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm-3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm-3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors.

PubMed

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-10-17

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm(-3), 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm(-3), which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

Mechanochemical synthesis of carbon-based nanocomposites for supercapacitors

NASA Astrophysics Data System (ADS)

Mateyshina, Yuliya G.; Ulihin, Artem S.; Uvarov, Nikolai F.

2014-12-01

New nanoporous carbon-SiO2 composite materials were synthesized from organic raw materials (rice shells) and their electrochemical properties were investigated by cyclic voltammetry in liquid electrolytes (6 M KOH or 1 M H2SO4). A correlation between specific capacitance and specific surface area was observed. Due to high specific capacitance of 90 F/g the carbon materials under study may be regarded as promising electrode materials for electrochemical supercapacitors.

Heteroatom Polymer-Derived 3D High-Surface-Area and Mesoporous Graphene Sheet-Like Carbon for Supercapacitors.

PubMed

Sheng, Haiyang; Wei, Min; D'Aloia, Alyssa; Wu, Gang

2016-11-09

Current supercapacitors suffer from low energy density mainly due to the high degree of microporosity and insufficient hydrophilicity of their carbon electrodes. Development of a supercapacitor capable of simultaneously storing as much energy as a battery, along with providing sufficient power and long cycle stability would be valued for energy storage applications and innovations. Differing from commonly studied reduced graphene oxides, in this work we identified an inexpensive heteroatom polymer (polyaniline-PANI) as a carbon/nitrogen precursor, and applied a controlled thermal treatment at elevated temperature to convert PANI into 3D high-surface-area graphene-sheet-like carbon materials. During the carbonization process, various transition metals including Fe, Co, and Ni were added, which play critical roles in both catalyzing the graphitization and serving as pore forming agents. Factors including post-treatments, heating temperatures, and types of metal were found crucial for achieving enhanced capacitance performance on resulting carbon materials. Using FeCl 3 as precursor along with optimal heating temperature 1000 °C and mixed acid treatment (HCl+HNO 3 ), the highest Brunauer-Emmett-Teller (BET) surface area of 1645 m 2 g -1 was achieved on the mesopore dominant graphene-sheet-like carbon materials. The unique morphologies featured with high-surface areas, dominant mesopores, proper nitrogen doping, and 3D graphene-like structures correspond to remarkably enhanced electrochemical specific capacitance up to 478 Fg -1 in 1.0 M KOH at a scan rate of 5 mV s -1 . Furthermore, in a real two-electrode system of a symmetric supercapacitor, a specific capacitance of 235 Fg -1 using Nafion binder is obtained under a current density of 1 Ag -1 by galvanostatic charge-discharge tests in 6.0 M KOH. Long-term cycle stability up to 5000 cycles by using PVDF binder in electrode was systematically evaluated as a function of types of metals and current densities.

Facile synthesis of mesoporous NiFe2O4/CNTs nanocomposite cathode material for high performance asymmetric pseudocapacitors

NASA Astrophysics Data System (ADS)

Kumar, Nagesh; Kumar, Amit; Huang, Guan-Min; Wu, Wen-Wei; Tseng, Tseung Yuen

2018-03-01

Morphology and synergistic effect of constituents are the two very important factors that greatly influence the physical, chemical and electrochemical properties of a composite material. In the present work, we report the enhanced electrochemical performance of mesoporous NiFe2O4 and multiwall carbon nanotubes (MWCNTs) nanocomposites synthesized via hexamethylene tetramine (HMT) assisted one-pot hydrothermal approach. The synthesized cubic phase spinel NiFe2O4 nanomaterial possesses high specific surface area (148 m2g-1) with narrow mesopore size distribution. The effect of MWCNTs addition on the electrochemical performance of nanocomposite has been probed thoroughly in a normal three electrode configuration using 2 M KOH electrolyte at room temperature. Experimental results show that the addition of mere 5 mg MWCNTs into fixed NiFe2O4 precursors amount enhances the specific capacitance up to 1291 F g-1 at 1 A g-1, which is the highest reported value for NiFe2O4 nanocomposites so far. NiFe2O4/CNT nanocomposite exhibits small relaxation time constant (1.5 ms), good rate capability and capacitance retention of 81% over 500 charge-discharge cycles. This excellent performance can be assigned to high surface area, mesoporous structure of NiFe2O4 and conducting network formed by MWCNTs in the composite. Further, to evaluate the device performance of the composite, an asymmetric pseudocapacitor has been designed using NiFe2O4/CNT nanocomposite as a positive and N-doped graphene as a negative electrode material, respectively. Our designed asymmetric pseudocapacitor gives maximum energy density of 23 W h kg-1 at power density of 872 W kg-1. These promising results assert the potential of synthesized nanocomposite in the development of efficient practical high-capacitive energy storage devices.

Vanadium Pentoxide Nanobelt-Reduced Graphene Oxide Nanosheet Composites as High-Performance Pseudocapacitive Electrodes: ac Impedance Spectroscopy Data Modeling and Theoretical Calculations

PubMed Central

Gupta, Sanju; Aberg, Bryce; Carrizosa, Sara B.; Dimakis, Nicholas

2016-01-01

Graphene nanosheets and graphene nanoribbons, G combined with vanadium pentoxide (VO) nanobelts (VNBs) and VNBs forming GVNB composites with varying compositions were synthesized via a one-step low temperature facile hydrothermal decomposition method as high-performance electrochemical pseudocapacitive electrodes. VNBs from vanadium pentoxides (VO) are formed in the presence of graphene oxide (GO), a mild oxidant, which transforms into reduced GO (rGOHT), assisting in enhancing the electronic conductivity coupled with the mechanical robustness of VNBs. From electron microscopy, surface sensitive spectroscopy and other complementary structural characterization, hydrothermally-produced rGO nanosheets/nanoribbons are decorated with and inserted within the VNBs’ layered crystal structure, which further confirmed the enhanced electronic conductivity of VNBs. Following the electrochemical properties of GVNBs being investigated, the specific capacitance Csp is determined from cyclic voltammetry (CV) with a varying scan rate and galvanostatic charging-discharging (V–t) profiles with varying current density. The rGO-rich composite V1G3 (i.e., VO/GO = 1:3) showed superior specific capacitance followed by VO-rich composite V3G1 (VO/GO = 3:1), as compared to V1G1 (VO/GO = 1:1) composite, besides the constituents, i.e., rGO, rGOHT and VNBs. Composites V1G3 and V3G1 also showed excellent cyclic stability and a capacitance retention of >80% after 500 cycles at the highest specific current density. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters, including charge transfer and solution resistance, double layer and low frequency capacitance, Warburg impedance and the constant phase element. The detailed analyses provided greater insights into physical-chemical processes occurring at the electrode-electrolyte interface and highlighted the comparative performance of thin heterogeneous composite electrodes. We attribute the superior performance to the open graphene topological network being beneficial to available ion diffusion sites and the faster transport kinetics having a larger accessible geometric surface area and synergistic integration with optimal nanostructured VO loading. Computational simulations via periodic density functional theory (DFT) with and without V2O5 adatoms on graphene sheets are also performed. These calculations determine the total and partial electronic density of state (DOS) in the vicinity of the Fermi level (i.e., higher electroactive sites), in turn complementing the experimental results toward surface/interfacial charge transfer on heterogeneous electrodes. PMID:28773738

Na/K-ATPase regulates bovine sperm capacitation through raft- and non-raft-mediated signaling mechanisms.

PubMed

Rajamanickam, Gayathri D; Kastelic, John P; Thundathil, Jacob C

2017-11-01

Highly dynamic lipid microdomains (rafts) in the sperm plasma membrane contain several signaling proteins that regulate sperm capacitation. Na/K-ATPase isoforms (testis-specific isoform ATP1A4 and ubiquitous isoform ATP1A1) are abundant in bovine sperm plasma membrane. We previously reported that incubation of bovine sperm with ouabain, a specific Na/K-ATPase ligand, induced tyrosine phosphorylation of several sperm proteins during capacitation. The objective of this study was to investigate the roles of lipid rafts and non-rafts in Na/K-ATPase enzyme activity and signaling during bovine sperm capacitation. Content of ATP1A4 and, to a lesser extent, ATP1A1 was increased in raft and non-raft fractions of capacitated sperm, although non-raft enzyme activities of both isoforms were higher than the corresponding activities in rafts from capacitated sperm. Yet, ATP1A4 was the predominant isoform responsible for total Na/K-ATPase activity in both rafts and non-rafts. A comparative increase in phosphorylation of signaling molecules was observed in both raft (CAV1) and non-raft (EGFR and ERK1/2) membrane fractions during capacitation. Although SRC was phosphorylated in both membrane fractions, the non-raft fraction possessed more of this activated form. We also inferred, by immunoprecipitation, that ATP1A4 interacted with CAV1 and EGFR in the raft fraction, whereas interactions of ATP1A4 with SRC, EGFR, and ERK1/2 occurred in the non-raft fraction of ouabain-capacitated sperm; conversely, ATP1A1 interacted only with CAV1 in both fractions of uncapacitated and capacitated sperm. In conclusion, both raft and non-raft cohorts of Na/K-ATPase isoforms contributed to phosphorylation of signaling molecules during bovine sperm capacitation. © 2017 Wiley Periodicals, Inc.

3D architecture of a graphene/CoMoO(4) composite for asymmetric supercapacitors usable at various temperatures.

PubMed

Jiang, Yaru; Zheng, Xin; Yan, Xiaoqin; Li, Yong; Zhao, Xuan; Zhang, Yue

2017-05-01

Designing and optimizing the electrode materials and studying the electrochemical performance or cycle life of the supercapacitor under different working conditions are crucial to its practical application. Herein, we proposed a rational design of 3D-graphene/CoMoO 4 nanoplates by a facile two-step hydrothermal method. Owing to the high electron transfer rate of graphene and the high activity of the CoMoO 4 nanoplates, the three-dimensional electrode architectures achieved remarkable electrochemical performances with high areal specific capacitance (1255.24F/g at 1A/g) and superior cycling stability (91.3% of the original specific capacitance after 3000 cycles at 1A/g). The all-solid-state asymmetric supercapacitor composed of 3D-graphene/CoMoO 4 and activated carbon (AC) exhibited a specific capacitance of 109F/g at 0.2A/g and an excellent cycling stability with only 12.1% of the initial specific capacitance off after 3000 cycles at 2A/g. The effects of temperature and charge-discharge current densities on the charge storage capacity of the supercapacitor were also investigated in detail for practical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Porous hollow Co₃O₄ with rhombic dodecahedral structures for high-performance supercapacitors.

PubMed

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-06

Porous hollow Co₃O₄ with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co₃O₄ rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g(-1) and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co₃O₄ with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.

In situ self-sacrificed template synthesis of vanadium nitride/nitrogen-doped graphene nanocomposites for electrochemical capacitors.

PubMed

Liu, Hong-Hui; Zhang, Hong-Ling; Xu, Hong-Bin; Lou, Tai-Ping; Sui, Zhi-Tong; Zhang, Yi

2018-03-15

Vanadium nitride and graphene have been widely used as pseudo-capacitive and electric double-layer capacitor electrode materials for electrochemical capacitors, respectively. However, the poor cycling stability of vanadium nitride and the low capacitance of graphene impeded their practical applications. Herein, we demonstrated an in situ self-sacrificed template method for the synthesis of vanadium nitride/nitrogen-doped graphene (VN/NGr) nanocomposites by the pyrolysis of a mixture of dicyandiamide, glucose, and NH 4 VO 3 . Vanadium nitride nanoparticles of the size in the range of 2 to 7 nm were uniformly embedded into the nitrogen-doped graphene skeleton. Furthermore, the VN/NGr nanocomposites with a high specific surface area and pore volume showed a high specific capacitance of 255 F g -1 at 10 mV s -1 , and an excellent cycling stability (94% capacitance retention after 2000 cycles). The excellent capacitive properties were ascribed to the excellent conductivity of nitrogen-doped graphene, high surface area, high pore volume, and the synergistic effect between vanadium nitride and nitrogen-doped graphene.

Three-dimensional cross-linked carbon network wrapped with ordered polyaniline nanowires for high-performance pseudo-supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Huan; Liu, Shuwu; Hanif, Muddasir; Chen, Shuiliang; Hou, Haoqing

2014-12-01

The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization. The PaNWs/3D-CCN composites exhibited a specific capacitance (Cs) of 1191.8 F g-1 at a current density of 0.5 A g-1 and a superior rate capability with 66.4% capacitance retention at 100.0 A g-1. The high specific capacitance is attributed to the thin PaNW coating and the spaced PANI nanowire array, which ensure a higher utilization of PANI due to the ease of diffusion of protons through/on the PANI nanowires. In addition, the unique 3D-CCN was used as a high-conductivity platform (or skeleton) with no contact resistance for fast electron transfer and facile charge transport within the composites. Therefore, the binder-free composites can process rapid gains or losses of electrons and ions, even at a high current density. As a result, the specific capacitance and rate capability of our composites are remarkably higher than those of other PANI composites.

MOF-Derived Hollow Cage Nix Co3-x O4 and Their Synergy with Graphene for Outstanding Supercapacitors.

PubMed

Jayakumar, Anjali; Antony, Rajini P; Wang, Ronghua; Lee, Jong-Min

2017-03-01

Highly optimized nickel cobalt mixed oxide has been derived from zeolite imidazole frameworks. While the pure cobalt oxide gives only 178.7 F g -1 as the specific capacitance at a current density of 1 A g -1 , the optimized Ni:Co 1:1 has given an extremely high and unprecedented specific capacitance of 1931 F g -1 at a current density of 1 A g -1 , with a capacitance retention of 69.5% after 5000 cycles in a three electrode test. This optimized Ni:Co 1:1 mixed oxide is further used to make a composite of nickel cobalt mixed oxide/graphene 3D hydrogel for enhancing the electrochemical performance by virtue of a continuous and porous graphene conductive network. The electrode made from GNi:Co 1:1 successfully achieves an even higher specific capacitance of 2870.8 F g -1 at 1 A g -1 and also shows a significant improvement in the cyclic stability with 81% capacitance retention after 5000 cycles. An asymmetric supercapacitor is also assembled using a pure graphene 3D hydrogel as the negative electrode and the GNi:Co 1:1 as the positive electrode. With a potential window of 1.5 V and binder free electrodes, the capacitor gives a high specific energy density of 50.2 Wh kg -1 at a high power density of 750 W kg -1 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation of neural stem cells by whole cell membrane capacitance using dielectrophoresis.

PubMed

Adams, Tayloria N G; Jiang, Alan Y L; Vyas, Prema D; Flanagan, Lisa A

2018-01-15

Whole cell membrane capacitance is an electrophysiological property of the plasma membrane that serves as a biomarker for stem cell fate potential. Neural stem and progenitor cells (NSPCs) that differ in ability to form neurons or astrocytes are distinguished by membrane capacitance measured by dielectrophoresis (DEP). Differences in membrane capacitance are sufficient to enable the enrichment of neuron- or astrocyte-forming cells by DEP, showing the separation of stem cells on the basis of fate potential by membrane capacitance. NSPCs sorted by DEP need not be labeled and do not experience toxic effects from the sorting procedure. Other stem cell populations also display shifts in membrane capacitance as cells differentiate to a particular fate, clarifying the value of sorting a variety of stem cell types by capacitance. Here, we describe methods developed by our lab for separating NSPCs on the basis of capacitance using several types of DEP microfluidic devices, providing basic information on the sorting procedure as well as specific advantages and disadvantages of each device. Copyright © 2017 Elsevier Inc. All rights reserved.

Synthesis of ultrathin nitrogen-doped graphitic carbon nanocages as advanced electrode materials for supercapacitor.

PubMed

Tan, Yueming; Xu, Chaofa; Chen, Guangxu; Liu, Zhaohui; Ma, Ming; Xie, Qingji; Zheng, Nanfeng; Yao, Shouzhuo

2013-03-01

Synthesis of nitrogen-doped carbons with large surface area, high conductivity, and suitable pore size distribution is highly desirable for high-performance supercapacitor applications. Here, we report a novel protocol for template synthesis of ultrathin nitrogen-doped graphitic carbon nanocages (CNCs) derived from polyaniline (PANI) and their excellent capacitive properties. The synthesis of CNCs involves one-pot hydrothermal synthesis of Mn3O4@PANI core-shell nanoparticles, carbonization to produce carbon coated MnO nanoparticles, and then removal of the MnO cores by acidic treatment. The CNCs prepared at an optimum carbonization temperature of 800 °C (CNCs-800) have regular frameworks, moderate graphitization, high specific surface area, good mesoporosity, and appropriate N doping. The CNCs-800 show high specific capacitance (248 F g(-1) at 1.0 A g(-1)), excellent rate capability (88% and 76% capacitance retention at 10 and 100 A g(-1), respectively), and outstanding cycling stability (~95% capacitance retention after 5000 cycles) in 6 M KOH aqueous solution. The CNCs-800 can also exhibit great pseudocapacitance in 0.5 M H2SO4 aqueous solution besides the large electrochemical double-layer capacitance. The excellent capacitance performance coupled with the facile synthesis of ultrathin nitrogen-doped graphitic CNCs indicates their great application potential in supercapacitors.

Transparent and flexible electrodes and supercapacitors using polyaniline/single-walled carbon nanotube composite thin films

NASA Astrophysics Data System (ADS)

Ge, Jun; Cheng, Guanghui; Chen, Liwei

2011-08-01

Large-scale transparent and flexible electronic devices have been pursued for potential applications such as those in touch sensors and display technologies. These applications require that the power source of these devices must also comply with transparent and flexible features. Here we present transparent and flexible supercapacitors assembled from polyaniline (PANI)/single-walled carbon nanotube (SWNT) composite thin film electrodes. The ultrathin, optically homogeneous and transparent, electrically conducting films of the PANI/SWNT composite show a large specific capacitance due to combined double-layer capacitance and pseudo-capacitance mechanisms. A supercapacitor assembled using electrodes with a SWNT density of 10.0 µg cm-2 and 59 wt% PANI gives a specific capacitance of 55.0 F g-1 at a current density of 2.6 A g-1, showing its possibility for transparent and flexible energy storage.

Nano-aggregates of cobalt nickel oxysulfide as a high-performance electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Lifeng

2013-11-01

Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates.Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates. Electronic supplementary information (ESI) available: Experimental details; supplementary tables. See DOI: 10.1039/c3nr03533f

Preparation of Shape-Controlled Graphene/Co3O4 Composites for Supercapacitors

NASA Astrophysics Data System (ADS)

Chen, Jun; Chen, Ningna; Feng, Xiaomiao; Hou, Wenhua

2016-09-01

Graphene/Co3O4 nanocomposites with different morphologies were fabricated by hydrothermal method. The morphology of nanocomposites was characterized by scanning electron microscopy. These composites could be used as the electrode materials for supercapacitors. The eletrochemical behavior of the composite was tested by cyclic voltammetry and galvanostatic charge-discharge measurements in 1.0 mol/L KOH solution. The results showed that the graphene/Co3O4 nanopetal composite exhibited excellent electrochemical performance. The specific capacitance value could reach up to 714 F/g at a scan rate of 2 mV/s. Besides, the capacitance of the graphene/Co3O4 nanopetal composite was 841 F/g at a current density of 0.1 A/g. After galvanostatic charge-discharge 1000 laps at the current density of 0.4 A/g, the specific capacitance could keep 96.7% of original capacitive value, demonstrating its good cycling stability.

Transparent and flexible electrodes and supercapacitors using polyaniline/single-walled carbon nanotube composite thin films.

PubMed

Ge, Jun; Cheng, Guanghui; Chen, Liwei

2011-08-01

Large-scale transparent and flexible electronic devices have been pursued for potential applications such as those in touch sensors and display technologies. These applications require that the power source of these devices must also comply with transparent and flexible features. Here we present transparent and flexible supercapacitors assembled from polyaniline (PANI)/single-walled carbon nanotube (SWNT) composite thin film electrodes. The ultrathin, optically homogeneous and transparent, electrically conducting films of the PANI/SWNT composite show a large specific capacitance due to combined double-layer capacitance and pseudo-capacitance mechanisms. A supercapacitor assembled using electrodes with a SWNT density of 10.0 µg cm(-2) and 59 wt% PANI gives a specific capacitance of 55.0 F g(-1) at a current density of 2.6 A g(-1), showing its possibility for transparent and flexible energy storage. This journal is © The Royal Society of Chemistry 2011

MnO2 nanowires-decorated carbon fiber cloth as electrodes for aqueous asymmetric supercapacitor

NASA Astrophysics Data System (ADS)

Hong, Congcong; Wang, Xing; Yu, Houlin; Wu, Huaping; Wang, Jianshan; Liu, Aiping

Manganese dioxide nanowires (MnO2 NWs) anchored on carbon fiber cloth (CFC) were fabricated through a simple hydrothermal reaction and used as integrated electrodes for supercapacitor. The morphology-dependent electrochemical performance of MnO2 NWs was confirmed, yielding good capacitance performance with a high specific capacitance of 3.88Fṡcm‑2 at a charge-discharge current density of 5mAṡcm‑2 and excellent stability of 91.5% capacitance retention after 3000 cycles. Moreover, the composite electrodes were used to fabricate supercapacitors, which showed a high specific capacitance of 194mFṡcm‑2 at a charge-discharge current density of 2mAṡcm‑2 and high energy density of 0.108mWhṡcm‑2 at power density of 2mWṡcm‑2, foreboding its potential application for high-performance supercapacitor.

Three-Dimensional Honeycomb-Like Porous Carbon with Both Interconnected Hierarchical Porosity and Nitrogen Self-Doping from Cotton Seed Husk for Supercapacitor Electrode.

PubMed

Chen, Hui; Wang, Gang; Chen, Long; Dai, Bin; Yu, Feng

2018-06-08

Hierarchical porous structures with surface nitrogen-doped porous carbon are current research topics of interest for high performance supercapacitor electrode materials. Herein, a three-dimensional (3D) honeycomb-like porous carbon with interconnected hierarchical porosity and nitrogen self-doping was synthesized by simple and cost-efficient one-step KOH activation from waste cottonseed husk (a-CSHs). The obtained a-CSHs possessed hierarchical micro-, meso-, and macro-pores, a high specific surface area of 1694.1 m²/g, 3D architecture, and abundant self N-doping. Owing to these distinct features, a-CSHs delivered high specific capacitances of 238 F/g and 200 F/g at current densities of 0.5 A/g and 20 A/g, respectively, in a 6 mol/L KOH electrolyte, demonstrating good capacitance retention of 84%. The assembled a-CSHs-based symmetric supercapacitor also displayed high specific capacitance of 52 F/g at 0.5 A/g, with an energy density of 10.4 Wh/Kg at 300 W/Kg, and 91% capacitance retention after 5000 cycles at 10 A/g.

Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires.

PubMed

He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

2017-06-16

In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g -1 at a scan rate of 20 mV s -1 , which is almost twice that of ZnO NWs (191.5 F g -1 ). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g -1 at a current density of 1.33 A g -1 with an energy density of 25.2 W h kg -1 at the power density of 896.44 W kg -1 . In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

Morphology engineering of ZnO nanostructures for high performance supercapacitors: enhanced electrochemistry of ZnO nanocones compared to ZnO nanowires

NASA Astrophysics Data System (ADS)

He, Xiaoli; Yoo, Joung Eun; Lee, Min Ho; Bae, Joonho

2017-06-01

In this work, the morphology of ZnO nanostructures is engineered to demonstrate enhanced supercapacitor characteristics of ZnO nanocones (NCs) compared to ZnO nanowires (NWs). ZnO NCs are obtained by chemically etching ZnO NWs. Electrochemical characteristics of ZnO NCs and NWs are extensively investigated to demonstrate morphology dependent capacitive performance of one dimensional ZnO nanostructures. Cyclic voltammetry measurements on these two kinds of electrodes in a three-electrode cell confirms that ZnO NCs exhibit a high specific capacitance of 378.5 F g-1 at a scan rate of 20 mV s-1, which is almost twice that of ZnO NWs (191.5 F g-1). The charge-discharge and electrochemical impedance spectroscopy measurements also clearly result in enhanced capacitive performance of NCs as evidenced by higher specific capacitances and lower internal resistance. Asymmetric supercapacitors are fabricated using activated carbon (AC) as the negative electrode and ZnO NWs and NCs as positive electrodes. The ZnO NC⫽AC can deliver a maximum specific capacitance of 126 F g-1 at a current density of 1.33 A g-1 with an energy density of 25.2 W h kg-1 at the power density of 896.44 W kg-1. In contrast, ZnO NW⫽AC displays 63% of the capacitance obtained from the ZnO NC⫽AC supercapacitor. The enhanced performance of NCs is attributed to the higher surface area of ZnO nanostructures after the morphology is altered from NWs to NCs.

A Novel Method for Proximity Detection of Moving Targets Using a Large-Scale Planar Capacitive Sensor System

PubMed Central

Ye, Yong; Deng, Jiahao; Shen, Sanmin; Hou, Zhuo; Liu, Yuting

2016-01-01

A novel method for proximity detection of moving targets (with high dielectric constants) using a large-scale (the size of each sensor is 31 cm × 19 cm) planar capacitive sensor system (PCSS) is proposed. The capacitive variation with distance is derived, and a pair of electrodes in a planar capacitive sensor unit (PCSU) with a spiral shape is found to have better performance on sensitivity distribution homogeneity and dynamic range than three other shapes (comb shape, rectangular shape, and circular shape). A driving excitation circuit with a Clapp oscillator is proposed, and a capacitance measuring circuit with sensitivity of 0.21 Vp−p/pF is designed. The results of static experiments and dynamic experiments demonstrate that the voltage curves of static experiments are similar to those of dynamic experiments; therefore, the static data can be used to simulate the dynamic curves. The dynamic range of proximity detection for three projectiles is up to 60 cm, and the results of the following static experiments show that the PCSU with four neighboring units has the highest sensitivity (the sensitivities of other units are at least 4% lower); when the attack angle decreases, the intensity of sensor signal increases. This proposed method leads to the design of a feasible moving target detector with simple structure and low cost, which can be applied in the interception system. PMID:27196905

Aloe vera Derived Activated High-Surface-Area Carbon for Flexible and High-Energy Supercapacitors.

PubMed

Karnan, M; Subramani, K; Sudhan, N; Ilayaraja, N; Sathish, M

2016-12-28

Materials which possess high specific capacitance in device configuration with low cost are essential for viable application in supercapacitors. Herein, a flexible high-energy supercapacitor device was fabricated using porous activated high-surface-area carbon derived from aloe leaf (Aloe vera) as a precursor. The A. vera derived activated carbon showed mesoporous nature with high specific surface area of ∼1890 m 2 /g. A high specific capacitance of 410 and 306 F/g was achieved in three-electrode and symmetric two-electrode system configurations in aqueous electrolyte, respectively. The fabricated all-solid-state device showed a high specific capacitance of 244 F/g with an energy density of 8.6 Wh/kg. In an ionic liquid electrolyte, the fabricated device showed a high specific capacitance of 126 F/g and a wide potential window up to 3 V, which results in a high energy density of 40 Wh/kg. Furthermore, it was observed that the activation temperature has significant role in the electrochemical performance, as the activated sample at 700 °C showed best activity than the samples activated at 600 and 800 °C. The electron microscopic images (FE-SEM and HR-TEM) confirmed the formation of pores by the chemical activation. A fabricated supercapacitor device in ionic liquid with 3 V could power up a red LED for 30 min upon charging for 20s. Also, it is shown that the operation voltage and capacitance of flexible all-solid-state symmetric supercapacitors fabricated using aloe-derived activated carbon could be easily tuned by series and parallel combinations. The performance of fabricated supercapacitor devices using A. vera derived activated carbon in all-solid-state and ionic liquid indicates their viable applications in flexible devices and energy storage.

Design, fabrication, and evaluation of on-chip micro-supercapacitors

NASA Astrophysics Data System (ADS)

Beidaghi, Majid

Due to the increasing demand for high power and reliable miniaturized energy storage devices, the development of micro-supercapacitors or electrochemical micro-capacitors have attracted much attention in recent years. This dissertation investigates several strategies to develop on-chip micro-supercapacitors with high power and energy density. Micro-supercapacitors based on interdigitated carbon micro-electrode arrays are fabricated through carbon microelectromechanical systems (C-MEMS) technique which is based on carbonization of patterned photoresist. To improve the capacitive behavior, electrochemical activation is performed on carbon micro-electrode arrays. The developed micro-supercapacitors show specific capacitances as high as 75 mFcm-2 at a scan rate of 5 mVs -1 after electrochemical activation for 30 minutes. The capacitance loss is less than 13% after 1000 cyclic voltammetry (CV) cycles. These results indicate that electrochemically activated C-MEMS micro-electrode arrays are promising candidates for on-chip electrochemical micro-capacitor applications. The energy density of micro-supercapacitors was further improved by conformal coating of polypyrrole (PPy) on C-MEMS structures. In these types of micro-devices the three dimensional (3D) carbon microstructures serve as current collectors for high energy density PPy electrodes. The electrochemical characterizations of these micro-supercapacitors show that they can deliver a specific capacitance of about 162.07 mFcm-2 and a specific power of 1.62mWcm -2 at a 20 mVs-1 scan rate. Addressing the need for high power micro-supercapacitors, the application of graphene as electrode materials for micro-supercapacitor was also investigated. The present study suggests a novel method to fabricate graphene-based micro-supercapacitors with thin film or in-plane interdigital electrodes. The fabricated micro-supercapacitors show exceptional frequency response and power handling performance and could effectively charge and discharge at rates as high as 50 Vs-1. CV measurements show that the specific capacitance of the micro-supercapacitor based on reduced graphene oxide and carbon nanotube composites is 6.1 mFcm -2 at scan rate of 0.01Vs-1. At a very high scan rate of 50 Vs-1, a specific capacitance of 2.8 mFcm-2 (stack capacitance of 3.1 Fcm-3) is recorded. This unprecedented performance can potentially broaden the future applications of micro-supercapacitors.

Preparation and electrochemical capacitance performances of super-hydrophilic conducting polyaniline

NASA Astrophysics Data System (ADS)

Li, Xingwei; Li, Xiaohan; Dai, Na; Wang, Gengchao; Wang, Zhun

Super-hydrophilic conducting polyaniline was prepared by surface modification of polyaniline using tetraethyl orthosilicate in water/ethanol solution, whereas its conductivity was 4.16 S cm -1 at 25 °C. And its electrochemical capacitance performances as an electrode material were evaluated by the cyclic voltammetry and galvanostatic charge/discharge test in 0.1 M H 2SO 4 aqueous solution. Its initial specific capacitance was 500 F g -1 at a constant current density of 1.5 A g -1, and the capacitance still reached about 400 F g -1 after 5000 consecutive cycles. Moreover, its capacitance retention ratio was circa 70% with the growth of current densities from 1.5 to 20 A g -1, indicating excellent rate capability. It would be a promising electrode material for aqueous redox supercapacitors.

Capacitive pressure-sensitive composites using nickel-silicone rubber: experiments and modeling

NASA Astrophysics Data System (ADS)

Fan, Yuqin; Liao, Changrong; Liao, Ganliang; Tan, Renbing; Xie, Lei

2017-07-01

Capacitive pressure (i.e., piezo-capacitive) sensors have manifested their superiority as a potential electronic skin. The mechanism of the traditional piezo-capacitive sensors is mainly to change the relative permittivity of the flexible composites by compressing the specially fabricated microstructures in the polymer matrix under pressure. Instead, we study the piezo-capacitive effect for a newly reported isotropic flexible composite consisting of silicone rubber (SR) and uniformly dispersed micron-sized conductive nickel particles experimentally and theoretically. The Young’s modulus of the nickel-SR composites (NSRCs) is designed to meet that of human skin. Experimental results show that the NSRCs exhibit remarkable particle concentration dependent capacitance response under uniaxial pressure, and the NSRCs present a good repeatability. We propose a mathematical model at particle level to provide deep insights into the piezo-capacitive mechanism, by considering the adjacent particles in the axial direction as micro capacitors connected in series and in parallel on the horizontal plane. The piezo-capacitive effect is determined by the relative permittivity induced by the particles rearrangement, longitudinal interparticle gap, and deflection angle of micro particle capacitors under pressure. Specifically, the relative capacitance of NSRC capacitor is deduced to be product of two factors: the degree of particle rearrangement, and the relative capacitance of a micro capacitor with the average longitudinal gap. The proposed model well matches and interprets the experimental results.

Tunable porous structure of carbon nanosheets derived from puffed rice for high energy density supercapacitors

NASA Astrophysics Data System (ADS)

Hou, Jianhua; Jiang, Kun; Tahir, Muhammad; Wu, Xiaoge; Idrees, Faryal; Shen, Ming; Cao, Chuanbao

2017-12-01

The development of green and clean synthetic techniques to overcome energy requirements have motivated the researchers for the utilization of sustainable biomass. Driven by this desire we choose rice as starting materials source. After the explosion effect, the precursor is converted into puffed rice with a honeycomb-like structures composed of thin sheets. These honeycomb-like macrostructures, effectively prevent the cross-linking tendency towards the adjacent nanosheets during activation process. Furthermore, tuneable micro/mesoporous structures with ultrahigh specific surface areas (SBET) are successfully designed by KOH activation. The highest SBET of 3326 m2 g-1 with optimized proportion of small-mesopores is achieved at 850 °C. The rice-derived porous N-doped carbon nanosheets (NCS-850) are used as the active electrode materials for supercapacitors. It exhibites high specific capacitance specifically of 218 F g-1 at 80 A g-1 in 6 M KOH and a high-energy density of 104 Wh kg-1 (53 Wh L-1) in the ionic liquid electrolytes. These are the highest values among the reported biomass-derived carbon materials for the best of our knowledge. The present work demonstrates that the combination of "puffing effect" and common chemical activation can turn natural products such as rice into functional products with prospective applications in high-performance energy storage devices.

Response to capacitating stimuli indicates extender-related differences in boar sperm function.

PubMed

Schmid, S; Henning, H; Petrunkina, A M; Weitze, K F; Waberski, D

2013-10-01

Spermatozoa, especially those of the porcine species, are highly susceptible to in vitro chilling and ageing. Extenders are continuously developed to protect boar spermatozoa from chilling injury. New semen extenders and other modified preservation strategies require sensitive testing for essential sperm functions. The key process on the pathway of fertilization is capacitation. The aim of the present study was to examine whether the specific response to capacitating stimuli is sensitive enough to indicate different preservation capacities of extenders during hypothermic storage of boar spermatozoa. Semen was diluted in Beltsville Thawing Solution (BTS) and Androstar Plus and kept for 3 h at 22°C or stored at 17°C, 10°C, and 5°C. Semen was analyzed at 24 and 96 h of storage. Motility and membrane integrity remained at high levels, except for lower values when stored in BTS at 5°C. Washed subsamples were incubated in capacitating medium (Tyrode) and control medium and were assessed for intracellular calcium concentration and integrity of plasma membranes using a flow cytometer. On the basis of the loss of low-calcium live cells in a kinetic approach, the specific response to capacitation stimuli was determined. There was a higher loss of response in semen stored hypothermically in the standard extender BTS compared to Androstar Plus. Assessment of the extent of phospholipid disorder under capacitating and control conditions by use of merocyanine staining did not reveal any significant extender-related differences. A field insemination trial with 778 sows was performed to relate in vitro results to fertility. Fertility parameters did not differ in semen stored up to 48 h at 10°C in Androstar Plus compared to controls stored at 17°C in BTS. In conclusion, assessment of specific reactivity to capacitating stimuli appears to be a sensitive tool for detection of extender-dependent alterations in functionality of chilled boar spermatozoa.

Nanocomposite of polyaniline nanorods grown on graphene nanoribbons for highly capacitive pseudocapacitors.

PubMed

Li, Lei; Raji, Abdul-Rahman O; Fei, Huilong; Yang, Yang; Samuel, Errol L G; Tour, James M

2013-07-24

A facile and cost-effective approach to the fabrication of a nanocomposite material of polyaniline (PANI) and graphene nanoribbons (GNRs) has been developed. The morphology of the composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron microscopy, and X-ray diffraction analysis. The resulting composite has a high specific capacitance of 340 F/g and stable cycling performance with 90% capacitance retention over 4200 cycles. The high performance of the composite results from the synergistic combination of electrically conductive GNRs and highly capacitive PANI. The method developed here is practical for large-scale development of pseudocapacitor electrodes for energy storage.

Synergistically Active NiCo2 S4 Nanoparticles Coupled with Holey Defect Graphene Hydrogel for High-Performance Solid-State Supercapacitors.

PubMed

Tiruneh, Sintayehu Nibret; Kang, Bong Kyun; Kwag, Sung Hoon; Lee, YoungHun; Kim, MinSeob; Yoon, Dae Ho

2018-03-02

Nickel cobalt sulfide nanoparticles embedded in holey defect graphene hydrogel (HGH) that exhibit highly porous structures and uniform nickel cobalt sulfide nanoparticle sizes are successfully prepared by a facile solvothermal-hydrothermal method. As an electrode material for supercapacitors, the as-prepared NiCo 2 S 4 @HGH shows ultra-high specific capacitances of 1000 F g -1 and 800 F g -1 at 0.5 and 6 A g -1 , respectively, owing to the outstanding electrical conductivity of HGH and high specific capacitance of NiCo 2 S 4 . After 2100 charge/discharge cycles at a current density of 6 A g -1 , 96.6 % of the specific capacitance was retained, signifying the superb durability of NiCo 2 S 4 @HGH. Moreover, remarkable specific capacitance (312.6 F g -1 ) and capacity retention (87 % after 5000 cycles) at 6 A g -1 were displayed by the symmetric solid-state supercapacitor fabricated by using NiCo 2 S 4 @HGH electrodes. These auspicious supercapacitor performances demonstrate that the as-developed solvothermal-hydrothermal approach can be widely used to prepare graphene-coupled binary metal sulfides for high-performance supercapacitor applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Template method to controllable synthesis 3D porous NiCo2O4 with enhanced capacitance and stability for supercapacitors.

PubMed

Bai, Yang; Wang, Ranran; Lu, Xiaoyu; Sun, Jing; Gao, Lian

2016-04-15

We present a facile template method to fabricate NiCo2O4 (NCO) composites with 3D porous structure as electrodes for supercapacitors. SiO2 sol is used as the template to prevent the aggregation of NCO and construct the porous structure with high specific surface area. Meanwhile, the binary metal oxides not only inherit the merits of single nickel oxides or cobalt oxides, but also show superior properties to promote the capacitance. The uniform structure of NCO12 (SiO2/NCO=1:2) is obtained through controlling the mass ratio of SiO2 and NCO. Owing to the dual advantages of porous structure and binary system, NCO12 composites exhibit highly enhanced electrochemical performance compared with those of directly prepared NCO, NCO21 (SiO2/NCO=1:0.5) and NCO14 (SiO2/NCO=1:4). The specific capacitance of NCO12 composite is about 1389 Fg(-1) at 1 Ag(-1). At 4 Ag(-1), the capacitance is still as high as 1090 Fg(-1) together with capacitance retention of 80% over 2500 cycles. The capacitance and stability are higher than those of most previously reported pure NCO composites, which make it a very promising electrode material for energy storage. Copyright © 2016 Elsevier Inc. All rights reserved.

Facile coating of manganese oxide on tin oxide nanowires with high-performance capacitive behavior.

PubMed

Yan, Jian; Khoo, Eugene; Sumboja, Afriyanti; Lee, Pooi See

2010-07-27

In this paper, a very simple solution-based method is employed to coat amorphous MnO2 onto crystalline SnO2 nanowires grown on stainless steel substrate, which utilizes the better electronic conductivity of SnO2 nanowires as the supporting backbone to deposit MnO2 for supercapacitor electrodes. Cyclic voltammetry (CV) and galvanostatic charge/discharge methods have been carried out to study the capacitive properties of the SnO2/MnO2 composites. A specific capacitance (based on MnO2) as high as 637 F g(-1) is obtained at a scan rate of 2 mV s(-1) (800 F g(-1) at a current density of 1 A g(-1)) in 1 M Na2SO4 aqueous solution. The energy density and power density measured at 50 A g(-1) are 35.4 W h kg(-1) and 25 kW kg(-1), respectively, demonstrating the good rate capability. In addition, the SnO2/MnO2 composite electrode shows excellent long-term cyclic stability (less than 1.2% decrease of the specific capacitance is observed after 2000 CV cycles). The temperature-dependent capacitive behavior is also discussed. Such high-performance capacitive behavior indicates that the SnO2/MnO2 composite is a very promising electrode material for fabricating supercapacitors.

In situ synthesized heteropoly acid/polyaniline/graphene nanocomposites to simultaneously boost both double layer- and pseudo-capacitance for supercapacitors.

PubMed

Cui, Zhiming; Guo, Chun Xian; Yuan, Weiyong; Li, Chang Ming

2012-10-05

It is challenging to simultaneously increase double layer- and pseudo-capacitance for supercapacitors. Phosphomolybdic acid/polyaniline/graphene nanocomposites (PMo(12)-PANI/GS) were prepared by using PMo(12) as a bifunctional reagent for not only well dispersing graphene for high electrochemical double layer capacitance but also in situ chemically polymerizing aniline for high pseudocapacitance, resulting in a specific capacitance of 587 F g(-1), which is ~1.5 and 6 times higher than that of PANI/GS (392 F g(-1)) and GS (103 F g(-1)), respectively. The nanocomposites also exhibit good reversibility and stability. Other kinds of heteropolyacids such as molybdovanadophosphoric acids (PMo(12-x)V(x), x = 1, 2 and 3) were also used to prepare PMo(12-x)V(x)-PANI/GS nanocomposites, also showing enhanced double layer- and pseudo-capacitance. This further proves the proposed concept to simultaneously boost both double layer- and pseudo-capacitance and demonstrates that it could be a universal approach to significantly improve the capacitance for supercapacitors.

The effect of radio-frequency self bias on ion acceleration in expanding argon plasmas in helicon sources

NASA Astrophysics Data System (ADS)

Wiebold, Matthew D.

Time-averaged plasma potential differences up to ˜ 165 V over several hundred Debye lengths are observed in low pressure (pn < 1 mTorr) expanding argon plasmas in the Madison Helicon Experiment. The potential gradient leads to ion acceleration exceeding Ei ≈ 7 kTe in some cases. Up to 1 kW of 13.56 MHz RF power is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field up to 1 kG. An RPA measures the IEDF and an emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in electron density as RF power is increased. In the capacitive mode, large fluctuations of the plasma potential (Vp--p ≳ 140 V, Vp--p/Vp ≈ 150%) exist at the RF frequency, leading to formation of a self-bias voltage. The mobile electrons can flow from the upstream region during an RF cycle whereas ions cannot, leading to an initial imbalance of flux, and the self-bias voltage builds as a result. The plasma potential in the expansion chamber is held near the floating potential for argon (Vp ≈ 5kTe/e). In the capacitive mode, the ion acceleration is not well described by an ambipolar relation. The accelerated population decay is consistent with that predicted by charge-exchange collisions. Grounding the upstream endplate increases the self-bias voltage compared to a floating endplate. In the inductive and helicon modes, the ion acceleration more closely follows an ambipolar relation, a result of decreased capacitive coupling due to the decreased RF skin depth. The scaling of the potential gradient with the argon flow rate, magnetic field and RF power are investigated, with the highest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees well with that predicted for RF sheaths. Use of the self-bias effect in a plasma thruster is explored, possibly for a low thrust, high specific impulse mode in a multi-mode helicon thruster. This work could also explain similar potential gradients in expanding helicon plasmas that are ascribed to double layer formation in the literature.

Facile synthesis of ultrafine cobalt oxide nanoparticles for high-performance supercapacitors.

PubMed

Liu, Fangyan; Su, Hai; Jin, Long; Zhang, Haitao; Chu, Xiang; Yang, Weiqing

2017-11-01

The ultrafine Co 3 O 4 nanoparticles are successfully prepared by a novel solvothermal-precipitation approach which exploits the supernatant liquid of Co 3 O 4 nanoflake micropheres synthesized by solvothermal method before. Interestingly, the water is only employed to obtain the ultrafine nanoparticles in supernatant liquid which was usually thrown away before. The microstructure measurement results of the as-grown samples present the homogeneous disperse ultrafine Co 3 O 4 nanoparticles with the size of around 5-10nm. The corresponding synthesis mechanism of the ultrafine Co 3 O 4 nanoparticles is proposed. More importantly, these ultrafine Co 3 O 4 nanoparticles obtained at 250°C show the highest specific capacitance of 523.0Fg -1 at 0.5Ag -1 , 2.6 times that of Co 3 O 4 nanoflake micropheres due to the quantum size effect. Meanwhile, the sample annealed under 350°C possesses the best cycling stability with capacitance retention of 104.9% after 1500 cycles. These results unambiguously demonstrate that this work not only provides a novel, facile, and eco-friendly approach to prepare high-performance Co 3 O 4 nanoparticles electrode materials for supercapacitors but also develops a widely used method for the preparation of other materials on a large scale. Copyright © 2017 Elsevier Inc. All rights reserved.

Facile Synthesis of Flower-Like Copper-Cobalt Sulfide as Binder-Free Faradaic Electrodes for Supercapacitors with Improved Electrochemical Properties

PubMed Central

Wang, Tianlei; Liu, Meitang; Ma, Hongwen

2017-01-01

Supercapacitors have been one of the highest potential candidates for energy storage because of their significant advantages beyond rechargeable batteries in terms of large power density, short recharging time, and long cycle lifespan. In this work, Cu–Co sulfides with uniform flower-like structure have been successfully obtained via a traditional two-step hydrothermal method. The as-fabricated Cu–Co sulfide vulcanized from precursor (P–Cu–Co sulfide) is able to deliver superior specific capacitance of 592 F g−1 at 1 A g−1 and 518 F g−1 at 10 A g−1 which are surprisingly about 1.44 times and 2.39 times higher than those of Cu–Co oxide electrode, respectively. At the same time, excellent cycling stability of P–Cu–Co sulfide is indicated by 90.4% capacitance retention at high current density of 10 A g−1 after 3000 cycles. Because of the introduction of sulfur during the vulcanization process, these new developed sulfides can get more flexible structure and larger reaction surface area, and will own richer redox reaction sites between the interfaces of active material/electrolyte. The uniform flower-like P–Cu–Co sulfide electrode materials will have more potential alternatives for oxides electrode materials in the future. PMID:28590417

Heavy Metal-Free Tannin from Bark for Sustainable Energy Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Alolika; Jiao, Yucong; Katahira, Rui

A novel renewable cathode made from earth abundant, low-cost materials can contribute to the intermittent storage needs of renewable energy-based society. In this work, we report for the first-time tannin from Nature as a cathode material. Our approach exploits the charge storage mechanism of the redox active quinone moiety. Tannins extracted from tree bark using environmental friendly aqueous solvents have the highest phenol content (5.56 mol g -1) among all the natural phenolic biopolymers, 5000 times higher than lignin. Tannins coupled with a conductive polymer polypyrrole acquire high specific capacitance values of 370 F g -1 at 0.5 A gmore » -1 as well as excellent rate performance of 196 F g -1 at 25 A g -1. Additionally, we employed carbonized wood as an electrode substrate to produce a sustainable electrochemical device with dramatically improved performance compared to conventional devices. The high surface area provided by the well-aligned, cellular porosity of wood-derived substrate combined with the high mobility of ions and electrons in the carbonized cell walls and deposited tannin can achieve an areal capacitance of 4.6 F cm -2 at 1 mA cm -2, which is 1.5 times higher than activated wood carbon.« less

High surface area monodispersed Fe3O4 nanoparticles alone and on physical exfoliated graphite for improved supercapacitors

NASA Astrophysics Data System (ADS)

Sarno, Maria; Ponticorvo, Eleonora; Cirillo, Claudia

2016-12-01

Highly conductive, unsophisticated and easy to be obtained physical exfoliated graphite (PHG) supporting well dispersed magnetite, Fe3O4/PHG nanocomposite, has been prepared by a one-step chemical strategy and physico-chemical characterized. The nanocomposite, favoured by the a-polar nanoparticles (NPs) capping, results in a self-assembled monolayer of monodispersed Fe3O4, covering perfectly the hydrophobic surfaces of PHG. The nanocomposite as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. It shows, after a suitable annealing, significant electrochemical properties (capacitance value of 787 F/g at 0.5 A g-1 and a Fe3O4/PHG weight ratio of 0.31) and good cycling stability (retention 91% after 30,000 cycles). Highly monodispersed very fine Fe3O4 NPs, covered by organic chains, have been also synthesized. The high surface area Fe3O4 NPs, after washing to leave a low content of organic chains able to avoid aggregation without excessively affecting the electrical properties of the material, exhibit remarkable pseudocapacitive activities, including the highest specific capacitance over reported for Fe3O4 (300 F/g at 0.5 A g-1).

Facile Synthesis of Flower-Like Copper-Cobalt Sulfide as Binder-Free Faradaic Electrodes for Supercapacitors with Improved Electrochemical Properties.

PubMed

Wang, Tianlei; Liu, Meitang; Ma, Hongwen

2017-06-07

Supercapacitors have been one of the highest potential candidates for energy storage because of their significant advantages beyond rechargeable batteries in terms of large power density, short recharging time, and long cycle lifespan. In this work, Cu-Co sulfides with uniform flower-like structure have been successfully obtained via a traditional two-step hydrothermal method. The as-fabricated Cu-Co sulfide vulcanized from precursor (P-Cu-Co sulfide) is able to deliver superior specific capacitance of 592 F g -1 at 1 A g -1 and 518 F g -1 at 10 A g -1 which are surprisingly about 1.44 times and 2.39 times higher than those of Cu-Co oxide electrode, respectively. At the same time, excellent cycling stability of P-Cu-Co sulfide is indicated by 90.4% capacitance retention at high current density of 10 A g -1 after 3000 cycles. Because of the introduction of sulfur during the vulcanization process, these new developed sulfides can get more flexible structure and larger reaction surface area, and will own richer redox reaction sites between the interfaces of active material/electrolyte. The uniform flower-like P-Cu-Co sulfide electrode materials will have more potential alternatives for oxides electrode materials in the future.

Heavy Metal-Free Tannin from Bark for Sustainable Energy Storage

DOE PAGES

Mukhopadhyay, Alolika; Jiao, Yucong; Katahira, Rui; ...

2017-11-30

A novel renewable cathode made from earth abundant, low-cost materials can contribute to the intermittent storage needs of renewable energy-based society. In this work, we report for the first-time tannin from Nature as a cathode material. Our approach exploits the charge storage mechanism of the redox active quinone moiety. Tannins extracted from tree bark using environmental friendly aqueous solvents have the highest phenol content (5.56 mol g -1) among all the natural phenolic biopolymers, 5000 times higher than lignin. Tannins coupled with a conductive polymer polypyrrole acquire high specific capacitance values of 370 F g -1 at 0.5 A gmore » -1 as well as excellent rate performance of 196 F g -1 at 25 A g -1. Additionally, we employed carbonized wood as an electrode substrate to produce a sustainable electrochemical device with dramatically improved performance compared to conventional devices. The high surface area provided by the well-aligned, cellular porosity of wood-derived substrate combined with the high mobility of ions and electrons in the carbonized cell walls and deposited tannin can achieve an areal capacitance of 4.6 F cm -2 at 1 mA cm -2, which is 1.5 times higher than activated wood carbon.« less

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors

PubMed Central

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-01-01

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm−3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm−3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs. PMID:24131954

Ultrathin NiO nanoflakes electrode materials for supercapacitors

NASA Astrophysics Data System (ADS)

Xiao, Huanhao; Qu, Fengyu; Wu, Xiang

2016-01-01

In this work, large scale ultrathin NiO nanoflakes grown on nickel foam have been successfully obtained by a facile, low cost and eco-friendly route under mild temperature. The average thickness of the as-obtained NiO nanoflakes is about 10 nm. And they possess large surface area of 89.56 m2 g-1 and the dominant pore size of 2.313 nm. The electrochemical properties of the obtained product were evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge measurement and electrochemical impedance spectroscopy (EIS). The electrochemical tests demonstrate the highest discharge areal capacitance of 870 mF cm-2 at 1 mA cm-2 and excellent long cycle-life stability with 84.2% of its discharge areal capacitance retention after 6000 cycles at the current density of 10 mA cm-2. The remarkable electrochemical capacitive performance revealed NiO nanoflakes grown on nickel foam might be promising supercapacitor electrode materials for future energy storage applications.

Fabrication of flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} and their electrochemical properties evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Ling-Bin, E-mail: konglb@lut.cn; School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050; Deng, Li

Graphical abstract: Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} nano-flakes materials, which have a flower-like structure, were successfully synthesized by a facile solvothermal method without adding any surfactant. The as-prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} possesses a maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Highlights: ► Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} materials were fabricated in a simple method. ► High specific capacitance of 2212.5 F g{sup −1} has been achieved. ► For the first time the effects of concentration andmore » temperature on its specific capacitance has been studied. -- Abstract: Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} was successfully synthesized by a facile solvothermal method. The microstructure and surface morphology of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} were physically characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and transmission electron microscope (TEM). The electrochemical properties studies were carried out using cyclic voltammetry (CV), chronopotentiometry technology and AC impedance spectroscopy, respectively. The results indicate that the flower-like structure has a profound impact on electrode performance at high discharge capacitance. A maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA could be achieved, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effects of Ni(NO{sub 3}){sub 2}·6H{sub 2}O concentration and temperature on the microstructure and specific capacitance of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} have also been systematically studied. The results show that flower-like structure can be formed when the concentration is appropriate, while the temperature has just little effect on its electrochemical properties.« less

Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

PubMed

Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

2015-12-01

High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microwave-Assisted Synthesis of Highly-Crumpled, Few-Layered Graphene and Nitrogen-Doped Graphene for Use as High-Performance Electrodes in Capacitive Deionization

NASA Astrophysics Data System (ADS)

Amiri, Ahmad; Ahmadi, Goodarz; Shanbedi, Mehdi; Savari, Maryam; Kazi, S. N.; Chew, B. T.

2015-12-01

Capacitive deionization (CDI) is a promising procedure for removing various charged ionic species from brackish water. The performance of graphene-based material in capacitive deionization is lower than the expectation of the industry, so highly-crumpled, few-layered graphene (HCG) and highly-crumpled nitrogen-doped graphene (HCNDG) with high surface area have been introduced as promising candidates for CDI electrodes. Thus, HCG and HCNDG were prepared by exfoliation of graphite in the presence of liquid-phase, microwave-assisted methods. An industrially-scalable, cost-effective, and simple approach was employed to synthesize HCG and HCNDG, resulting in few-layered graphene and nitrogen-doped graphene with large specific surface area. Then, HCG and HCNDG were utilized for manufacturing a new class of carbon nanostructure-based electrodes for use in large-scale CDI equipment. The electrosorption results indicated that both the HCG and HCNDG have fairly large specific surface areas, indicating their huge potential for capacitive deionization applications.

Electrochemically Active Polyaniline (PANi) Coated Carbon Nanopipes and PANi Nanofibers Containing Composite.

PubMed

Ramana, G Venkata; Kumar, P Sampath; Srikanth, Vadali V S S; Padya, Balaji; Jain, P K

2015-02-01

A composite constituted by carbon nanopipes (CNPs) and polyaniline nanofibers (PANi NFs) is synthesized using in-situ chemical oxidative polymerization. Owing to its electrochemical activity the composite is found to be suitable as a working electrode material in hybrid type supercapacitors. Microstructural and phase analyses of the composite showed that (i) CNP surfaces are coated with PANi and (ii) PANi coated CNPs are distributed among PANi NFs. The composite shows an excellent electrochemical activity and a high specific capacitance of ~224.39 F/g. The electro-chemical activity of the composite is explicated in correlation with crystallinity, intrinsic oxidation state, and doping degree of PANi in the composite. The electro-chemical activity of the composite is also explicated in correlation with BET surface area and ordered meso-porosity pertaining to the composite. Charge/discharge curves indicate that the specific capacitance of the composite is a result of electric double-layer capacitance offered by CNPs and Faradaic pseudo capacitance offered by PANi NFs.

Hierarchical NiCo2 S4 Nanotube@NiCo2 S4 Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors.

PubMed

Chen, Haichao; Chen, Si; Shao, Hongyan; Li, Chao; Fan, Meiqiang; Chen, Da; Tian, Guanglei; Shu, Kangying

2016-01-01

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of a highly efficient 3D graphene-CNT-MnO2-PANI nanocomposite as a binder free electrode material for supercapacitors.

PubMed

Asif, Muhammad; Tan, Yi; Pan, Lujun; Rashad, Muhammad; Li, Jiayan; Fu, Xin; Cui, Ruixue

2016-09-29

Graphene based nanocomposites have been investigated intensively, as electrode materials for energy storage applications. In the current work, a graphene-CNT-MnO 2 -PANI (GCM@PANI) nanocomposite has been synthesized on 3D graphene grown on nickel foam, as a highly efficient binder free electrode material for supercapacitors. Interestingly, the specific capacitance of the synthesized electrode increases up to the first 1500 charge-discharge cycles, and is thus referred to as an electrode activation process. The activated GCM@PANI nanocomposite electrode exhibits an extraordinary galvanostatic specific capacitance of 3037 F g -1 at a current density of 8 A g -1 . The synthesized nanocomposite exhibits an excellent cyclic stability with a capacitance retention of 83% over 12 000 charge-discharge cycles, and a high rate capability by retaining a specific capacitance of 84.6% at a current density of 20 A g -1 . The structural and electrochemical analysis of the synthesized nanocomposite suggests that the astonishing electrochemical performance might be attributed to the growth of a novel PANI nanoparticle layer and the synergistic effect of CNT/MnO 2 nanostructures.

A highly sensitive and specific capacitive aptasensor for rapid and label-free trace analysis of Bisphenol A (BPA) in canned foods.

PubMed

Mirzajani, Hadi; Cheng, Cheng; Wu, Jayne; Chen, Jiangang; Eda, Shigotoshi; Najafi Aghdam, Esmaeil; Badri Ghavifekr, Habib

2017-03-15

A rapid, highly sensitive, specific and low-cost capacitive affinity biosensor is presented here for label-free and single step detection of Bisphenol A (BPA). The sensor design allows rapid prototyping at low-cost using printed circuit board material by benchtop equipment. High sensitivity detection is achieved through the use of a BPA-specific aptamer as probe molecule and large electrodes to enhance AC-electroelectrothermal effect for long-range transport of BPA molecules toward electrode surface. Capacitive sensing technique is used to determine the bounded BPA level by measuring the sample/electrode interfacial capacitance of the sensor. The developed biosensor can detect BPA level in 20s and exhibits a large linear range from 1 fM to 10 pM, with a limit of detection (LOD) of 152.93 aM. This biosensor was applied to test BPA in canned food samples and could successfully recover the levels of spiked BPA. This sensor technology is demonstrated to be highly promising and reliable for rapid, sensitive and on-site monitoring of BPA in food samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of bimetallic metal-organic framework nanosheets and their derived porous nickel-cobalt sulfides for supercapacitors.

PubMed

Chen, Chen; Wu, Meng-Ke; Tao, Kai; Zhou, Jiao-Jiao; Li, Yan-Li; Han, Xue; Han, Lei

2018-04-24

Metal-organic frameworks (MOFs) show great advantages as new kinds of active materials for energy storage. In this study, bimetallic metal-organic frameworks (Ni/Co-MOFs) with nanosheet-assembled flower-like structures were synthesized by etching Ni-MOF microspheres in a cobalt nitrate solution. It can be clearly observed that the amount of Co(NO3)2 and etching time play crucial roles in the formation of Ni/Co-MOF nanosheets. The Ni/Co-MOFs were used as electrode materials for supercapacitors and the optimized Ni/Co-MOF-5 exhibited the highest capacitances of 1220.2 F g-1 and 986.7 F g-1 at current densities of 1 A g-1 and 10 A g-1, respectively. Ni/Co-MOF-5 was further sulfurized, and the derived Ni-Co-S electrode showed a higher specific capacitance of 1377.5 F g-1 at a current density of 1 A g-1 and a retention of 89.4% when the current density was increased to 10 A g-1, indicating superior rate capability. Furthermore, Ni/Co-MOF-5 and Ni-Co-S showed excellent cycling stability, i.e. about 87.8% and 93.7% of initial capacitance can be still maintained after 3000 cycles of charge-discharge. More interestingly, the Ni/Co-MOF-5//AC ASC shows an energy density of 30.9 W h kg-1 at a power density of 1132.8 W kg-1, and the Ni-Co-S//AC ASC displays a high energy density of 36.9 W h kg-1 at a power density of 1066.42 W kg-1. These results demonstrate that the as-synthesized bimetallic Ni/Co-MOF nanosheets and their derived nickel-cobalt sulfides have promising applications in electrochemical supercapacitors.

Facial synthesis of nanostructured ZnCo2O4 on carbon cloth for supercapacitor application

NASA Astrophysics Data System (ADS)

Patil, Swati J.; Park, Jungsung; Lee, Dong-Weon

2017-12-01

In this work, we have synthesized the ZnCo2O4 electrode by a facial one-step hydrothermal method on a carbon cloth for the supercapacitor application. The structural and phase purity of the prepared electrode material was confirmed by X-ray diffraction (XRD) technique. The surface morphology and elemental stoichiometry were studied using field emission scanning electron microscopy (FE-SEM). The FE-SEM micrograph illustrates that the ZnCo2O4 material is composed of microstrips with a ~0.5 μm width and length in micron uniformly covered the carbon cloth surface. The ZnCo2O4 electrode material further investigated for electrochemical analyses. The cyclic voltammetry results showed that the ZnCo2O4 microstrips electrode exhibited the highest specific capacitance of 1084 F/g at 2 mV/s scan rate. Remarkably, a maximum energy density of 12.5 Wh/kg was attained at a current density of 2 mA/cm2 with the power density of 3.6 kW/kg for the ZnCo2O4 microstrips electrode. Furthermore, the 96.2 % capacitive retention is obtained at a higher scan rate of 100 mV/s after 1000 CV cycles, indicating excellent cycling stability of the ZnCo2O4 microstrips electrode. The frequency-dependent rate capability and an ideal capacitive behaviour of the ZnCo2O4 microstrips electrode were analyzed using impedance analyses; a representing the ion diffusion structure of the material. These results show that the ZnCo2O4 microstrips electrode could be a promising material for supercapacitor application.

Helically coiled carbon nanotube forests for use as electrodes in supercapacitors

NASA Astrophysics Data System (ADS)

Childress, Anthony; Ferri, Kevin; Podila, Ramakrishna; Rao, Apparao

Supercapacitors are a class of devices which combine the high energy density of batteries with the power delivery of capacitors, and have benefitted greatly from the incorporation of carbon nanomaterials. In an effort to improve the specific capacitance of these devices, we have produced binder-free electrodes composed of helically coiled carbon nanotube forests grown on stainless steel current collectors with a performance superior to traditional carbon nanomaterials. By virtue of their helicity, the coiled nanotubes provide a greater surface area for energy storage than their straight counterparts, thus improving the specific capacitance. Furthermore, we used an Ar plasma treatment to increase the electronic density of states, and thereby the quantum capacitance, through the introduction of defects.

Effects of adding ethanol to KOH electrolyte on electrochemical performance of titanium carbide-derived carbon

NASA Astrophysics Data System (ADS)

Xu, Jiang; Zhang, Ruijun; Chen, Peng; Ge, Shanhai

2014-01-01

Porous carbide-derived carbons (CDCs) are synthesized from TiC at different chlorination temperatures as electrode materials for electrochemical capacitors. It is found that the microstructure of the produced CDCs has significant influence on both the hydrophilicity in aqueous KOH electrolyte and the resultant electrochemical performance. Because the TiC-CDC synthesized at higher temperature (e.g. 1000 °C) contains well-ordered graphite ribbons, it shows lower hydrophilicity and specific capacitance. It is also found that addition of a small amount of ethanol to KOH electrolyte effectively improves the wettability of the CDCs synthesized at higher temperature and the corresponding specific capacitance. Compared with the CDC synthesized at 600 °C, the CDC synthesized at 1000 °C shows fast ion transport and excellent capacitive behavior in KOH electrolyte with addition of ethanol because of the existences of mesopores and high specific surface area.

Reduced Graphene Oxide/Carbon Nanotube Composites as Electrochemical Energy Storage Electrode Applications.

PubMed

Yang, Wenyao; Chen, Yan; Wang, Jingfeng; Peng, Tianjun; Xu, Jianhua; Yang, Bangchao; Tang, Ke

2018-06-15

We demonstrate an electrochemical reduction method to reduce graphene oxide (GO) to electrochemically reduced graphene oxide (ERGO) with the assistance of carbon nanotubes (CNTs). The faster and more efficient reduction of GO can be achieved after proper addition of CNTs into GO during the reduction process. This nanotube/nanosheet composite was deposited on electrode as active material for electrochemical energy storage applications. It has been found that the specific capacitance of the composite film was strongly affected by the mass ratio of GO/CNTs and the scanning ratio of cyclic voltammetry. The obtained ERGO/CNT composite electrode exhibited a 279.4 F/g-specific capacitance and showed good cycle rate performance with the evidence that the specific capacitance maintained above 90% after 6000 cycles. The synergistic effect between ERGO and CNTs as well as crossing over of CNTs into ERGO is attributed to the high electrochemical performance of composite electrode.

3D flower-like hierarchical Ag@nickel-cobalt hydroxide microsphere with enhanced electrochemical properties

NASA Astrophysics Data System (ADS)

Lv, Zijian; Zhong, Qin; Bu, Yunfei; Wu, Junpeng

2016-10-01

The morphology and electrical conductivity are essential to electrochemical performance of electrode materials in renewable energy conversion and storage technologies such as fuel cells and supercapacitors. Here, we explored a facile method to grow Ag@nickel-cobalt layered double hydroxide (Ag@Ni/Co-LDHs) with 3D flower-like microsphere structure. The results show the morphology of Ni/Co-LDHs varies with the introduction of Ag species. The prepared Ag@Ni/Co-LDHs not only exhibits an open hierarchical structure with high specific capacitance but also shows good electrical conductivity to support fast electron transport. Benefiting from the unique structural features, these flower-like Ag@Ni/Co-LDHs microspheres have impressive specific capacitance as high as 1768 F g-1 at 1 A g-1. It can be concluded that engineering the structure of the electrode can increase the efficiency of the specific capacitance as a battery-type electrode for hybrid supercapacitors.

Explore the influence of agglomeration on electrochemical performance of an amorphous MnO2/C composite by controlling drying process

NASA Astrophysics Data System (ADS)

Cui, Mangwei; Kang, Litao; Shi, Mingjie; Xie, Lingli; Wang, Xiaomin; Zhao, Zhe; Yun, Shan; Liang, Wei

2017-09-01

Amorphous MnO2/C composite is prepared by a facile redox reaction between potassium permanganate (KMnO4) and commercial black pen ink. Afterwards, two different drying processes, air drying or freeze drying, are employed to adjust the agglomeration state of particles in samples and explore its influence on capacitive performance. Experimental results indicate that the air-dried sample demonstrates much better cycling stability than the freeze-dried one (capacity retention at 5000 cycles: 70.9 vs. 60.7%), probably because of the relatively strong agglomeration between particles in this sample. Nevertheless, strong agglomeration seems to deteriorate the specific capacitance (from 492 down to 440.5 F/g at 1 A/g) due to the decrease of porosity and specific surface area. This study suggests that agglomeration of primary particles plays an important role to balance the specific capacitance and cycling stability for electrode materials.

Copper oxide nanowires as better performance electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Yar, A.; Dennis, J. O.; Mohamed, N. M.; Mian, M. U.; Irshad, M. I.; Mumtaz, A.

2016-11-01

Supercapacitors are highly attractive energy storage devices which are capable of delivering high power, with fast charging and long cycle life. Carbon based material rely on physical charging with less capacitance while metal oxide store charge by fast redox reaction with increased capacitance. Among metal oxide, copper oxide compounds are widely use in the form of nano and micro structures with no definite control over structure. In this work we utilized the well-controlled structure copper wires, originated from AAO template. Such well controlled structure offer better capacitance values due to easily excess of ions to the surface of wires. Performance of material was check in 3 M of potassium hydroxide (KOH). Specific capacitance (Cs) was calculated by using cyclic voltammetry (CV) and Charge discharge (CDC) test. The capacitance calculate on base on CV at 25 mV/s was 101.37 F/g while CDC showed the capacitance of 90 F/g at 2 A/g.

Vertically porous nickel thin film supported Mn3O4 for enhanced energy storage performance.

PubMed

Li, Xiao-Jun; Song, Zhi-Wei; Zhao, Yong; Wang, Yue; Zhao, Xiu-Chen; Liang, Minghui; Chu, Wei-Guo; Jiang, Peng; Liu, Ying

2016-12-01

Three-dimensionally porous metal materials are often used as the current collectors and support for the active materials of supercapacitors. However, the applications of vertically porous metal materials in supercapacitors are rarely reported, and the effect of vertically porous metal materials on the energy storage performance of supported metal oxides is not explored. To this end, the Mn3O4-vertically porous nickel (VPN) electrodes are fabricated via a template-free method. The Mn3O4-VPN electrode shows much higher volumetric specific capacitances than that of flat nickel film supported Mn3O4 with the same loading under the same measurement conditions. The volumetric specific capacitance of the vertically porous nickel supported Mn3O4 electrode can reach 533Fcm(-3) at the scan rate of 2mVs(-1). The fabricated flexible all-solid microsupercapacitor based on the interdigital Mn3O4-VPN electrode has a volumetric specific capacitance of 110Fcm(-3) at the current density of 20μAcm(-2). The capacitance retention rate of this microsupercapacitor reaches 95% after 5000 cycles under the current density of 20μAcm(-2). The vertical pores in the nickel electrode not only fit the micro/nanofabrication process of the Mn3O4-VPN electrode, but also play an important role in enhancing the capacitive performances of supported Mn3O4 particles. Copyright © 2016 Elsevier Inc. All rights reserved.

Design, Fabrication, and Characterization of Hematite (α-Fe2O3) Nanostructures

NASA Astrophysics Data System (ADS)

Jansi Rani, B.; Mageswari, R.; Ravi, G.; Ganesh, V.; Yuvakkumar, R.

2017-12-01

The influence of processing parameters on the physicochemical properties of hematite α-Fe2O3 nanostructures was investigated. X-ray diffraction results revealed the hematite phase rhombohedral structure. Scanning electron microscope results explored nanospheres, nanohexagonal platelets, nanoellipsoids, distorted nanocubes, and interconnected platelets nanostructures. Rhombohedral single-phase hematite was confirmed through five Raman active modes. 2 P 3/2 (1) → 2 P 1/2 transition in photoluminescence spectra and Fourier-transform infrared spectroscopy band observed at 555 cm-1 revealed the hematite formation. The highest specific capacitance value of 151.09 F/g for scan rate of 10 mV/s was obtained for the hydrothermal-assisted product using an Fe(NO3)2·9H2O precursor in KOH electrolyte solutions.

Hierarchically porous nitrogen-doped carbon derived from the activation of agriculture waste by potassium hydroxide and urea for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Zou, Kaixiang; Deng, Yuanfu; Chen, Juping; Qian, Yunqian; Yang, Yuewang; Li, Yingwei; Chen, Guohua

2018-02-01

Nitrogen-doped carbon with an ultra-high specific surface area and a hierarchically interconnected porous structure is synthesized in large scale from a green route, that is, the activation of bagasse via a one-step method using KOH and urea. KOH and urea play a synergistic effect for the enhancement of the specific surface area and the modification of pore size of the as-prepared material. Benefiting from the multiple synergistic roles originated from an ultra-high specific area (2905.4 m2 g-1), a high porous volume (2.05 mL g-1 with 75.6 vol% micropores, which is an ideal proportion of micropores for obtaining high specific capacitance), a suitable nitrogen content (2.63 wt%), and partial graphitization, the hierarchically interconnected porous N-doped carbon exhibits an excellent electrochemical performance with a high specific capacitance (350.8, 301.9, and 259.5 F g-1 at 1.0 A g-1 in acidic, alkaline, and neutral electrolytes, respectively), superior rate capability and excellent cycling stability (almost no capacitance loss up to 5000 cycles). Furthermore, the symmetric device assembled by this material achieves high energy densities of 39.1 and 23.5 Wh kg-1 at power densities of 1.0 and 20 kW kg-1, respectively, and exhibits an excellent long-term cycling stability (with capacitance retention above 95.0% after 10 000 cycles).

Electrostatic Spray Deposition-Based Manganese Oxide Films-From Pseudocapacitive Charge Storage Materials to Three-Dimensional Microelectrode Integrands.

PubMed

Agrawal, Richa; Adelowo, Ebenezer; Baboukani, Amin Rabiei; Villegas, Michael Franc; Henriques, Alexandra; Wang, Chunlei

2017-07-26

In this study, porous manganese oxide (MnO x ) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g -1 to 225 F∙g -1 , with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn₃O₄ to the conducting layered birnessite MnO₂. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnO x /C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm -2 and stack capacitances as high as 7.4 F·cm -3 , with maximal stack energy and power densities of 0.51 mWh·cm -3 and 28.3 mW·cm -3 , respectively. The excellent areal capacitance of the MnO x -MEs is attributed to the pseudocapacitive MnO x as well as the three-dimensional architectural framework provided by the carbon micro-pillars.

Preparation of titanium dioxide films on etched aluminum foil by vacuum infiltration and anodizing

NASA Astrophysics Data System (ADS)

Xiang, Lian; Park, Sang-Shik

2016-12-01

Al2O3-TiO2 (Al-Ti) composite oxide films are a promising dielectric material for future use in capacitors. In this study, TiO2 films were prepared on etched Al foils by vacuum infiltration. TiO2 films prepared using a sol-gel process were annealed at various temperatures (450, 500, and 550 °C) for different time durations (10, 30, and 60 min) for 4 cycles, and then anodized at 100 V. The specimens were characterized using X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy. The results show that the tunnels of the specimens feature a multi-layer structure consisting of an Al2O3 outer layer, an Al-Ti composite oxide middle layer, and an aluminum hydrate inner layer. The electrical properties of the specimens, such as the withstanding voltage and specific capacitance, were also measured. Compared to specimens without TiO2 coating, the specific capacitances of the TiO2-coated specimens are increased. The specific capacitance of the anode Al foil with TiO2 coating increased by 42% compared to that of a specimen without TiO2 coating when annealed at 550 °C for 10 min. These composite oxide films could enhance the specific capacitance of anode Al foils used in dielectric materials.

Few-layered Ni(OH)2 nanosheets for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Sun, Wenping; Rui, Xianhong; Ulaganathan, Mani; Madhavi, Srinivasan; Yan, Qingyu

2015-11-01

Few-layered Ni(OH)2 nanosheets (4-5 nm in thickness) are synthesized towards high-performance supercapacitors. The ultrathin Ni(OH)2 nanosheets show high specific capacitance and good rate capability in both three-electrode and asymmetric devices. In the three-electrode device, the Ni(OH)2 nanosheets deliver a high capacitance of 2064 F g-1 at 2 A g-1, and the capacitance still has a retention of 1837 F g-1 at a high current density of 20 A g-1. Such excellent performance is by far one of the best for Ni(OH)2 electrodes. In the two-electrode asymmetric device, the specific capacitance is 248 F g-1 at 1 A g-1, and reaches 113 F g-1 at 20 A g-1. The capacitance of the asymmetric device maintains to be 166 F g-1 during the 4000th cycle at 2 A g-1, suggesting good cycling stability of the device. Besides, the asymmetric device exhibits gravimetric energy density of 22 Wh kg-1 at a power density of 0.8 kW kg-1. The present results demonstrate that the ultrathin Ni(OH)2 nanosheets are highly attractive electrode materials for achieving fast charging/discharging and high-capacity supercapacitors.

High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes

NASA Astrophysics Data System (ADS)

Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

2017-03-01

Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g-1, which is 6 times higher than disordered CNTs in HClO4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g-1), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g-1) and high energy density (98.1 Wh kg-1) in EMIBF4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation.

Improved capacitance characteristics of electrospun ACFs by pore size control and vanadium catalyst.

PubMed

Im, Ji Sun; Woo, Sang-Wook; Jung, Min-Jung; Lee, Young-Seak

2008-11-01

Nano-sized carbon fibers were prepared by using electrospinning, and their electrochemical properties were investigated as a possible electrode material for use as an electric double-layer capacitor (EDLC). To improve the electrode capacitance of EDLC, we implemented a three-step optimization. First, metal catalyst was introduced into the carbon fibers due to the excellent conductivity of metal. Vanadium pentoxide was used because it could be converted to vanadium for improved conductivity as the pore structure develops during the carbonization step. Vanadium catalyst was well dispersed in the carbon fibers, improving the capacitance of the electrode. Second, pore-size development was manipulated to obtain small mesopore sizes ranging from 2 to 5 nm. Through chemical activation, carbon fibers with controlled pore sizes were prepared with a high specific surface and pore volume, and their pore structure was investigated by using a BET apparatus. Finally, polyacrylonitrile was used as a carbon precursor to enrich for nitrogen content in the final product because nitrogen is known to improve electrode capacitance. Ultimately, the electrospun activated carbon fibers containing vanadium show improved functionality in charge/discharge, cyclic voltammetry, and specific capacitance compared with other samples because of an optimal combination of vanadium, nitrogen, and fixed pore structures.

High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes.

PubMed

Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

2017-03-08

Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g -1 , which is 6 times higher than disordered CNTs in HClO 4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g -1 ), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g -1 ) and high energy density (98.1 Wh kg -1 ) in EMIBF 4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation.

High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes

PubMed Central

Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

2017-01-01

Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g−1, which is 6 times higher than disordered CNTs in HClO4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g−1), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g−1) and high energy density (98.1 Wh kg−1) in EMIBF4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation. PMID:28272474

cGMP and cyclic nucleotide-gated channels participate in mouse sperm capacitation.

PubMed

Cisneros-Mejorado, Abraham; Sánchez Herrera, Daniel P

2012-01-20

During capacitation of mammalian sperm intracellular [Ca(2+)] and cyclic nucleotides increase, suggesting that CNG channels play a role in the physiology of sperm. Here we study the effect of capacitation, 8Br-cAMP (8-bromoadenosine 3',5'-cyclic monophosphate) and 8Br-cGMP (8-bromoguanosine 3',5'-cyclic monophosphate) on the macroscopic ionic currents of mouse sperm, finding the existence of different populations of sperm, in terms of the recorded current and its response to cyclic nucleotides. Our results show that capacitation and cyclic nucleotides increase the ionic current, having a differential sensitivity to cGMP (cyclic guanosine monophosphate) and cAMP (cyclic adenosine monophosphate). Using a specific inhibitor we determine the contribution of CNG channels to macroscopic current and capacitation. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Dioxythiophene-based polymer electrodes for supercapacitor modules.

PubMed

Liu, David Y; Reynolds, John R

2010-12-01

We report on the electrochemical and capacitive behaviors of poly(2,2-dimethyl-3,4-propylene-dioxythipohene) (PProDOT-Me2) films as polymeric electrodes in Type I electrochemical supercapacitors. The supercapacitor device displays robust capacitive charging/discharging behaviors with specific capacitance of 55 F/g, based on 60 μg of PProDOT-Me2 per electrode, that retains over 85% of its storage capacity after 32 000 redox cycles at 78% depth of discharge. Moreover, an appreciable average energy density of 6 Wh/kg has been calculated for the device, along with well-behaved and rapid capacitive responses to 1.0 V between 5 to 500 mV s(-1). Tandem electrochemical supercapacitors were assembled in series, in parallel, and in combinations of the two to widen the operating voltage window and to increase the capacitive currents. Four supercapacitors coupled in series exhibited a 4.0 V charging/discharging window, whereas assembly in parallel displayed a 4-fold increase in capacitance. Combinations of both serial and parallel assembly with six supercapacitors resulted in the extension of voltage to 3 V and a 2-fold increase in capacitive currents. Utilization of bipolar electrodes facilitated the encapsulation of tandem supercapacitors as individual, flexible, and lightweight supercapacitor modules.

Influences of internal resistance and specific surface area of electrode materials on characteristics of electric double layer capacitors

NASA Astrophysics Data System (ADS)

Suda, Yoshiyuki; Mizutani, Akitaka; Harigai, Toru; Takikawa, Hirofumi; Ue, Hitoshi; Umeda, Yoshito

2017-01-01

We fabricated electric double layer capacitors (EDLCs) using particulate and fibrous types of carbon nanomaterials with a wide range of specific surface areas and resistivity as an active material. The carbon nanomaterials used in this study are carbon nanoballoons (CNBs), onion-like carbon (OLC), and carbon nanocoils (CNCs). A commercially used activated carbon (AC) combined with a conductive agent was used as a comparison. We compared the EDLC performance using cyclic voltammetry (CV), galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS). OLC showed a poor EDLC performance, although it has the lowest resistivity among the carbon nanomaterials. CNB, which has a 1/16 lower specific surface area than AC but higher specific surface area than CNC and OLC, had a higher specific capacitance than CNC and OLC. Moreover, at current densities of 1.5 Ag-1 and larger, the specific capacitance of the EDLC using CNB was almost the same as that using AC. Electrochemical impedance spectroscopy of the EDLCs revealed that the CNB and CNC electrodes had a much lower internal resistance than the AC electrode, which correlated with a low capacitance maintenance factor as the current density increased.

Mesoporous coaxial titanium nitride-vanadium nitride fibers of core-shell structures for high-performance supercapacitors.

PubMed

Zhou, Xinhong; Shang, Chaoqun; Gu, Lin; Dong, Shanmu; Chen, Xiao; Han, Pengxian; Li, Lanfeng; Yao, Jianhua; Liu, Zhihong; Xu, Hongxia; Zhu, Yuwei; Cui, Guanglei

2011-08-01

In this study, titanium nitride-vanadium nitride fibers of core-shell structures were prepared by the coaxial electrospinning, and subsequently annealed in the ammonia for supercapacitor applications. These core-shell (TiN-VN) fibers incorporated mesoporous structure into high electronic conducting transition nitride hybrids, which combined higher specific capacitance of VN and better rate capability of TiN. These hybrids exhibited higher specific capacitance (2 mV s(-1), 247.5 F g(-1)) and better rate capability (50 mV s(-1), 160.8 F g(-1)), which promise a good candidate for high-performance supercapacitors. It was also revealed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) characterization that the minor capacitance fade originated from the surface oxidation of VN and TiN.

Highly-wrinkled reduced graphene oxide-conductive polymer fibers for flexible fiber-shaped and interdigital-designed supercapacitors

NASA Astrophysics Data System (ADS)

Li, Bo; Cheng, Jianli; Wang, Zhuanpei; Li, Yinchuan; Ni, Wei; Wang, Bin

2018-02-01

Flexible supercapacitors have attracted great interest due to outstanding flexibility and light weight. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers have the great potential in using as electrodes for flexible supercapacitors due to the good flexibility. However, the reported conductivity and specific capacitance of these PEDOT: PSS fibers are not very high, which limit their electrochemical performances. In this work, composite fibers of reduced graphene oxide(rGO)-PEDOT: PSS with a highly-wrinkled structure on the surface and pores inside are prepared by wet spinning. The fibers with different ratios of graphene to PEDOT:PSS show a distinctly enhanced conductivity up to ca. 590 S·cm-1 and high strength up to ca. 18.4 MPa. Meanwhile, the composite fibers show an improved electrochemical performances, including a high specific areal capacitance of 131 mF cm-2 and high specific areal energy density of 4.55 μWh·cm-2. The flexible supercapacitors including fiber-shaped supercapacitors and interdigital designed supercapacitors not only could work in different bending states without obvious capacitance decay, but also have small leakage current. The interdigital design can further improve the performances of composite fibers with high capacitance and high utilization compared with traditional parallel connected structure.

Nitrogen doped activated carbon from pea skin for high performance supercapacitor

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Ahmed, Ahsan; Rafat, M.

2018-04-01

In this work, nitrogen doped porous carbon (NDC) has been synthesized employing a facile two-step process. Firstly, carbon precursor (pea skin) was heated with melamine (acting as nitrogen source) followed by activation with KOH in different ratios. The dependence of porosity and nitrogen content on impregnation ratio was extensively studied. Other textural properties of prepared NDC sample were studied using standard techniques of material characterization. The electrochemical performance of NDC sample as an electrode was studied in two-electrode symmetric supercapacitor system. 1 M LiTFSI (lithium bis-trifluoromethanesulfonimide) solution in IL EMITFSI (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), was used as electrolyte. It was found that the fabricated supercapacitor cell offers high values of specific capacitance (141.1 F g‑1), specific energy (19.6 Wh kg‑1) and specific power (25.4 kW kg‑1) at current density of 1.3 A g‑1. More importantly, the fabricated supercapacitor cell shows capacitance retention of ∼75%, for more than 5000 cycles. The enhanced performance of NDC sample is primarily due to large surface area with favorable surface structure (contributing to double layer capacitance) and presence of nitrogen functionalities (contributing to pseudo-capacitance). Such important features make the synthesized NDC sample, an attractive choice for electrode material in high performance supercapacitor.

Microstructure and supercapacitive properties of buserite-type manganese oxide with a large basal spacing

NASA Astrophysics Data System (ADS)

Sun, Zhenjie; Shu, Dong; Chen, Hongyu; He, Chun; Tang, Shaoqing; Zhang, Jie

2012-10-01

A hydration-layered structure of buserite-type manganese oxide (Mg-buserite) was successfully synthesized by an ion exchange method. The as-prepared Mg-buserite possesses a large basal spacing of 10 Å, and contains Mg2+ ions and two sheets of water molecules in the interlayer region. The supercapacitive behaviors of Mg-buserite were systematically investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (CD) experiments and electrochemical impedance spectroscopy (EIS). The results showed that the specific capacitance of the Mg-buserite electrode sharply increased during the initial 500 cycles and reached a maximum of 164 F g-1 at approximately the 500th cycle at a scan rate of 1 mV s-1, and then it remained an almost constant value and decreased slightly upon prolonged cycling. After 22,000 cycles, the specific capacitance decreased by approximately 6% of the maximum specific capacitance. The superior capacitive behavior and excellent cycling stability of the as-prepared Mg-buserite are attributed to the large basal spacing, which can accommodate a larger amount of electrolyte cations and provide more favorable pathways for electrolyte cations intercalation and deintercalation. The experimental results demonstrate that Mg-buserite is a promising candidate as an electrode material for supercapacitors.

Carbon nanotube balls and their application in supercapacitors.

PubMed

Kang, Da-Young; Moon, Jun Hyuk

2014-01-08

We have provided a design of the macroscopic morphology of carbon nanotubes (CNTs) using emulsion droplet confinement. The evaporation of CNT-dispersed aqueous emulsion droplets in oil produces spherical CNT assemblies, i.e., CNT balls. In this emulsion-assisted method, compact packing of CNT was obtained by the presence of capillary pressure during droplet evaporation. The size of the CNT balls could be controlled by changing the concentration of the CNT dispersion solution; typically, CNT balls with an average size in the range of 8-12 μm were obtained with a Brunauer-Emmett-Teller (BET) specific area of 200 m(2)/g. Heat treatment of the CNT balls, which was required to remove residual solvent, and cement CNTs was followed, and their effect has been characterized; the heat treatment at high temperature desorbed surface oxygenated groups of CNTs and created defective carbon structures, but did not change pore structure. The dispersion of CNT balls was applied to form CNT ball-assembled film for a supercapacitor electrode. The specific capacitance of 80 F/g was obtained at 500 °C heat treatment, but the CNT balls prepared at a higher temperature actually decreased the capacitance, because of the removal of surface oxygenated groups, thereby decreasing the pseudo-capacitance. The capacitive properties of CNT ball-assembled electrodes were compared to CNT films; the CNT ball electrodes showed 40% higher specific electrochemical capacitance and higher rate performance, which is attributed to the compact packing of CNTs in the CNT ball and the hierarchical porous structures in the ball assemblies.

High Energy Density Asymmetric Supercapacitor Based on NiOOH/Ni3S2/3D Graphene and Fe3O4/Graphene Composite Electrodes

PubMed Central

Lin, Tsung-Wu; Dai, Chao-Shuan; Hung, Kuan-Chung

2014-01-01

The application of the composite of Ni3S2 nanoparticles and 3D graphene as a novel cathode material for supercapacitors is systematically investigated in this study. It is found that the electrode capacitance increases by up to 111% after the composite electrode is activated by the consecutive cyclic voltammetry scanning in 1 M KOH. Due to the synergistic effect, the capacitance and the diffusion coefficient of electrolyte ions of the activated composite electrode are ca. 3.7 and 6.5 times higher than those of the Ni3S2 electrode, respectively. Furthermore, the activated composite electrode exhibits an ultrahigh specific capacitance of 3296 F/g and great cycling stability at a current density of 16 A/g. To obtain the reasonable matching of cathode/anode electrodes, the composite of Fe3O4 nanoparticles and chemically reduced graphene oxide (Fe3O4/rGO) is synthesized as the anode material. The Fe3O4/rGO electrode exhibits the specific capacitance of 661 F/g at 1 A/g and excellent rate capability. More importantly, an asymmetric supercapacitor fabricated by two different composite electrodes can be operated reversibly between 0 and 1.6 V and obtain a high specific capacitance of 233 F/g at 5 mV/s, which delivers a maximum energy density of 82.5 Wh/kg at a power density of 930 W/kg. PMID:25449978

Functionalized graphene hydrogel-based high-performance supercapacitors.

PubMed

Xu, Yuxi; Lin, Zhaoyang; Huang, Xiaoqing; Wang, Yang; Huang, Yu; Duan, Xiangfeng

2013-10-25

Functionalized graphene hydrogels are prepared by a one-step low-temperature reduction process and exhibit ultrahigh specific capacitances and excellent cycling stability in the aqueous electrolyte. Flexible solid-state supercapacitors based on functionalized graphene hydrogels are demonstrated with superior capacitive performances and extraordinary mechanical flexibility. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Extraordinary Sulfonated-Graphenal-Polymer-Based Electrolyte Separator for All-Solid-State Supercapacitors.

PubMed

Liu, Xubo; Men, Chuanling; Zhang, Xiaohua; Li, Qingwen

2016-09-01

Sulfonated graphenal polymers can be assembled up by poly(vinyl alcohol) adhesion. The porous assembly structure results in a remarkably improved ionic conductivity and thus enhances electrochemical performances such as specific capacitance, capacitance retention, and cycling stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and property of novel MnO2@polypyrrole coaxial nanotubes as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Yao, Wei; Zhou, Hui; Lu, Yun

2013-11-01

Novel MnO2@polypyrrole (PPy) coaxial nanotubes have been prepared via a simple and green approach without any surfactant and additional oxidant. Under the acidic condition, MnO2 nanotubes act as both template and oxidant to initiate the polymerization of pyrrole monomers on its fresh-activated surface. Fourier transform infrared spectra (FT-IR), X-ray diffraction patterns (XRD), thermo-gravimetric analysis data (TG) and X-ray photoelectron spectra (XPS) suggest the formation of composite structure of MnO2@PPy. Also, FESEM and TEM images intuitively confirm that the PPy shell is coated uniformly on the surface of MnO2 nanotubes. Adjusting the concentrations of sulfuric acid or adding oxidant can modulate the morphology of the products accordingly. Due to the synergic effect between MnO2 core and PPy shell, the MnO2@PPy coaxial nanotubes possess better rate capability, larger specific capacitance of 380 F g-1, doubling the specific capacitance of MnO2 nanotubes, and good capacitance retention of 90% for its initial capacitance after 1000 cycles.

Hierarchical MoS2 nanowires/NiCo2O4 nanosheets supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Zhu, Fangfang; Shao, Rong; Xu, Wei

2018-01-01

The hierarchical MoS2 nanowires/NiCo2O4 nanosheets (MS/NCO) supercapacitor electrode materials supported on Ni foam were synthesized by a two-step hydrothermal method. The capacitance was investigated by using various electrochemical methods including cyclic voltammetry, constant-current galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. The MS/NCO networks show 7 times more capacitance (7.1 F cm-2) than pure NiCo2O4 nanosheets by CV at a scan rate of 2 mV s-1. The specific capacitance of the assembled MS/NCO//active carbon (AC) asymmetric supercapacitor could reach up to 51.7 F g-1 at a current density of 1.5 A g-1. Also, the maximum energy density of 18.4 W h kg-1 at a power density of 1200.2 W kg-1 was achieved, with 98.2% specific capacitance retention after 8000 cycles. These exciting results exhibit potential application in developing energy storage devices with high energy density and high power density.

Porous NiCo2O4 nanosheets/reduced graphene oxide composite: facile synthesis and excellent capacitive performance for supercapacitors.

PubMed

Ma, Lianbo; Shen, Xiaoping; Ji, Zhenyuan; Cai, Xiaoqing; Zhu, Guoxing; Chen, Kangmin

2015-02-15

A composite with porous NiCo2O4 nanosheets attached on reduced graphene oxide (RGO) sheets is synthesized through a facile solution-based method combined with a simple thermal annealing process. The capacitive performances of the as-prepared NiCo2O4/RGO (NCG) composites as electrode materials are investigated. It is found that the NCG composites exhibit a high specific capacitance up to 1186.3 F g(-1) at the current density of 0.5 A g(-1), and superior cycling stability with about 97% of the initial capacitance after 100 cycles. The greatly enhanced capacitive performance of the NCG electrode can be attributed to the existence of RGO support, which serves as both conductive channels and active interface. The approach used in the synthesis provides a facile route for preparing graphene-binary metal oxide electrode materials. The remarkable capacitive performance of NCG composites will undoubtedly make them be attractive for high performance energy storage applications. Copyright © 2014 Elsevier Inc. All rights reserved.

Highly Compressible Carbon Sponge Supercapacitor Electrode with Enhanced Performance by Growing Nickel-Cobalt Sulfide Nanosheets.

PubMed

Liang, Xu; Nie, Kaiwen; Ding, Xian; Dang, Liqin; Sun, Jie; Shi, Feng; Xu, Hua; Jiang, Ruibin; He, Xuexia; Liu, Zonghuai; Lei, Zhibin

2018-03-28

The development of compressible supercapacitor highly relies on the innovative design of electrode materials with both superior compression property and high capacitive performance. This work reports a highly compressible supercapacitor electrode which is prepared by growing electroactive NiCo 2 S 4 (NCS) nanosheets on the compressible carbon sponge (CS). The strong adhesion of the metallic conductive NCS nanosheets to the highly porous carbon scaffolds enable the CS-NCS composite electrode to exhibit an enhanced conductivity and ideal structural integrity during repeated compression-release cycles. Accordingly, the CS-NCS composite electrode delivers a specific capacitance of 1093 F g -1 at 0.5 A g -1 and remarkable rate performance with 91% capacitance retention in the range of 0.5-20 A g -1 . Capacitance performance under the strain of 60% shows that the incorporation of NCS nanosheets in CS scaffolds leads to over five times enhancement in gravimetric capacitance and 17 times enhancement in volumetric capacitance. These performances enable the CS-NCS composite to be one of the promising candidates for potential applications in compressible electrochemical energy storage devices.

Electrostatic Induced Stretch Growth of Homogeneous β-Ni(OH)2 on Graphene with Enhanced High-Rate Cycling for Supercapacitors

PubMed Central

Wu, Zhong; Huang, Xiao-Lei; Wang, Zhong-Li; Xu, Ji-Jing; Wang, Heng-Guo; Zhang, Xin-Bo

2014-01-01

Supercapacitors, as one of alternative energy devices, have been characterized by the rapid rate of charging and discharging, and high power density. But they are now challenged to achieve their potential energy density that is related to specific capacitance. Thus it is extremely important to make such materials with high specific capacitances. In this report, we have gained homogenous Ni(OH)2 on graphene by efficiently using of a facile and effective electrostatic induced stretch growth method. The electrostatic interaction triggers advantageous change in morphology and the ordered stacking of Ni(OH)2 nanosheets on graphene also enhances the crystallization of Ni(OH)2. When the as-prepared Ni(OH)2/graphene composite is applied to supercapacitors, they show superior electrochemical properties including high specific capacitance (1503 F g−1 at 2 mV s−1) and excellent cycling stability up to 6000 cycles even at a high scan rate of 50 mV s−1. PMID:24413283

Free-standing and porous hierarchical nanoarchitectures constructed with cobalt cobaltite nanowalls for supercapacitors with high specific capacitances

NASA Astrophysics Data System (ADS)

Xiao, Yuanhua; Zhang, Aiqin; Liu, Shaojun; Zhao, Jihong; Fang, Shaoming; Jia, Dianzeng; Li, Feng

2012-12-01

Free-standing and porous hierarchical nanoarchitectures constructed with cobalt cobaltite (Co3O4) nanowalls have been successfully synthesized in large scale by calcining three dimensional (3D) hierarchical nanostructures consisting of single crystalline cobalt carbonate hydroxide hydrate - Co(CO3)0.5(OH)·0.11H2O nanowalls prepared with a solvothermal method. The step-by-step decomposition of the precursor can generate porous Co3O4 nanowalls with BET surface area of 88.34 m2 g-1. The as-prepared Co3O4 nanoarchitectures show superior specific capacitance to the most Co3O4 supercapacitor electrode materials to date. After continuously cycled for 1000 times of charge-discharge at 4 A g-1, the supercapacitors can retain ca 92.3% of their original specific capacitances. The excellent performances of the devices can be attributed to the porous and hierarchical 3D nanostructure of the materials.

Aligned carbon nanotube/zinc oxide nanowire hybrids as high performance electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Al-Asadi, Ahmed S.; Henley, Luke Alexander; Wasala, Milinda; Muchharla, Baleeswaraiah; Perea-Lopez, Nestor; Carozo, Victor; Lin, Zhong; Terrones, Mauricio; Mondal, Kanchan; Kordas, Krisztian; Talapatra, Saikat

2017-03-01

Carbon nanotube/metal oxide based hybrids are envisioned as high performance electrochemical energy storage electrodes since these systems can provide improved performances utilizing an electric double layer coupled with fast faradaic pseudocapacitive charge storage mechanisms. In this work, we show that high performance supercapacitor electrodes with a specific capacitance of ˜192 F/g along with a maximum energy density of ˜3.8 W h/kg and a power density of ˜ 28 kW/kg can be achieved by synthesizing zinc oxide nanowires (ZnO NWs) directly on top of aligned multi-walled carbon nanotubes (MWCNTs). In comparison to pristine MWCNTs, these constitute a 12-fold of increase in specific capacitance as well as corresponding power and energy density values. These electrodes also possess high cycling stability and were able to retain ˜99% of their specific capacitance value over 2000 charging discharging cycles. These findings indicate potential use of a MWCNT/ZnO NW hybrid material for future electrochemical energy storage applications.

Supercapacitors based on ordered mesoporous carbon derived from furfuryl alcohol: effect of the carbonized temperature.

PubMed

Li, Na; Xu, Jianxiong; Chen, Han; Wang, Xianyou

2014-07-01

Supercapacitors are successfully prepared from ordered mesoporous carbon (OMC) synthesized by employing the mesoporous silica, SBA-15 as template and furfuryl alcohol as carbon source. It is found that the carbonized temperature greatly influences the physical properties of the synthesized mesoporous carbon materials. The optimal carbonized temperature is measured to be 600 degrees C under which OMC with the specific surface area of 1219 m2/g and pore volume of 1.31 cm3/g and average pore diameter of - 3 nm are synthesized. The OMC materials synthesized under different carbonized temperature are used as electrode material of supercapacitors and the electrochemical properties of the OMC materials are compared by using cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge-discharge and self-discharge tests. The results show that the electrochemical properties of the OMC materials are directly related to the specific surface area and pore volume of the mesoporous carbon and the electrode prepared from the OMC synthesized under the carbonized temperature of 600 degrees C (OMC-600) exhibits the most excellent electrochemical performance with the specific capacitance of 207.08 F/g obtained from cyclic voltammetry at the scan rate of 1 mV/s, small resistance and low self-discharge rate. Moreover, the supercapacitor based on the OMC-600 material exhibits good capacitance properties and stable cycle behavior with the specific capacitance of 105 F/g at the current density of 700 mA/g, and keeps a specific capacitance of 98 F/g after 20000 consecutive charge/discharge cycles.

Controllable in situ synthesis of epsilon manganese dioxide hollow structure/RGO nanocomposites for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Lin, Mei; Chen, Bolei; Wu, Xiao; Qian, Jiasheng; Fei, Linfeng; Lu, Wei; Chan, Lai Wa Helen; Yuan, Jikang

2016-01-01

Well-organized epsilon-MnO2 hollow spheres/reduced graphene oxide (MnO2HS/RGO) composites have been successfully constructed via a facile and one-pot synthetic route. The ε-MnO2 hollow spheres with the diameter of ~500 nm were grown in situ with homogeneous distribution on both sides of graphene oxide (GO) sheets in aqueous suspensions. The formation mechanism of the MnO2HS/RGO composites has been systematically investigated, and a high specific capacitance and good cycling capability were achieved on using the composites as supercapacitors. The galvanostatic charge/discharge curves show a specific capacitance of 471.5 F g-1 at 0.8 A g-1. The hollow structures of ε-MnO2 and the crumpled RGO sheets can enhance the electroactive surface area and improve the electrical conductivity, thus further facilitating the charge transport. The MnO2HS/RGO composite exhibits a high capacitance of 272 F g-1 at 3 A g-1 (92% retention) even after 1000 cycles. The prominent electrochemical performance might be attributed to the combination of the pseudo-capacitance of the MnO2 nanospheres with a hollow structure and to the good electrical conductivity of the RGO sheets. This work explores a new concept in designing metal oxides/RGO composites as electrode materials.Well-organized epsilon-MnO2 hollow spheres/reduced graphene oxide (MnO2HS/RGO) composites have been successfully constructed via a facile and one-pot synthetic route. The ε-MnO2 hollow spheres with the diameter of ~500 nm were grown in situ with homogeneous distribution on both sides of graphene oxide (GO) sheets in aqueous suspensions. The formation mechanism of the MnO2HS/RGO composites has been systematically investigated, and a high specific capacitance and good cycling capability were achieved on using the composites as supercapacitors. The galvanostatic charge/discharge curves show a specific capacitance of 471.5 F g-1 at 0.8 A g-1. The hollow structures of ε-MnO2 and the crumpled RGO sheets can enhance the electroactive surface area and improve the electrical conductivity, thus further facilitating the charge transport. The MnO2HS/RGO composite exhibits a high capacitance of 272 F g-1 at 3 A g-1 (92% retention) even after 1000 cycles. The prominent electrochemical performance might be attributed to the combination of the pseudo-capacitance of the MnO2 nanospheres with a hollow structure and to the good electrical conductivity of the RGO sheets. This work explores a new concept in designing metal oxides/RGO composites as electrode materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07900d

Chemical splitting of multiwalled carbon nanotubes to enhance electrochemical capacitance for supercapacitors

NASA Astrophysics Data System (ADS)

Li, Xinlu; Li, Tongtao; Zhang, Xinlin; Zhong, Qineng; Li, Hongyi; Huang, Jiamu

2014-06-01

Multiwalled carbon nanotubes (MWCNTs) were chemically split and self-assembled to a flexible porous paper made of graphene oxide nanoribbons (GONRs). The morphology and microstructure of the pristine MWCNTs and GONRs were analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. And the specific surface area and porosity structure were measured by N2 adsorption-desorption. The longitudinally split MWCNTs show an enhancement in specific capacitance from 21 F g-1 to 156 F g-1 compared with the pristine counterpart at 0.1 A g-1 in a 6 M KOH aqueous electrolytes. The electrochemical experiments prove that the chemical splitting of MWCNTs will make inner carbon layers opened and exposed to electrochemical double layers, which can effectively improve the electrochemical capacitance for supercapacitors.

New Supercapacitors Based on the Synergetic Redox Effect between Electrode and Electrolyte

PubMed Central

Zhang, You; Cui, Xiuguo; Zu, Lei; Cai, Xiaomin; Liu, Yang; Wang, Xiaodong; Lian, Huiqin

2016-01-01

Redox electrolytes can provide significant enhancement of capacitance for supercapacitors. However, more important promotion comes from the synergetic effect and matching between the electrode and electrolyte. Herein, we report a novel electrochemical system consisted of a polyanilline/carbon nanotube composite redox electrode and a hydroquinone (HQ) redox electrolyte, which exhibits a specific capacitance of 7926 F/g in a three-electrode system when the concentration of HQ in H2SO4 aqueous electrolyte is 2 mol/L, and the maximum energy density of 114 Wh/kg in two-electrode symmetric configuration. Moreover, the specific capacitance retention of 96% after 1000 galvanostatic charge/discharge cycles proves an excellent cyclic stability. These ultrahigh performances of the supercapacitor are attributed to the synergistic effect both in redox polyanilline-based electrolyte and the redox hydroquinone electrode. PMID:28773855

An Approach to Preparing Ni-P with Different Phases for Use as Supercapacitor Electrode Materials.

PubMed

Wang, Dan; Kong, Ling-Bin; Liu, Mao-Cheng; Luo, Yong-Chun; Kang, Long

2015-12-01

Herein, we describe a simple two-step approach to prepare nickel phosphide with different phases, such as Ni2 P and Ni5 P4 , to explain the influence of material microstructure and electrical conductivity on electrochemical performance. In this approach, we first prepared a Ni-P precursor through a ball milling process, then controlled the synthesis of either Ni2 P or Ni5 P4 by the annealing method. The as-prepared Ni2 P and Ni5 P4 are investigated as supercapacitor electrode materials for potential energy storage applications. The Ni2 P exhibits a high specific capacitance of 843.25 F g(-1) , whereas the specific capacitance of Ni5 P4 is 801.5 F g(-1) . Ni2 P possesses better cycle stability and rate capability than Ni5 P4 . In addition, the Fe2 O3 //Ni2 P supercapacitor displays a high energy density of 35.5 Wh kg(-1) at a power density of 400 W kg(-1) and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles, whereas the Fe2 O3 //Ni5 P4 supercapacitor exhibits a high energy density of 29.8 Wh kg(-1) at a power density of 400 W kg(-1) and a specific capacitance retention rate of 86 % after 1000 cycles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anchoring alpha-manganese oxide nanocrystallites on multi-walled carbon nanotubes as electrode materials for supercapacitor

NASA Astrophysics Data System (ADS)

Li, Li; Qin, Zong-Yi; Wang, Ling-Feng; Liu, Hong-Jin; Zhu, Mei-Fang

2010-09-01

The partial coverage of manganese oxide (MnO2) particles was achieved on the surfaces of multi-walled carbon nanotubes (MWCNTs) through a facile hydrothermal process. These particles were demonstrated to be alpha-manganese dioxide (α-MnO2) nanocrystallites, and exhibited the appearance of the whisker-shaped crystals with the length of 80-100 nm. In such a configuration, the uncovered CNTs in the nanocomposite acted as a good conductive pathway and the whisker-shaped MnO2 nanocrystallites efficiently increased the contact of the electrolyte with the active materials. Thus, the highest specific capacitance of 550 F g-1 was achieved using the resulting nanocomposites as the supercapacitor electrode. In addition, the enhancement of the capacity retention was observed, with the nanocomposite losing only 10% of the maximum capacity after 1,500 cycles.

Analog and RF performance of a multigate FinFET at nano scale

NASA Astrophysics Data System (ADS)

Kumar, Abhishek

2016-12-01

In this paper, analog and RF performance of the Fin field effect transistor (FET) at Nano scale is observed through 3D simulation. FinFET devices like rectangular gate all around (RE-GAA) FinFET, cylindrical gate all around (CY-GAA) FinFET and triple gate (TG) FinFET are observed. The figure of merit (FOMs) such as input-output characteristics, trans-conductance (gm), output-conductance (gd), intrinsic gain (gm/gd), gate capacitance (gate to source and total gate capacitance), unity gain cut-off frequency (ft), trans-conductance generation factor (TGF), gain frequency product (GFP), gain bandwidth product (GBP) and gain transconductance frequency product (GTFP) are observed. The analog performance of a FinFETs are observed by realising source follower circuit with NMOS transistor as a current source. The source follower circuit gain is observed. It has been observed that maximum capacitance is observed in case gate all around condition. Rectangular gate all around has the highest transconductance. In the source follower circuit, the gain curve (Vout/Vin) is sharper for TG-FinFET.

Solvothermal synthesis, electromagnetic and electrochemical properties of jellylike cylinder graphene-Mn3O4 composite with highly coupled effect

NASA Astrophysics Data System (ADS)

Long, Yuting; Xie, Junliang; Li, Hong; Liu, Zirui; Xie, Yahong

2017-12-01

Jellylike cylinder graphene-Mn3O4 composite with highly coupled effect was successfully synthesized by a simple solvothermal process. Without using toxic reducing agent and expensive equipment, this method is environmental compatible and suitable for low cost mass production. High capacitance Mn3O4 nanoparticles are homogeneously anchored on excellent conductivity graphene framework and a growth mechanism is hypothesized. Excellent electron conductivity and unique structure of Mn3O4-graphene composite give rise to various applications such as microwave absorber and electrode material. As a microwave absorber, the composite exhibits lowest reflection loss of -14.2 dB in the frequency range of 2-18 GHz. Good microwave absorption performance is due to the structure of the composite where conductive channels form between nano sized Mn3O4 and high conductivity graphene with defects and dangling bonds. As for electrochemical property, Mn3O4-graphene composite with coupled effect shows excellent performance with highest specific capacitance of 246.7 F g-1 in saturated K2SO4 at a scan rate of 5 mV s-1. Good electrochemical property is also attributed to the structure with high utilization of Mn3O4, fast charge carrier transmission, and excellent electronic conductivity. This composite shows a promising application in absorbing materials and electrodes.

Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

NASA Astrophysics Data System (ADS)

Li, Mingji; Guo, Wenlong; Li, Hongji; Xu, Sheng; Qu, Changqing; Yang, Baohe

2014-10-01

This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3-3.4 nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10 mm and a diameter of 0.6 mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1 M Na2SO4 aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5 F g-1 at current density of 0.5 A g-1. The capacitance remains at about 84% after 1000 cycles at 10 A g-1. The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices.

Two-dimensional nickel hydroxide nanosheets as high performance pseudo-capacitor electrodes

NASA Astrophysics Data System (ADS)

Bhat, Karthik S.; Nagaraja, H. S.

2018-04-01

Electrochemical supercapacitor is a vital technology for the progress of consistent energy harvesting devices. Herein, we report the fabrication of supercapacitor electrodes based on nickel hydroxide nanosheets synthesized via one-pot hydrothermal method. Structure and shape of synthesized materials were analyzed with XRD and SEM measurements. Pseudo-capacitive performances of the fabricated electrodes were evaluated through cyclic voltammetry and galvanostatic charge-discharge measurements with three-electrode configurations. Results indicated the specific capacitance of l80 F g-1 at 5 mV s-1 scan rate and complimented with capacitance retention of 76% for l500 cycles.

In vivo skin imaging for hydration and micro relief-measurement.

PubMed

Kardosova, Z; Hegyi, V

2013-01-01

We present the results of our work with device used for measurement of skin capacitance before and after application of moisturizing creams and results of experiment performed on cellulose filter papers soaked with different solvents. The measurements were performed by a device built on capacitance sensor, which provides an investigator with a capacitance image of the skin. The capacitance values are coded in a range of 256 gray levels then the skin hydration can be characterized using parameters derived from gray level histogram by specific software. The images obtained by device allow a highly precise observation of skin topography. Measuring of skin capacitance brings new, objective, reliable information about topographical, physical and chemical parameters of the skin. The study shows that there is a good correlation between the average grayscale values and skin hydration. In future works we need to complete more comparison studies, interpret the average grayscale values to skin hydration levels and use it for follow-up of dynamics of skin micro-relief and hydration changes (Fig. 6, Ref. 15).

Organic memory device with self-assembly monolayered aptamer conjugated nanoparticles

NASA Astrophysics Data System (ADS)

Oh, Sewook; Kim, Minkeun; Kim, Yejin; Jung, Hunsang; Yoon, Tae-Sik; Choi, Young-Jin; Jung Kang, Chi; Moon, Myeong-Ju; Jeong, Yong-Yeon; Park, In-Kyu; Ho Lee, Hyun

2013-08-01

An organic memory structure using monolayered aptamer conjugated gold nanoparticles (Au NPs) as charge storage nodes was demonstrated. Metal-pentacene-insulator-semiconductor device was adopted for the non-volatile memory effect through self assembly monolayer of A10-aptamer conjugated Au NPs, which was formed on functionalized insulator surface with prostate-specific membrane antigen protein. The capacitance versus voltage (C-V) curves obtained for the monolayered Au NPs capacitor exhibited substantial flat-band voltage shift (ΔVFB) or memory window of 3.76 V under (+/-)7 V voltage sweep. The memory device format can be potentially expanded to a highly specific capacitive sensor for the aptamer-specific biomolecule detection.

Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

NASA Astrophysics Data System (ADS)

Zhao, Hui

2012-11-01

Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse-charge dynamics of the double layer with ion specificity and steric effects.

Synthesis and capacitance properties of N-doped porous carbon/NiO nanosheet composites using coal-based polyaniline as carbon and nitrogen source

NASA Astrophysics Data System (ADS)

Wang, Xiaoqin; Li, Qiaoqin; Zhang, Yong; Yang, Yufei; Cao, Zhi; Xiong, Shanxin

2018-06-01

A novel synthesis approach of N-doped porous carbon (NPC)/NiO composites possessing some honeycomb-shaped nanoporous carbon and plentiful NiO nanosheets is exploited. First NPC/Ni composites are achieved with NPC yield of 52.9% through a catalytic pyrolysis method, using coal-based polyaniline particles prepared by an in-situ polymerization method as a carbon and nitrogen source, and nickel particles as a catalyst, respectively. Next NPC/NiO composites are achieved unexpectedly with plentiful NiO nanosheets and N content of 1.00 wt% after a liquid oxidation process. In NPC/NiO composites, porous carbon mainly presents in the amorphous state, while the incorporated nitrogen mainly presents in the form of pyrrolic N (92.9 at.%) and oxidized N (7.1 at.%). Plentiful NiO nanosheets are embedded in the pores or on the NPC surface. 33.3 at.% Ni2O3 components exist in the surface of NiO nanosheets. NPC/NiO composites possess not only rich micropores, but also significant mesopores and nanoscale macropores. The BET specific surface area, BET average pore width and BJH adsorption average pore diameter are 627.5 m2/g, 2.0 nm and 5.1 nm, respectively. NPC/NiO composites demonstrate a high specific capacitance of 404.1 F/g at 1 A/g, and a good cycling stability maintaining high specific capacitance of 212.4 F/g (84.3% of the initial capacitance) at 5 A/g after 5000 cycles of charge and discharge, attributed to some honeycomb-shaped nanopores of carbon and large specific surface area of NiO nanosheets, and the synergistic effects between electric double-layer capacitance of NPC and pseudocapacitance of NiO. This study may provide a novel approach for the value-added applications of low-rank coal.

Inhibiting Sperm Pyruvate Dehydrogenase Complex and Its E3 Subunit, Dihydrolipoamide Dehydrogenase Affects Fertilization in Syrian Hamsters

PubMed Central

Sailasree, Purnima; Singh, Durgesh K.; Kameshwari, Duvurri B.; Shivaji, Sisinthy

2014-01-01

Background/Aims The importance of sperm capacitation for mammalian fertilization has been confirmed in the present study via sperm metabolism. Involvement of the metabolic enzymes pyruvate dehydrogenase complex (PDHc) and its E3 subunit, dihydrolipoamide dehydrogenase (DLD) in hamster in vitro fertilization (IVF) via in vitro sperm capacitation is being proposed through regulation of sperm intracellular lactate, pH and calcium. Methodology and Principal Findings Capacitated hamster spermatozoa were allowed to fertilize hamster oocytes in vitro which were then assessed for fertilization, microscopically. PDHc/DLD was inhibited by the use of the specific DLD-inhibitor, MICA (5-methoxyindole-2-carboxylic acid). Oocytes fertilized with MICA-treated (MT) [and thus PDHc/DLD-inhibited] spermatozoa showed defective fertilization where 2nd polar body release and pronuclei formation were not observed. Defective fertilization was attributable to capacitation failure owing to high lactate and low intracellular pH and calcium in MT-spermatozoa during capacitation. Moreover, this defect could be overcome by alkalinizing spermatozoa, before fertilization. Increasing intracellular calcium in spermatozoa pre-IVF and in defectively-fertilized oocytes, post-fertilization rescued the arrest seen, suggesting the role of intracellular calcium from either of the gametes in fertilization. Parallel experiments carried out with control spermatozoa capacitated in medium with low extracellular pH or high lactate substantiated the necessity of optimal sperm intracellular lactate levels, intracellular pH and calcium during sperm capacitation, for proper fertilization. Conclusions This study confirms the importance of pyruvate/lactate metabolism in capacitating spermatozoa for successful fertilization, besides revealing for the first time the importance of sperm PDHc/ DLD in fertilization, via the modulation of sperm intracellular lactate, pH and calcium during capacitation. In addition, the observations made in the IVF studies in hamsters suggest that capacitation failures could be a plausible cause of unsuccessful fertilization encountered during human assisted reproductive technologies, like IVF and ICSI. Our studies indicate a role of sperm capacitation in the post-penetration events during fertilization. PMID:24852961

Facile one-step synthesis of nanocomposite based on carbon nanotubes and Nickel-Aluminum layered double hydroxides with high cycling stability for supercapacitors.

PubMed

Bai, Caihui; Sun, Shiguo; Xu, Yongqian; Yu, Ruijin; Li, Hongjuan

2016-10-15

Nickel-Aluminum Layered Double Hydroxide (NiAl-LDH) and nanocomposite of Carbon Nanotubes (CNTs) and NiAl-LDH (CNTs/NiAl-LDH) were prepared by using a facile one-step homogeneous precipitation approach. The morphology, structure and electrochemical properties of the as-prepared CNTs/NiAl-LDH nanocomposite were then systematically studied. According to the galvanostatic charge-discharge curves, the CNTs/NiAl-LDH nanocomposite exhibited a high specific capacitance of 694Fg(-1) at the 1Ag(-1). Furthermore, the specific capacitance of the CNTs/NiAl-LDH nanocomposite still retained 87% when the current density was increased from 1 to 10Ag(-1). These results indicated that the CNTs/NiAl-LDH nanocomposite displayed a higher specific capacitance and rate capability than pure NiAl-LDH. And the participation of CNTs in the NiAl-LDH composite improved the electrochemical properties. Additionally, the capacitance of the CNTs/NiAl-LDH nanocomposite kept at least 92% after 3000cycles at 20Ag(-1), suggesting that the nanocomposite exhibited excellent cycling durability. This strategy provided a facile and effective approach for the synthesis of nanocomposite based on CNTs and NiAl-LDH with enhanced supercapacitor behaviors, which can be potentially applied in energy storage conversion devices. Copyright © 2016 Elsevier Inc. All rights reserved.

Interfacial Engineered Polyaniline/Sulfur-Doped TiO2 Nanotube Arrays for Ultralong Cycle Lifetime Fiber-Shaped, Solid-State Supercapacitors.

PubMed

Li, Chun; Wang, Zhuanpei; Li, Shengwen; Cheng, Jianli; Zhang, Yanning; Zhou, Jingwen; Yang, Dan; Tong, Dong-Ge; Wang, Bin

2018-05-30

Fiber-shaped supercapacitors (FSCs) have great promises in wearable electronics applications. However, the limited specific surface area and inadequate structural stability caused by the weak interfacial interactions of the electrodes result in relatively low specific capacitance and unsatisfactory cycle lifetime. Herein, solid-state FSCs with high energy density and ultralong cycle lifetime based on polyaniline (PANI)/sulfur-doped TiO 2 nanotube arrays (PANI/S-TiO 2 ) are fabricated by interfacial engineering. The experimental results and ab initio calculations reveal that S doping can effectively promote the conductivity of titania nanotubes and increase the binding energy of PANI anchored on the electrode surface, leading to a much stronger binding of PANI on the surface of the electrode and excellent electrode structure stability. As a result, the FSCs using the PANI/S-TiO 2 electrodes deliver a high specific capacitance of 91.9 mF cm -2 , a capacitance retention of 93.78% after 12 000 charge-discharge cycles, and an areal energy density of 3.2 μW h cm -2 . Meanwhile, the all-solid-state FSC device retains its excellent flexibility and stable electrochemical capacitance even after bending 150 cycles. The enhanced performances of FSCs could be attributed to the large surface area, reduced ion diffusion path, improved electrical conductivity, and engineered interfacial interaction of the rationally designed electrodes.

Chloride and salicylate influence prestin-dependent specific membrane capacitance: support for the area motor model.

PubMed

Santos-Sacchi, Joseph; Song, Lei

2014-04-11

The outer hair cell is electromotile, its membrane motor identified as the protein SLC26a5 (prestin). An area motor model, based on two-state Boltzmann statistics, was developed about two decades ago and derives from the observation that outer hair cell surface area is voltage-dependent. Indeed, aside from the nonlinear capacitance imparted by the voltage sensor charge movement of prestin, linear capacitance (Clin) also displays voltage dependence as motors move between expanded and compact states. Naturally, motor surface area changes alter membrane capacitance. Unit linear motor capacitance fluctuation (δCsa) is on the order of 140 zeptofarads. A recent three-state model of prestin provides an alternative view, suggesting that voltage-dependent linear capacitance changes are not real but only apparent because the two component Boltzmann functions shift their midpoint voltages (Vh) in opposite directions during treatment with salicylate, a known competitor of required chloride binding. We show here using manipulations of nonlinear capacitance with both salicylate and chloride that an enhanced area motor model, including augmented δCsa by salicylate, can accurately account for our novel findings. We also show that although the three-state model implicitly avoids measuring voltage-dependent motor capacitance, it registers δCsa effects as a byproduct of its assessment of Clin, which increases during salicylate treatment as motors are locked in the expanded state. The area motor model, in contrast, captures the characteristics of the voltage dependence of δCsa, leading to a better understanding of prestin.

Analysis of temperature changes on three-phase synchronous generator using infrared: comparison between balanced and unbalanced load

NASA Astrophysics Data System (ADS)

Amien, S.; Yoga, W.; Fahmi, F.

2018-02-01

Synchronous generators are a major tool in an electrical energy generating systems, the load supplied by the generator is unbalanced. This paper discusses the effect of synchronous generator temperature on the condition of balanced load and unbalanced load, which will then be compared with the measurement result of both states of the generator. Unbalanced loads can be caused by various asymmetric disturbances in the power system and the failure of load forecasting studies so that the load distribution in each phase is not the same and causing the excessive heat of the generator. The method used in data collection was by using an infrared thermometer and resistance calculation method. The temperature comparison result between the resistive, inductive and capacitive loads in the highest temperature balance occured when the generator is loaded with a resistive load, where T = 31.9 ° C and t = 65 minutes. While in a state of unbalanced load the highest temperature occured when the generator is loaded with a capacitive load, where T = 40.1 ° C and t = 60 minutes. By understanding this behavior, we can maintain the generator for longer operation life.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors

NASA Astrophysics Data System (ADS)

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-08-01

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g-1 at a current density of 2 A g-1, which is higher than the capacitance of bare G (145 F g-1) and bare Ni (3 F g-1). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g-1 at a current density of 5 A g-1 and a capacitance of 144 F g-1 at a current density of 10 A g-1. The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors.

PubMed

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-08-24

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g(-1) at a current density of 2 A g(-1), which is higher than the capacitance of bare G (145 F g(-1)) and bare Ni (3 F g(-1)). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g(-1) at a current density of 5 A g(-1) and a capacitance of 144 F g(-1) at a current density of 10 A g(-1). The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.

Superior supercapacitors based on nitrogen and sulfur co-doped hierarchical porous carbon: Excellent rate capability and cycle stability

NASA Astrophysics Data System (ADS)

Zhang, Deyi; Han, Mei; Wang, Bing; Li, Yubing; Lei, Longyan; Wang, Kunjie; Wang, Yi; Zhang, Liang; Feng, Huixia

2017-08-01

Vastly improving the charge storage capability of supercapacitors without sacrificing their high power density and cycle performance would bring bright application prospect. Herein, we report a nitrogen and sulfur co-doped hierarchical porous carbon (NSHPC) with very superior capacitance performance fabricated by KOH activation of nitrogen and sulfur co-doped ordered mesoporous carbon (NSOMC). A high electrochemical double-layer (EDL) capacitance of 351 F g-1 was observed for the reported NSHPC electrodes, and the capacitance remains at 288 F g-1 even under a large current density of 20 A g-1. Besides the high specific capacitance and outstanding rate capability, symmetrical supercapacitor cell based on the NSHPC electrodes also exhibits an excellent cycling performance with 95.61% capacitance retention after 5000 times charge/discharge cycles. The large surface area caused by KOH activation (2056 m2 g-1) and high utilized surface area owing to the ideal micro/mesopores ratio (2.88), large micropores diameter (1.38 nm) and short opened micropores structure as well as the enhanced surface wettability induced by N and S heteroatoms doping and improved conductivity induced by KOH activation was found to be responsible for the very superior capacitance performance.

A binder-free NiCo2O4 nanosheet/3D elastic N-doped hollow carbon nanotube sponge electrode with high volumetric and gravimetric capacitances for asymmetric supercapacitors.

PubMed

Tong, Hao; Yue, Shihong; Lu, Liang; Jin, Fengqiao; Han, Qiwei; Zhang, Xiaogang; Liu, Jie

2017-11-09

To increase the volumetric and gravimetric capacitances of supercapacitors, a new class of electrode materials with high electrochemical activity and favorable structures is extremely desired. In this work, a hollow novel nitrogen-doped 3D elastic single-walled carbon nanotube sponge (NSCS) which is ultra lightweight with the lowest density of 0.8 mg cm -3 , and has a high open surface structure for electrolyte accessibility and excellent compressible properties as the electrode scaffold has been successfully fabricated by the pyrolysis method which could produce the carbon nanotube sponge easily on a large scale without high-cost and time-consuming processes. Moreover, a NiCo 2 O 4 nanosheet supported on the NSCS has been successfully fabricated. The highest volumetric and gravimetric capacitance of this electrode is 790 F cm -3 at 1.43 g cm -3 and 1618 F g -1 at 0.54 g cm -3 with excellent cycling stability. The density of NiCo 2 O 4 /NSCS electrode was adjusted by mechanical compression and the most favorable density of the film for both high volumetric and gravimetric capacitances obtained was 1.21 g cm -3 . The thick NiCo 2 O 4 /NSCS film of 72 μm has been fabricated at this favorable density, presenting both high volumetric and gravimetric capacitances of 597 F cm -3 and 1074 F g -1 at 1 A g -1 , respectively, indicating that the structure of the NSCS is extremely feasible for obtaining a thick film electrode with excellent volumetric and gravimetric capacitances. Furthermore, an asymmetric supercapacitor of NiCo 2 O 4 /NSCS//NGN/CNTs was fabricated, exhibiting a high gravimetric energy density of 47.65 W h kg -1 at 536 W kg -1 and a volumetric energy density of 33.44 W h L -1 at 376.16 W L -1 .

Stretchable V2O5/PEDOT supercapacitors: a modular fabrication process and charging with triboelectric nanogenerators.

PubMed

Qi, Ruijie; Nie, Jinhui; Liu, Mingyang; Xia, Mengyang; Lu, Xianmao

2018-04-26

Stretchable energy storage devices are of great importance for the viable applications of wearable/stretchable electronics. Studies on stretchable energy storage devices, especially supercapacitors (SCs), have shown encouraging progress. However, challenges still remain in the pursuit of high specific capacitances and facile fabrication methods. Herein, we report a modular materials fabrication and assembly process for stretchable SCs. With a V2O5/PEDOT composite as the active material, the resulting stretchable SCs exhibited high areal specific capacitances up to 240 mF cm-2 and good capacitance retention at a strain of 50%. To demonstrate the facile assembly process, a stretchable wristband was fabricated by simply assembling SC cells in series to deliver a voltage higher than 2 V. Charging the wristband with a triboelectric nanogenerator (TENG) to light an LED was further demonstrated, indicating the potential to integrate our SCs with environmental energy harvesters for self-powered stretchable devices.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Yan, Hailong; Zhang, Deyang; Xu, Jinyou; Lu, Yang; Liu, Yunxin; Qiu, Kangwen; Zhang, Yihe; Luo, Yongsong

2014-08-01

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g-1 at current densities of 5, 10, 15, 20, and 25 A g-1, respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.

Graphene oxide - Polyvinyl alcohol nanocomposite based electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Pawar, Pranav Bhagwan; Shukla, Shobha; Saxena, Sumit

2016-07-01

Supercapacitors are high capacitive energy storage devices and find applications where rapid bursts of power are required. Thus materials offering high specific capacitance are of fundamental interest in development of these electrochemical devices. Graphene oxide based nanocomposites are mechanically robust and have interesting electronic properties. These form potential electrode materials efficient for charge storage in supercapacitors. In this perspective, we investigate low cost graphene oxide based nanocomposites as electrode material for supercapacitor. Nanocomposites of graphene oxide and polyvinyl alcohol were synthesized in solution phase by integrating graphene oxide as filler in polyvinyl alcohol matrix. Structural and optical characterizations suggest the formation of graphene oxide and polyvinyl alcohol nanocomposites. These nanocomposites were found to have high specific capacitance, were cyclable, ecofriendly and economical. Our studies suggest that nanocomposites prepared by adding 0.5% wt/wt of graphene oxide in polyvinyl alcohol can be used an efficient electrode material for supercapacitors.

Soft and wrinkled carbon membranes derived from petals for flexible supercapacitors

PubMed Central

Yu, Xiuxiu; Wang, Ying; Li, Li; Li, Hongbian; Shang, Yuanyuan

2017-01-01

Biomass materials are promising precursors for the production of carbonaceous materials due to their abundance, low cost and renewability. Here, a freestanding wrinkled carbon membrane (WCM) electrode material for flexible supercapacitors (SCs) was obtained from flower petal. The carbon membrane was fabricated by a simple thermal pyrolysis process and further activated by heating the sample in air. As a binder and current collector-free electrode, the activated wrinkled carbon membrane (AWCM) exhibited a high specific capacitance of 332.7 F/g and excellent cycling performance with 92.3% capacitance retention over 10000 cycles. Moreover, a flexible all-solid supercapacitor with AWCM electrode was fabricated and showed a maximum specific capacitance of 154 F/g and great bending stability. The development of this flower petal based carbon membrane provides a promising cost-effective and environmental benign electrode material for flexible energy storage. PMID:28361914

Preparation and the Electrochemical Performance of MnO2/PANI@CNT Composite for Supercapacitors.

PubMed

Wang, Hongjuan; Wang, Xiaohui; Peng, Cheng; Peng, Feng; Yu, Hao

2015-01-01

Polyaniline (PANI) was settled on the surface of CNTs in advance and then used as self-sacrifice reducing agent that would react with KMnO4 to prepare MnO2/PANI@CNT supercapacitor material. With PANI substituting for CNTs to participant the redox reaction, CNTs was protected from being destroyed and could maintain its original morphology and conductivity. The results of cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) show that the optimal capacitive performance can be reached at the MnO2 loading of 64.4 wt% and the pH of 1 during the deposition of MnO2. With the protective PANI, MnO2/PANI@CNT composite exhibits the superior specific capacitance of 215.8 F/g at a current density of 200 mA/g and remains 86.5% of its maximal specific capacitance at a current density of 1000 mA/g.

Facile preparation and electrochemical characterization of kassite-based materials for supercapacitor applications

NASA Astrophysics Data System (ADS)

Meng, Weijie; Zhao, Gaoling; Song, Bin; Xie, Junliang; Lu, Wangwei; Han, Gaorong

2017-12-01

In this study, kassite was synthesized by employing a simple, green hydrothermal method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy were carried out to study its crystal phases, morphologies and electrochemical performance. With the extension of reaction time, the crystallinity of the samples became higher and the specific capacitance increased correspondingly. The result shows that kassite has a promising application in electrode material for capacitors. To improve the electrical conductivity of kassite and the accessibility of the surface area, graphene nanosheet (GNS) was introduced to form composites with kassite. The capacitive performance improved with increasing weight percentage of GNS and reached an optimum with the specific capacitance of 129.8 F/g at weight percentage of 10%, then decreased with further increasing GNS, showing a synergistic effect of kassite and the GNS.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors.

PubMed

Yan, Hailong; Zhang, Deyang; Xu, Jinyou; Lu, Yang; Liu, Yunxin; Qiu, Kangwen; Zhang, Yihe; Luo, Yongsong

2014-01-01

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g(-1) at current densities of 5, 10, 15, 20, and 25 A g(-1), respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.

Surfactant free nickel sulphide nanoparticles for high capacitance supercapacitors

NASA Astrophysics Data System (ADS)

Nandhini, S.; Muralidharan, G.

2018-04-01

The surfactant free nickel sulphide nanoparticles were synthesized via facile hydrothermal method towards supercapacitor applications. The formation of crystalline spherical nanoparticles was confirmed through structural and morphological studies. Electrochemical behaviour of the electrode was analyzed using cyclic voltammetry (CV), galvanostatic charge-discharge studies (GCD) and electrochemical impedance spectroscopy (EIS). The CV studies imply that specific capacitance of the electrode arises from a combination of surface adsorption and Faradic reaction. The NiS electrode delivered a specific capacitance of about 529 F g-1 at a current density of 2 A g-1 (GCD measurements). A profitable charge transfer resistance of 0.5 Ω was obtained from EIS. The 100 % of capacity retention even after 2000 repeated charge-discharge cycles could be observed in 2 M KOH electrolyte at a much larger rate of 30 A g-1. The experimental results suggest that nickel sulphide is a potential candidate for supercapacitor applications.

High voltage electrochemical double layer capacitors using conductive carbons as additives

NASA Astrophysics Data System (ADS)

Michael, M. S.; Prabaharan, S. R. S.

We describe here an interesting approach towards electrochemical capacitors (ECCs) using graphite materials (as being used as conductive additives in rechargeable lithium-ion battery cathodes) in a Li + containing organic electrolyte. The important result is that we achieved a voltage window of >4 V, which is rather large, compared to the standard window of 2.5 V for ordinary electric double layer capacitors (DLCs). The capacitor performance was evaluated by cyclic voltammetry (CV) and galvanostatic charge/discharge techniques. From charge-discharge studies of the symmetrical device (for instance, SFG6 carbon electrode), a specific capacitance of up to 14.5 F/g was obtained at 16 mA/cm 2 current rate and at a low current rate (3 mA/cm 2), a higher value was obtained (63 F/g). The specific capacitance decreased about 25% after 1000 cycles compared to the initial discharge process. The performances of these graphites are discussed in the light of both double layer capacitance (DLC) and pseudocapacitance (battery-like behavior). The high capacitance obtained was not only derived from the current-transient capacitive behavior but is also attributed to pseudocapacitance associated with some kind of faradaic reaction, which could probably occur due to Li + intercalation/deintercalation reactions into graphitic layers of the carbons used. The ac impedance (electrochemical impedances spectroscopy, EIS) measurements were also carried out to evaluate the capacitor parameters such as equivalent series resistance (ESR) and frequency dependent capacitance ( Cfreq). Cyclic voltammetry measurements were also performed to evaluate the cycling behavior of the carbon electrodes and the non-rectangular shaped voltammograms revealed the non-zero time constant [ τ( RC)≠0] confirming that the current contains a transient as well as steady-state components.

Hierarchically structured Ni(3)S(2)/carbon nanotube composites as high performance cathode materials for asymmetric supercapacitors.

PubMed

Dai, Chao-Shuan; Chien, Pei-Yi; Lin, Jeng-Yu; Chou, Shu-Wei; Wu, Wen-Kai; Li, Ping-Hsuan; Wu, Kuan-Yi; Lin, Tsung-Wu

2013-11-27

The Ni3S2 nanoparticles with the diameters ranging from 10 to 80 nm are grown on the backbone of conductive multiwalled carbon nanotubes (MWCNTs) using a glucose-assisted hydrothermal method. It is found that the Ni3S2 nanoparticles deposited on MWCNTs disassemble into smaller components after the composite electrode is activated by the consecutive cyclic voltammetry scan in a 2 M KOH solution. Therefore, the active surface area of the Ni3S2 nanoparticles is increased, which further enhances the capacitive performance of the composite electrode. Because the synergistic effect of the Ni3S2 nanoparticles and MWCNTs on the capacitive performance of the composite electrode is pronounced, the composite electrode shows a high specific capacitance of 800 F/g and great cycling stability at a current density of 3.2 A/g. To examine the capacitive performance of the composite electrode in a full-cell configuration, an asymmetric supercapacitor device was fabricated by using the composite of Ni3S2 and MWCNTs as the cathode and activated carbon as the anode. The fabricated device can be operated reversibly between 0 and 1.6 V, and obtain a high specific capacitance of 55.8 F/g at 1 A/g, which delivers a maximum energy density of 19.8 Wh/kg at a power density of 798 W/kg. Furthermore, the asymmetric supercapacitor shows great stability based on the fact that the device retains 90% of its initial capacitance after a consecutive 5000 cycles of galvanostatic charge-discharge performed at a current density of 4 A/g.

The simple preparation of birnessite-type manganese oxide with flower-like microsphere morphology and its remarkable capacity retention

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Gang; Deng, Lingjuan; Wang, Jianfang

Graphical abstract: Flower-like birnessite-type manganese oxide microspheres with large specific surface area and excellent electrochemical properties have been prepared by a facile hydrothermal method. Highlights: ► Birnessite-type manganese oxide with flower-like microsphere morphology and large specific surface area. ► A facile low-temperature hydrothermal method. ► Novel flower-like microsphere consists of the thin nano-platelets. ► Birnessite-type manganese oxide exhibits an ideal capacitive behavior and excellent cycling stability. -- Abstract: Birnessite-type manganese oxide with flower-like microsphere morphology and large specific surface area has been prepared by hydrothermal treating a mixture solution of KMnO{sub 4} and (NH{sub 4}){sub 2}SO{sub 4} at 90 °Cmore » for 24 h. The obtained material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N{sub 2} adsorption–desorption. Results indicate that the birnessite-type manganese oxide shows novel flower-like microsphere morphology and a specific surface area of 280 m{sup 2} g{sup −1}, and the flower-like microsphere consists of the thin nano-platelets. Electrochemical characterization indicates that the prepared material exhibits an ideal capacitive behavior with a capacitance value of 278 F g{sup −1} in 1 mol L{sup −1} Na{sub 2}SO{sub 4} aqueous solution at a scan rate of 5 mV s{sup −1}. Moreover, the prepared manganese oxide electrode shows excellent cycle stability, and the specific capacitance can maintain 98.6% of the initial one after 5000 cycles.« less

SWCNT Supercapacitor Electrode Fabrication Methods

DTIC Science & Technology

2011-02-01

supercapacitor electrodes out of single-wall carbon nanotubes (SWCNT). We have found that it is best to use SWCNT solutions free from additives that...effect on the resulting specific capacitance, as did the deposition methods compared here. 15. SUBJECT TERMS Carbon nanotube , electrochemical...area may increase the capacitance of supercapacitors. Two materials being studied for this are carbon nanotubes (CNTs) and graphene. Graphene is a

One-Pot Synthesis of Tunable Crystalline Ni3 S4 @Amorphous MoS2 Core/Shell Nanospheres for High-Performance Supercapacitors.

PubMed

Zhang, Yu; Sun, Wenping; Rui, Xianhong; Li, Bing; Tan, Hui Teng; Guo, Guilue; Madhavi, Srinivasan; Zong, Yun; Yan, Qingyu

2015-08-12

Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS(2) is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni(3)S(4)@MoS(2)) is prepared by a facile one-pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni(3)S(4) @amorphous MoS(2) nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g(-1) at 2 A g(-1) and a good capacitance retention of 90.7% after 3000 cycles at 10 A g(-1). This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Asymmetric supercapacitors based on electrospun carbon nanofiber/sodium-pre-intercalated manganese oxide electrodes with high power and energy densities

NASA Astrophysics Data System (ADS)

Lin, Sheng-Chi; Lu, Yi-Ting; Chien, Yu-An; Wang, Jeng-An; Chen, Po-Yu; Ma, Chen-Chi M.; Hu, Chi-Chang

2018-07-01

The sodium-pre-intercalated δ-MnO2 is in-situ grown on carbon nanofiber via a simple, one-step method for the application of asymmetric supercapacitors. The pre-intercalation of Na ions into the layered structure of δ-MnO2 reduces the crystallinity, beneficial to Na+ diffusion into/out the interlayer structure and pseudocapacitive utilization of MnO2. This NaxMnO2@CNF nanocomposite with desirable pseudo-capacitance from δ-NaxMnO2 and high electric conductivity from CNF network shows a high specific capacitance of 321 F g-1 at 1 A g-1 with ca. 75.2% capacitance retention from 1 to 32 A g-1. An ASC cell consisting of this nanocomposite and activated carbon as the positive and negative electrodes can be reversibly charged and discharged to a cell voltage of 2.0 V in 1 M Na2SO4 and 4 mM NaHCO3 with specific energy and power of 21 Wh kg-1 and 1 kW kg-1, respectively. This ASC also shows excellent cell capacitance retention (7% decay) in the 2 V, 10,000-cycle stability test, revealing superior performance.

High-Performance Flexible Asymmetric Supercapacitor Based on CoAl-LDH and rGO Electrodes

NASA Astrophysics Data System (ADS)

Li, Shuoshuo; Cheng, Pengpeng; Luo, Jiaxian; Zhou, Dan; Xu, Weiming; Li, Jingwei; Li, Ruchun; Yuan, Dingsheng

2017-07-01

A flexible asymmetric supercapacitor (ASC) based on a CoAl-layered double hydroxide (CoAl-LDH) electrode and a reduced graphene oxide (rGO) electrode was successfully fabricated. The CoAl-LDH electrode as a positive electrode was synthesized by directly growing CoAl-LDH nanosheet arrays on a carbon cloth (CC) through a facile hydrothermal method, and it delivered a specific capacitance of 616.9 F g-1 at a current density of 1 A g-1. The rGO electrode as a negative electrode was synthesized by coating rGO on the CC via a simple dip-coating method and revealed a specific capacitance of 110.0 F g-1 at a current density of 2 A g-1. Ultimately, the advanced ASC offered a broad voltage window (1.7 V) and exhibited a high superficial capacitance of 1.77 F cm-2 at 2 mA cm-2 and a high energy density of 0.71 mWh cm-2 at a power density of 17.05 mW cm-2, along with an excellent cycle stability (92.9% capacitance retention over 8000 charge-discharge cycles).

Facile synthesis of amorphous FeOOH/MnO2 composites as screen-printed electrode materials for all-printed solid-state flexible supercapacitors

NASA Astrophysics Data System (ADS)

Lu, Qiang; Liu, Li; Yang, Shuanglei; Liu, Jun; Tian, Qingyong; Yao, Weijing; Xue, Qingwen; Li, Mengxiao; Wu, Wei

2017-09-01

More convenience and intelligence life lead by flexible/wearable electronics requires innovation and hommization of power sources. Here, amorphous FeOOH/MnO2 composite as screen-printed electrode materials for supercapacitors (SCs) is synthesized by a facile method, and solid-state flexible SCs with aesthetic design are fabricated by fully screen-printed process on different substrates, including PET, paper and textile. The amorphous FeOOH/MnO2 composite shows a high specific capacitance and a good rate capability (350.2 F g-1 at a current density of 0.5 A g-1 and 159.5 F g-1 at 20 A g-1). It also possesses 95.6% capacitance retention even after 10 000 cycles. Moreover, the all-printed solid-state flexible SC device exhibits a high area specific capacitance of 5.7 mF cm-2 and 80% capacitance retention even after 2000 cycles. It also shows high mechanical flexibility. Simultaneously, these printed SCs on different substrates in series are capable to light up a 1.9 V yellow light emitting diode (LED), even after bending and stretching.

Bendable solid-state supercapacitors with Au nanoparticle-embedded graphene hydrogel films

PubMed Central

Yang, Kyungwhan; Cho, Kyoungah; Yoon, Dae Sung; Kim, Sangsig

2017-01-01

In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded GH supercapacitors (NP-GH SCs) exhibit excellent capacitive performances, with large specific capacitance (135 F/g) and high energy density (15.2 W·h/kg). Moreover, the NP-GH SCs exhibit comparable areal capacitance (168 mF/cm2) and operate under tensile/compressive bending. PMID:28074865

Capacitive behavior of highly-oxidized graphite

NASA Astrophysics Data System (ADS)

Ciszewski, Mateusz; Mianowski, Andrzej

2014-09-01

Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

Synthesis and characterization of RuO(2)/poly(3,4-ethylenedioxythiophene) composite nanotubes for supercapacitors.

PubMed

Liu, Ran; Duay, Jonathon; Lane, Timothy; Bok Lee, Sang

2010-05-07

We report the synthesis of composite RuO(2)/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO(2)/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO(2)/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO(2) and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO(2) into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO(2) from breaking and detaching from the current collector while the rigid RuO(2) keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO(2)/PEDOT nanotube can reach a high power density of 20 kW kg(-1) while maintaining 80% energy density (28 Wh kg(-1)) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO(2), which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g(-1)) which is contributed by the RuO(2) in the composite RuO(2)/PEDOT nanotube is realized because of the high specific surface area of the nanotubular structures. Such PEDOT/RuO(2) composite nanotube materials are an ideal candidate for the development of high-energy and high-power supercapacitors.

Boosting the Supercapacitance of Nitrogen-Doped Carbon by Tuning Surface Functionalities.

PubMed

Biemolt, Jasper; Denekamp, Ilse M; Slot, Thierry K; Rothenberg, Gadi; Eisenberg, David

2017-10-23

The specific capacitance of a highly porous, nitrogen-doped carbon is nearly tripled by orthogonal optimization of the microstructure and surface chemistry. First, the carbons' hierarchical pore structure and specific surface area were tweaked by controlling the temperature and sequence of the thermal treatments. The best process (pyrolysis at 900 °C, washing, and subsequent annealing at 1000 °C) yielded a carbon with a specific capacitance of 117 F g -1 -nearly double that of a carbon made by a typical single-step synthesis at 700 °C. Following the structural optimization, the surface chemistry of the carbons was enriched by applying an oxidation routine based on a mixture of nitric and sulfuric acid in a 1:4 ratio at two different treatment temperatures (0 and 20 °C) and different treatment times. The optimal treatment times were 4 h at 0 °C and only 1 h at 20 °C. Overall, the specific capacitance nearly tripled relative to the original carbon, reaching 168 F g -1 . The inherent nitrogen doping of the carbon comes into interplay with the acid-induced surface functionalization, creating a mixture of oxygen- and nitrogen-oxygen functionalities. The evolution of the surface chemistry was carefully followed by X-ray photoelectron spectroscopy and by N 2 sorption porosimetry, revealing stepwise surface functionalization and simultaneous carbon etching. Overall, these processes are responsible for the peak-shaped capacitance trends in the carbons. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly flexible binder-free core-shell nanofibrous electrode for lightweight electrochemical energy storage using recycled water bottles

NASA Astrophysics Data System (ADS)

Shi, HaoTian H.; Naguib, Hani E.

2016-08-01

The creation of a novel flexible nanocomposite fiber with conductive polymer polyaniline (PAni) coating on a polyethylene terephthalate (PET) substrate allowed for increased electrochemical performance while retaining ideal mechanical properties such as very high flexibility. Binder-free PAni-wrapped PET (PAni@PET) fiber with a core-shell structure was successfully fabricated through a novel technique. The PET nanofiber substrate was fabricated through an optimized electrospinning method, while the PAni shell was chemically polymerized onto the surface of the nanofibers. The PET substrate can be made directly from recycled PETE1 grade plastic water bottles. The resulting nanofiber with an average diameter of 121 nm ± 39 nm, with a specific surface area of 83.72 m2 g-1, led to better ionic interactions at the electrode/electrolyte interface. The PAni active layer coating was found to be 69 nm in average thickness. The specific capacitance was found to have increased dramatically from pure PAni with carbon binders. The specific capacitance was found to be 347 F g-1 at a relatively high scan rate of 10 mV s-1. The PAni/PET fiber also experienced very little degradation (4.4%) in capacitance after 1500 galvanostatic charge/discharge cycles at a specific current of 1.2 A g-1. The mesoporous structure of the PAni@PET fibrous mat also allowed for tunable capacitance by controlling the pore sizes. This novel fabrication method offers insights for the utilization of recycled PETE1 based bottles as a high performance, low cost, highly flexible supercapacitor device.

Fabrication of hierarchical porous nickel based metal-organic framework (Ni-MOF) constructed with nanosheets as novel pseudo-capacitive material for asymmetric supercapacitor.

PubMed

Du, Pengcheng; Dong, Yuman; Liu, Chang; Wei, Wenli; Liu, Dong; Liu, Peng

2018-05-15

Hierarchical porous nickel based metal-organic framework (Ni-MOF) constructed with nanosheets is fabricated by a facile hydrothermal process with the existence of trimesic acid and nickel ions. Various structures of Ni-MOFs can be obtained through adjusting the molar ratio of trimesic acid and nickel ion, the obtained hierarchical porous Ni-MOF exhibits optimal porous structure, which also possesses largest specific surface area. The hierarchical porous structure constructed with nanosheets can supply more active sites for electrochemical reactions to realize the excellent electrochemical properties, thus the hierarchical porous Ni-MOF reveals an outstanding specific capacitance of 1057 F/g at current density of 1 A/g, and delivers high specific capacitance of 649 F/g at current density of 30 A/g, indicating that it exhibits good rate capability of 63.4% even up to 30 A/g. The hierarchical porous Ni-MOF keeps 70% of its original value up to 2 500 charge-discharge cycles at the current density of 10 A/g. Furthermore, asymmetric supercapacitors (ASCs) were assembled based on hierarchical porous Ni-MOF and activated carbon (AC), the ASCs reveal specific capacitance of 87 F/g at current density of 0.5 A/g, and exhibit high energy density of 21.05 Wh/kg and power density of 6.03 kW/kg. Additionally, the tandem ASCs can light up a red LED. The hierarchical porous Ni-MOF exhibits promising applications in high performance supercapacitors. Copyright © 2018 Elsevier Inc. All rights reserved.

Why doesn't conventional IVF work in the horse? The equine oviduct as a microenvironment for capacitation/fertilization.

PubMed

Leemans, Bart; Gadella, Bart M; Stout, Tom A E; De Schauwer, Catharina; Nelis, Hilde; Hoogewijs, Maarten; Van Soom, Ann

2016-12-01

In contrast to man and many other mammalian species, conventional in vitro fertilization (IVF) with horse gametes is not reliably successful. The apparent inability of stallion spermatozoa to penetrate the zona pellucida in vitro is most likely due to incomplete activation of spermatozoa (capacitation) because of inadequate capacitating or fertilizing media. In vivo, the oviduct and its secretions provide a microenvironment that does reliably support and regulate interaction between the gametes. This review focuses on equine sperm-oviduct interaction. Equine sperm-oviduct binding appears to be more complex than the presumed species-specific calcium-dependent lectin binding phenomenon; unfortunately, the nature of the interaction is not understood. Various capacitation-related events are induced to regulate sperm release from the oviduct epithelium and most data suggest that exposure to oviduct secretions triggers sperm capacitation in vivo However, only limited information is available about equine oviduct secreted factors, and few have been identified. Another aspect of equine oviduct physiology relevant to capacitation is acid-base balance. In vitro, it has been demonstrated that stallion spermatozoa show tail-associated protein tyrosine phosphorylation after binding to oviduct epithelial cells containing alkaline secretory granules. In response to alkaline follicular fluid preparations (pH 7.9), stallion spermatozoa also show tail-associated protein tyrosine phosphorylation, hyperactivated motility and (limited) release from oviduct epithelial binding. However, these 'capacitating conditions' are not able to induce the acrosome reaction and fertilization. In conclusion, developing a defined capacitating medium to support successful equine IVF will depend on identifying as yet uncharacterized capacitation triggers present in the oviduct. © 2016 Society for Reproduction and Fertility.

Oviduct binding and elevated environmental ph induce protein tyrosine phosphorylation in stallion spermatozoa.

PubMed

Leemans, Bart; Gadella, Bart M; Sostaric, Edita; Nelis, Hilde; Stout, Tom A E; Hoogewijs, Maarten; Van Soom, Ann

2014-07-01

Sperm-oviduct binding is an essential step in the capacitation process preparing the sperm for fertilization in several mammalian species. In many species, capacitation can be induced in vitro by exposing spermatozoa to bicarbonate, Ca(2+), and albumin; however, these conditions are insufficient in the horse. We hypothesized that binding to the oviduct epithelium is an essential requirement for the induction of capacitation in stallion spermatozoa. Sperm-oviduct binding was established by coincubating equine oviduct explants for 2 h with stallion spermatozoa (2 × 10(6) spermatozoa/ml), during which it transpired that the highest density (per mm(2)) of oviduct-bound spermatozoa was achieved under noncapacitating conditions. In subsequent experiments, sperm-oviduct incubations were performed for 6 h under noncapacitating versus capacitating conditions. The oviduct-bound spermatozoa showed a time-dependent protein tyrosine phosphorylation response, which was not observed in unbound spermatozoa or spermatozoa incubated in oviduct explant conditioned medium. Both oviduct-bound and unbound sperm remained motile with intact plasma membrane and acrosome. Since protein tyrosine phosphorylation can be induced in equine spermatozoa by media with high pH, the intracellular pH (pHi) of oviduct explant cells and bound spermatozoa was monitored fluorometrically after staining with BCECF-AM dye. The epithelial secretory cells contained large, alkaline vesicles. Moreover, oviduct-bound spermatozoa showed a gradual increase in pHi, presumably due to an alkaline local microenvironment created by the secretory epithelial cells, given that unbound spermatozoa did not show pHi changes. Thus, sperm-oviduct interaction appears to facilitate equine sperm capacitation by creating an alkaline local environment that triggers intracellular protein tyrosine phosphorylation in bound sperm. © 2014 by the Society for the Study of Reproduction, Inc.

Electrodes of carbonized MWCNT-cellulose paper for supercapacitor

NASA Astrophysics Data System (ADS)

Sun, Xiaogang; Cai, Manyuan; Chen, Long; Qiu, Zhiwen; Liu, Zhenghong

2017-07-01

A flexible composite paper of multi-walled carbon nanotube (MWCNT) and cellulose fiber (CF) were fabricated by traditional paper-making method. Then, the MWCNT/CF papers were carbonized at high temperature in vacuum to remove organic component. The carbonized MWCNT/CF (MWCNT/CCF) papers are consisted of MWCNT and carbon fiber. The papers were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and four-point probe resistance meter. The electrochemical performances of the supercapacitors were tested by cyclic voltammetry and galvanostatic charge/discharge >with 1 moL/L LiPF6 as electrolyte. The MWCNT/CCF electrode yielded a specific capacitance of 156F/g at a current density of 50 mA/g by galvanostatic charge/discharge measurement, which is 1.29 times higher than MWCNT/CF electrode of 68F/g. The MWCNT/CCF electrodes also displayed an excellent specific capacitance retention of 84% after 2000 continuous charge/discharge cycles at a current density of 400 mA/g. The increase of specific capacitance can be attributed to enhanced electrical conductivity of MWCNT/CCF papers and improved contact interface between electrolyte and electrodes.

Supercapacitors based on self-assembled graphene organogel.

PubMed

Sun, Yiqing; Wu, Qiong; Shi, Gaoquan

2011-10-14

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

Effects of surface chemical properties of activated carbon modified by amino-fluorination for electric double-layer capacitor.

PubMed

Jung, Min-Jung; Jeong, Euigyung; Cho, Seho; Yeo, Sang Young; Lee, Young-Seak

2012-09-01

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1 M H(2)SO(4) electrolyte, in which it was observed that the specific capacitances increased from 215 to 389 Fg(-1) and 119 and 250 Fg(-1) with the current densities of 0.1 and 1.0 Ag(-1), respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43 mol L(-1) ammonium hydroxide and 2.06 mol L(-1) hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material. Copyright © 2012 Elsevier Inc. All rights reserved.

Supercapacitive behaviors and their temperature dependence of sol-gel synthesized nanostructured manganese dioxide in lithium hydroxide electrolyte

NASA Astrophysics Data System (ADS)

Wang, Xiuling; Yuan, Anbao; Wang, Yuqin

In the present work, a nanostructured manganese dioxide material was synthesized by a sol-gel method starting with manganese acetate (MnAc 2·4H 2O) and citric acid (C 6H 8O 7·H 2O) raw materials, and characterized by X-ray diffraction, infrared spectroscopic and transmission electron microscope techniques. The electrochemical properties and the influence of temperature on supercapacitive behaviors of the nano-MnO 2 electrode in 1 M LiOH electrolyte were investigated using electrochemical methods. Experimental results show that the MnO 2 electrode can exhibit an excellent pseudocapacitive behavior in 1 M LiOH electrolyte, and a high specific capacitance of 317 F g -1 can be obtained at a charge/discharge current rate of 100 mA g -1 and at the temperature of 25 °C. We found that temperature has a crucial influence on the discharge specific capacitance of the electrode. The specific capacitance at 25 °C is higher than that at 15 or 35 °C.

Reduced graphene oxide and vertically aligned carbon nanotubes superhydrophilic films for supercapacitors devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zanin, H., E-mail: hudsonzanin@gmail.com; Departamento de Semicondutores, Instrumentos e Fotônica, Faculdade de Engenharia Elétrica e Computação, Universidade Estadual de Campinas, UNICAMP, Campinas 13083-970; Saito, E., E-mail: esaito135@gmail.com

2014-01-01

Graphical abstract: - Highlights: • Graphene nanosheets were produced onto wire rods. • RGO and VACNT-O were evaluated and compared as supercapacitor electrode. • RGO and VACNT-O have structural and electrochemical properties quite similars. • The materials present good specific capacitance, energy storage and power delivery. - Abstract: Reduced graphene oxide (RGO) and vertically aligned carbon nanotubes (VACNT) superhydrophilic films were prepared by chemical vapor deposition techniques for electrical energy storage investigations. These electrodes were characterized in terms of their material and electrochemical properties by scanning electron microscopy (SEM), surface wettability, Fourier transform infrared spectroscopy (FTIR), energy dispersive and Ramanmore » spectroscopies, cyclic voltammetry (CV) and galvanostatic charge–discharge. We observed several physical structural and electrochemical similarities between these carbon-based materials with particular attention to very good specific capacitance, ultra-high energy storage and fast power delivery. Our results showed that the main difference between specific capacitance values is attributed to pseudocapacitive contribution and high density of multiwall nanotubes tips. In this work we have tested a supercapacitor device using the VACNT electrodes.« less

High-surface-area nitrogen-doped reduced graphene oxide for electric double-layer capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youn, Hee-Chang; Bak, Seong-Min; Kim, Myeong-Seong

A two-step method consisting of solid-state microwave irradiation and heat treatment under NH₃ gas was used to prepare nitrogen-doped reduced graphene oxide (N-RGO) with a high specific surface area (1007m²g⁻¹), high electrical conductivity (1532S m⁻¹), and low oxygen content (1.5 wt%) for electric double-layer capacitor applications. The specific capacitance of N-RGO was 291 Fg⁻¹ at a current density of 1 A g⁻¹, and a capacitance of 261 F g⁻¹ was retained at 50 A g⁻¹, indicating a very good rate capability. N-RGO also showed excellent cycling stability, preserving 96% of the initial specific capacitance after 100,000 cycles. Near-edge X-ray absorptionmore » fine-structure spectroscopy evidenced the recover of π-conjugation in the carbon networks with the removal of oxygenated groups and revealed the chemical bonding of the nitrogen atoms in N-RGO. The good electrochemical performance of N-RGO is attributed to its high surface area, high electrical conductivity, and low oxygen content.« less

High-surface-area nitrogen-doped reduced graphene oxide for electric double-layer capacitors

DOE PAGES

Youn, Hee-Chang; Bak, Seong-Min; Kim, Myeong-Seong; ...

2015-06-08

A two-step method consisting of solid-state microwave irradiation and heat treatment under NH₃ gas was used to prepare nitrogen-doped reduced graphene oxide (N-RGO) with a high specific surface area (1007m²g⁻¹), high electrical conductivity (1532S m⁻¹), and low oxygen content (1.5 wt%) for electric double-layer capacitor applications. The specific capacitance of N-RGO was 291 Fg⁻¹ at a current density of 1 A g⁻¹, and a capacitance of 261 F g⁻¹ was retained at 50 A g⁻¹, indicating a very good rate capability. N-RGO also showed excellent cycling stability, preserving 96% of the initial specific capacitance after 100,000 cycles. Near-edge X-ray absorptionmore » fine-structure spectroscopy evidenced the recover of π-conjugation in the carbon networks with the removal of oxygenated groups and revealed the chemical bonding of the nitrogen atoms in N-RGO. The good electrochemical performance of N-RGO is attributed to its high surface area, high electrical conductivity, and low oxygen content.« less

Ultrahigh-performance pseudocapacitor based on phase-controlled synthesis of MoS2 nanosheets decorated Ni3S2 hybrid structure through annealing treatment

NASA Astrophysics Data System (ADS)

Huang, Long; Hou, Huijie; Liu, Bingchuan; Zeinu, Kemal; Zhu, Xiaolei; Yuan, Xiqing; He, Xiulin; Wu, Longsheng; Hu, Jingping; Yang, Jiakuan

2017-12-01

In this work, a hierarchical Ni3S2@MoS2 hybrid structure was synthesized by an effective strategy with a combined hydrothermal route and subsequent annealing treatment. When tested as supercapacitor electrodes, the Ni3S2@MoS2 composites exhibited high specific capacitance of 1418.5 F g-1 at 0.5 A g-1, which also showed a good capacitance retention of 75.8% at 5 A g-1 after 1250 cycles. The Ni3S2@MoS2 composites demonstrated 1.9 fold higher specific capacitance compared to the amorphous shell counterpart (NixSy@MoS2). Furthermore, the assembled asymmetric supercapacitor (Ni3S2@MoS2//rGO) also demonstrated a capacitance of 61 F g-1 at 0.5 A g-1, with energy and power densities of 21.7 Wh kg-1 at 400 W kg-1 and 12 Wh kg-1 at 2400 W kg-1 under an operating window of 1.6 V. The asymmetric supercapacitor also showed a favorable cycle stability with 72% capacity retention over 4000 cycles at 10 A g-1. The improved electrochemical performance is attributed to the synergetic effect of the large accessible surface area and optimal contacts between the MoS2 and the electrolyte, as well as high capacitance of the metallic Ni3S2 core.

Gram-scale production of B, N co-doped graphene-like carbon for high performance supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Chen, Zhuo; Hou, Liqiang; Cao, Yan; Tang, Yushu; Li, Yongfeng

2018-03-01

Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.

Porous carbon nanotube/graphene composites for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Li, Jing; Tang, Jie; Yuan, Jinshi; Zhang, Kun; Yu, Xiaoliang; Sun, Yige; Zhang, Han; Qin, Lu-Chang

2018-02-01

Carbon nanotubes (CNTs) are an effective spacer to prevent the re-stacking of graphene layers. However, the aggregation of CNTs always reduces the specific surface area of resulting CNT/graphene composites. Meanwhile, different pores always have different contributions to the specific capacitance. In this study, CNT/graphene composites with different porous structures are synthesized by co-reduction of oxidized CNTs and graphene oxide with different mixing ratios. With an optimized CNT content of 20%, the CNT/graphene composite shows 206 F g-1 in 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. It is found that pores larger than twice the size of electrolyte ions can make greater contributions to the specific capacitance.

Nanoporous graphene obtained by hydrothermal process in H2O2 and its application for supercapacitors

NASA Astrophysics Data System (ADS)

Lv, Jinlong; Liang, Tongxiang

2016-08-01

Nanohole graphene oxide (NHGO) was obtained in a homogeneous aqueous mixture of graphene oxide (GO) and H2O2 at 120 °C. Supercapacitors were fabricated as the electrode material by using NHGO. A specific capacitance of 240.1 F g-1 was obtained at a current density of 1 A g-1 in 6 m KOH electrolyte and specific capacitance remained 193.6 F g-1 at the current density of 20 A g-1. This was attributed to reducing the inner space between the double-layers, enhanced ion diffusion and large specific surface area. Supercapacitor prepared with NHGO electrodes also exhibited an excellent cycle stability.

Plasma-induced highly efficient synthesis of boron doped reduced graphene oxide for supercapacitors.

PubMed

Li, Shaobo; Wang, Zhaofeng; Jiang, Hanmei; Zhang, Limei; Ren, Jingzheng; Zheng, Mingtao; Dong, Lichun; Sun, Luyi

2016-09-21

In this work, we presented a novel route to synthesize boron doped reduced graphene oxide (rGO) by using the dielectric barrier discharge (DBD) plasma technology under ambient conditions. The doping of boron (1.4 at%) led to a significant improvement in the capacitance of rGO and supercapacitors based on the as-synthesized B-rGO exhibited an outstanding specific capacitance.

A facile synthesis of reduced holey graphene oxide for supercapacitors.

PubMed

Hu, Xinjun; Bai, Dongchen; Wu, Yiqi; Chen, Songbo; Ma, Yu; Lu, Yue; Chao, Yuanzhi; Bai, Yongxiao

2017-12-12

Hydroxyl radicals (˙OH) generated from a UV/O 3 solution reaction is used to efficiently etch graphene oxide nanosheets under moderate conditions. Reduced holey graphene oxide is directly used as a supercapacitor electrode material and exhibits high specific capacitance (224 F g -1 at a current density of 1 A g -1 ) and high volumetric capacitance (up to 206 F cm -3 ).

Copper Salts Mediated Morphological Transformation of Cu2O from Cubes to Hierarchical Flower-like or Microspheres and Their Supercapacitors Performances

PubMed Central

Chen, Liang; Zhang, Yu; Zhu, Pengli; Zhou, Fengrui; Zeng, Wenjin; Lu, Daoqiang Daniel; Sun, Rong; Wong, Chingping

2015-01-01

Monodisperse Cu2O of different microstructures, such as cubes, flower-like, and microspheres, have been extensively synthesized by a simple polyol reduction method using different copper salts, i.e. (Cu(acac)2, Cu(OH)2, and Cu(Ac)2·H2O). The effects of copper salts on the morphology of Cu2O were investigated in details through various characterization methods, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV-Vis absorption spectra. The effects of morphology on the electrochemical properties were further studied. Among the different structures, Cu2O with the microspheric morphology shows the highest specific capacitance and the best cycling stability compared with those of the other two structures, thus bear larger volume charge during the electrochemical reaction due to the microspheres of small nanoparticles. PMID:25857362

CTAB-Aided Synthesis of Stacked V2O5 Nanosheets: Morphology, Electrochemical Features and Asymmetric Device Performance

NASA Astrophysics Data System (ADS)

Saravanakumar, B.; Maruthamuthu, S.; Umadevi, V.; Saravanan, V.

To accomplish superior performance in supercapacitors, a fresh class of electrode materials with advantageous structures is essential. Owing to its rich electrochemical activity, vanadium oxides are considered to be an attractive electrode material for energy storing devices. In this work, vanadium pentoxide (V2O5) nanostructures were prepared using surfactant (CTAB)-assisted hydrothermal route. Stacked V2O5 sheets enable additional channels for electrolyte ion intercalation. These stacked V2O5 nanosheets show highest specific capacitance of 466Fg-1 at 0.5Ag-1. In addition, it exhibits good rate capacity, lower value of charge transfer resistance and good stability when used as an electrode material for supercapacitors. Further, an asymmetric supercapacitor device was assembled utilizing the stacked V2O5 sheets and activated carbon as electrodes. The electrochemical features of the device are also discussed.

Superelastic supercapacitors with high performances during stretching.

PubMed

Zhang, Zhitao; Deng, Jue; Li, Xueyi; Yang, Zhibin; He, Sisi; Chen, Xuli; Guan, Guozhen; Ren, Jing; Peng, Huisheng

2015-01-14

A fiber-shaped supercapacitor that can be stretched over 400% is developed by using two aligned carbon nanotube/polyaniline composite sheets as electrodes. A high specific capacitance of approximately 79.4 F g(-1) is well maintained after stretching at a strain of 300% for 5000 cycles or 100.8 F g(-1) after bending for 5000 cycles at a current density of 1 A g(-1). In particular, the high specific capacitance is maintained by 95.8% at a stretching speed as high as 30 mm s(-1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Activated carbon derived from harmful aquatic plant for high stable supercapacitors

NASA Astrophysics Data System (ADS)

Li, Jiangfeng; Wu, Qingsheng

2018-01-01

Considering cost and environmental protection, the harmful aquatic plant altemanthera philoxeroides derived carbon material with super high specific surface area (2895 m2 g-1) is an ideal electrode material for supercapacitor. The structure and composition of these carbon materials were characterized by SEM, EDS, XPS and BET measurements. The obtained material exhibits a maximum specific capacitance of 275 F g-1 at 0.5 A g-1 and retains a capacitance of 210 F g-1 even at 50 A g-1. In addition, it also shows excellent capacity retention of 5000 cycles at 10 A g-1.

Self-assembly of monodisperse starburst carbon spheres into hierarchically organized nanostructured supercapacitor electrodes.

PubMed

Kim, Sung-Kon; Jung, Euiyeon; Goodman, Matthew D; Schweizer, Kenneth S; Tatsuda, Narihito; Yano, Kazuhisa; Braun, Paul V

2015-05-06

We report a three-dimensional (3D) porous carbon electrode containing both nanoscale and microscale porosity, which has been hierarchically organized to provide efficient ion and electron transport. The electrode organization is provided via the colloidal self-assembly of monodisperse starburst carbon spheres (MSCSs). The periodic close-packing of the MSCSs provides continuous pores inside the 3D structure that facilitate ion and electron transport (electrode electrical conductivity ∼0.35 S m(-1)), and the internal meso- and micropores of the MSCS provide a good specific capacitance. The capacitance of the 3D-ordered porous MSCS electrode is ∼58 F g(-1) at 0.58 A g(-1), 48% larger than that of disordered MSCS electrode at the same rate. At 1 A g(-1) the capacitance of the ordered electrode is 57 F g(-1) (95% of the 0.24 A g(-1) value), which is 64% greater than the capacitance of the disordered electrode at the same rate. The ordered electrode preserves 95% of its initial capacitance after 4000 charging/discharging cycles.

A porous ceramic membrane tailored high-temperature supercapacitor

NASA Astrophysics Data System (ADS)

Zhang, Xin; He, Benlin; Zhao, Yuanyuan; Tang, Qunwei

2018-03-01

The supercapacitor that can operate at high-temperature are promising for markedly increase in capacitance because of accelerated charge movement. However, the state-of-the-art polymer-based membranes will decompose at high temperature. Inspired by solid oxide fuel cells, we present here the experimental realization of high-temperature supercapacitors (HTSCs) tailored with porous ceramic separator fabricated by yttria-stabilized zirconia (YSZ) and nickel oxide (NiO). Using activated carbon electrode and supporting electrolyte from potassium hydroxide (KOH) aqueous solution, a category of symmetrical HTSCs are built in comparison with a conventional polymer membrane based device. The dependence of capacitance performance on temperature is carefully studied, yielding a maximized specific capacitance of 272 F g-1 at 90 °C for the optimized HTSC tailored by NiO/YSZ membrane. Moreover, the resultant HTSC has relatively high durability when suffer repeated measurement over 1000 cycles at 90 °C, while the polymer membrane based supercapacitor shows significant reduction in capacitance at 60 °C. The high capacitance along with durability demonstrates NiO/YSZ membrane tailored HTSCs are promising in future advanced energy storage devices.

From rice bran to high energy density supercapacitors: a new route to control porous structure of 3D carbon.

PubMed

Hou, Jianhua; Cao, Chuanbao; Ma, Xilan; Idrees, Faryal; Xu, Bin; Hao, Xin; Lin, Wei

2014-12-01

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m(2) g(-1) with optimized pore volume of 1.21 cm(3) g(-1) (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g(-1) and 100 A g(-1) i.e., 265 F g(-1) and 182 F g(-1) in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg(-1) (550 W L(-1)) and energy density 70 W h kg(-1) (32 W h L(-1)) are achieved on the base of active material loading (~10 mg cm(2)) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.

From Rice Bran to High Energy Density Supercapacitors: A New Route to Control Porous Structure of 3D Carbon

NASA Astrophysics Data System (ADS)

Hou, Jianhua; Cao, Chuanbao; Ma, Xilan; Idrees, Faryal; Xu, Bin; Hao, Xin; Lin, Wei

2014-12-01

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m2 g-1 with optimized pore volume of 1.21 cm3 g-1 (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g-1 and 100 A g-1 i.e., 265 F g-1 and 182 F g-1 in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg-1 (550 W L-1) and energy density 70 W h kg-1 (32 W h L-1) are achieved on the base of active material loading (~10 mg cm2) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.

From Rice Bran to High Energy Density Supercapacitors: A New Route to Control Porous Structure of 3D Carbon

PubMed Central

Hou, Jianhua; Cao, Chuanbao; Ma, Xilan; Idrees, Faryal; Xu, Bin; Hao, Xin; Lin, Wei

2014-01-01

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m2 g−1 with optimized pore volume of 1.21 cm3 g−1 (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g−1 and 100 A g−1 i.e., 265 F g−1 and 182 F g−1 in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg−1 (550 W L−1) and energy density 70 W h kg−1 (32 W h L−1) are achieved on the base of active material loading (~10 mg cm2) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices. PMID:25434348

The challenges of achieving good electrical and mechanical properties when making structural supercapacitors

NASA Astrophysics Data System (ADS)

Ciocanel, C.; Browder, C.; Simpson, C.; Colburn, R.

2013-04-01

The paper presents results associated with the electro-mechanical characterization of a composite material with power storage capability, identified throughout the paper as a structural supercapacitor. The structural supercapacitor uses electrodes made of carbon fiber weave, a separator made of Celgard 3501, and a solid PEG-based polymer blend electrolyte. To be a viable structural supercapacitor, the material has to have good mechanical and power storage/electrical properties. The literature in this area is inconsistent on which electrical properties are evaluated, and how those properties are assessed. In general, measurements of capacitance or specific capacitance (i.e. capacitance per unit area or per unit volume) are made, without considering other properties such as leakage resistance and equivalent series resistance of the supercapacitor. This paper highlights the significance of these additional electrical properties, discusses the fluctuation of capacitance over time, and proposes methods to improve the stability of the material's electric properties over time.

Hydrothermal synthesis of cobalt sulfide nanotubes: The size control and its application in supercapacitors

NASA Astrophysics Data System (ADS)

Wan, Houzhao; Ji, Xiao; Jiang, Jianjun; Yu, Jingwen; Miao, Ling; Zhang, Li; Bie, Shaowei; Chen, Haichao; Ruan, Yunjun

2013-12-01

Cobalt sulfide nanotubes are synthesized by hydrothermal method. The precursor is characterized by XRD, FTIR and SEM. We study the influence of temperature on the evolution of this special coarse shape nanostructure and analyze relationship between the sizes of cobalt sulfide nanotubes and the capacitive properties of active materials. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are used to study the effects of microstructure and morphology of the samples on their capacitance and conductivity. The specific capacitance of cobalt sulfide nanotubes (obtained in 80 °C) electrode exhibits a capacitance of 285 F g-1 at the current density of 0.5 A g-1 as well as rather good cycling stability. Moreover, during the cycling process, the coulombic efficiency remains 99%. The as-prepared cobalt sulfide nanotubes electrode exhibits excellent electrochemical performance as electrode materials for supercapacitors.

Synthesis of Co3O4 nanosheets via electrodeposition followed by ozone treatment and their application to high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Kung, Chung-Wei; Chen, Hsin-Wei; Lin, Chia-Yu; Vittal, R.; Ho, Kuo-Chuan

2012-09-01

A thin film of Co3O4 nanosheets is electrodeposited on a flexible Ti substrate by a one-step potentiostatic method, followed by an UV-ozone treatment for 30 min. The films before and after the UV-ozone treatment are characterized with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The film is composed of Co(OH)2 before UV-ozone treatment, and of Co3O4 after the treatment. The morphologies of both films are examined by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The obtained films are composed of nanosheets, and there is no change in their sheet-like morphology before and after the UV-ozone treatment. When applied for a supercapacitor, the Co3O4 modified Ti electrode (Co3O4/Ti) shows a far higher capacitance than that of the Co(OH)2 modified Ti electrode. The electrodeposition time and NaOH concentration in the electrolyte are optimized. A remarkably high specific capacitance of 1033.3 F g-1 is obtained for the Co3O4 thin film at a charge-discharge current density of 2.5 A g-1. The long-term stability data shows that there is still 77% of specific capacitance remaining after 3000 repeated charge-discharge cycles. The high specific capacitance and long-term stability suggest the potential use of Co3O4/Ti for making a flexible supercapacitor.

Activated Porous Carbon Spheres with Customized Mesopores through Assembly of Diblock Copolymers for Electrochemical Capacitor.

PubMed

Tang, Jing; Wang, Jie; Shrestha, Lok Kumar; Hossain, Md Shahriar A; Alothman, Zeid Abdullah; Yamauchi, Yusuke; Ariga, Katsuhiko

2017-06-07

A series of porous carbon spheres with precisely adjustable mesopores (4-16 nm), high specific surface area (SSA, ∼2000 m 2 g -1 ), and submicrometer particle size (∼300 nm) was synthesized through a facile coassembly of diblock polymer micelles with a nontoxic dopamine source and a common postactivation process. The mesopore size can be controlled by the diblock polymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO) templates, and has an almost linear dependence on the square root of the degree of polymerization of the PS blocks. These advantageous structural properties make the product a promising electrode material for electrochemical capacitors. The electrochemical capacitive performance was studied carefully by using symmetrical cells in a typical organic electrolyte of 1 M tetraethylammonium tetrafluoroborate/acetonitrile (TEA BF 4 /AN) or in an ionic liquid electrolyte of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4 ), displaying a high specific capacitance of 111 and 170 F g -1 at 1 A g -1 , respectively. The impacts of pore size distribution on the capacitance performance were thoroughly investigated. It was revealed that large mesopores and a relatively low ratio of micropores are ideal for realizing high SSA-normalized capacitance. These results provide us with a simple and reliable way to screen future porous carbon materials for electrochemical capacitors and encourage researchers to design porous carbon with high specific surface area, large mesopores, and a moderate proportion of micropores.

Rational Synthesis of Branched CoMoO4@CoNiO2 Core/Shell Nanowire Arrays for All-Solid-State Supercapacitors with Improved Performance.

PubMed

Ai, Yuanfei; Geng, Xuewen; Lou, Zheng; Wang, Zhiming M; Shen, Guozhen

2015-11-04

Effectively composite materials with optimized structures exhibited promising potential in continuing improving the electrochemical performances of supercapacitors in the past few years. Here, we proposed a rational design of branched CoMoO4@CoNiO2 core/shell nanowire arrays on Ni foam by two steps of hydrothermal processing. Owing to the high activity of the scaffold-like CoMoO4 nanowires and the well-defined CoNiO2 nanoneedles, the three-dimensional (3D) electrode architectures achieved remarkable electrochemical performances with high areal specific capacitance (5.31 F/cm(2) at 5 mA/cm(2)) and superior cycling stability(159% of the original specific capacitance, i.e., 95.7% of the maximum retained after 5000 cycles at 30 mA/cm(2)). The all-solid-state asymmetric supercapacitors composed of such electrode and activated carbon (AC) exhibited an areal specific capacitance of 1.54 F/cm(2) at 10 mA/cm(2) and a rate capability (59.75 Wh/kg at a 1464 W/kg) comparable with Li-ion batteries. It also showed an excellent cycling stability with no capacitance attenuation after 50000 cycles at 100 mA/cm(2). After rapid charging (1 s), such supercapacitors in series could lighten a red LED for a long time and drive a mini motor effectively, demonstrating advances in energy storage, scalable integrated applications, and promising commercial potential.

Carbon-ionogel supercapacitors for integrated microelectronics.

PubMed

Leung, Greg; Smith, Leland; Lau, Jonathan; Dunn, Bruce; Chui, Chi On

2016-01-22

To exceed the performance limits of dielectric capacitors in microelectronic circuit applications, we design and demonstrate on-chip coplanar electric double-layer capacitors (EDLCs), or supercapacitors, employing carbon-coated gold electrodes with ionogel electrolyte. The formation of carbon-coated microelectrodes is accomplished by solution processing and results in a ten-fold increase in EDLC capacitance compared to bare gold electrodes without carbon. At frequencies up to 10 Hz, an areal capacitance of 2.1 pF μm(-2) is achieved for coplanar carbon-ionogel EDLCs with 10 μm electrode gaps and 0.14 mm(2) electrode area. Our smallest devices, comprised of 5 μm electrode gaps and 80 μm(2) of active electrode area, reach areal capacitance values of ∼0.3 pF μm(-2) at frequencies up to 1 kHz, even without carbon. To our knowledge, these are the highest reported values to date for on-chip EDLCs with sub-mm(2) areas. A physical EDLC model is developed through the use of computer-aided simulations for design exploration and optimization of coplanar EDLCs. Through modeling and comparison with experimental data, we highlight the importance of reducing the electrode gap and electrolyte resistance to achieve maximum performance from on-chip EDLCs.

Carbon-ionogel supercapacitors for integrated microelectronics

NASA Astrophysics Data System (ADS)

Leung, Greg; Smith, Leland; Lau, Jonathan; Dunn, Bruce; Chui, Chi On

2016-01-01

To exceed the performance limits of dielectric capacitors in microelectronic circuit applications, we design and demonstrate on-chip coplanar electric double-layer capacitors (EDLCs), or supercapacitors, employing carbon-coated gold electrodes with ionogel electrolyte. The formation of carbon-coated microelectrodes is accomplished by solution processing and results in a ten-fold increase in EDLC capacitance compared to bare gold electrodes without carbon. At frequencies up to 10 Hz, an areal capacitance of 2.1 pF μm-2 is achieved for coplanar carbon-ionogel EDLCs with 10 μm electrode gaps and 0.14 mm2 electrode area. Our smallest devices, comprised of 5 μm electrode gaps and 80 μm2 of active electrode area, reach areal capacitance values of ˜0.3 pF μm-2 at frequencies up to 1 kHz, even without carbon. To our knowledge, these are the highest reported values to date for on-chip EDLCs with sub-mm2 areas. A physical EDLC model is developed through the use of computer-aided simulations for design exploration and optimization of coplanar EDLCs. Through modeling and comparison with experimental data, we highlight the importance of reducing the electrode gap and electrolyte resistance to achieve maximum performance from on-chip EDLCs.

Water relations of Calycanthus flowers: Hydraulic conductance, capacitance, and embolism resistance.

PubMed

Roddy, Adam B; Simonin, Kevin A; McCulloh, Katherine A; Brodersen, Craig R; Dawson, Todd E

2018-03-30

For most angiosperms, producing and maintaining flowers is critical to sexual reproduction, yet little is known about the physiological processes involved in maintaining flowers throughout anthesis. Among extant species, flowers of the genus Calycanthus have the highest hydraulic conductance and vein densities of species measured to date, yet they can wilt by late morning under hot conditions. Here, we combine diurnal measurements of gas exchange and water potential, pressure-volume relations, functional responses of gas exchange, and characterization of embolism formation using high resolution X-ray computed microtomography to determine drought responses of Calycanthus flowers. Transpiration from flowers frequently exceeded transpiration from leaves, and flowers were unable to limit transpiration under conditions of high vapour pressure deficit. As a result, they rely heavily on hydraulic capacitance to prevent water potential declines. Despite having high water potentials at turgor loss, flowers were very resistant to embolism formation, with no embolism apparent until tepal water potentials had declined to -2 MPa. Although Calycanthus flowers remain connected to the stem xylem and have high hydraulic capacitance, their inability to curtail transpiration leads to turgor loss. These results suggest that extreme climate events may cause flower failure, potentially preventing successful reproduction. © 2018 John Wiley & Sons Ltd.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors

PubMed Central

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-01-01

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g−1 at a current density of 2 A g−1, which is higher than the capacitance of bare G (145 F g−1) and bare Ni (3 F g−1). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g−1 at a current density of 5 A g−1 and a capacitance of 144 F g−1 at a current density of 10 A g−1. The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor. PMID:27553290

Three-dimensional reduced graphene oxide/polyaniline nanocomposite film prepared by diffusion driven layer-by-layer assembly for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Hong, Xiaodong; Zhang, Binbin; Murphy, Elizabeth; Zou, Jianli; Kim, Franklin

2017-03-01

As a simple and versatile method, diffusion driven Layer-by-Layer assembly (dd-LbL) is developed to assemble graphene oxide (GO) into three-dimensional (3D) structure. The assembled GO macrostructure can be reduced through a hydrothermal treatment and used as a high volumetric capacitance electrode in supercapacitors. In this report we use rGO framework created from dd-LbL as a scaffold for in situ polymerization of aniline within the pores of the framework to form rGO/polyaniline (rGO/PANI) composite. The rGO/PANI composite affords a robust and porous structure, which facilitates electrolyte diffusion and exhibits excellent electrochemical performance as binder-free electrodes in a sandwich-configuration supercapacitor. Combining electric double layer capacitance and pseudo-capacitance, rGO/PANI electrodes exhibit a specific capacitance of 438.8 F g-1 at discharge rate of 5 mA (mass of electrodes were 10.0 mg, 0.5 A g-1) in 1 mol L-1 H2SO4 electrolyte; furthermore, the generated PANI nanoparticles in rGO template achieve a higher capacitance of 763 F g-1. The rGO/PANI composite electrodes also show an improved recyclability, 76.5% of capacitance retains after recycled 2000 times.

Controllable Synthesis of Functional Hollow Carbon Nanostructures with Dopamine As Precursor for Supercapacitors.

PubMed

Liu, Chao; Wang, Jing; Li, Jiansheng; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

2015-08-26

N-doped hollow carbon spheres (N-HCSs) are promising candidates as electrode material for supercapacitor application. In this work, we report a facile one-step synthesis of discrete and highly dispersible N-HCSs with dopamine (DA) as a carbon precursor and TEOS as a structure-assistant agent in a mixture containing water, ethanol, and ammonia. The architectures of resultant N-HCSs, including yolk-shell hollow carbon spheres (YS-HCSs), single-shell hollow carbon spheres (SS-HCSs), and double-shells hollow carbon spheres (DS-HCSs), can be efficiently controlled through the adjustment of the amount of ammonia. To explain the relation and formation mechanism of these hollow carbon structures, the samples during the different synthetic steps, including polymer/silica spheres, carbon/silica spheres and silica spheres by combustion in air, were characterized by TEM. Electrochemical measurements performed on YS-HCSs, SS-HCSs, and DS-HCSs showed high capacitance with 215, 280, and 381 F g(-1), respectively. Moreover, all the nitrogen-doped hollow carbon nanospheres showed a good cycling stability 97.0% capacitive retention after 3000 cycles. Notably, the highest capacitance of DS-HCSs up to 381 F g(-1) is higher than the capacitance reported so far for many carbon-based materials, which may be attributed to the high surface area, hollow structure, nitrogen functionalization, and double-shell architecture. These kinds of N-doped hollow-structured carbon spheres may show promising prospects as advanced energy storage materials and catalyst supports.

Construction of high-energy-density supercapacitors from pine-cone-derived high-surface-area carbons.

PubMed

Karthikeyan, Kaliyappan; Amaresh, Samuthirapandiyan; Lee, Sol Nip; Sun, Xueliang; Aravindan, Vanchiappan; Lee, Young-Gi; Lee, Yun Sung

2014-05-01

Very high surface area activated carbons (AC) are synthesized from pine cone petals by a chemical activation process and subsequently evaluated as an electrode material for supercapacitor applications in a nonaqueous medium. The maximum specific surface area of ∼3950 m(2)  g(-1) is noted for the material treated with a 1:5 ratio of KOH to pine cone petals (PCC5), which is much higher than that reported for carbonaceous materials derived from various other biomass precursors. A symmetric supercapacitor is fabricated with PCC5 electrodes, and the results showed enhanced supercapacitive behavior with the highest energy density of ∼61 Wh kg(-1). Furthermore, outstanding cycling ability is evidenced for such a configuration, and ∼90 % of the initial specific capacitance after 20,000 cycles under harsh conditions was observed. This result revealed that the pine-cone-derived high-surface-area AC can be used effectively as a promising electrode material to construct high-energy-density supercapacitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrothermal synthesis of novel Mn3O4 nano-octahedrons with enhanced supercapacitors performances

NASA Astrophysics Data System (ADS)

Jiang, Hao; Zhao, Ting; Yan, Chaoyi; Ma, Jan; Li, Chunzhong

2010-10-01

Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors.Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors. Electronic supplementary information (ESI) available: TEM images; EDTA-2Na reaction details. See DOI: 10.1039/c0nr00257g

Nano-aggregates of cobalt nickel oxysulfide as a high-performance electrode material for supercapacitors.

PubMed

Liu, Lifeng

2013-12-07

Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g(-1) and 1628 mF cm(-2), respectively, at a current density of 0.5 A g(-1)/1.375 mA cm(-2). They also show high capacitance retention upon extended cycling at high rates.

Influence of vanadium doping on the electrochemical performance of nickel oxide in supercapacitors.

PubMed

Park, Hae Woong; Na, Byung-Ki; Cho, Byung Won; Park, Sun-Min; Roh, Kwang Chul

2013-10-28

In this study, V-doped NiO materials were prepared by simple coprecipitation and thermal decomposition, and the effect of the vanadium content on the morphology, structural properties, electrochemical behavior, and cycling stability of NiO upon oxidation and reduction was analyzed for supercapacitor applications. The results show an improvement in the capacitive characteristics of the V-doped NiO, including increases in the specific capacitance after the addition of just 1.0, 2.0, and 4.0 at% V. All VxNi1-xO electrodes (x = 0.01, 0.02, 0.04) exhibited higher specific capacitances of 371.2, 365.7, and 386.2 F g(-1) than that of pure NiO (303.2 F g(-1)) at a current density of 2 A g(-1) after 500 cycles, respectively. The V0.01Ni0.99O electrode showed good capacitance retention of 73.5% at a current density of 2 A g(-1) for more than 500 cycles in a cycling test. Importantly, the rate capability of the V0.01Ni0.99O electrode was maintained at about 84.7% as discharge current density was increased from 0.5 A g(-1) to 4 A g(-1).

Comparison of carbon onions and carbon blacks as conductive additives for carbon supercapacitors in organic electrolytes

NASA Astrophysics Data System (ADS)

Jäckel, N.; Weingarth, D.; Zeiger, M.; Aslan, M.; Grobelsek, I.; Presser, V.

2014-12-01

This study investigates carbon onions (∼400 m2 g-1) as a conductive additive for supercapacitor electrodes of activated carbon and compares their performance with carbon black with high or low internal surface area. We provide a study of the electrical conductivity and electrochemical behavior between 2.5 and 20 mass% addition of each of these three additives to activated carbon. Structural characterization shows that the density of the resulting film electrodes depends on the degree of agglomeration and the amount of additive. Addition of low surface area carbon black (∼80 m2 g-1) enhances the power handling of carbon electrodes but significantly lowers the specific capacitance even when adding small amounts of carbon black. A much lower decrease in specific capacitance is observed for carbon onions and the best values are seen for carbon black with a high surface area (∼1390 m2 g-1). The overall performance benefits from the addition of any of the studied additives only at either high scan rates and/or electrolytes with high ion mobility. Normalization to the volume shows a severe decrease in volumetric capacitance and only at high current densities nearing 10 A g-1 we can see an improvement of the electrode capacitance.

Converting Ni-loaded biochars into supercapacitors: Implication on the reuse of exhausted carbonaceous sorbents

NASA Astrophysics Data System (ADS)

Wang, Yifan; Zhang, Yue; Pei, Lei; Ying, Diwen; Xu, Xiaoyun; Zhao, Ling; Jia, Jinping; Cao, Xinde

2017-01-01

Biochar derived from waste biomass has proven as a promising sorbent for removal of heavy metals from wastewater. However, proper disposal of such a heavy metal-containing biochar is challengeable. The major objective of this study is to create a reuse way by converting the heavy metal-loaded biochar into supercapacitor. Two biochars were produced from dairy manure and sewage sludge, respectively, and subjected to sorption of Ni from solution, and then the Ni-loaded biochar underwent microwave treatments for fabrication of supercapacitor. The specific capacitance of biochar supercapacitor increased with Ni loading, especially the Ni-loaded biochar further treated with microwave in which the capacitance increased by over 2 times, compared to the original biochar supercapacitors. The increase of capacitance in the Ni-loaded biochar supercapacitor following microwave treatment was mainly attributed to the conversion of Ni into NiO and NiOOH, which was evidenced by X-ray diffraction and X-ray photoelectron spectroscopy. The biochar supercapacitors, especially microwave-treated Ni-loaded biochar supercapacitors exhibited the high stability of specific capacitance, with less than 2% loss after 1000 charge-discharge cycles. This study demonstrated that Ni-loaded biochar can be further utilized for generation of supercapacitor, providing a potential way for the reuse of exhausted carbonaceous sorbents.

Capacitive charge storage at an electrified interface investigated via direct first-principles simulations

NASA Astrophysics Data System (ADS)

Radin, Maxwell D.; Ogitsu, Tadashi; Biener, Juergen; Otani, Minoru; Wood, Brandon C.

2015-03-01

Understanding the impact of interfacial electric fields on electronic structure is crucial to improving the performance of materials in applications based on charged interfaces. Supercapacitors store energy directly in the strong interfacial field between a solid electrode and a liquid electrolyte; however, the complex interplay between the two is often poorly understood, particularly for emerging low-dimensional electrode materials that possess unconventional electronic structure. Typical descriptions tend to neglect the specific electrode-electrolyte interaction, approximating the intrinsic "quantum capacitance" of the electrode in terms of a fixed electronic density of states. Instead, we introduce a more accurate first-principles approach for directly simulating charge storage in model capacitors using the effective screening medium method, which implicitly accounts for the presence of the interfacial electric field. Applying this approach to graphene supercapacitor electrodes, we find that results differ significantly from the predictions of fixed-band models, leading to improved consistency with experimentally reported capacitive behavior. The differences are traced to two key factors: the inhomogeneous distribution of stored charge due to poor electronic screening and interfacial contributions from the specific interaction with the electrolyte. Our results are used to revise the conventional definition of quantum capacitance and to provide general strategies for improving electrochemical charge storage, particularly in graphene and similar low-dimensional materials.

Converting Ni-loaded biochars into supercapacitors: Implication on the reuse of exhausted carbonaceous sorbents

PubMed Central

Wang, Yifan; Zhang, Yue; Pei, Lei; Ying, Diwen; Xu, Xiaoyun; Zhao, Ling; Jia, Jinping; Cao, Xinde

2017-01-01

Biochar derived from waste biomass has proven as a promising sorbent for removal of heavy metals from wastewater. However, proper disposal of such a heavy metal-containing biochar is challengeable. The major objective of this study is to create a reuse way by converting the heavy metal-loaded biochar into supercapacitor. Two biochars were produced from dairy manure and sewage sludge, respectively, and subjected to sorption of Ni from solution, and then the Ni-loaded biochar underwent microwave treatments for fabrication of supercapacitor. The specific capacitance of biochar supercapacitor increased with Ni loading, especially the Ni-loaded biochar further treated with microwave in which the capacitance increased by over 2 times, compared to the original biochar supercapacitors. The increase of capacitance in the Ni-loaded biochar supercapacitor following microwave treatment was mainly attributed to the conversion of Ni into NiO and NiOOH, which was evidenced by X-ray diffraction and X-ray photoelectron spectroscopy. The biochar supercapacitors, especially microwave-treated Ni-loaded biochar supercapacitors exhibited the high stability of specific capacitance, with less than 2% loss after 1000 charge-discharge cycles. This study demonstrated that Ni-loaded biochar can be further utilized for generation of supercapacitor, providing a potential way for the reuse of exhausted carbonaceous sorbents. PMID:28128297

Novel MnOOH–graphene nanocomposites: Preparation, characterization and electrochemical properties for supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Jun; Zhang, Long, E-mail: zhanglongzhl@163.com

2015-01-15

In this paper, we report a simple and controlled synthesis of novel MnOOH–graphene nanocomposites with a one-step facile hydrothermal method. It is template-free and easy to reproduce. Electrochemical properties are investigated in different media. The values of specific capacitance achieved are 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. The assembly of multiple branched MnOOH and graphene flakes results in synergistic effects, forming new electron transfer channels to accelerate electron transfer and provide the pseudocapacitance to increase the overall capacitance. The novel composites have potential applications inmore » the fields of supercapacitors, lithium battery and so on. - Graphical abstract: The MnOOH–graphene nanocomposites shows better specific capacitance with the values achieved 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. - Highlights: • Novel MnOOH–graphene nanocomposites were prepared by a one-step hydrothermal method. • The assembly can form new electron transfer channels to accelerate electron transfer. • The capacitive and rate performances are enhanced in both neutral and alkaline medium.« less

Ultra-facile fabrication of phosphorus doped egg-like hierarchic porous carbon with superior supercapacitance performance by microwave irradiation combining with self-activation strategy

NASA Astrophysics Data System (ADS)

Zhang, Deyi; Han, Mei; Li, Yubing; He, Jingjing; Wang, Bing; Wang, Kunjie; Feng, Huixia

2017-12-01

Herein, we report an ultra-facile fabrication method for a phosphorus doped egg-like hierarchic porous carbon by microwave irradiation combining with self-activation strategy under air atmosphere. Comparing with the traditional pyrolytic carbonization method, the reported method exhibits incomparable merits, such as high energy efficiency, ultra-fast and inert atmosphere protection absent fabrication process. Similar morphology and graphitization degree with the sample fabricated by the traditional pyrolytic carbonization method under inert atmosphere protection for 2 h can be easily achieved by the reported microwave irradiation method just for 3 min under ambient atmosphere. The samples fabricated by the reported method display a unique phosphorus doped egg-like hierarchic porous structure, high specific surface area (1642 m2 g-1) and large pore volume (2.04 cm3 g-1). Specific capacitance of the samples fabricated by the reported method reaches up to 209 F g-1, and over 96.2% of initial capacitance remains as current density increasing from 0.5 to 20 A g-1, indicating the superior capacitance performance of the fabricated samples. The hierarchic porous structure, opened microporosity, additional pseudocapacitance, high electrolyte-accessible surface area and good conductivity make essential contribution to its superior capacitance performance.

Skeleton/skin structured (RGO/CNTs)@PANI composite fiber electrodes with excellent mechanical and electrochemical performance for all-solid-state symmetric supercapacitors.

PubMed

Liu, Dong; Du, Pengcheng; Wei, Wenli; Wang, Hongxing; Wang, Qi; Liu, Peng

2018-03-01

Polyaniline coated reduced graphene oxide/carbon nanotube composite fibers ((RGO/CNTs)@PANI, RCP) with skeleton/skin structure are designed as fiber-shaped electrodes for high performance all-solid-state symmetric supercapacitor. The one-dimensional reduced graphene oxide/carbon nanotube composite fibers (RGO/CNTs, RC) are prepared via a simple in-situ reduction of graphene oxide in presence of carbon nanotubes in quartz glass pipes, which exhibit excellent mechanical performance of >193.4 MPa of tensile strength. Then polyaniline is coated onto the RC fibers by electrodepositing technique. The electrochemical properties of the RCP fiber-shaped electrodes are optimized by adjusting the feeding ratio of carbon nanotubes. The optimized one exhibits good electrochemical characteristic such as highest volumetric specific capacitance of 193.1 F cm -3 at 1 A cm -3 , as well as excellent cyclic retention of 92.60% after 2000 cyclic voltammetry cycles. Furthermore, the all-solid-state symmetric supercapacitor, fabricated by using the final composite fiber as both positive and negative electrodes pre-coated with the poly(vinyl alcohol)/H 2 SO 4 gel polyelectrolyte, possesses volumetric capacitance of 36.7 F cm -3 at 0.2 A cm -3 and could light up a red light-emitting diode easily. The excellent mechanical and electrochemical performances make the designed supercapacitor as promising high performance wearable energy storage device. Copyright © 2017 Elsevier Inc. All rights reserved.

Nitrogen-doped amorphous carbon-silicon core-shell structures for high-power supercapacitor electrodes.

PubMed

Tali, S A Safiabadi; Soleimani-Amiri, S; Sanaee, Z; Mohajerzadeh, S

2017-02-10

We report successful deposition of nitrogen-doped amorphous carbon films to realize high-power core-shell supercapacitor electrodes. A catalyst-free method is proposed to deposit large-area stable, highly conformal and highly conductive nitrogen-doped amorphous carbon (a-C:N) films by means of a direct-current plasma enhanced chemical vapor deposition technique (DC-PECVD). This approach exploits C 2 H 2 and N 2 gases as the sources of carbon and nitrogen constituents and can be applied to various micro and nanostructures. Although as-deposited a-C:N films have a porous surface, their porosity can be significantly improved through a modification process consisting of Ni-assisted annealing and etching steps. The electrochemical analyses demonstrated the superior performance of the modified a-C:N as a supercapacitor active material, where specific capacitance densities as high as 42 F/g and 8.5 mF/cm 2 (45 F/cm 3 ) on silicon microrod arrays were achieved. Furthermore, this supercapacitor electrode showed less than 6% degradation of capacitance over 5000 cycles of a galvanostatic charge-discharge test. It also exhibited a relatively high energy density of 2.3 × 10 3  Wh/m 3 (8.3 × 10 6  J/m 3 ) and ultra-high power density of 2.6 × 10 8  W/m 3 which is among the highest reported values.

Flexible carbon micro-supercapacitors prepared by direct cw-laser writing

NASA Astrophysics Data System (ADS)

Cai, Jinguang; Watanabe, Akira

2016-03-01

Micro-/nano-scale power supply units with high energy and high power densities are critical components for the development of compact miniaturized portable electronic devices. Supercapacitors have attracted many research attentions due to their high power density, robust cycle performance, pollution-free operation, and maintenance-free features. Besides, the properties of small size, light weight, and flexibility are also required. On-chip microsupercapacitors (MSCs) have the potential acting as power supply units in portable devices, due to their simplified packaging processes and compatibility to the integrated circuits. However, the fabrication methods and materials should be cost-effective, scalable, and compatible to current electronic industry. Carbon materials own high specific surface areas, electrochemical stability, and high electrical conductivity, which are critical parameters for high-power supercapacitors. Moreover, the high mechanical tolerance makes them good candidates for flexible wearable devices. Therefore, MSCs based on carbon materials would satisfy the requirements of portable electronics. In this work, we demonstrated the fabrication of carbon MSCs by laser direct writing on commercial polyimide sheets in Ar with lowcost semiconductor cw-laser with a wavelength of 405nm. The obtained structures are macro-nanostructures comprising graphitized and amorphous carbon with relatively smooth surfaces and low resistance, in compared with the structures obtained by laser writing in air. As-prepared micro-supercapacitors show a high capacitance of about 14.9 mF/cm2 at a scanning rate of 10 mV/s, which is comparable to the reported highest capacitance of carbon-based supercapacitors fabricated by pulse-laser writing.

Development of Electrochemical Supercapacitors for EMA Applications

NASA Technical Reports Server (NTRS)

Kosek, John A.; Dunning, Thomas; LaConti, Anthony B.

1996-01-01

A limitation of the typical electrochemical capacitor is the maximum available power and energy density, and an improvement in capacitance per unit weight and volume is needed. A solid-ionomer electrochemical capacitor having a unit cell capacitance greater than 2 F/sq cm and a repeating element thickness of 6 mils has been developed. This capacitor could provide high-current pulses for electromechanical actuation (EMA). Primary project objectives were to develop high-capacitance particulates, to increase capacitor gravimetric and volumetric energy densities above baseline and to fabricate a 10-V capacitor with a repeating element thickness of 6 mils or less. Specific EMA applications were identified and capacitor weight and volume projections made.

Three-Dimensional Tubular MoS2/PANI Hybrid Electrode for High Rate Performance Supercapacitor.

PubMed

Ren, Lijun; Zhang, Gaini; Yan, Zhe; Kang, Liping; Xu, Hua; Shi, Feng; Lei, Zhibin; Liu, Zong-Huai

2015-12-30

By using three-dimensional (3D) tubular molybdenum disulfide (MoS2) as both an active material in electrochemical reaction and a framework to provide more paths for insertion and extraction of ions, PANI nanowire arrays with a diameter of 10-20 nm can be controllably grown on both the external and internal surface of 3D tubular MoS2 by in situ oxidative polymerization of aniline monomers and 3D tubular MoS2/PANI hybrid materials with different amounts of PANI are prepared. A controllable growth of PANI nanowire arrays on the tubular MoS2 surface provides an opportunity to optimize the capacitive performance of the obtained electrodes. When the loading amount of PANI is 60%, the obtained MoS2/PANI-60 hybrid electrode not only shows a high specific capacitance of 552 F/g at a current density of 0.5 A/g, but also gives excellent rate capability of 82% from 0.5 to 30 A/g. The remarkable rate performance can be mainly attributed to the architecture with synergistic effect between 3D tubular MoS2 and PANI nanowire arrays. Moreover, the MoS2/PANI-60 based symmetric supercapacitor also exhibits the excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 124 F/g at a current density of 1 A/g and 79% of its initial capacitance is remained after 6000 cycles. The 3D tubular structure provides a good and favorable method for improving the capacitance retention of PANI electrode.

Robust electrodes based on coaxial TiC/C-MnO2 core/shell nanofiber arrays with excellent cycling stability for high-performance supercapacitors.

PubMed

Zhang, Xuming; Peng, Xiang; Li, Wan; Li, Limin; Gao, Biao; Wu, Guosong; Huo, Kaifu; Chu, Paul K

2015-04-17

A coaxial electrode structure composed of manganese oxide-decorated TiC/C core/shell nanofiber arrays is produced hydrothermally in a KMnO4 solution. The pristine TiC/C core/shell structure prepared on the Ti alloy substrate provides the self-sacrificing carbon shell and highly conductive TiC core, thus greatly simplifying the fabrication process without requiring an additional reduction source and conductive additive. The as-prepared electrode exhibits a high specific capacitance of 645 F g(-1) at a discharging current density of 1 A g(-1) attributable to the highly conductive TiC/C and amorphous MnO2 shell with fast ion diffusion. In the charging/discharging cycling test, the as-prepared electrode shows high stability and 99% capacity retention after 5000 cycles. Although the thermal treatment conducted on the as-prepared electrode decreases the initial capacitance, the electrode undergoes capacitance recovery through structural transformation from the crystalline cluster to layered birnessite type MnO2 nanosheets as a result of dissolution and further electrodeposition in the cycling. 96.5% of the initial capacitance is retained after 1000 cycles at high charging/discharging current density of 25 A g(-1). This study demonstrates a novel scaffold to construct MnO2 based SCs with high specific capacitance as well as excellent mechanical and cycling stability boding well for future design of high-performance MnO2-based SCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-Potential Metalless Nanocarbon Foam Supercapacitors Operating in Aqueous Electrolyte.

PubMed

Liu, Chueh; Li, Changling; Ahmed, Kazi; Mutlu, Zafer; Lee, Ilkeun; Zaera, Francisco; Ozkan, Cengiz S; Ozkan, Mihrimah

2018-04-01

Light-weight graphite foam decorated with carbon nanotubes (dia. 20-50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g -1 , 22.85 and 12.58 Wh kg -1 , 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4-0.45 g cm -3 ) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nitrogen-doped ordered mesoporous carbon with a high surface area, synthesized through organic-inorganic coassembly, and its application in supercapacitors.

PubMed

Song, Yanfang; Li, Li; Wang, Yonggang; Wang, Congxiao; Guo, Zaipin; Xia, Yongyao

2014-07-21

A new nitrogen-doped ordered mesoporous carbon (N-doped OMC) is synthesized by using an organic-inorganic coassembly method, in which resol is used as the carbon precursor, dicyandiamide as the nitrogen precursor, silicate oligomers as the inorganic precursors, and F127 as the soft template. The N-doped OMC possesses a surface area as high as 1374 m(2)  g(-1) and a large pore size of 7.4 nm. As an electrode material for supercapacitors, the obtained carbon exhibits excellent cycling stability and delivers a reversible specific capacitance as high as 308 F g(-1) in 1 mol L(-1) H(2)SO(4) aqueous electrolyte, of which 58 % of the capacity is due to pseudo-capacitance. The large specific capacitance is attributed to proper pore size distributions, large surface area, and high nitrogen content. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid NiS/CoO mesoporous nanosheet arrays on Ni foam for high-rate supercapacitors

NASA Astrophysics Data System (ADS)

Wu, Jianghong; Ouyang, Canbin; Dou, Shuo; Wang, Shuangyin

2015-08-01

A new hybrid of NiS/CoO porous nanosheets was synthesized on Ni foam by one-step electrodeposition method and used as an electrode for high-performance pseudocapacitance. The as-synthesized NiS/CoO porous nanosheets hybrid shows a high specific capacitance of 1054 F g-1 at a high current density of 6 A g-1, a good rate capability even at high current density (760 F g-1 at 20 A g-1) and a good long-term cycling stability (91.7% of the maximum specific capacitance after 3000 cycles). These excellent properties can be mainly attributed to the unique hierarchical porous structure with large surface area and interspaces which facilitate charge transfer and redox reaction. The enhancement in the interface contact between active material and substrate results in excellent conductivity of the electrode and a strong synergistic effect of NiS and CoO as individual constituents contributed to high capacitance of the hybrid electrode.

Hybrid NiS/CoO mesoporous nanosheet arrays on Ni foam for high-rate supercapacitors.

PubMed

Wu, Jianghong; Ouyang, Canbin; Dou, Shuo; Wang, Shuangyin

2015-08-14

A new hybrid of NiS/CoO porous nanosheets was synthesized on Ni foam by one-step electrodeposition method and used as an electrode for high-performance pseudocapacitance. The as-synthesized NiS/CoO porous nanosheets hybrid shows a high specific capacitance of 1054 F g(-1) at a high current density of 6 A g(-1), a good rate capability even at high current density (760 F g(-1) at 20 A g(-1)) and a good long-term cycling stability (91.7% of the maximum specific capacitance after 3000 cycles). These excellent properties can be mainly attributed to the unique hierarchical porous structure with large surface area and interspaces which facilitate charge transfer and redox reaction. The enhancement in the interface contact between active material and substrate results in excellent conductivity of the electrode and a strong synergistic effect of NiS and CoO as individual constituents contributed to high capacitance of the hybrid electrode.

Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors

PubMed Central

2014-01-01

Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g-1 at current densities of 5, 10, 15, 20, and 25 A g-1, respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands. PMID:25276099

A Flexible Cotton-Based Supercapacitor Electrode with High Stability Prepared by Multiwalled CNTs/PANI

NASA Astrophysics Data System (ADS)

Hao, Tianqi; Wang, Wei; Yu, Dan

2018-05-01

Multiwalled nanotubes/cotton composite was prepared firstly as conductive fabric, and then, polyaniline (PANI) doped with multi-walled carbon nanotubes (MWCNTs) were fabricated on the conductive fabric to make flexible cotton-based supercapacitor electrodes. The doping of MWCNTs cannot only provide good conductivity and large specific surface area of the electrode, but also help to increase the loading of aniline monomer in the polyaniline polymerization. Field emission scanning electron microscopy was applied to observe the surface morphology of the composite, and Fourier transform infrared and Energy dispersion spectrum were used to analysis the existence of PANI. Electrochemical tests were adopted to measure the electrochemical performance. The results demonstrated the multivariate mixture composite flexible electrode exhibited a specific capacitance of 590.93 F g-1 at a scan rate of 0.001 V s-1 and an excellent capacitance retention of 89% at 0.1 V s-1 after 3000 cycles. Based on our method, the cycle stability of the composite was great and so was the capacitance retention.

A porous carbon material from pyrolysis of fructus cannabis’s shells for supercapacitor electrode application

NASA Astrophysics Data System (ADS)

Li, Kai; Zhang, Wei-Bin; Zhao, Zhi-Yun; Zhao, Yue; Chen, Xi-Wen; Kong, Ling-Bin

2018-02-01

The porous carbon material is obtained via pyrolysis and activation of fructus cannabis’s shells, an easy-to-get biomass source, and is used as an active electrode material for supercapacitors. The obtained carbon exhibit a high specific surface area of 2389 m2 g-1. And the result of x-ray photoelectron spectroscopy (XPS) shows that the obtained porous carbon possess numerous oxygen groups, which can facilitate the wettability of the electrode. The prepared porous carbon also exhibit remarkable electrochemical properties, such as high specific capacitance of 357 F g-1 at a current density of 0.5 A g-1 in 6 mol L-1 aqueous KOH electrolyte, good rate capability of 77% capacitance retention as the current density increase from 0.5 A g-1 to 10 A g-1. In addition, it also presents a superior cycling stability of 100% capacitance retention after 10 000 cycles at the current density of 1 A g-1.

Ternary manganese ferrite/graphene/polyaniline nanostructure with enhanced electrochemical capacitance performance

NASA Astrophysics Data System (ADS)

Xiong, Pan; Hu, Chenyao; Fan, Ye; Zhang, Wenyao; Zhu, Junwu; Wang, Xin

2014-11-01

A ternary manganese ferrite/graphene/polyaniline (MGP) nanostructure is designed and synthesized via a facile two-step approach. This nanostructure exhibits outstanding electrochemical performances, such as high specific capacitance (454.8 F g-1 at 0.2 A g-1), excellent rate capability (75.8% capacity retention at 5 A g-1), and good cycling stability (76.4% capacity retention after 5000 cycles at 2 A g-1), which are superior to those of its individual components (manganese ferrite, reduced-graphene oxide, polyaniline) and corresponding binary hybrids (manganese ferrite/graphene (MG), manganese ferrite/polyaniline (MP), and graphene/polyaniline (GP)). A symmetric supercapacitor device using the as-obtained hybrid has been fabricated and tested. The device exhibits a high specific capacitance of 307.2 F g-1 at 0.1 A g-1 with a maximum energy density of 13.5 W h kg-1. The high electrochemical performance of ternary MGP can be attributed to its well-designed nanostructure and the synergistic effect of the individual components.

Synthesis of carbon core–shell pore structures and their performance as supercapacitors

DOE PAGES

Ariyanto, Teguh; Dyatkin, Boris; Zhang, Gui-Rong; ...

2015-07-15

High-power supercapacitors require excellent electrolyte mobility within the pore network and high electrical conductivity for maximum capacitance and efficiency. Achieving high power typically requires sacrificing energy densities, as the latter demands a high specific surface area and narrow porosity that impedes ion transport. Here, we present a novel solution for this optimization problem: a nanostructured core–shell carbonaceous material that exhibits a microporous carbon core surrounded by a mesoporous, graphitic shell. The tunable synthesis parameters yielded a structure that features either a sharp or a gradual transition between the core and shell sections. Electrochemical supercapacitor testing using organic electrolyte revealed thatmore » these novel core–shell materials outperform carbons with homogeneous pore structures. The hybrid core–shell materials showed a combination of good capacitance retention, typical for the carbon present in the shell and high specific capacitance, typical for the core material. These materials achieved power densities in excess of 40 kW kg -1 at energy densities reaching 27 Wh kg -1.« less

A Flexible Cotton-Based Supercapacitor Electrode with High Stability Prepared by Multiwalled CNTs/PANI

NASA Astrophysics Data System (ADS)

Hao, Tianqi; Wang, Wei; Yu, Dan

2018-07-01

Multiwalled nanotubes/cotton composite was prepared firstly as conductive fabric, and then, polyaniline (PANI) doped with multi-walled carbon nanotubes (MWCNTs) were fabricated on the conductive fabric to make flexible cotton-based supercapacitor electrodes. The doping of MWCNTs cannot only provide good conductivity and large specific surface area of the electrode, but also help to increase the loading of aniline monomer in the polyaniline polymerization. Field emission scanning electron microscopy was applied to observe the surface morphology of the composite, and Fourier transform infrared and Energy dispersion spectrum were used to analysis the existence of PANI. Electrochemical tests were adopted to measure the electrochemical performance. The results demonstrated the multivariate mixture composite flexible electrode exhibited a specific capacitance of 590.93 F g-1 at a scan rate of 0.001 V s-1 and an excellent capacitance retention of 89% at 0.1 V s-1 after 3000 cycles. Based on our method, the cycle stability of the composite was great and so was the capacitance retention.

Semi-Interpenetrating Polymer Networks for Enhanced Supercapacitor Electrodes.

PubMed

Fong, Kara D; Wang, Tiesheng; Kim, Hyun-Kyung; Kumar, R Vasant; Smoukov, Stoyan K

2017-09-08

Conducting polymers show great promise as supercapacitor materials due to their high theoretical specific capacitance, low cost, toughness, and flexibility. Poor ion mobility, however, can render active material more than a few tens of nanometers from the surface inaccessible for charge storage, limiting performance. Here, we use semi-interpenetrating networks (sIPNs) of a pseudocapacitive polymer in an ionically conductive polymer matrix to decrease ion diffusion length scales and make virtually all of the active material accessible for charge storage. Our freestanding poly(3,4-ethylenedioxythiophene)/poly(ethylene oxide) (PEDOT/PEO) sIPN films yield simultaneous improvements in three crucial elements of supercapacitor performance: specific capacitance (182 F/g, a 70% increase over that of neat PEDOT), cycling stability (97.5% capacitance retention after 3000 cycles), and flexibility (the electrodes bend to a <200 μm radius of curvature without breaking). Our simple and controllable sIPN fabrication process presents a framework to develop a range of polymer-based interpenetrated materials for high-performance energy storage technologies.

Layered conductive polymer on nylon membrane templates for high performance, thin-film supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Shi, HaoTian Harvey; Naguib, Hani E.

2016-04-01

Flexible Thin-film Electrochemical Capacitors (ECs) are emerging technology that plays an important role as energy supply for various electronics system for both present era and the future. Intrinsically conductive polymers (ICPs) are promising pseudo-capacitive materials as they feature both good electrical conductivity and high specific capacitance. This study focuses on the construction and characterization of ultra-high surface area porous electrodes based on coating of nano-sized conductive polymer materials on nylon membrane templates. Herein, a novel nano-engineered electrode material based on nylon membranes was presented, which allows the creation of super-capacitor devices that is capable of delivering competitive performance, while maintaining desirable mechanical characteristics. With the formation of a highly conductive network with the polyaniline nano-layer, the electrical conductivity was also increased dramatically to facilitate the charge transfer process. Cyclic voltammetry and specific capacitance results showed promising application of this type of composite materials for future smart textile applications.

Synthesis and Characterization of Self-Standing and Highly Flexible δ-MnO2@CNTs/CNTs Composite Films for Direct Use of Supercapacitor Electrodes.

PubMed

Wu, Peng; Cheng, Shuang; Yang, Lufeng; Lin, Zhiqiang; Gui, Xuchun; Ou, Xing; Zhou, Jun; Yao, Minghai; Wang, Mengkun; Zhu, Yuanyuan; Liu, Meilin

2016-09-14

Self-standing and flexible films worked as pseudocapacitor electrodes have been fabricated via a simple vacuum-filtration procedure to stack δ-MnO2@carbon nanotubes (CNTs) composite layer and pure CNT layer one by one with CNT layers ended. The lightweight CNTs layers served as both current collector and supporter, while the MnO2@CNTs composite layers with birnessite-type MnO2 worked as active layer and made the main contribution to the capacitance. At a low discharge current of 0.2 A g(-1), the layered films displayed a high areal capacitance of 0.293 F cm(-2) with a mass of 1.97 mg cm(-2) (specific capacitance of 149 F g(-1)) and thickness of only 16.5 μm, and hence an volumetric capacitance of about 177.5 F cm(-3). Moreover, the films also exhibited a good rate capability (only about 15% fading for the capacitance when the discharge current increased to 5 A g(-1) from 0.2 A g(-1)), outstanding cycling stability (about 90% of the initial capacitance was remained after 5,000 cycles) and high flexibility (almost no performance change when bended to different angles). In addition, the capacitance of the films increased proportionally with the stacked layers and the geometry area. E.g., when the stacked layers were three times many with a mass of 6.18 mg cm(-2), the areal capacitance of the films was increased to 0.764 F cm(-2) at 0.5 A g(-1), indicating a high electronic conductivity. It is not overstated to say that the flexible and lightweight layered films emerged high potential for future practical applications as supercapacitor electrodes.

Nitrogen-doped hierarchical porous carbon microsphere through KOH activation for supercapacitors.

PubMed

Jiang, Jingui; Chen, Hao; Wang, Zhao; Bao, Luke; Qiang, Yiwei; Guan, Shiyou; Chen, Jianding

2015-08-15

A porous carbon microsphere with moderate specific surface area and superior specific capacitance for supercapacitors is fabricated from polyphosphazene microsphere as the single heteroatoms source by the carbonization and subsequent KOH activation under N2 atmosphere. With KOH activation, X-ray photoelectron spectroscopy analysis confirms that the phosphorus of polyphosphazene microsphere totally vanishes, and the doping content of nitrogen and its population of various functionalities on porous carbon microsphere surface are tuned. Compared with non-porous carbon microsphere, the texture property of the resultant porous carbon microsphere subjected to KOH activation has been remarkably developed with the specific surface area growing from 315 to 1341 m(2) g(-1)and the pore volume turning from 0.17 to 0.69 cm(3) g(-1). Prepared with the KOH/non-porous carbon microsphere weight ratio at 1.0, the porous carbon microsphere with moderate specific surface area of 568 m(2) g(-1), exhibits intriguing electrochemical behavior in 1 M H2SO4 aqueous electrolyte, with superior specific capacitance (278 F g(-1) at 0.1 A g(-1)), good rate capability (147 F g(-1) remained at 10 A g(-1)) and robust cycling durability (No capacitance loss after 5000 cycles). The promising electrochemical performance could be ascribed to the synergy of nitrogen heteroatom functionalities and the porous morphology. Copyright © 2015 Elsevier Inc. All rights reserved.

Ag incorporated Mn3O4/AC nanocomposite based supercapacitor devices with high energy density and power density.

PubMed

Nagamuthu, S; Vijayakumar, S; Muralidharan, G

2014-12-14

Silver incorporated Mn3O4/amorphous carbon (AC) nanocomposites are synthesized by a green chemistry method. X-ray diffraction studies revealed the structural changes in Mn3O4/AC nanocomposites attributable to the addition of silver. Cyclic voltammetry, charge-discharge and ac-impedance studies indicated that the Ag-Mn3O4/AC-5 electrode was the most suitable candidate for supercapacitor applications. From the galvanostatic charge-discharge studies, a higher specific capacitance of 981 F g(-1) at a specific current of 1 A g(-1) was obtained. An Ag-Mn3O4/AC-symmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as an anode as well as a cathode, and an asymmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as a cathode and an activated carbon as an anode have been fabricated. The symmetric device exhibits a specific cell capacitance of 72 F g(-1) at a specific current of 1 A g(-1) whereas the asymmetric device delivers a specific cell capacitance of 180 F g(-1) at a high current rate of 10 A g(-1). The asymmetric supercapacitor device yields a high energy density of 81 W h kg(-1). This is higher than that of lead acid batteries and comparable with that of nickel hydride batteries.

Wideband Monolithic Tile for Reconfigurable Phased Arrays

DTIC Science & Technology

2017-03-01

has been developed for Reconfigurable Phased Array applications. Low loss and high isolation interconnection of switches within the radiating...there is no ground to connect shunt elements to. An integral part of the design was bias control. Mesa resistors are used for biasing. MIM...highest in resistance had the best performance over bandwidth because of reduced capacitive loading of the “off” arms of the Quad Switch on the central

Electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes as hierarchical electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Zhou, Zhengping; Wu, Xiang-Fa; Fong, Hao

2012-01-01

This letter reports the fabrication and electrochemical properties of electrospun carbon nanofibers surface-grafted with vapor-grown carbon nanotubes (CNTs) as hierarchical electrodes for supercapacitors. The specific capacitance of the fabricated electrodes was measured up to 185 F/g at the low discharge current density of 625 mA/g; a decrease of 38% was detected at the high discharge current density of 2.5 A/g. The morphology and microstructure of the electrodes were examined by electron microscopy, and the unique connectivity of the hybrid nanomaterials was responsible for the high specific capacitance and low intrinsic contact electric resistance of the hierarchical electrodes.

Hierarchical porous nickel oxide-carbon nanotubes as advanced pseudocapacitor materials for supercapacitors

NASA Astrophysics Data System (ADS)

Su, Aldwin D.; Zhang, Xiang; Rinaldi, Ali; Nguyen, Son T.; Liu, Huihui; Lei, Zhibin; Lu, Li; Duong, Hai M.

2013-03-01

Hierarchical porous carbon anode and metal oxide cathode are promising for supercapacitor with both high energy density and high power density. This Letter uses NiO and commercial carbon nanotubes (CNTs) as electrode materials for electrochemical capacitors with high energy storage capacities. Experimental results show that the specific capacitance of the electrode materials for 10%, 30% and 50% CNTs are 279, 242 and 112 F/g, respectively in an aqueous 1 M KOH electrolyte at a charge rate of 0.56 A/g. The maximum specific capacitance is 328 F/g at a charge rate of 0.33 A/g.

One pot synthesis of ilmenite-type NiMnO3-"nitrogen-doped" graphene nanocomposite as next generation supercapacitors.

PubMed

Giri, Soumen; Ghosh, Debasis; Das, Chapal Kumar

2013-10-28

NiMnO3-nitrogen doped graphene composite has been synthesized by a simple hydrothermal method and its supercapacitor performance investigated. The composite exhibits a specific capacitance of 750.2 F g(-1) in 1 M Na2SO4 at a scan rate of 1 mV s(-1). Nitrogen insertion inside the carbon lattice plays a crucial role in the enhancement of the overall specific capacitance and its long-term stability. This reproducible and superior performance of NiMnO3-nitrogen doped graphene composite make it attractive as a candidate for energy storage materials.

Chemical Synthesis of Sea-Urchin Shaped 3D-MnO2 Nano Structures and Their Application in Supercapacitors.

PubMed

Singu, Bal Sydulu; Hong, Sang Eun; Yoon, Kuk Ro

2016-06-01

Sea-urchin shaped α-MnO2 hierarchical nano structures have been synthesized by facile thermal method without using any hard or soft template under the mild conditions. The structural and morphology of the 3D-MnO2 was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). From the XRD analysis indicates that MnO2 present in the α form. Morphology analysis shows that α-MnO2 sea-urchins are made by stacked nanorods, the diameter and length of the stacked nanorods present in the range of 50-120 nm and 200-400 nm respectively. The electrochemical behaviour of α-MnO2 has been investigated by cyclic voltammetry (CV) and charge-discharge (CD). The specific capacitance, energy density and power density are 212.0 F g(-1), 21.2 Wh kg(-1) and 1200 W kg(-1) respectively at the current density of 2 A g(-1). The retention of the specific capacitance after completion of 1000 charge-discharge cycles is around 97%. The results reveal that the prepared Sea-urchin shaped α-MnO2 has high specific capacitance and exhibit excellent cycle life.

The synthesis of carbon electrode supercapacitor from durian shell based on variations in the activation time

NASA Astrophysics Data System (ADS)

Taer, E.; Dewi, P.; Sugianto, Syech, R.; Taslim, R.; Salomo, Susanti, Y.; Purnama, A.; Apriwandi, Agustino, Setiadi, R. N.

2018-02-01

The synthesis of carbon electrode from durian shell based on variations in the activation time has been carried out. Synthesis of carbon electrode was started by a carbonization process at a temperature of 600°C in nitrogen gas and then followed by physical activation process using water vapor at a temperature of 900°C by varying time of 1, 2 and 3 h. All of the variations of the samples were chemically activated using an activator of ZnCl2 with a concentration of 0.4 M. The physical properties such as density, surface morphology, degree of crystallinity and elemental content were analyzed. Moreover, the electrochemical properties such as specific capacitance of supercapacitor cells were studied using Cyclic Voltammetry methods. The density, stack height and carbon content were increased as activation time increases, while the specific capacitance of the supercapacitor cell decreases against the increase of activation time. Specific capacitances for 1, 2 and 3 h activation time are 88.39 F/g, 80.08 F/g and 74.61 F/g, respectively. Based on the surface morphology study it was shown that the increased in activation time causes narrowing of the pores between particles.

High-Surface-Area Nitrogen-Doped Reduced Graphene Oxide for Electric Double-Layer Capacitors.

PubMed

Youn, Hee-Chang; Bak, Seong-Min; Kim, Myeong-Seong; Jaye, Cherno; Fischer, Daniel A; Lee, Chang-Wook; Yang, Xiao-Qing; Roh, Kwang Chul; Kim, Kwang-Bum

2015-06-08

A two-step method consisting of solid-state microwave irradiation and heat treatment under NH3 gas was used to prepare nitrogen-doped reduced graphene oxide (N-RGO) with a high specific surface area (1007 m(2)  g(-1) ), high electrical conductivity (1532 S m(-1) ), and low oxygen content (1.5 wt %) for electrical double-layer capacitor applications. The specific capacitance of N-RGO was 291 F g(-1) at a current density of 1 A g(-1) , and a capacitance of 261 F g(-1) was retained at 50 A g(-1) , which indicated a very good rate capability. N-RGO also showed excellent cycling stability and preserved 96 % of the initial specific capacitance after 100 000 cycles. Near-edge X-ray absorption fine-structure spectroscopy results provided evidenced for the recovery of π conjugation in the carbon networks with the removal of oxygenated groups and revealed chemical bonding of the nitrogen atoms in N-RGO. The good electrochemical performance of N-RGO is attributed to its high surface area, high electrical conductivity, and low oxygen content. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile synthesis of a nitrogen-doped graphene flower-like MnO2 nanocomposite and its application in supercapacitors

NASA Astrophysics Data System (ADS)

Dong, Jinyang; Lu, Gang; Wu, Fan; Xu, Chenxi; Kang, Xiaohong; Cheng, Zhiming

2018-01-01

A flower-like MnO2 nanocomposite embedded in nitrogen-doped graphene (NG-MnO2) is fabricated by a hydrothermal method. It is a mesoporous nanomaterial with a pore size of approximately 0.765 cm3 g-1 and specific surface area of 201.8 m2 g-1. NG-MnO2 exhibits a superior average specific capacitance of 220 F g-1 at 0.5 A g-1 and a preferable capacitance of 189.1 F g-1, even at 10 A g-1. After 1000 cycles, over 98.3% of the original specific capacitance retention of the NG-MnO2 electrode is maintained, and it can even activate a red light emitting diode (LED) after being charged, which indicates that it has excellent cycling stability as an electrode material. This prominent electrochemical performance is primarily attributed to the nitrogen doping and mesoporous structures of NG-MnO2, which can be attributed to its numerous electroactive sites as well as faster ion and electron transfer for redox reactions than general graphene-MnO2 nanocomposites (G-MnO2).

Improved electrochemical performance of polyindole/carbon nanotubes composite as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Cai, Zhi-Jiang; Zhang, Qin; Song, Xian-You

2016-09-01

Polyindole/carbon nanotubes (PIN/CNTs) composite was prepared by an in-situ chemical oxidative polymerization of indole monomer with CNTs using ammonium persulfate as oxidant. The obtained composite material was characterized by SEM, TEM, FT-IR, Raman spectroscopy, XPS, XRD and BET surface areas measurements. It was found that the CNTs were incorporated into the PIN matrix and nanoporous structure was formed. Spectroscopy results showed that interfacial interaction bonds might be formed between the polyindole chains and CNTs during the in-situ polymerization. PIN/CNTs composite was evaluated by electrochemical impedance spectroscopy, cyclic voltammetry and charge/discharge tests to determine electrode performances in relation to supercapacitors properties in both aqueous and non-aqueous system. A maximum specific capacitance and specific volumetric capacitance of 555.6 F/g and 222.2 F/cm3 can be achieved at 0.5 A/g in non-aqueous system. It also displayed good rate performance and cycling stability. The specific capacitance retention is over 60% at 10 A/g and 91.3% after 5000 cycles at 2 A/g, respectively. These characteristics point to its promising applications in the electrode material for supercapacitors.

Facile synthesis of NiS anchored carbon nanofibers for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Xu, Jinling; Zhang, Li; Xu, Guancheng; Sun, Zhipeng; Zhang, Chi; Ma, Xin; Qi, Chunling; Zhang, Lu; Jia, Dianzeng

2018-03-01

Transition metal sulfide compounds with carbon materials are promising for high-performance supercapacitors. Carbon nanofibers (CNFs) wrapped with NiS nanoparticles were herein obtained through electrospinning and calcination. NiS nanoparticles in composite nanofibers are covered by a layer of graphitic carbon, which not only increase the conductivity but also provide active regions for nanoparticle growth to prevent aggregation. The CNFs-NiS electrode has high specific capacity of 177.1 mAh g-1 at 1 A g-1 (0.41 mAh cm-2 at a current density of 2.3 mA cm-2) and long-term cycling stability, with 88.7% capacitance retention after 5000 cycles. The excellent electrochemical activity may be attributed to the accessible specific surface, unique porous structure of CNFs and high specific capacitance of NiS. In addition, the asymmetric supercapacitor has an enhanced volumetric energy density of 13.32 mWh cm-3 at a volumetric power density of 180 mW cm-3 and high cycling stability, with 89.5% capacitance retention after 5000 cycles. It also successfully lights up a light-emitting diode. The CNFs-NiS composite has significant potential applications in supercapacitor.

Microwave-assisted rapid synthesis of birnessite-type MnO{sub 2} nanoparticles for high performance supercapacitor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiong; Miao, Wang; Li, Chen

Highlights: • Birnessite-type MnO{sub 2} nanoparticles were prepared by the microwave-assisted reflux. • The microwave reaction duration was only 5 min. • A specific capacitance of 329 F g{sup −1} was obtained for birnessite-type MnO{sub 2}. - Abstract: Birnessite-type MnO{sub 2} nanoparticles have been successfully synthesized by the microwave-assisted reflux as short as 5 min. The microstructure and morphology of the products were characterized by X-ray diffraction, N{sub 2} adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy. The electrochemical properties of the as-prepared MnO{sub 2} as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurementsmore » in 1 M Na{sub 2}SO{sub 4} electrolyte, and a high specific capacitance of 329 F g{sup −1} was achieved at a current density of 0.2 A g{sup −1}. The specific capacitance retention was 92% after 1000 cycles at 2 A g{sup −1}, suggesting that it is a promising electrode material for supercapacitors.« less

Supercapacitors based on nitrogen-doped reduced graphene oxide and borocarbonitrides

NASA Astrophysics Data System (ADS)

Gopalakrishnan, K.; Moses, Kota; Govindaraj, A.; Rao, C. N. R.

2013-12-01

Nitrogen-doped reduced graphene oxide (RGO) samples with different nitrogen content, prepared by two different methods, as well as nitrogen-doped few-layer graphene have been investigated as supercapacitor electrodes. Two electrode measurements have been carried out both in aqueous (6M KOH) and in ionic liquid media. Nitrogen-doped reduced graphene oxides exhibit satisfactory specific capacitance, the values reaching 126F/g at a scan rate of 10mV/s in aqueous medium. Besides providing supercapacitor characteristics, the study has shown the nitrogen content and surface area to be important factors. High surface-area borocarbonitrides, BxCyNz, prepared by the urea route appear to be excellent supercapacitor electrode materials. Thus, BC4.5N exhibits a specific capacitance of 169F/g at a scan rate of 10mV/s in aqueous medium. In an ionic liquid medium, nitrogen-doped RGO and BC4.5N exhibit specific capacitance values of 258F/g and 240F/g at a scan rate of 5mV/s. The ionic liquid enables a larger operating voltage range of 0.0-2.5V compared to 0.0-1V in aqueous medium.

Facilitated charge transport in ternary interconnected electrodes for flexible supercapacitors with excellent power characteristics

NASA Astrophysics Data System (ADS)

Chen, Wanjun; He, Yongmin; Li, Xiaodong; Zhou, Jinyuan; Zhang, Zhenxing; Zhao, Changhui; Gong, Chengshi; Li, Shuankui; Pan, Xiaojun; Xie, Erqing

2013-11-01

Flexible and high performance supercapacitors are very critical in modern society. In order to develop the flexible supercapacitors with high power density, free-standing and flexible three-dimensional graphene/carbon nanotubes/MnO2 (3DG/CNTs/MnO2) composite electrodes with interconnected ternary 3D structures were fabricated, and the fast electron and ion transport channels were effectively constructed in the rationally designed electrodes. Consequently, the obtained 3DG/CNTs/MnO2 composite electrodes exhibit superior specific capacitance and rate capability compared to 3DG/MnO2 electrodes. Furthermore, the 3DG/CNTs/MnO2 based asymmetric supercapacitor demonstrates the maximum energy and power densities of 33.71 W h kg-1 and up to 22 727.3 W kg-1, respectively. Moreover, the asymmetric supercapacitor exhibits excellent cycling stability with 95.3% of the specific capacitance maintained after 1000 cycle tests. Our proposed synthesis strategy to construct the novel ternary 3D structured electrodes can be efficiently applied to other high performance energy storage/conversion systems.Flexible and high performance supercapacitors are very critical in modern society. In order to develop the flexible supercapacitors with high power density, free-standing and flexible three-dimensional graphene/carbon nanotubes/MnO2 (3DG/CNTs/MnO2) composite electrodes with interconnected ternary 3D structures were fabricated, and the fast electron and ion transport channels were effectively constructed in the rationally designed electrodes. Consequently, the obtained 3DG/CNTs/MnO2 composite electrodes exhibit superior specific capacitance and rate capability compared to 3DG/MnO2 electrodes. Furthermore, the 3DG/CNTs/MnO2 based asymmetric supercapacitor demonstrates the maximum energy and power densities of 33.71 W h kg-1 and up to 22 727.3 W kg-1, respectively. Moreover, the asymmetric supercapacitor exhibits excellent cycling stability with 95.3% of the specific capacitance maintained after 1000 cycle tests. Our proposed synthesis strategy to construct the novel ternary 3D structured electrodes can be efficiently applied to other high performance energy storage/conversion systems. Electronic supplementary information (ESI) available: Additional experimental details; calculations of the specific capacitances, and energy and power densities; additional SEM and optical images; XPS results; additional electrochemical results. See DOI: 10.1039/c3nr03923d

Amorphous V-O-C composite nanofibers electrospun from solution precursors as binder- and conductive additive-free electrodes for supercapacitors with outstanding performance

NASA Astrophysics Data System (ADS)

Chen, Xia; Zhao, Bote; Cai, Yong; Tadé, Moses O.; Shao, Zongping

2013-11-01

Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m2 g-1 was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m2 g-1). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g-1 at 1 A g-1. V10 was also able to retain a specific capacitance of 380 F g-1, even at a current density of 10 A g-1. Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g-1 at 5 A g-1 after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications.Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m2 g-1 was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m2 g-1). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g-1 at 1 A g-1. V10 was also able to retain a specific capacitance of 380 F g-1, even at a current density of 10 A g-1. Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g-1 at 5 A g-1 after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications. Electronic supplementary information (ESI) available: FE-SEM image. See DOI: 10.1039/c3nr04484j

A p-nitroaniline redox-active solid-state electrolyte for battery-like electrochemical capacitive energy storage combined with an asymmetric supercapacitor based on metal oxide functionalized β-polytype porous silicon carbide electrodes.

PubMed

Kim, Myeongjin; Yoo, Jeeyoung; Kim, Jooheon

2017-05-23

A unique redox active flexible solid-state asymmetric supercapacitor with ultra-high capacitance and energy density was fabricated using a composite comprising MgCo 2 O 4 nanoneedles and micro and mesoporous silicon carbide flakes (SiCF) (SiCF/MgCo 2 O 4 ) as the positive electrode material. Due to the synergistic effect of the two materials, this hybrid electrode has a high specific capacitance of 516.7 F g -1 at a scan rate of 5 mV s -1 in a 1 M KOH aqueous electrolyte. To obtain a reasonable matching of positive and negative electrode pairs, a composite of Fe 3 O 4 nanoparticles and SiCF (SiCF/Fe 3 O 4 ) was synthesized for use as a negative electrode material, which shows a high capacitance of 423.2 F g -1 at a scan rate of 5 mV s -1 . Therefore, by pairing the SiCF/MgCo 2 O 4 positive electrode and the SiCF/Fe 3 O 4 negative electrode with a redox active quasi-solid-state PVA-KOH-p-nitroaniline (PVA-KOH-PNA) gel electrolyte, a novel solid-state asymmetric supercapacitor device was assembled. Because of the synergistic effect between the highly porous SiCF and the vigorous redox-reaction of metal oxides, the hybrid nanostructure electrodes exhibited outstanding charge storage and transport. In addition, the redox active PVA-KOH-PNA electrolyte adds additional pseudocapacitance, which arises from the nitro-reduction and oxidation and reduction process of the reduction product of p-phenylenediamine, resulting in an enhancement of the capacitance (a specific capacitance of 161.77 F g -1 at a scan rate of 5 mV s -1 ) and energy density (maximum energy density of 72.79 Wh kg -1 at a power density of 727.96 W kg -1 ).

Vehicle routing problem and capacitated vehicle routing problem frameworks in fund allocation problem

NASA Astrophysics Data System (ADS)

Mamat, Nur Jumaadzan Zaleha; Jaaman, Saiful Hafizah; Ahmad, Rokiah@Rozita

2016-11-01

Two new methods adopted from methods commonly used in the field of transportation and logistics are proposed to solve a specific issue of investment allocation problem. Vehicle routing problem and capacitated vehicle routing methods are applied to optimize the fund allocation of a portfolio of investment assets. This is done by determining the sequence of the assets. As a result, total investment risk is minimized by this sequence.

Effect of polyaniline on MWCNTs supercapacitor properties prepared by electrophoretic deposition

NASA Astrophysics Data System (ADS)

Razak, Rozelia Azila Abd; Eleas, Nor Hamizah; Mohammad, Nurul Nazwa; Yusof, Azmi Mohamed; Zaine, Intan Syaffinazzilla

2017-08-01

Multi-walled carbon nanotubes (MWCNTs) is widely used as supercapacitor electrode material. However, the specific capacitance of MWCNTs cannot achieve optimum value to facilitate required demand. Conducting polymers have been introduced to achieve optimum energy density and power density of supercapacitor electrode material. Previous work had demonstrated the effects of adding conducting polymer into carbon base material to get pseudocapacitance effect. Nevertheless the effects specifically of polyaniline (PANi) to MWCNTs were significantly low. This work describes the effect of PANi adding on MWCNTs film prepared by electrophoretic deposition (EPD) technique in order to increase the specific capacitance of MWCNTs. The commercial MWCNTs is dispersed in deionized water by using crystal violet. The admixtures without PANi (sample A), 5wt.% of PANi (sample B) and 10wt.% of PANi (sample C) have been prepared by ex-situ polymerization. The voltage supplied for film deposition is 8 V for 5 minutes. The morphology, functional group and electrochemical properties of MWCNTs due to the presence of PANi had been studied. From FESEM analysis, the presence of PANi can be clearly observed for sample B and sample C while FTIR analysis, proves PANi structure on MWCNTs with its functional group presence in sample B and sample C through the absorbtion band which obviously shifted to higher value compare to sample A. Cyclic voltammogram (CV) analysis shown redox activity occurred in sample B and sample C with identical anodic and cathodic peaks. Sample B hold the higher specific capacitance and higher energy density compared than sample A and sample B. From galvanostatic charge-discharge (CD) measurement, the charge and discharge process for sample B is longer than sample A and sample C which consequently lower its power density. The presence of PANi at 5wt.% is able to increase specific capacitance as well as energy density to optimum value.

Redox-active triazatruxene-based conjugated microporous polymers for high-performance supercapacitors† †Electronic supplementary information (ESI) available: Synthetic procedures and characterization data for all new compounds; general experimental method; thermogravimetry curves; PXRD patterns; SEM and TEM images; XPS spectra. See DOI: 10.1039/c6sc05532j Click here for additional data file.

PubMed Central

Li, Xiang-Chun; Zhang, Yizhou; Wang, Chun-Yu; Wan, Yi

2017-01-01

Conjugated polymers (CPs) have been intensively explored for various optoelectronic applications in the last few decades. Nevertheless, CP based electrochemical energy storage devices such as supercapacitors remain largely unexplored. This is mainly owing to the low specific capacitance, poor structural/electrochemical stability, and low energy density of most existing CPs. In this contribution, a novel set of redox-active conjugated microporous polymers, TAT-CMP-1 and TAT-CMP-2, based on nitrogen-rich and highly conductive triazatruxene building blocks, were successfully designed and synthesized to explore their potential application as efficient and stable electrode materials for supercapacitors. Despite a moderate surface area of 88 m2 g–1 for TAT-CMP-1 and 106 m2 g–1 for TAT-CMP-2, exceptional specific capacitances of 141 F g–1 and 183 F g–1 were achieved at a current density of 1 A g–1. The resulting polymers exhibited unusually high areal specific capacitance (>160 μF cm–2), which is attributed to the pseudocapacitance resulting from redox-active structures with high nitrogen content. More importantly, the TAT-CMP-2 electrode exhibits excellent cycling stability: only 5% capacitance fading is observed after 10 000 cycles at a high current density of 10 A g–1, enabling the possible use of these materials as electrodes in electrochemical devices. PMID:28451362

Nanoarchitectured Nb2O5 hollow, Nb2O5@carbon and NbO2@carbon Core-Shell Microspheres for Ultrahigh-Rate Intercalation Pseudocapacitors

NASA Astrophysics Data System (ADS)

Kong, Lingping; Zhang, Chuanfang; Wang, Jitong; Qiao, Wenming; Ling, Licheng; Long, Donghui

2016-02-01

Li-ion intercalation materials with extremely high rate capability will blur the distinction between batteries and supercapacitors. We construct a series of nanoarchitectured intercalation materials including orthorhombic (o-) Nb2O5 hollow microspheres, o-Nb2O5@carbon core-shell microspheres and tetragonal (t-) NbO2@carbon core-shell microspheres, through a one-pot hydrothermal method with different post-treatments. These nanoarchitectured materials consist of small nanocrystals with highly exposed active surface, and all of them demonstrate good Li+ intercalation pseudocapacitive properties. In particular, o-Nb2O5 hollow microspheres can deliver the specific capacitance of 488.3 F g-1, and good rate performance of 126.7 F g-1 at 50 A g-1. The o-Nb2O5@carbon core-shell microspheres show enhanced specific capacitance of 502.2 F g-1 and much improved rate performance (213.4 F g-1 at 50 A g-1). Furthermore, we demonstrate for the first time, t-NbO2 exhibits much higher rate capability than o-Nb2O5. For discharging time as fast as 5.9 s (50 A g-1), it still exhibits a very high specific capacitance of 245.8 F g-1, which is 65.2% retention of the initial capacitance (377.0 F g-1 at 1 A g-1). The unprecedented rate capability is an intrinsic feature of t-NbO2, which may be due to the conductive lithiated compounds.

Preparation of porous carbon spheres from 2-keto-l-gulonic acid mother liquor by oxidation and activation for electric double-layer capacitor application.

PubMed

Hao, Zhi-Qiang; Cao, Jing-Pei; Zhao, Xiao-Yan; Wu, Yan; Zhu, Jun-Sheng; Dang, Ya-Li; Zhuang, Qi-Qi; Wei, Xian-Yong

2018-03-01

A novel strategy is proposed for the increase of specific surface area (SSA) of porous carbon sphere (PCS) by oxidation and activation. 2-keto-l-gulonic acid mother liquor (GAML) as a high-pollution waste has a relatively high value of reutilization. For its high value-added utilization, GAML is used as the precursor for preparation of PCS as carbon-based electrode materials for electric double-layer capacitor. PCS is prepared by hydrothermal carbonization, carbonization and KOH activation, and Fe(NO 3 ) 3 9H 2 O is used as an oxidizing agent during carbonization. The as-prepared PCS has excellent porosity and high SSA of 2478 m 2  g -1 . Meanwhile, the pore structure of PCS can be controlled by the adjustment of carbonization parameters (carbonization temperature and the loading of Fe(NO 3 ) 3 9H 2 O). Besides, the SSA and specific capacitance of PCS can be increased remarkably when Fe(NO 3 ) 3 9H 2 O is added in carbonization. The specific capacitance of PCS can reach 303.7 F g -1 at 40 mA g -1 . PCSs as electrode material have superior electrochemical stability. After 8000 cycles, the capacitance retention is 98.3% at 2 A g -1 . The electric double-layer capacitance of PCS is improved when CS is carbonized with Fe(NO 3 ) 3 9H 2 O, and the economic and environmental benefits are achieved by the effective recycle of GAML. Copyright © 2017 Elsevier Inc. All rights reserved.

Nanoarchitectured Nb2O5 hollow, Nb2O5@carbon and NbO2@carbon Core-Shell Microspheres for Ultrahigh-Rate Intercalation Pseudocapacitors

PubMed Central

Kong, Lingping; Zhang, Chuanfang; Wang, Jitong; Qiao, Wenming; Ling, Licheng; Long, Donghui

2016-01-01

Li-ion intercalation materials with extremely high rate capability will blur the distinction between batteries and supercapacitors. We construct a series of nanoarchitectured intercalation materials including orthorhombic (o-) Nb2O5 hollow microspheres, o-Nb2O5@carbon core-shell microspheres and tetragonal (t-) NbO2@carbon core-shell microspheres, through a one-pot hydrothermal method with different post-treatments. These nanoarchitectured materials consist of small nanocrystals with highly exposed active surface, and all of them demonstrate good Li+ intercalation pseudocapacitive properties. In particular, o-Nb2O5 hollow microspheres can deliver the specific capacitance of 488.3 F g−1, and good rate performance of 126.7 F g−1 at 50 A g−1. The o-Nb2O5@carbon core-shell microspheres show enhanced specific capacitance of 502.2 F g−1 and much improved rate performance (213.4 F g−1 at 50 A g−1). Furthermore, we demonstrate for the first time, t-NbO2 exhibits much higher rate capability than o-Nb2O5. For discharging time as fast as 5.9 s (50 A g−1), it still exhibits a very high specific capacitance of 245.8 F g−1, which is 65.2% retention of the initial capacitance (377.0 F g−1 at 1 A g−1). The unprecedented rate capability is an intrinsic feature of t-NbO2, which may be due to the conductive lithiated compounds. PMID:26880276

Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

PubMed Central

Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

2016-01-01

Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm−2 & 19.1 Wh Kg−1 and 194 mF cm−2 & 4.5 Wh Kg−1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm−2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices. PMID:26936283

Nonlinear dynamics of capacitive charging and desalination by porous electrodes.

PubMed

Biesheuvel, P M; Bazant, M Z

2010-03-01

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the "supercapacitor regime" of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the "desalination regime" of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes

NASA Astrophysics Data System (ADS)

Biesheuvel, P. M.; Bazant, M. Z.

2010-03-01

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the “supercapacitor regime” of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the “desalination regime” of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

A sensitive capacitive immunosensor for direct detection of human heart fatty acid-binding protein (h-FABP).

PubMed

Mihailescu, Carmen-Marinela; Stan, Dana; Iosub, Rodica; Moldovan, Carmen; Savin, Mihaela

2015-01-01

The fabrication of a capacitive interdigitated immunosensor (CID) based on a mixed self-assembled monolayer (mSAM) film for the direct detection of heart fatty-acid binding protein (h-FABP) without any labeling is described. The capacitance changes of mSAMs vs. homogenous ordered self-assembled monolayers (hSAMs) on gold work electrodes/covalently bonded antibodies/buffered medium are utilized for monitoring the specific antibody-antigen interaction. Capacitance measurements in the absence and presence of Faradaic currents were performed. The electrochemical properties of mixed monolayers were compared with those of a pure monolayer of 11-mercaptoundecanoic acid (MUA) self-assembled on gold surfaces. Taking into account the stability of the studied monolayers during the electrochemical experiments with the Faradaic process, the best SAM functionalization method was used for developing a sensitive capacitive immunosensor with a non-Faradaic process for direct immune detection of human h-FABP. Under the optimized conditions, the proposed mixed self-assembled monolayer (mSAM1) on gold electrode exhibited good insulating properties such as a capacitive behavior when detecting h-FABP from human serum in the range of 98 pg ml(-1)-100 ng ml(-1), with a detection limit of 0.836 ng ml(-1) comparative with a homogenous self-assembled monolayer (hSAM). Copyright © 2014 Elsevier B.V. All rights reserved.

Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

NASA Astrophysics Data System (ADS)

Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

2016-03-01

Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm-2 & 19.1 Wh Kg-1 and 194 mF cm-2 & 4.5 Wh Kg-1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm-2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices.

DNA mediated wire-like clusters of self-assembled TiO2 nanomaterials: supercapacitor and dye sensitized solar cell applications

NASA Astrophysics Data System (ADS)

Nithiyanantham, U.; Ramadoss, Ananthakumar; Ede, Sivasankara Rao; Kundu, Subrata

2014-06-01

A new route for the formation of wire-like clusters of TiO2 nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO2 nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO2 NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 +/- 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO2 nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO2 nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g-1 was observed for TiO2 having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO2 nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO2 nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water.A new route for the formation of wire-like clusters of TiO2 nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO2 nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO2 NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 +/- 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO2 nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO2 nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g-1 was observed for TiO2 having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO2 nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO2 nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water. Electronic supplementary information (ESI) available: The details about the instrument used for various characterizations and figures related to FE-SEM analysis, EDS analysis, photoluminescence (PL) and LASER Raman study are provided. Table related to FT-IR analysis is also provided. See DOI: 10.1039/c4nr01836b

Anomalous effects of radioactive decay rates and capacitance values measured inside a modified Faraday cage: Correlations with space weather

NASA Astrophysics Data System (ADS)

Scholkmann, F.; Milián-Sánchez, V.; Mocholí-Salcedo, A.; Milián, C.; Kolombet, V. A.; Verdú, G.

2017-03-01

Recently we reported (Milián-Sánchez V. et al., Nucl. Instrum. Methods A, 828 (2016) 210) our experimental results involving 226Ra decay rate and capacitance measurements inside a modified Faraday cage. Our measurements exhibited anomalous effects of unknown origin. In this letter we report new results regarding our investigation into the origins of the observed effects. We report preliminary findings of a correlation analysis between the radioactive decay rates and capacitance time series and space weather related variables (geomagnetic field disturbances and cosmic-ray neutron counts). A significant correlation was observed for specific data sets. The results are presented and possible implications for future work discussed.

Tracking ion irradiation effects using buried interface devices

NASA Astrophysics Data System (ADS)

Cutshall, D. B.; Kulkarni, D. D.; Miller, A. J.; Harriss, J. E.; Harrell, W. R.; Sosolik, C. E.

2018-05-01

We discuss how a buried interface device, specifically a metal-oxide-semiconductor (MOS) capacitor, can be utilized to track effects of ion irradiation on insulators. We show that the exposure of oxides within unfinished capacitor devices to ions can lead to significant changes in the capacitance of the finished devices. For multicharged ions, these capacitive effects can be traced to defect production within the oxide and ultimately point to a role for charge-dependent energy loss. In particular, we attribute the stretchout of the capacitance-voltage curves of MOS devices that include an irradiated oxide to the ion irradiation. The stretchout shows a power law dependence on the multicharged ion charge state (Q) that is similar to that observed for multicharged ion energy loss in other systems.

Hierarchical network architectures of carbon fiber paper supported cobalt oxide nanonet for high-capacity pseudocapacitors.

PubMed

Yang, Lei; Cheng, Shuang; Ding, Yong; Zhu, Xingbao; Wang, Zhong Lin; Liu, Meilin

2012-01-11

We present a high-capacity pseudocapacitor based on a hierarchical network architecture consisting of Co(3)O(4) nanowire network (nanonet) coated on a carbon fiber paper. With this tailored architecture, the electrode shows ideal capacitive behavior (rectangular shape of cyclic voltammograms) and large specific capacitance (1124 F/g) at high charge/discharge rate (25.34 A/g), still retaining ~94% of the capacitance at a much lower rate of 0.25 A/g. The much-improved capacity, rate capability, and cycling stability may be attributed to the unique hierarchical network structures, which improves electron/ion transport, enhances the kinetics of redox reactions, and facilitates facile stress relaxation during cycling. © 2011 American Chemical Society

Humic acids as pseudocapacitive electrolyte additive for electrochemical double layer capacitors

NASA Astrophysics Data System (ADS)

Wasiński, Krzysztof; Walkowiak, Mariusz; Lota, Grzegorz

2014-06-01

Novel electrolyte additive for electrochemical capacitors has been reported. It has been demonstrated for the first time that addition of humic acids (HA) to KOH-based electrolyte significantly increases capacitance of symmetrical capacitors with electrodes made of activated carbon. Specific capacitances determined by means of galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy consistently showed increases for HA concentrations ranging from 2% w/w up to saturated solution with maximum positive effect observed for 5% w/w of the additive. The capacitance increase has been attributed to complex faradaic processes involving oxygen-containing groups of HA molecules. Due to abundant resources, low cost and easy processability the reported solution can find application in electrochemical capacitor technologies.

Decrease in the cytosolic NADP+-dependent isocitrate dehydrogenase activity through porcine sperm capacitation.

PubMed

Katoh, Yuki; Tamba, Michiko; Matsuda, Manabu; Kikuchi, Kazuhiro; Okamura, Naomichi

2018-02-26

In order to understand the molecular mechanisms involved in the sperm capacitation, we have identified the proteins tyrosine-phosphorylated during the capacitation especially in conjunction with the regulation of the levels of reactive oxygen species (ROS) in sperm. In the present study, the effects of the tyrosine phosphorylation of cytosolic NADP + -dependent isocitrate dehydrogenase (IDPc) on its catalytic activity and on the levels of ROS in sperm have been studied. The tyrosine phosphorylated IDPc showed a significantly lowered enzymatic activity. The immunocytochemical analyses using the highly specific antisera against IDPc revealed that IDPc was mainly localized to the principal piece of the porcine sperm flagellum. As IDPc is one of the major NADPH regenerating enzymes in porcine sperm, it is strongly suggested that the decrease in IDPc activity is involved in the increased levels of ROS, which results in the induction of hyperactivated flagellar movement and capacitation. Copyright © 2018 Elsevier Inc. All rights reserved.

Thermal Transients Excite Neurons through Universal Intramembrane Mechanoelectrical Effects

NASA Astrophysics Data System (ADS)

Plaksin, Michael; Shapira, Einat; Kimmel, Eitan; Shoham, Shy

2018-01-01

Modern advances in neurotechnology rely on effectively harnessing physical tools and insights towards remote neural control, thereby creating major new scientific and therapeutic opportunities. Specifically, rapid temperature pulses were shown to increase membrane capacitance, causing capacitive currents that explain neural excitation, but the underlying biophysics is not well understood. Here, we show that an intramembrane thermal-mechanical effect wherein the phospholipid bilayer undergoes axial narrowing and lateral expansion accurately predicts a potentially universal thermal capacitance increase rate of ˜0.3 % /°C . This capacitance increase and concurrent changes in the surface charge related fields lead to predictable exciting ionic displacement currents. The new MechanoElectrical Thermal Activation theory's predictions provide an excellent agreement with multiple experimental results and indirect estimates of latent biophysical quantities. Our results further highlight the role of electro-mechanics in neural excitation; they may also help illuminate subthreshold and novel physical cellular effects, and could potentially lead to advanced new methods for neural control.

Titanium nitride films for micro-supercapacitors: Effect of surface chemistry and film morphology on the capacitance

NASA Astrophysics Data System (ADS)

Achour, Amine; Porto, Raul Lucio; Soussou, Mohamed-Akram; Islam, Mohammad; Boujtita, Mohammed; Aissa, Kaltouma Ait; Le Brizoual, Laurent; Djouadi, Abdou; Brousse, Thierry

2015-12-01

Electrochemical capacitors (EC) in the form of packed films can be integrated in various electronic devices as power source. A fabrication process of EC electrodes, which is compatible with micro-fabrication, should be addressed for practical applications. Here, we show that titanium nitride films with controlled porosity can be deposited on flat silicon substrates by reactive DC-sputtering for use as high performance micro-supercapacitor electrodes. A superior volumetric capacitance as high as 146.4 F cm-3, with an outstanding cycling stability over 20,000 cycles, was measured in mild neutral electrolyte of potassium sulfate. The specific capacitance of the films as well as their capacitance retentions were found to depend on thickness, porosity and surface chemistry of electrodes. The one step process used to fabricate these TiN electrodes and the wide use of this material in the field of semiconductor technology make it promising for miniaturized energy storage systems.

Nitrogen-doped mesoporous carbons for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Wu, Kai; Liu, Qiming

2016-08-01

The mesoporous carbons have been synthesized by using α-D(+)-Glucose, D-Glucosamine hydrochloride or their mixture as carbon precursors and mesoporous silicas (SBA-15 or MCF) as hard templates. The as-prepared products show a large pore volume (0.59-0.97 cm3 g-1), high surface areas (352.72-1152.67 m2 g-1) and rational nitrogen content (ca. 2.5-3.9 wt.%). The results of electrochemical tests demonstrate that both heteroatom doping and suitable pore structure play a decisive role in the performance of supercapacitors. The representative sample of SBA-15 replica obtained using D-Glucosamine hydrochloride only exhibits high specific capacitance (212.8 F g-1 at 0.5 A g-1) and good cycle durability (86.1% of the initial capacitance after 2000 cycles) in 6 M KOH aqueous electrolyte, which is attributed to the contribution of double layer capacitance and pseudo-capacitance. The excellent electrochemical performance makes it a promising electrode material for supercapacitors.

A Triblock Copolymer Design Leads to Robust Hybrid Hydrogels for High-Performance Flexible Supercapacitors.

PubMed

Zhang, Guangzhao; Chen, Yunhua; Deng, Yonghong; Wang, Chaoyang

2017-10-18

We report here an intriguing hybrid conductive hydrogel as electrode for high-performance flexible supercapacitor. The key is using a rationally designed water-soluble ABA triblock copolymer (termed as IAOAI) containing a central poly(ethylene oxide) block (A) and terminal poly(acrylamide) (PAAm) block with aniline moieties randomly incorporated (B), which was synthesized by reversible additional fragment transfer polymerization. The subsequent copolymerization of aniline monomers with the terminated aniline moieties on the IAOAI polymer generates a three-dimensional cross-linking hybrid network. The hybrid hydrogel electrode demonstrates robust mechanical flexibility, remarkable electrochemical capacitance (919 F/g), and cyclic stability (90% capacitance retention after 1000 cycles). Moreover, the flexible supercapacitor based on this hybrid hydrogel electrode presents a large specific capacitance (187 F/g), superior to most reported conductive hydrogel-based supercapacitors. With the demonstrated additional favorable cyclic stability and excellent capacitive and rate performance, this hybrid hydrogel-based supercapacitor holds great promise for flexible energy-storage device.

Fabricate BC/Fe3O4@PPy 3D nanofiber film as flexible electrode for supercapacitor application

NASA Astrophysics Data System (ADS)

Lv, Xvdan; Li, Guohui; Pang, Zengyuan; Li, Dawei; Lei, Luo; Lv, Pengfei; Mushtaq, Muhammad; Wei, Qufu

2018-05-01

For flexible film supercapacitor, high areal capacitance is a main evaluating indicator. In this paper, bacterial cellulose (BC) with special three-dimensional structure was used as the natural flexible base material. Fe3O4 nanoparticles with average diameter of 20 nm were synthesized on the surface of BC fibers. The conductive path polypyrrole (PPy) was introduced as shell of BC/Fe3O4 fibers to further improve the pseudo capacitance in 1 mol/L H2SO4 solution. Besides, the BC/Fe3O4@PPy was used for supercapacitor application in acid electrolyte, and delivered higher areal capacitance compared to other Fe3O4 composites in previous reports. The obtained BC/Fe3O4@PPy film showed excellent mechanical strength (tensile strength reached 11 MPa), high areal specific capacitance (5.4 F cm-2 at active mass of 8.4 mg cm-2), and long cycle life (1.95 F cm-2 over 3500 cycles).

Highly conductive porous Na-embedded carbon nanowalls for high-performance capacitive deionization

NASA Astrophysics Data System (ADS)

Chang, Liang; Hu, Yun Hang

2018-05-01

Highly conductive porous Na-embedded carbon nanowalls (Na@C), which were recently invented, have exhibited excellent performance for dye-sensitized solar cells and electric double-layer capacitors. In this work, Na@C was demonstrated as an excellent electrode material for capacitive deionization (CDI). In a three-electrode configuration system, the specific capacity of the Na@C electrodes can achieve 306.4 F/g at current density of 0.2 A/g in 1 M NaCl, which is higher than that (235.2 F/g) of activated carbon (AC) electrodes. Furthermore, a high electrosorption capacity of 8.75 mg g-1 in 100 mg/L NaCl was obtained with the Na@C electrodes in a batch-mode capacitive deionization cell. It exceeds the electrosorption capacity (4.08 mg g-1) of AC electrodes. The Na@C electrode also showed a promising cycle stability. The excellent performance of Na@C electrode for capacitive deionization (CDI) can be attributed to its high electrical conductivity and large accessible surface area.

Design and Application of a Collocated Capacitance Sensor for Magnetic Bearing Spindle

NASA Technical Reports Server (NTRS)

Shin, Dongwon; Liu, Seon-Jung; Kim, Jongwon

1996-01-01

This paper presents a collocated capacitance sensor for magnetic bearings. The main feature of the sensor is that it is made of a specific compact printed circuit board (PCB). The signal processing unit has been also developed. The results of the experimental performance evaluation on the sensitivity, resolution and frequency response of the sensor are presented. Finally, an application example of the sensor to the active control of a magnetic bearing is described.

Changes in membrane conductances and areas associated with bicarbonate secretion in turtle bladder.

PubMed

Rich, A; Dixon, T E; Clausen, C

1990-02-01

Transepithelial impedance-analysis studies were performed in turtle bladder epithelium in order to measure changes in the different epithelial membranes resulting from stimulation of electrogenic bicarbonate secretion. Changes in membrane conductance relate to changes in ionic permeability, whereas changes in membrane capacitance relate to changes in membrane area, since most biological membranes exhibit a specific capacitance of approximately 1 muF/cm2. The results of this investigation are summarized as follows: (i) cAMP and carbachol, agents which have been shown previously to stimulate electrogenic bicarbonate secretion, result in increases in apical-membrane conductance and capacitance; (ii) these changes occur concomitantly with the observed change in transport (measured using the short-circuit-current technique), thereby suggesting that bicarbonate secretion may be regulated in part by changes in the chloride conductance of the apical membrane; (iii) the increase in conductance does not reflect an increase in the membrane's specific conductance, thereby indicating that it results from the addition of membrane possessing similar ionic permeability as the existing apical membrane; (iv) the magnitude of the changes in capacitance indicate that a minor cell population (beta-type carbonic-anhydrase-rich cells) increase their apical-membrane area by several-fold; (v) a lack of transport-associated changes in the basolateral-membrane parameters suggest that transport is not regulated by alterations in basolateral-membrane ionic conductance or area; (vi) a lack of colchicine sensitivity, coupled with the magnitude of the changes in apical-membrane capacitance, indicate that the membrane remodeling processes are different from those involved in the regulation of proton secretion in a different cell population (alpha-type carbonic-anhydrase-rich cells).

CoNi2 S4 Nanoparticle/Carbon Nanotube Sponge Cathode with Ultrahigh Capacitance for Highly Compressible Asymmetric Supercapacitor.

PubMed

Cao, Xin; He, Jin; Li, Huan; Kang, Liping; He, Xuexia; Sun, Jie; Jiang, Ruibing; Xu, Hua; Lei, Zhibin; Liu, Zong-Huai

2018-05-30

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi 2 S 4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi 2 S 4 on CNT sponge, in which CoNi 2 S 4 nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g -1 . Meanwhile, Fe 2 O 3 /CNT sponge anode with specific capacitance of 460 F g -1 in a prolonged voltage window is also prepared by electrodepositing Fe 2 O 3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT) is assembled by using CoNi 2 S 4 /CNT sponge as positive electrode and Fe 2 O 3 /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg -1 at a power density of 847 W kg -1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible and freestanding supercapacitor based on nanostructured poly(m-aminophenol)/carbon nanofiber hybrid mats with high energy and power densities

NASA Astrophysics Data System (ADS)

Choudhury, Arup; Dey, Baban; Sinha Mahapatra, Susanta; Kim, Doo-Won; Yang, Kap-Seung; Yang, Duck-Joo

2018-04-01

Nanostructured poly(m-aminophenol) (PmAP) coated freestanding carbon nanofiber (CNF) mats were fabricated through simple in situ rapid-mixing polymerization of m-aminophenol in the presence of a CNF mat for flexible solid-state supercapacitors. The surface compositions, morphology and pore structure of the hybrid mats were characterized by using various techniques, e.g., FTIR, Raman, XRD, FE-SEM, TEM, and N2 absorption. The results show that the PmAP nanoparticles were homogeneously deposited on CNF surfaces and formed a thin flexible hybrid mat, which were directly used to made electrodes for electrochemical analysis without using any binders or conductive additives. The electrochemical performances of the hybrid mats were easily tailored by varying the PmAP loading on a hybrid electrode. The PmAP/CNF-10 hybrid electrode with a relatively low PmAP loading (> 42 wt%) showed a high specific capacitance of 325.8 F g-1 and a volumetric capacitance of 273.6 F cm-3 at a current density of 0.5 A g-1, together with a specific capacitance retention of 196.2 F g-1 at 20 A g-1. The PmAP/CNF-10 hybrid electrode showed good cycling stability with 88.2% capacitance retention after 5000 cycles. A maximum energy density of 45.2 Wh kg-1 and power density of 20.4 kW kg-1 were achieved for the PmAP/CNF-10 hybrid electrode. This facile and cost-effective synthesis of a flexible binder-free PmAP/CNF hybrid mat with excellent capacitive performances encourages its possible commercial exploitation.

Porous ZnO-Coated Co3O4 Nanorod as a High-Energy-Density Supercapacitor Material.

PubMed

Gao, Miao; Wang, Wei-Kang; Rong, Qing; Jiang, Jun; Zhang, Ying-Jie; Yu, Han-Qing

2018-06-27

Co 3 O 4 with a high theoretical capacitance has been widely recognized as a promising electrode material for supercapacitor, but its poor electrical conductivity and stability limit its practical applications. Here, we developed an effective synthetic route to synthesize one-dimensional (1D) porous ZnO/Co 3 O 4 heterojunction composites. Benefiting from the heterostructure to promote the charge transfer and protect Co 3 O 4 from corrosion and the 1D porous structure to improve ion diffusion and prevent structural collapse in charge and discharge process, the as-prepared ZnO/Co 3 O 4 composites exhibited an excellent capacitive performance and good cycling stability. The specific capacitance of the ZnO/Co 3 O 4 -450 (1135 F g -1 at 1 A g -1 ) was 1.4 times higher than that of Co 3 O 4 (814 F g -1 ), and the high-rate performance for ZnO/Co 3 O 4 -450 was 4.9 times better than that of Co 3 O 4 . Also, approximately 83% of its specific capacitance was retained after 5000 cycles at 10 A g -1 . Most importantly, the as-fabricated asymmetric supercapacitor, with a ZnO/Co 3 O 4 -450 positive electrode and an activated carbon negative electrode, delivered a prominent energy density of 47.7 W h kg -1 and a high power density of 7500 W kg -1 . Thus, the ZnO/Co 3 O 4 composites could serve as a high-activity material for supercapacitor and the preparation method also offers an attractive strategy to enhance the capacitive performance of Co 3 O 4 .

All-solid-state asymmetric supercapacitors based on Fe-doped mesoporous Co3O4 and three-dimensional reduced graphene oxide electrodes with high energy and power densities.

PubMed

Zhang, Cheng; Wei, Jun; Chen, Leiyi; Tang, Shaolong; Deng, Mingsen; Du, Youwei

2017-10-19

An asymmetric supercapacitor offers opportunities to effectively utilize the full potential of the different potential windows of the two electrodes for a higher operating voltage, resulting in an enhanced specific capacitance and significantly improved energy without sacrificing the power delivery and cycle life. To achieve high energy and power densities, we have synthesized an all-solid-state asymmetric supercapacitor with a wider voltage range using Fe-doped Co 3 O 4 and three-dimensional reduced graphene oxide (3DrGO) as the positive and negative electrodes, respectively. In contrast to undoped Co 3 O 4 , the increased density of states and modified charge spatial separation endow the Fe-doped Co 3 O 4 electrode with greatly improved electrochemical capacitive performance, including high specific capacitance (1997 F g -1 and 1757 F g -1 at current densities of 1 and 20 A g -1 , respectively), excellent rate capability, and superior cycling stability. Remarkably, the optimized all-solid-state asymmetric supercapacitor can be cycled reversibly in a wide range of 0-1.8 V, thus delivering a high energy density (270.3 W h kg -1 ), high power density (9.0 kW kg -1 at 224.2 W h kg -1 ), and excellent cycling stability (91.8% capacitance retention after 10 000 charge-discharge cycles at a constant current density of 10 A g -1 ). The superior capacitive performance suggests that such an all-solid-state asymmetric supercapacitor shows great potential for developing energy storage systems with high levels of energy and power delivery.

Application of biomass-derived flexible carbon cloth coated with MnO2 nanosheets in supercapacitors

NASA Astrophysics Data System (ADS)

He, Shuijian; Chen, Wei

2015-10-01

Successful application of inexpensive energy storage devices lies in the exploitation of fabrication approaches that are based on cost-efficient materials and that can be easily scaled up. Here, inexpensive textile weaved by natural flax fiber is selected as raw material in preparing flexible and binder-free electrode material for supercapacitors. Although carbon fiber cloth obtained from the direct carbonization of flax textile exhibits a low specific capacitance of 0.78 F g-1, carbon fiber cloth electrode shows a very short relaxation time of 39.1 m s and good stability with almost 100% capacitance retaining after 104 cycles at 5 A g-1. To extend the application of the resulting carbon cloth in supercapacitor field, a layer of MnO2 nanosheets is deposited on the surface of carbon fiber via in situ redox reaction between carbon and KMnO4. The specific capacitance of MnO2 reaches 683.73 F g-1 at 2 A g-1 and still retains 269.04 F g-1 at 300 A g-1, indicating the excellent rate capacitance performance of the carbon cloth/MnO2 hybrids. The present study shows that carbon cloth derived from flax textile can provide a low-cost material platform for the facile, cost-efficient and large scale fabrication of binder-free electrode materials for energy storage devices.

Ethanedithiol-treated manganese oxide nanoparticles for rapidly responsive and transparent supercapacitors

NASA Astrophysics Data System (ADS)

Ryu, Ilhwan; Kim, Green; Park, Dasom; Yim, Sanggyu

2015-11-01

Metal oxide nanoparticles (NPs) provide a large surface area and short diffusion pathways for ions in supercapacitor electrode materials. However, binders and conductive additives used for tight connections with current collectors and improved conductivity hamper these benefits. In this work, we successfully fix manganese oxide (Mn3O4) NPs onto ITO current collectors by a simple 1,2-ethanedithiol (EDT) treatment without using any binders or conductive additives. As compared to the electrode fabricated using binder-mixed Mn3O4 NPs, the EDT-treated electrode shows significantly improved specific capacitance of 403 F g-1 at a scan rate of 10 mV s-1. The EDT-treatment is more effective at higher scan rates. The specific capacitances, 278 F g-1 at 100 mV s-1 and 202 F g-1 at 200 mV s-1, are larger than those reported so far at scan rates ≥100 mV s-1. The deconvolution of capacitive elements indicates that these improved capacitive properties are attributed to large insertion elements of the binder-free NP electrodes. Furthermore, this additive-free electrode is highly transparent and can be easily fabricated by simple spray-coating on various substrates including polymer films, implying that this new method is promising for the fabrication of large-area, transparent and flexible electrodes for next-generation supercapacitors.

P-Doped NiCo2S4 nanotubes as battery-type electrodes for high-performance asymmetric supercapacitors.

PubMed

Lin, Jinghuang; Wang, Yiheng; Zheng, Xiaohang; Liang, Haoyan; Jia, Henan; Qi, Junlei; Cao, Jian; Tu, Jinchun; Fei, Weidong; Feng, Jicai

2018-06-19

NiCo2S4 is a promising electrode material for supercapacitors, due to its rich redox reactions and intrinsically high conductivity. Unfortunately, in most cases, NiCo2S4-based electrodes often suffer from low specific capacitance, low rate capability and fast capacitance fading. Herein, we have rationally designed P-doped NiCo2S4 nanotube arrays to improve the electrochemical performance through a phosphidation reaction. Characterization results demonstrate that the P element is successfully doped into NiCo2S4 nanotube arrays. Electrochemical results demonstrate that P-doped NiCo2S4 nanotube arrays exhibit better electrochemical performance than pristine NiCo2S4, e.g. higher specific capacitance (8.03 F cm-2 at 2 mA cm-2), good cycling stability (87.5% capacitance retention after 5000 cycles), and lower charge transfer resistance. More importantly, we also assemble an asymmetric supercapacitor using P-doped NiCo2S4 nanotube arrays and activated carbon on carbon cloth, which delivers a maximum energy density of 42.1 W h kg-1 at a power density of 750 W kg-1. These results demonstrate that the as-fabricated P-doped NiCo2S4 nanotube arrays on carbon cloth show great potential as a battery-type electrode for high-performance supercapacitors.

A facile approach to fabricate flexible all-solid-state supercapacitors based on MnFe2O4/graphene hybrids

NASA Astrophysics Data System (ADS)

Cai, Weihua; Lai, Ting; Dai, Wanlin; Ye, Jianshan

2014-06-01

A critical challenge for the construction of flexible electrochemical capacitors is the preparation of flexible electrodes with large specific capacitance and robust mechanical strength. Here, we demonstrate a facile approach to make high performance and flexible electrodes by dropping MnFe2O4/graphene hybrid inks onto flexible graphite sheets (as current collectors and substrates) and drying under an infrared lamp. MnFe2O4/graphene hybrid inks are synthesized by immobilizing the MnFe2O4 microspheres on the graphene nanosheets via a simple solvothermal route. Electrochemical studies show that MnFe2O4/graphene exhibits a high capacitance of 300 F g-1 at a current density of 0.3 A g-1. In addition, the excellent electrochemical performance of a supercapacitor consisting of a sandwich structure of two pieces of MnFe2O4/graphene hybrids modified electrodes separated by polyvinyl alcohol (PVA)-H2SO4 gel electrolyte is further explored. Our studies reveal that the flexible supercapacitor device with 227 μm thickness can achieve a maximum specific capacitance of 120 F g-1 at a current density of 0.1 A g-1 and excellent cycle performance retaining 105% capacitance after 5000 cycles. This research may offer a method for the fabrication of lightweight, stable, flexible and high performance energy storage devices.

Capacitive charge storage at an electrified interface investigated via direct first-principles simulations [Direct Simulation of Capacitive Charging of Graphene and Implications for Supercapacitor Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radin, Maxwell D.; Ogitsu, Tadashi; Biener, Juergen

Understanding the impact of interfacial electric fields on electronic structure is crucial to improving the performance of materials in applications based on charged interfaces. Supercapacitors store energy directly in the strong interfacial field between a solid electrode and a liquid electrolyte; however, the complex interplay between the two is often poorly understood, particularly for emerging low-dimensional electrode materials that possess unconventional electronic structure. Typical descriptions tend to neglect the specific electrode-electrolyte interaction, approximating the intrinsic “quantum capacitance” of the electrode in terms of a fixed electronic density of states. Instead, we introduce a more accurate first-principles approach for directly simulatingmore » charge storage in model capacitors using the effective screening medium method, which implicitly accounts for the presence of the interfacial electric field. Applying this approach to graphene supercapacitor electrodes, we find that results differ significantly from the predictions of fixed-band models, leading to improved consistency with experimentally reported capacitive behavior. The differences are traced to two key factors: the inhomogeneous distribution of stored charge due to poor electronic screening and interfacial contributions from the specific interaction with the electrolyte. Lastly, our results are used to revise the conventional definition of quantum capacitance and to provide general strategies for improving electrochemical charge storage, particularly in graphene and similar low-dimensional materials.« less

Capacitive charge storage at an electrified interface investigated via direct first-principles simulations [Direct Simulation of Capacitive Charging of Graphene and Implications for Supercapacitor Design

DOE PAGES

Radin, Maxwell D.; Ogitsu, Tadashi; Biener, Juergen; ...

2015-03-11

Understanding the impact of interfacial electric fields on electronic structure is crucial to improving the performance of materials in applications based on charged interfaces. Supercapacitors store energy directly in the strong interfacial field between a solid electrode and a liquid electrolyte; however, the complex interplay between the two is often poorly understood, particularly for emerging low-dimensional electrode materials that possess unconventional electronic structure. Typical descriptions tend to neglect the specific electrode-electrolyte interaction, approximating the intrinsic “quantum capacitance” of the electrode in terms of a fixed electronic density of states. Instead, we introduce a more accurate first-principles approach for directly simulatingmore » charge storage in model capacitors using the effective screening medium method, which implicitly accounts for the presence of the interfacial electric field. Applying this approach to graphene supercapacitor electrodes, we find that results differ significantly from the predictions of fixed-band models, leading to improved consistency with experimentally reported capacitive behavior. The differences are traced to two key factors: the inhomogeneous distribution of stored charge due to poor electronic screening and interfacial contributions from the specific interaction with the electrolyte. Lastly, our results are used to revise the conventional definition of quantum capacitance and to provide general strategies for improving electrochemical charge storage, particularly in graphene and similar low-dimensional materials.« less

High Volumetric Energy Density Asymmetric Supercapacitors Based on Well-Balanced Graphene and Graphene-MnO2 Electrodes with Densely Stacked Architectures.

PubMed

Sheng, Lizhi; Jiang, Lili; Wei, Tong; Fan, Zhuangjun

2016-10-01

The well-matched electrochemical parameters of positive and negative electrodes, such as specific capacitance, rate performance, and cycling stability, are important for obtaining high-performance asymmetric supercapacitors. Herein, a facile and cost-effective strategy is demonstrated for the fabrication of 3D densely stacked graphene (DSG) and graphene-MnO 2 (G-MnO 2 ) architectures as the electrode materials for asymmetric supercapacitors (ASCs) by using MnO 2 -intercalated graphite oxide (GO-MnO 2 ) as the precursor. DSG has a stacked graphene structure with continuous ion transport network in-between the sheets, resulting in a high volumetric capacitance of 366 F cm -3 , almost 2.5 times than that of reduced graphene oxide, as well as long cycle life (93% capacitance retention after 10 000 cycles). More importantly, almost similar electrochemical properties, such as specific capacitance, rate performance, and cycling stability, are obtained for DSG as the negative electrode and G-MnO 2 as the positive electrode. As a result, the assembled ASC delivers both ultrahigh gravimetric and volumetric energy densities of 62.4 Wh kg -1 and 54.4 Wh L -1 (based on total volume of two electrodes) in 1 m Na 2 SO 4 aqueous electrolyte, respectively, much higher than most of previously reported ASCs in aqueous electrolytes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Decorating Graphene Oxide with Ionic Liquid Nanodroplets: An Approach Leading to Energy-Dense, High-Voltage Supercapacitors.

PubMed

She, Zimin; Ghosh, Debasis; Pope, Michael A

2017-10-24

A major stumbling block in the development of high energy density graphene-based supercapacitors has been maintaining high ion-accessible surface area combined with high electrode density. Herein, we develop an ionic liquid (IL)-surfactant microemulsion system that is found to facilitate the spontaneous adsorption of IL-filled micelles onto graphene oxide (GO). This adsorption distributes the IL over all available surface area and provides an aqueous formulation that can be slurry cast onto current collectors, leaving behind a dense nanocomposite film of GO/IL/surfactant. By removing the surfactant and reducing the GO through a low-temperature (360 °C) heat treatment, the IL plays a dual role of spacer and electrolyte. We study the effect of IL content and operating temperature on the performance, demonstrating a record high gravimetric capacitance (302 F/g at 1 A/g) for 80 wt % IL composites. At 60 wt % IL, combined high capacitance and bulk density (0.76 g/cm 3 ), yields one of the highest volumetric capacitances (218 F/cm 3 , at 1 A/g) ever reported for a high-voltage IL-based supercapacitor. While achieving promising rate performance and cycle-life, the approach also eliminates the long and costly electrolyte imbibition step of cell assembly as the electrolyte is cast directly with the electrode material.

Effect of various commercial buffers on sperm viability and capacitation.

PubMed

Andrisani, Alessandra; Donà, Gabriella; Ambrosini, Guido; Bonanni, Guglielmo; Bragadin, Marcantonio; Cosmi, Erich; Clari, Giulio; Armanini, Decio; Bordin, Luciana

2014-08-01

A wide variety of sperm preparation protocols are currently available for assisted conception. They include density gradient separation and washing methods. Both aim at isolating and capacitating as much motile sperm as possible for subsequent oocyte fertilization. The aim of this study was to examine the effects of four commercial sperm washing buffers on sperm viability and capacitation. Semen samples from 48 healthy donors (normal values of sperm count, motility, morphology, and volume) were analyzed. After separation (density gradient 40/80%), sperm were incubated in various buffers then analysed for reactive oxygen species (ROS) production, viability, tyrosine phosphorylation (Tyr-P), cholera toxin B subunit (CTB) labeling, and the acrosome reaction (AR). The buffers affected ROS generation in various ways resulting either in rapid cell degeneration (when the amount of ROS was too high for cell survival) or the inability of the cells to maintain correct functioning (when ROS were too few). Only when the correct ROS generation curve was maintained, suitable membrane reorganization, evidenced by CTB labeling was achieved, leading to the highest percentages of both Tyr-P- and acrosome-reacted-cells. Distinguishing each particular pathological state of the sperm sample would be helpful to select the preferred buffer treatment since both ROS production and membrane reorganization can be significantly altered by commercial buffers.

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Jun; Ren, Chang E.; Maleski, Kathleen

A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self-assembly between positively charged rGO modified with poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in-between MXene layers. As a result, the self-restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO-5 wt% electrode displays a volumetric capacitance of 1040 F cm –3 at a scan rate of 2 mV s –1, an impressivemore » rate capability with 61% capacitance retention at 1 V s –1 and long cycle life. Moreover, the fabricated binder-free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L –1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. Furthermore, this work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next-generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances.« less

A Capacitive Touch Screen Sensor for Detection of Urinary Tract Infections in Portable Biomedical Devices

PubMed Central

Honrado, Carlos; Dong, Tao

2014-01-01

Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria. However, the urine sampling and analysis required for these methods can be both time-consuming and complex. This work proposes a capacitive touch screen sensor (CTSS) concept as feasible alternative for a portable UTI detection device. Finite element method (FEM) simulations were conducted with a CTSS model. An exponential response of the model to increasing amounts of E. coli and liquid samples was observed. A measurable capacitance change due to E. coli presence and a tangible difference in the response given to urine and water samples were also detected. Preliminary experimental studies were also conducted on a commercial CTSS using liquid solutions with increasing amounts of dissolved ions. The CTSS was capable of distinguishing different volumes of liquids, also giving an exponential response. Furthermore, the CTSS gave higher responses to solutions with a superior amount of ions. Urine samples gave the top response among tested liquids. Thus, the CTSS showed the capability to differentiate solutions by their ionic content. PMID:25196109

PolyHIPE Derived Freestanding 3D Carbon Foam for Cobalt Hydroxide Nanorods Based High Performance Supercapacitor

NASA Astrophysics Data System (ADS)

Patil, Umakant M.; Ghorpade, Ravindra V.; Nam, Min Sik; Nalawade, Archana C.; Lee, Sangrae; Han, Haksoo; Jun, Seong Chan

2016-10-01

The current paper describes enhanced electrochemical capacitive performance of chemically grown Cobalt hydroxide (Co(OH)2) nanorods (NRs) decorated porous three dimensional graphitic carbon foam (Co(OH)2/3D GCF) as a supercapacitor electrode. Freestanding 3D porous GCF is prepared by carbonizing, high internal phase emulsion (HIPE) polymerized styrene and divinylbenzene. The PolyHIPE was sulfonated and carbonized at temperature up to 850 °C to obtain graphitic 3D carbon foam with high surface area (389 m2 g-1) having open voids (14 μm) interconnected by windows (4 μm) in monolithic form. Moreover, entangled Co(OH)2 NRs are anchored on 3D GCF electrodes by using a facile chemical bath deposition (CBD) method. The wide porous structure with high specific surface area (520 m2 g-1) access offered by the interconnected 3D GCF along with Co(OH)2 NRs morphology, displays ultrahigh specific capacitance, specific energy and power. The Co(OH)2/3D GCF electrode exhibits maximum specific capacitance about ~1235 F g-1 at ~1 A g-1 charge-discharge current density, in 1 M aqueous KOH solution. These results endorse potential applicability of Co(OH)2/3D GCF electrode in supercapacitors and signifies that, the porous GCF is a proficient 3D freestanding framework for loading pseudocapacitive nanostructured materials.

Hierarchical porous carbon materials derived from petroleum pitch for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Abudu, Patiman; Wang, Luxiang; Xu, Mengjiao; Jia, Dianzeng; Wang, Xingchao; Jia, Lixia

2018-06-01

In this work, a honeycomb-like carbon material derived from petroleum pitch was synthesized by a simple one-step carbonization/activation method using silica nanospheres as the hard templates. The obtained hierarchical porous carbon materials (HPCs) with a large specific surface area and uniform macropore distribution provide abundant active sites and sufficient ion migration channels. When used as an electrode material for supercapacitors, the HPCs exhibit a high specific capacitance of 341.0 F g-1 at 1 A g-1, excellent rate capability with a capacitance retention of 55.6% at 50 A g-1 (189.5 F g-1), and outstanding cycling performance in the three-electrode system.

Nanocoating covalent organic frameworks on nickel nanowires for greatly enhanced-performance supercapacitors

NASA Astrophysics Data System (ADS)

Han, Yang; Hu, Nantao; Liu, Shuai; Hou, Zhongyu; Liu, Jiaqiang; Hua, Xiaolin; Yang, Zhi; Wei, Liangming; Wang, Lin; Wei, Hao

2017-08-01

Nanocoatings of covalent organic frameworks (COFs) on nickel nanowires (NiNWs) have been designed and successfully fabricated for the first time, which showed greatly enhanced electrochemical performances for supercapacitors. The specific capacitance of electrodes based on as-fabricated COFs nanocoatings reached up to 314 F g-1 at 50 A g-1, which retained 74% of the specific capacitance under the current density of 2 A g-1. The ultrahigh current density makes the charge-discharge process extremely rapid. The outstanding electrochemical performances of COFs nanocoating on NiNWs make it an ideal candidate for supercapacitors. And the nanocoating-design can also give a guidance for application of COFs in high-performance energy storages.

Electrodeposition of Manganese-Nickel Oxide Films on a Graphite Sheet for Electrochemical Capacitor Applications.

PubMed

Lee, Hae-Min; Lee, Kangtaek; Kim, Chang-Koo

2014-01-09

Manganese-nickel (Mn-Ni) oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers. The X-ray diffractometer pattern revealed the presence of separate manganese oxide (g-MnO₂) and nickel oxide (NiO) in the films. The electrodeposited Mn-Ni oxide electrode exhibited a specific capacitance of 424 F/g in Na₂SO₄ electrolyte. This electrode maintained 86% of its initial specific capacitance over 2000 cycles of the charge-discharge operation, showing good cycling stability.

Electrophoretic deposition of multi-walled carbon nanotubes on porous anodic aluminum oxide using ionic liquid as a dispersing agent

NASA Astrophysics Data System (ADS)

Hekmat, F.; Sohrabi, B.; Rahmanifar, M. S.; Jalali, A.

2015-06-01

Multi-wall carbon nanotubes (MW-CNTs) have been arranged in nanochannels of anodic aluminum oxide template (AAO) by electrophoretic deposition (EPD) to make a vertically-aligned carbon nanotube (VA-CNT) based electrode. Well ordered AAO templates were prepared by a two-step anodizing process by applying a constant voltage of 45 V in oxalic acid solution. The stabilized CNTs in a water-soluble room temperature ionic liquid (1-methyl-3-octadecylimidazolium bromide), were deposited in the pores of AAO templates which were conductive by deposition of Ni nanoparticles in the bottom of pores. In order to obtain ideal results, different EPD parameters, such as concentration of MWCNTs and ionic liquid on stability of MWCNT suspensions, deposition time and voltage which are applied in EPD process and also optimal conditions for anodizing of template were investigated. The capacitive performance of prepared electrodes was analyzed by measuring the specific capacitance from cyclic voltammograms and the charge-discharge curves. A maximum value of 50 Fg-1 at the scan rate of 20 mV s-1was achieved for the specific capacitance.

Supercapacitors based on modified graphene electrodes with poly(ionic liquid)

NASA Astrophysics Data System (ADS)

Trigueiro, João Paulo C.; Lavall, Rodrigo L.; Silva, Glaura G.

2014-06-01

The improved accessibility of the electrolyte to the surface of carbon nanomaterials is a challenge to be overcome in supercapacitors based on ionic liquid electrolytes. In this study, we report the preparation of supercapacitors based on reduced graphene oxide (RGO) electrodes and ionic liquid as the electrolyte (specifically, 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide or [MPPy][TFSI]). Two types of electrodes were compared: the RGO-based electrode and a poly(ionic liquid)-modified RGO electrode (PIL:RGO). The supercapacitor produced with the PIL:RGO electrode and [MPPy][TFSI] showed an electrochemical stability of 3 V and provided a capacitance of 71.5 F g-1 at room temperature; this capacitance is 130% higher with respect to the RGO-based supercapacitor. The decrease of the specific capacitance after 2000 cycles is only 10% for the PIL:RGO-based device. The results revealed the potential of the PIL:RGO material as an electrode for supercapacitors. This composite electrode increases the compatibility with the ionic liquid electrolyte compared to an RGO electrode, promoting an increase in the effective surface area of the electrode accessible to the electrolyte ions.

Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

PubMed

Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

2015-10-01

In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices. Copyright © 2015 Elsevier Inc. All rights reserved.

Few-layered MoSe2 nanosheets as an advanced electrode material for supercapacitors.

PubMed

Balasingam, Suresh Kannan; Lee, Jae Sung; Jun, Yongseok

2015-09-21

We report the synthesis of few-layered MoSe2 nanosheets using a facile hydrothermal method and their electrochemical charge storage behavior. A systematic study of the structure and morphology of the as-synthesized MoSe2 nanosheets was performed. The downward peak shift in the Raman spectrum and the high-resolution transmission electron microscopy images confirmed the formation of few-layered nanosheets. The electrochemical energy-storage behavior of MoSe2 nanosheets was also investigated for supercapacitor applications in a symmetric cell configuration. The MoSe2 nanosheet electrode exhibited a maximum specific capacitance of 198.9 F g(-1) and the symmetric device showed 49.7 F g(-1) at a scan rate of 2 mV s(-1). A capacitance retention of approximately 75% was observed even after 10 000 cycles at a high charge-discharge current density of 5 A g(-1). The two-dimensional MoSe2 nanosheets exhibited a high specific capacitance and good cyclic stability, which makes it a promising electrode material for supercapacitor applications.

Free-standing 3D graphene/polyaniline composite film electrodes for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Shiyong; Ma, Li; Gan, Mengyu; Fu, Shenna; Dai, Wenqin; Zhou, Tao; Sun, Xiaowu; Wang, Huihui; Wang, Huining

2015-12-01

The research paper describes polyaniline (PANI) nanowires array on flexible polystyrene microsphere/reduced graphene (PS/rGN) film is synthesized by dilute polymerization, and then the PS microspheres are removed to form free-standing three-dimensional (3D) rGN/PANI composite film. The chemical and structural properties of the 3D rGN/PANI film are characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET), and the results confirm the 3D rGN/PANI film is synthesized successfully. When the film is used as a supercapacitor electrode, the maximum specific capacitance is as high as 740 F g-1 (or 581 F cm-3 for volumetric capacitance) at a current density of 0.5 A g-1 and the specific capacitance retains 87% of the initial after constant charge-discharge 1000 cycles at current density of 10 A g-1. It is believed that the free-standing 3D rGN/PANI film will have a great potential for application in supercapacitors.

Nitrogen-doped graphitic hierarchically porous carbon nanofibers obtained via bimetallic-coordination organic framework modification and their application in supercapacitors.

PubMed

Yao, Yuechao; Liu, Peng; Li, Xiaoyan; Zeng, Shaozhong; Lan, Tongbin; Huang, Haitao; Zeng, Xierong; Zou, Jizhao

2018-05-17

Herein, N-doped graphitic hierarchically porous carbon nanofibers (NGHPCF) were prepared by electrospinning the composite of bimetallic-coordination metal-organic frameworks and polyacrylonitrile, followed by a pyrolysis and acid wash process. Control over the N content, specific surface area, and degree of graphitization of NGHPCF materials has been realized by adjusting the Co/Zn metal coordination content as well as the pyrolysis temperature. The obtained NGHPCF with a high specific surface area (623 m2 g-1) and nitrogen content (13.83 wt%) exhibit a high capacitance of 326 F g-1 at 0.5 A g-1. In addition, the capacitance of 170 F g-1 is still maintained at a high current density (40 A g-1); this indicates a high capacitance retention capability. Furthermore, a superb energy density (9.61 W h kg-1) is obtained with a high power density (62.4 W kg-1) using an organic electrolyte. These results fully illustrate that the prepared NGHPCF binder-free electrodes are promising candidates for high-performance supercapacitors.

Flower-like Copper Cobaltite Nanosheets on Graphite Paper as High-Performance Supercapacitor Electrodes and Enzymeless Glucose Sensors.

PubMed

Liu, Shude; Hui, K S; Hui, K N

2016-02-10

Flower-like copper cobaltite (CuCo2O4) nanosheets anchored on graphite paper have been synthesized using a facile hydrothermal method followed by a postannealing treatment. Supercapacitor electrodes employing CuCo2O4 nanosheets exhibit an enhanced capacitance of 1131 F g(-1) at a current density of 1 A g(-1) compared with previously reported supercapacitor electrodes. The CuCo2O4 electrode delivers a specific capacitance of up to 409 F g(-1) at a current density of as high as 50 A g(-1), and a good long-term cycling stability, with 79.7% of its specific capacitance retained after 5000 cycles at 10 A g(-1). Furthermore, the as-prepared CuCo2O4 nanosheets on graphite paper can be fabricated as electrodes and used as enzymeless glucose sensors, which exhibit good sensitivity (3.625 μA μM(-1) cm(-2)) and an extraordinary linear response ranging up to 320 μM with a low detection limit (5 μM).

Hydrothermal synthesis of nanostructured graphene/polyaniline composites as high-capacitance electrode materials for supercapacitors

PubMed Central

Wang, Ronghua; Han, Meng; Zhao, Qiannan; Ren, Zonglin; Guo, Xiaolong; Xu, Chaohe; Hu, Ning; Lu, Li

2017-01-01

As known to all, hydrothermal synthesis is a powerful technique for preparing inorganic and organic materials or composites with different architectures. In this reports, by controlling hydrothermal conditions, nanostructured polyaniline (PANi) in different morphologies were composited with graphene sheets (GNS) and used as electrode materials of supercapacitors. Specifically, ultrathin PANi layers with total thickness of 10–20 nm are uniformly composited with GNS by a two-step hydrothermal-assistant chemical oxidation polymerization process; while PANi nanofibers with diameter of 50~100 nm are obtained by a one-step direct hydrothermal process. Benefitting from the ultrathin layer and porous structure, the sheet-like GNS/PANi composites can deliver specific capacitances of 532.3 to 304.9 F/g at scan rates of 2 to 50 mV/s. And also, this active material showed very good stability with capacitance retention as high as ~99.6% at scan rate of 50 mV/s, indicating a great potential for using in supercapacitors. Furthermore, the effects of hydrothermal temperatures on the electrochemical performances were systematically studied and discussed. PMID:28291246

High performance asymmetric supercapacitor based on molybdenum disulphide/graphene foam and activated carbon from expanded graphite.

PubMed

Masikhwa, Tshifhiwa M; Madito, Moshawe J; Bello, Abdulhakeem; Dangbegnon, Julien K; Manyala, Ncholu

2017-02-15

Molybdenum disulphide which has a graphene-like single layer structure has excellent mechanical and electrical properties and unique morphology, which might be used with graphene foam as composite in supercapacitor applications. In this work, Molybdenum disulphide (MoS 2 )/graphene foam (GF) composites with different graphene foam loading were synthesized by the hydrothermal process to improve on specific capacitance of the composites. Asymmetric supercapacitor device was fabricated using the best performing MoS 2 /GF composite and activated carbon derived from expanded graphite (AEG) as positive and negative electrodes, respectively, in 6M KOH electrolyte. The asymmetric MoS 2 /GF//AEG device exhibited a maximum specific capacitance of 59Fg -1 at a current density of 1Ag -1 with maximum energy and power densities of 16Whkg -1 and 758Wkg -1 , respectively. The supercapacitor also exhibited a good cyclic stability with 95% capacitance retention over 2000 constant charge-discharge cycles. The results obtained demonstrate the potential of MoS 2 /GF//AEG as a promising material for electrochemical energy storage application. Copyright © 2016 Elsevier Inc. All rights reserved.

Novel ultrathin Bi2O3 nanowires for supercapacitor electrode materials with high performance

NASA Astrophysics Data System (ADS)

Qiu, Yongfu; Fan, Hongbo; Chang, Xueyi; Dang, Haifeng; Luo, Qun; Cheng, Zhiyu

2018-03-01

In this paper, the ultrathin Bi2O3 nanowires are synthesized by an oxidative metal vapor transport deposition technique. Their diameters and length are about 10 nm and several tens of micrometers, the growth direction is along [101] and the specific surface area is about 7.34 m2 g-1. The galvanostatic charge-discharge measurement results show that the specific capacitances of the Bi2O3 nanowires-based electrodes increase with the decrease of the current densities. The maximum capacitance is 691.3 F g-1 at the current density of 2.0 A g-1. The Ragone plot shows that the Bi2O3 nanowires has excellent supercapacitive performance. Moreover, the cyclic stability is measured by the galvanostatic charge/discharge technique at a constant current density of 10.0 A g-1 in 6.0 M KOH electrolyte. The results show the excellent capacitance retention of 75.5% over 3000 cycles. In a word, the Bi2O3 nanowires should be the ideal potential electrode materials for low-costing and effective electrochemical supercapacitors.

Flexible Fe3O4@Carbon Nanofibers Hierarchically Assembled with MnO2 Particles for High-Performance Supercapacitor Electrodes.

PubMed

Iqbal, Nousheen; Wang, Xianfeng; Babar, Aijaz Ahmed; Zainab, Ghazala; Yu, Jianyong; Ding, Bin

2017-11-09

Increasing use of wearable electronic devices have resulted in enhanced demand for highly flexible supercapacitor electrodes with superior electrochemical performance. In this study, flexible composite membranes with electrosprayed MnO 2 particles uniformly anchored on Fe 3 O 4 doped electrospun carbon nanofibers (Fe 3 O 4 @CNF Mn ) have been prepared as flexible electrodes for high-performance supercapacitors. The interconnected porous beaded structure ensures free movement of electrolyte within the composite membranes, therefore, the developed supercapacitor electrodes not only offer high specific capacitance of ~306 F/g, but also exhibit good capacitance retention of ~85% after 2000 cycles, which certify that the synthesized electrodes offer high and stable electrochemical performance. Additionally, the supercapacitors fabricated from our developed electrodes well maintain their performance under flexural stress and exhibit a very minute change in specific capacitance even up to 180° bending angle. The developed electrode fabrication strategy integrating electrospinning and electrospray techniques paves new insights into the development of potential functional nanofibrous materials for light weight and flexible wearable supercapacitors.

Synthesis of NiMn-LDH Nanosheet@Ni3S2 Nanorod Hybrid Structures for Supercapacitor Electrode Materials with Ultrahigh Specific Capacitance.

PubMed

Yu, Shuai; Zhang, Yingxi; Lou, Gaobo; Wu, Yatao; Zhu, Xinqiang; Chen, Hao; Shen, Zhehong; Fu, Shenyuan; Bao, Binfu; Wu, Limin

2018-03-27

One of the key challenges for pseudocapacitive electrode materials with highly effective capacitance output and future practical applications is how to rationally construct hierarchical and ordered hybrid nanoarchitecture through the simple process. Herein, we design and synthesize a novel NiMn-layered double hydroxide nanosheet@Ni 3 S 2 nanorod hybrid array supported on porous nickel foam via a one-pot hydrothermal method. Benefited from the ultrathin and rough nature, the well-defined porous structure of the hybrid array, as well as the synergetic effect between NiMn-layered double hydroxide nanosheets and Ni 3 S 2 nanorods, the as-fabricated hybrid array-based electrode exhibits an ultrahigh specific capacitance of 2703 F g -1 at 3 A g -1 . Moreover, the asymmetric supercapacitor with this hybrid array as a positive electrode and wood-derived activated carbon as a negative electrode demonstrates high energy density (57 Wh Kg -1 at 738 W Kg -1 ) and very good electrochemical cycling stability.

Investigation on VOX/CNTS Nanocomposites Act as Electrode of Supercapacitors

NASA Astrophysics Data System (ADS)

Zhu, Quanyao; Li, Zhaolong; Zhang, Xiaoyan; Huang, Shengnan; Yu, Yue; Chen, Wen; Zakharova, Galina S.

2013-07-01

The VOx/CNTs nanocomposites were synthesized by the hydrothermal method. The structure and morphologies of the nanocomposites were characteristic by XRD, SEM and TEM. The electrochemical properties of the nanocomposites were explored by cyclic voltammetry, constant current charge/discharge testing and electrochemical impedance spectroscopy in 1M KNO3 aqueous solution. The results showed that the nanocomposites perform characteristics of electrical both double-layer capacitance and pseudocapacitance. The specific capacitances were 136.5F/g, when the current density was 0.15A/g.

Quality assurance: recommended guidelines for safe heating by capacitive-type heating technique to treat patients with metallic implants.

PubMed

Kato, Hirokazu; Kondo, Motoharu; Imada, Hajime; Kuroda, Masahiro; Kamimura, Yoshitsugu; Saito, Kazuyuki; Kuroda, Kagayaki; Ito, Koichi; Takahashi, Hideaki; Matsuki, Hidetoshi

2013-05-01

This article is a redissemination of the previous Japanese Quality Assurance Guide guidelines. Specific absorption rate and temperature distribution were investigated with respect to various aspects including metallic implant size and shape, insertion site, insertion direction, blood flow and heating power, and simulated results were compared with adverse reactions of patients treated by radio frequency capacitive-type heating. Recommended guidelines for safe heating methods for patients with metallic implants are presented based on our findings.

Transforming Pristine Carbon Fiber Tows into High Performance Solid-State Fiber Supercapacitors.

PubMed

Yu, Dingshan; Zhai, Shengli; Jiang, Wenchao; Goh, Kunli; Wei, Li; Chen, Xudong; Jiang, Rongrong; Chen, Yuan

2015-09-02

A facile activation strategy can transform pristine carbon fiber tows into high-performance fiber electrodes with a specific capacitance of 14.2 F cm(-3) . The knottable fiber supercapacitor shows an energy density of 0.35 mW h cm(-3) , an ultrahigh power density of 3000 mW cm(-3) , and a remarkable capacitance retention of 68%, when the scan rate increases from 10 to 1000 mV s(-1) . © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MnO2 nanorods/SiO2 sphere coated on single-wall carbon nanotubes as supercapacitor electrode for high energy storage applications

NASA Astrophysics Data System (ADS)

Iro, Zaharaddeen S.; Subramani, C.; Kesavan, T.; Dash, S. S.; Sasidharan, M.; Sundramoorthy, Ashok K.

2017-12-01

A composite of MnO2/SiO2 sphere was coated on single-wall carbon nanotubes (MnO2/SiO2/SWCNT) using one-pot hydrothermal synthesis method. KMnO4 was used as an oxidizing agent for mild functionalization of single-wall carbon nanotubes (SWCNT), and also as a precursor of MnO2. A comparative study in the presence of SiO2 and SWCNT was carried out using bare MnO2 as a reference. After addition of SiO2, the composite obtained showed an increase in both the specific capacitance and cycle life which can be associated with spherical shape of SiO2 which offered reduction sites for MnO2. With the addition of SWCNT less than 5%, the composite further showed an increase in capacitance and cycle life, this is because of the good conductive nature, excellent mechanical property and chemical stability of SWCNT. The electrochemical behaviour was studied using cyclic voltammetry and galvanostatic charge/discharge method in 1 M Na2SO4 electrolyte. The specific capacitance of MnO2, MnO2/SiO2 and MnO2/SiO2/SWCNT composite is 73.6 F g-1, 108.7 F g-1 and 136 F g-1 at a current density of 1 A g-1, respectively. The MnO2/SiO2/SWCNT energy density was 68 Wh kg-1 with power density of 444.4 W kg-1. The MnO2/SiO2/SWCNT composite retained 88% of its specific capacitance after 500 cycles. We envisage that this hybrid material could be applied for preparation of supercapacitor electrode.

NiCo2O4 particles with diamond-shaped hexahedron structure for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Li, Yanfang; Hou, Xiaojuan; Zhang, Zengxing; Hai, Zhenyin; Xu, Hongyan; Cui, Danfeng; Zhuiykov, Serge; Xue, Chenyang

2018-04-01

Nickel cobalt oxide (NiCo2O4) particles with a diamond-shaped hexahedral porous sheet structure are successfully synthesized by a facile hydrothermal method, followed by calcination in one step. NiCo2O4-I and NiCo2O4-II particles are prepared using the same method with different contents of urea (CO(NH2)2) and ammonium fluoride (NH4F). The different morphologies of the NiCo2O4-I and NiCo2O4-II particles illustrate that CO(NH2)2 and NH4F play an important role in crystal growth. To verify the influence of NH4F and CO(NH2)2 on the morphology of the NiCo2O4 particles, the theory of crystal growth morphology is analyzed. The electrochemical measurements show that NiCo2O4 particles exhibit a high specific capacitance. At a current density of 1.0 mA cm-2, the mass specific capacitances of the NiCo2O4-I and NiCo2O4-II electrodes are 690.75 and 1710.9 F g-1, respectively, in a 6 M KOH aqueous electrolyte. The specific capacitances of the NiCo2O4-I and NiCo2O4-II electrodes remain ∼95.95% and ∼70.58% of the initial capacitance values after 5000 cycles, respectively. According to the two-electrode test, the NiCo2O4-II//AC asymmetric electrodes exhibited an ultrahigh energy density of 64.67 Wh kg-1 at the power density of 12 kW kg-1, demonstrating its excellent application potential as an electrode material for supercapacitors.

Investigations on silver/polyaniline electrodes for electrochemical supercapacitors.

PubMed

Patil, Dipali S; Shaikh, J S; Pawar, S A; Devan, R S; Ma, Y R; Moholkar, A V; Kim, J H; Kalubarme, R S; Park, C J; Patil, P S

2012-09-14

Polyaniline (PANI) and silver doped polyaniline (Ag/PANI) thin films were deposited on stainless steel substrates by a dip coating technique. To study the effect of doping concentration of Ag on the specific capacitance of PANI the concentration of Ag was varied from 0.3 to 1.2 weight percent. Fourier transform-infrared and Fourier transform-Raman spectroscopy, and energy dispersion X-ray techniques were used for the phase identification and determination of the doping content in the PANI films, respectively. The surface morphology of the films was examined by Field Emission Scanning Electron Microscopy, which revealed a nanofiber like structure for PANI and nanofibers with bright spots of Ag particles for the Ag/PANI films. There was decrease in the room temperature electrical resistivity of the Ag/PANI films of the order of 10(2) with increasing Ag concentration. The supercapacitive behavior of the electrodes was tested in a three electrode system using 1.0 M H(2)SO(4) electrolyte. The specific capacitance increased from 285 F g(-1) (for PANI) to 512 F g(-1) for Ag/PANI at 0.9 weight percent doping of Ag, owing to the synergic effect of PANI and silver nanoparticles. This work demonstrates a simple strategy of improving the specific capacitance of polymer electrodes and may also be easily adopted for other dopants.

Ultra-light Hierarchical Graphene Electrode for Binder-Free Supercapacitors and Lithium-Ion Battery Anodes.

PubMed

Zuo, Zicheng; Kim, Tae Young; Kholmanov, Iskandar; Li, Huifeng; Chou, Harry; Li, Yuliang

2015-10-07

A mild and environmental-friendly method is developed for fabricating a 3D interconnected graphene electrode with large-scale continuity. Such material has interlayer pores between reduced graphene oxide nanosheets and in-plane pores. Hence, a specific surface area up to 835 m(2) g(-1) and a high powder conductivity up to 400 S m(-1) are achieved. For electrochemical applications, the interlayer pores can serve as "ion-buffering reservoirs" while in-plane ones act as "channels" for shortening the mass cross-plane diffusion length, reducing the ion response time, and prevent the interlayer restacking. As binder-free supercapacitor electrode, it delivers a specific capacitance up to 169 F g(-1) with surface-normalized capacitance close to 21 μF cm(-2) (intrinsic capacitance) and power density up to 7.5 kW kg(-1), in 6 m KOH aqueous electrolyte. In the case of lithium-ion battery anode, it shows remarkable advantages in terms of the initiate reversible Coulombic efficiency (61.3%), high specific capacity (932 mAh g(-1) at 100 mA g(-1)), and robust long-term retention (93.5% after 600 cycles at 2000 mAh g(-1)). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous Carbon with Willow-Leaf-Shaped Pores for High-Performance Supercapacitors.

PubMed

Shi, Yanhong; Zhang, Linlin; Schon, Tyler B; Li, Huanhuan; Fan, Chaoying; Li, Xiaoying; Wang, Haifeng; Wu, Xinglong; Xie, Haiming; Sun, Haizhu; Seferos, Dwight S; Zhang, Jingping

2017-12-13

A novel kind of biomass-derived, high-oxygen-containing carbon material doped with nitrogen that has willow-leaf-shaped pores was synthesized. The obtained carbon material has an exotic hierarchical pore structure composed of bowl-shaped macropores, willow-leaf-shaped pores, and an abundance of micropores. This unique hierarchical porous structure provides an effective combination of high current densities and high capacitance because of a pseudocapacitive component that is afforded by the introduction of nitrogen and oxygen dopants. Our synthetic optimization allows further improvements in the performance of this hierarchical porous carbon (HPC) material by providing a high degree of control over the graphitization degree, specific surface area, and pore volume. As a result, a large specific surface area (1093 m 2 g -1 ) and pore volume (0.8379 cm 3 g -1 ) are obtained for HPC-650, which affords fast ion transport because of its short ion-diffusion pathways. HPC-650 exhibits a high specific capacitance of 312 F g -1 at 1 A g -1 , retaining 76.5% of its capacitance at 20 A g -1 . Moreover, it delivers an energy density of 50.2 W h kg -1 at a power density of 1.19 kW kg -1 , which is sufficient to power a yellow-light-emitting diode and operate a commercial scientific calculator.

Construction of Core-Shell NiMoO4@Ni-Co-S Nanorods as Advanced Electrodes for High-Performance Asymmetric Supercapacitors.

PubMed

Chen, Chao; Yan, Dan; Luo, Xin; Gao, Wenjia; Huang, Guanjie; Han, Ziwu; Zeng, Yan; Zhu, Zhihong

2018-02-07

In this work, hierarchical core-shell NiMoO 4 @Ni-Co-S nanorods were first successfully grown on nickel foam by a facile two-step method to fabricate a bind-free electrode. The well-aligned electrode wrapped by Ni-Co-S nanosheets displays excellent nanostructural properties and outstanding electrochemical performance, owing to the synergistic effects of both nickel molybdenum oxides and nickel cobalt sulfides. The prepared core-shell nanorods in a three-electrode cell yielded a high specific capacitance of 2.27 F cm -2 (1892 F g -1 ) at a current density of 5 mA cm -2 and retained 91.7% of the specific capacitance even after 6000 cycles. Their electrochemical performance was further investigated for their use as positive electrode for asymmetric supercapacitors. Notably, the energy density of the asymmetric supercapacitor device reached 2.45 mWh cm -3 at a power density of 0.131 W cm -3 , and still retained a remarkable 80.3% of the specific capacitance after 3500 cycles. There is great potential for the electrode composed of the core-shell NiMoO 4 @Ni-Co-S nanorods for use in an all-solid-state asymmetric supercapacitor device.

NiCoO2 flowers grown on the aligned-flakes coated Ni foam for application in hybrid energy storage

NASA Astrophysics Data System (ADS)

Xu, Xiaoyang; Zhao, Huilin; Zhou, JingKuo; Xue, Ruinan; Gao, Jianping

2016-10-01

Many NiCoO2 flowers with an average diameter of about 4 μm were grown on the NiCoO2 flakes coated Ni foam (denoted as NiCoO2/Ni foam) through a simple hydrothermal method and confirmed by scanning and transmission electron microscopies, X-ray diffraction and X-ray photoelectron spectrum measurements. The NiCoO2/Ni foam with high specific area and porosity was directly used as the working electrode without any binders. The measured specific capacitance of NiCoO2 grown on Ni foam is 756 F/g at 0.75 A/g using a three-electrode setup in 1 M KOH. Considering the high capacity of NiCoO2 and the good stability of rGO, the NiCoO2/Ni foam//rGO hybrid supercapacitor combining NiCoO2/Ni foam and rGO shows very good properties, such as high specific capacitance (82 F/g at 2 A/g based on the total mass of active materials), high energy density (25.7 Wh/kg at 1500 W/kg based on the total mass of active materials), good stability (about 90% capacitance retention after 2000-cycle at 100 mV/s), and low charge ion transfer resistance.

Supercapacitive properties of hybrid films of manganese dioxide and polyaniline based on active carbon in organic electrolyte

NASA Astrophysics Data System (ADS)

Zou, Wu-yuan; Wang, Wei; He, Ben-lin; Sun, Ming-liang; Yin, Yan-sheng

This is the first report about supercapacitive performance of hybrid film of manganese dioxide (MnO 2) and polyaniline (PANI) in an organic electrolyte (1.0 M LiClO 4 in acetonitrile). In this work, a high surface area and conductivity of active carbon (AC) electrode is used as a substrate for PANI/MnO 2 film electro-codeposition. The redox properties of the coated PANI/MnO 2 thin film exhibit ideal capacitive behaviour in 1 M LiClO 4/AN. The specific capacitance (SC) of PANI/MnO 2 hybrid film is as high as 1292 F g -1 and maintains about 82% of the initial capacitance after 1500 cycles at a current density of 4.0 mA cm -2, and the coulombic efficiency (η) is higher than 95%. An asymmetric capacitor has been developed with the PANI/MnO 2/AC positive and pure AC negative electrodes, which is able to deliver a specific energy as high as 61 Wh kg -1 at a specific power of 172 W kg -1 in the range of 0-2.0 V. These results indicate that the organic electrolyte is a promising candidate for PANI/MnO 2 material application in supercapacitors.

Capacitive Detection of Low-Enthalpy, Higher-Order Phase Transitions in Synthetic and Natural Composition Lipid Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, Graham J.; Heberle, Frederick A.; Seinfeld, Jason S.

In-plane lipid organization and phase separation in natural membranes play key roles in regulating many cellular processes. Highly cooperative, first-order phase transitions in model membranes consisting of few lipid components are well understood and readily detectable via calorimetry, densitometry, and fluorescence. However, far less is known about natural membranes containing numerous lipid species and high concentrations of cholesterol, for which thermotropic transitions are undetectable by the above-mentioned techniques. We demonstrate that membrane capacitance is highly sensitive to low-enthalpy thermotropic transitions taking place in complex lipid membranes. Specifically, we measured the electrical capacitance as a function of temperature for droplet interfacemore » bilayer model membranes of increasing compositional complexity, namely, (a) a single lipid species, (b) domain-forming ternary mixtures, and (c) natural brain total lipid extract (bTLE). We observed that, for single-species lipid bilayers and some ternary compositions, capacitance exhibited an abrupt, temperature-dependent change that coincided with the transition detected by other techniques. In addition, capacitance measurements revealed transitions in mixed-lipid membranes that were not detected by the other techniques. Most notably, capacitance measurements of bTLE bilayers indicated a transition at ~38 °C not seen with any other method. Likewise, capacitance measurements detected transitions in some well-studied ternary mixtures that, while known to yield coexisting lipid phases, are not detected with calorimetry or densitometry. These results indicate that capacitance is exquisitely sensitive to low-enthalpy membrane transitions because of its sensitivity to changes in bilayer thickness that occur when lipids and excess solvent undergo subtle rearrangements near a phase transition. Our findings also suggest that heterogeneity confers stability to natural membranes that function near transition temperatures by preventing unwanted defects and macroscopic demixing associated with high-enthalpy transitions commonly found in simpler mixtures.« less

Capacitive Detection of Low-Enthalpy, Higher-Order Phase Transitions in Synthetic and Natural Composition Lipid Membranes

DOE PAGES

Taylor, Graham J.; Heberle, Frederick A.; Seinfeld, Jason S.; ...

2017-08-15

In-plane lipid organization and phase separation in natural membranes play key roles in regulating many cellular processes. Highly cooperative, first-order phase transitions in model membranes consisting of few lipid components are well understood and readily detectable via calorimetry, densitometry, and fluorescence. However, far less is known about natural membranes containing numerous lipid species and high concentrations of cholesterol, for which thermotropic transitions are undetectable by the above-mentioned techniques. We demonstrate that membrane capacitance is highly sensitive to low-enthalpy thermotropic transitions taking place in complex lipid membranes. Specifically, we measured the electrical capacitance as a function of temperature for droplet interfacemore » bilayer model membranes of increasing compositional complexity, namely, (a) a single lipid species, (b) domain-forming ternary mixtures, and (c) natural brain total lipid extract (bTLE). We observed that, for single-species lipid bilayers and some ternary compositions, capacitance exhibited an abrupt, temperature-dependent change that coincided with the transition detected by other techniques. In addition, capacitance measurements revealed transitions in mixed-lipid membranes that were not detected by the other techniques. Most notably, capacitance measurements of bTLE bilayers indicated a transition at ~38 °C not seen with any other method. Likewise, capacitance measurements detected transitions in some well-studied ternary mixtures that, while known to yield coexisting lipid phases, are not detected with calorimetry or densitometry. These results indicate that capacitance is exquisitely sensitive to low-enthalpy membrane transitions because of its sensitivity to changes in bilayer thickness that occur when lipids and excess solvent undergo subtle rearrangements near a phase transition. Our findings also suggest that heterogeneity confers stability to natural membranes that function near transition temperatures by preventing unwanted defects and macroscopic demixing associated with high-enthalpy transitions commonly found in simpler mixtures.« less

Plasma-assisted nitrogen doping of VACNTs for efficiently enhancing the supercapacitor performance

NASA Astrophysics Data System (ADS)

Mashayekhi, Alireza; Hosseini, Seyed Mahmoud; Hassanpour Amiri, Morteza; Namdar, Naser; Sanaee, Zeinab

2016-06-01

Nitrogen doping of vertically aligned carbon nanotubes (VACNTs) using plasma-enhanced chemical vapour deposition has been investigated to improve the supercapacitance performance of CNTs. Incorporating electrochemical measurements on the open-ended nitrogen-doped CNTs, showed the achievement of 6 times improvement in the capacitance value. For nitrogen-doped CNTs on silicon substrate, specific capacitance of 60 F g-1 was obtained in 0.5 M KCl solution, with capacity retention ratio above 90 % after cycled at 0.1 A g-1 for 5000 cycles. Using this sample, a symmetric supercapacitance was fabricated which showed the power density of 37.5 kW kg-1. The facile fabrication approach and its excellent capacitance improvement, propose it as an efficient technique for enhancing the supercapacitance performance of the carbon-based electrodes.

Nitrogen-doped biomass/polymer composite porous carbons for high performance supercapacitor

NASA Astrophysics Data System (ADS)

Shu, Yu; Maruyama, Jun; Iwasaki, Satoshi; Maruyama, Shohei; Shen, Yehua; Uyama, Hiroshi

2017-10-01

Nitrogen-doped porous monolithic carbon (NDPMC) is obtained from biomass-derived activated carbon/polyacrylonitrile composite for the first time via a template-free thermally induced phase separation (TIPS) approach followed by KOH activation. The electrochemical results indicate that NDPMC possesses ultrahigh specific capacitance of 442 F g-1 at 1 A g-1, excellent rate capability with 81% retention rate from 1 to 100 A g-1 and outstanding cycling stability with 98% capacitance retention at 20 A g-1 after 5000 cycles. Furthermore, the evaluation of NDPMC on the practical symmetrical system also exhibits desired electrochemical performances. The novel composite carbon displays remarkable capacitance properties and the feasible, low-cost synthetic route demonstrates great potential for large-scale production of high-performance electrode materials for supercapacitors.

Capacitance probe for fluid flow and volume measurements

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)

1995-01-01

Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a microgravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

Nitrogen/Sulfur-Codoped Carbon Materials from Chitosan for Supercapacitors

NASA Astrophysics Data System (ADS)

Li, Mei; Han, Xianlong; Chang, Xiaoqing; Yin, Wenchao; Ma, Jingyun

2016-08-01

d-Methionine and chitosan have been used for fabrication of nitrogen/sulfur-codoped carbon materials by a hydrothermal process followed by carbonization at 750°C for 3 h. The as-prepared carbon materials showed enhanced electrochemical performance, combining electrical double-layer capacitance with pseudocapacitance owing to the doping with sulfur and nitrogen. The specific capacitance of the obtained carbon material reached 135 F g-1 at current density of 1 A g-1, which is much higher than undoped chitosan (67 F g-1). The capacitance retention of the carbon material was almost 97.2% after 5000 cycles at current density of 1 A g-1. With such improved electrochemical performance, the nitrogen/sulfur-codoped carbon material may have promising potential for use in energy-storage electrodes of supercapacitors.

Fabrication of 3-D nanodimensioned electric double layer capacitor structures using block copolymer templates.

PubMed

Rasappa, Sozaraj; Borah, Dipu; Senthamaraikannan, Ramsankar; Faulkner, Colm C; Holmes, Justin D; Morris, Michael A

2014-07-01

The need for materials for high energy storage has led to very significant research in supercapacitor systems. These can exhibit electrical double layer phenomena and capacitances up to hundreds of F/g. Here, we demonstrate a new supercapacitor fabrication methodology based around the microphase separation of PS-b-PMMA which has been used to prepare copper nanoelectrodes of dimension -13 nm. These structures provide excellent capacitive performance with a maximum specific capacitance of -836 F/g for a current density of 8.06 A/g at a discharge current as high as 75 mA. The excellent performance is due to a high surface area: volume ratio. We suggest that this highly novel, easily fabricated structure might have a number of important applications.

Capacitance Probe for Fluid Flow and Volume Measurements

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)

1997-01-01

Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a micro-gravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

Freestanding hierarchically porous carbon framework decorated by polyaniline as binder-free electrodes for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Miao, Fujun; Shao, Changlu; Li, Xinghua; Wang, Kexin; Lu, Na; Liu, Yichun

2016-10-01

Freestanding hierarchically porous carbon electrode materials with favorable features of large surface areas, hierarchical porosity and continuous conducting pathways are very attractive for practical applications in electrochemical devices. Herein, three-dimensional freestanding hierarchically porous carbon (HPC) materials have been fabricated successfully mainly by the facile phase separation method. In order to further improve the energy storage ability, polyaniline (PANI) with high pseudocapacitance has been decorated on HPC through in situ chemical polymerization of aniline monomers. Benefiting from the synergistic effects between HPC and PANI, the resulting HPC/PANI composites as electrode materials present dramatic electrochemical performance with high specific capacitance up to 290 F g-1 at 0.5 A g-1 and good rate capability with ∼86% (248 F g-1) capacitance retention at 64 A g-1 of initial capacitance in three-electrode configuration. Moreover, the as-assembled symmetric supercapacitor based on HPC/PANI composites also demonstrates good capacitive properties with high energy density of 9.6 Wh kg-1 at 223 W kg-1 and long-term cycling stability with 78% capacitance retention after 10 000 cycles. Therefore, this work provides a new approach for designing high-performance electrodes with exceptional electrochemical performance, which are very promising for practical application in the energy storage field.

Design and analysis of optimised class E power amplifier using shunt capacitance in the output structure

NASA Astrophysics Data System (ADS)

Hayati, Mohsen; Roshani, Sobhan; Zirak, Ali Reza

2017-05-01

In this paper, a class E power amplifier (PA) with operating frequency of 1 MHz is presented. MOSFET non-linear drain-to-source parasitic capacitance, linear external capacitance at drain-to-source port and linear shunt capacitance in the output structure are considered in design theory. One degree of freedom is added to the design of class E PA, by assuming the shunt capacitance in the output structure in the analysis. With this added design degree of freedom it is possible to achieve desired values for several parameters, such as output voltage, load resistance and operating frequency, while both zero voltage and zero derivative switching (ZVS and ZDS) conditions are satisfied. In the conventional class E PA, high value of peak switch voltage results in limitations for the design of amplifier, while in the presented structure desired specifications could be achieved with the safe margin of peak switch voltage. The results show that higher operating frequency and output voltage can also be achieved, compared to the conventional structure. PSpice software is used in order to simulate the designed circuit. The presented class E PA is designed, fabricated and measured. The measured results are in good agreement with simulation and theory results.

Polypyrrole electrodes doped with sulfanilic acid azochromotrop for electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Chen, S.; Zhitomirsky, I.

2013-12-01

In this work we demonstrate the feasibility of deposition of polypyrrole (PPy) films by electropolymerization on stainless steel substrates and fabrication of PPy powders by chemical polymerization using sulfanilic acid azochromotrop (SPADNS) as a new anionic dopant. The problem of low adhesion of PPy films to stainless steel substrates is addressed by the use of SPADNS, which exhibits chelating properties, promoting film formation. The use of fine particles, prepared by the chemical polymerization method, allows impregnation of Ni foams and fabrication of porous electrodes with high materials loading for electrochemical supercapacitors (ES). PPy films and Ni foam based PPy electrodes show capacitive behaviour in Na2SO4 electrolyte. The electron microscopy studies, impedance spectroscopy data and analysis of the SPADNS structure provide an insight into the factors, controlling capacitive behaviour. The Ni foam based electrodes offer advantages of improved capacitive behaviour at high materials loadings and good cycling stability. The area normalized and volume normalized specific capacitances are as high as 5.43 F cm-2 and 93.6 F cm-3, respectively, for materials loading of 35.4 mg cm-2. The capacitance retention of Ni foam based electrodes is 91.5% after 1000 cycles. The Ni foam based PPy electrodes are promising for application in ES.

Synthesis and properties of ternary mixture of nickel/cobalt/tin oxides for supercapacitors

NASA Astrophysics Data System (ADS)

Ferreira, C. S.; Passos, R. R.; Pocrifka, L. A.

2014-12-01

The present study reports the synthesis and morphological, structural and electrochemical characterization of ternary oxides mixture containing nickel, cobalt and tin. The ternary oxide is synthesized by Pechini method with subsequent deposition onto a titanium substrate in a thin-film form. XRD and EDS analysis confirm the formation of ternary film with amorphous nature. SEM analysis show that cracks on the film favor the gain of the surface area that is an interesting feature for electrochemical capacitors. The ternary film is investigated in KOH electrolyte solution using cyclic voltammetry and charge-discharge study with a specific capacitance of 328 F g-1, and a capacitance retention of 86% over 600 cycles. The values of specific power and specific energy was 345.7 W kg-1 and 18.92 Wh kg-1, respectively.

C-IOP/NiO/Ni7S6 composite with the inverse opal lattice as an electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Sukhinina, Nadezhda S.; Masalov, Vladimir M.; Zhokhov, Andrey A.; Zverkova, Irina I.; Emelchenko, Gennadi A.

2015-06-01

In this work, we demonstrate the results of studies on the synthesis, the structure and properties of carbon inverted opal (C-IOP) nanostructures, the surface of which is modified by oxide and sulfide of nickel. It is shown that the modification of the matrix C-IOP by nickel compounds led to a decreasing the specific surface area more than three times and was 250 m2/g. The specific capacitance of the capacitor with the C-IOP/NiO/Ni7S6 composite as electrode has increased more than 4 times, from 130 F/g to 600 F/g, as compared with the sample C-IOP without the modification by nickel compounds. The significant contribution of the faradaic reactions in specific capacitance of the capacitor electrodes of the composites is marked.

Preparation of graphene foam with high performance by modified self-assembly method

NASA Astrophysics Data System (ADS)

Zhang, Wenhui; Sun, Youyi; Liu, Tantan; Li, Diansen; Hou, Chunlin; Gao, Li; Liu, Yaqing

2016-03-01

Recently, self-assembly method was applied for preparation of graphene foam. However, it is still a great challenge to obtain a three-dimensional graphene network with high performance (e.g., low density, high mechanical strength and high conductivity together) for the self-assembly method. Herein, a modified self-assembly method applied for preparation of graphene foam was investigated, in which, L-ascorbic acid and HI were firstly chosen as the reducing agent, and further reduced by hydrazine hydrate. The results demonstrated that the graphene foam showed high compressive strength (ca. 320 kPa), high electrical conductivity (20.6 S/m) and low density (14.7 mg/cm-1). Especially, the obtained compressive strength (ca. 320 kPa) is the highest value compared to the data of graphene foam reported in previous works. This phenomenon may be due to following three reasons: (1) the reaction between hydrazine hydrate and graphene brought some covalent bonds among graphene sheets; (2) graphene foam was achieved by high hydrophobicity and electrostatic repulsion which inhibit the restacking of graphene sheets; (3) the removal of the oxygen groups by hydrazine hydrate efficiently restores conjugation of sp2 regions and the π-π interaction in the cross-linking sites, which tightly bonds the sheets together. The obtained graphene foam not only had good porous structure and mechanical strength, but also showed excellent satisfactory double-layer capacitive behavior with good electrochemical cyclic stability and high specific capacitance of 171.0 F/g for application in electrode of supercapacitors and absorption capacities for the removal of various oils and dyes from water.

Novel graphene-like electrodes for capacitive deionization.

PubMed

Li, Haibo; Zou, Linda; Pan, Likun; Sun, Zhuo

2010-11-15

Capacitive deionization (CDI) is a novel technology that has been developed for removal of charged ionic species from salty water, such as salt ions. The basic concept of CDI, as well as electrosorption, is to force charged ions toward oppositely polarized electrodes through imposing a direct electric field to form a strong electrical double layer and hold the ions. Once the electric field disappears, the ions are instantly released back to the bulk solution. CDI is an alternative low-energy consumption desalination technology. Graphene-like nanoflakes (GNFs) with relatively high specific surface area have been prepared and used as electrodes for capacitive deionization. The GNFs were synthesized by a modified Hummers' method using hydrazine for reduction. They were characterized by atomic force microscopy, N2 adsorption at 77 K and electrochemical workstation. It was found that the ratio of nitric acid and sulfuric acid plays a vital role in determining the specific surface area of GNFs. Its electrosorption performance was much better than commercial activated carbon (AC), suggesting a great potential in capacitive deionisation application. Further, the electrosorptive performance of GNFs electrodes with different bias potentials, flow rates and ionic strengths were measured and the electrosorption isotherm and kinetics were investigated. The results showed that GNFs prepared by this process had the specific surface area of 222.01 m²/g. The specific electrosorptive capacity of the GNFs was 23.18 µmol/g for sodium ions (Na+) when the initial concentration was at 25 mg/L, which was higher than that of previously reported data using graphene and AC under the same experimental condition. In addition, the equilibrium electrosorption capacity was determined as 73.47 µmol/g at 2.0 V by fitting data through the Langmuir isotherm, and the rate constant was found to be 1.01 min⁻¹ by fitting data through pseudo first-order adsorption. The results suggested that the chemically synthesized GNFs can be used as effective electrode materials in CDI process for brackish water desalination.

Porous dimanganese trioxide microflowers derived from microcoordinations for flexible solid-state asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Pang, Huan; Li, Xinran; Li, Bing; Zhang, Yizhou; Zhao, Qunxing; Lai, Wen-Yong; Huang, Wei

2016-06-01

Dimanganese trioxide microflowers are easily obtained from a Mn(ii) 8-hydroxyquinoline microcoordination after calcination in air. We also look into the possible formation mechanism of the flower-like morphology, and find that the reaction time affects the morphology of the coordination. Furthermore, the as-prepared porous Mn2O3 microflowers are made of many nanoplates which form many nanogaps and nanochannels. Interestingly, the assembled electrode based on the as-prepared porous Mn2O3 microflowers proves to be a high-performance electrode material for supercapacitors. The electrode shows a specific capacitance of 994 F g-1, which can work well even after 4000 cycles at 0.75 A g-1. More importantly, the porous Mn2O3 microflowers and activated carbons are assembled into a high-performance flexible solid-state asymmetric supercapacitor with a specific capacitance of 312.5 mF cm-2. The cycle test shows that the device can offer 95.6% capacity of the initial capacitance at 2.0 mA cm-2 after 5000 cycles with little decay. The maximum energy density of the device can achieve 6.56 mWh cm-3 and the maximum power density can also achieve 283.5 mW cm-3, which are among the best results for manganese based materials.Dimanganese trioxide microflowers are easily obtained from a Mn(ii) 8-hydroxyquinoline microcoordination after calcination in air. We also look into the possible formation mechanism of the flower-like morphology, and find that the reaction time affects the morphology of the coordination. Furthermore, the as-prepared porous Mn2O3 microflowers are made of many nanoplates which form many nanogaps and nanochannels. Interestingly, the assembled electrode based on the as-prepared porous Mn2O3 microflowers proves to be a high-performance electrode material for supercapacitors. The electrode shows a specific capacitance of 994 F g-1, which can work well even after 4000 cycles at 0.75 A g-1. More importantly, the porous Mn2O3 microflowers and activated carbons are assembled into a high-performance flexible solid-state asymmetric supercapacitor with a specific capacitance of 312.5 mF cm-2. The cycle test shows that the device can offer 95.6% capacity of the initial capacitance at 2.0 mA cm-2 after 5000 cycles with little decay. The maximum energy density of the device can achieve 6.56 mWh cm-3 and the maximum power density can also achieve 283.5 mW cm-3, which are among the best results for manganese based materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02267g

DNA mediated wire-like clusters of self-assembled TiO₂ nanomaterials: supercapacitor and dye sensitized solar cell applications.

PubMed

Nithiyanantham, U; Ramadoss, Ananthakumar; Ede, Sivasankara Rao; Kundu, Subrata

2014-07-21

A new route for the formation of wire-like clusters of TiO₂ nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO₂ nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO₂ NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 ± 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO₂ nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO₂ nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g(-1) was observed for TiO₂ having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO₂ nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO₂ nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water.

Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion

DOE PAGES

Hatzell, Marta C.; Raju, Muralikrishna; Watson, Valerie J.; ...

2014-11-03

We report that the amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10 –5) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g –1) had a positive rise potential of 59 ± 4 mVmore » in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g –1) had a negative rise potential (₋31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to ₋6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. In conclusion, these results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.« less

Graphene-based Material Systems for Nanoelectronics and Energy Storage Devices

NASA Astrophysics Data System (ADS)

Guo, Shirui

Graphene is an allotrope of carbon in two-dimensional crystal form that has extraordinary electrical and optical properties. In this dissertation, we present the use of graphene in applications for chemical sensors, photovoltaics and supercapacitors. Firstly, carrier transport properties of single layer graphene films grown via chemical vapor deposition technique are tuned with functionalized molecules, polymers and inorganic nanoparticles. For example, cylindrical microdomains of polystyrene-4-polyvinylpyridine (PS-P4VP) block-copolymers (BCP) on graphene film provide spatial doping effects due to two distinct functional groups. Further, preferred interactions between CFx or fluorine radicals and BCP micro domains on graphene introduce localized doping of graphene film leading to controlling of Dirac point shift. Interaction between graphene and inorganic nanoparticles is studied by using CdSe quantum dots as a model system. Femtosecond time-resolved spectroscopy allowes us to demonstrate for the first time fast interfacial charge transfer for such systems in the picosecond and in the hundreds of femtosecond time domains, which also demonstrates high potential for photoelectrochemical cell. Secondly, graphene field effect transistors (GFET) as single strand DNA sensors are fabricated and detection limit as low as 3x10-9 M is demonstrated. Assembled BCP film on GFET sensor improved the sensor's stability and selectivity. The orientation and periodicity of the resulting cylindrical microdomains of BCP can facilitate the selective sensing property. With protective layer of BCP, sensor's stability under ambient atmosphere is improved up to 4 months. Thirdly, two different types of carbon nanotubes (CNT)/graphene hybrids are synthesized and used in fabrication of supercapacitors. The first type hybrid is graphene and vertically aligned carbon nanotubes which is successfully grown via one step chemical vapor deposition method. Our custom seamless growth method for such hybrids provides an attractive pathway for the fabrication of novel 3-Dimensional hybrid nanostructures. The second type hybrid is graphene oxide (GO) and SWCNT composite ink (GO-SWCNT ink). SWCNTs are dispersed using a GO aqueous solution (2mg/ml) with sonication support to achieve a SWCNT concentration of 12mg/ml, the highest reported value so far without surfactant assistance. Paper based electrodes for supercapacitors are fabricated using GO-SWCNT composite ink via dip casting method. By employing different concentrations of SWCNT inside the ink, supercapacitors demonstrated different capacitance values. The highest value of specific capacitance reaches up to 295 F/g at a current density of 0.5A/g with a GO/SWCNT weight ratio of 1:5. The cycling stability for the GO-SWCNT paper electrode supercapacitors indicates capacitance retention of 85% over 60,000 cycles. Finally, engineered interactions between nanomaterials, polymers, molecules and graphene/carbon nanotube can lead to the development of new types of devices for myriad applications.

Enhanced electrochemical performance of monoclinic WO3 thin film with redox additive aqueous electrolyte.

PubMed

Shinde, Pragati A; Lokhande, Vaibhav C; Chodankar, Nilesh R; Ji, Taeksoo; Kim, Jin Hyeok; Lokhande, Chandrakant D

2016-12-01

To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices. Copyright © 2016 Elsevier Inc. All rights reserved.

Redox reaction between graphene oxide and In powder to prepare In2O3/reduced graphene oxide hybrids for supercapacitors

NASA Astrophysics Data System (ADS)

Xu, Xiaoyang; Wu, Tao; Xia, Fengling; Li, Yi; Zhang, Congcong; Zhang, Lei; Chen, Mingxi; Li, Xichuan; Zhang, Li; Liu, Yu; Gao, Jianping

2014-11-01

A facile and quick route for the chemical reduction of graphene oxide (GO) using In powder as a reductant has been established. The reduction of GO by In powder is traced by UV-visible absorption spectroscopy, and the obtained reduced graphene oxide (rGO) is analyzed. The In3+ ions produced during the reaction between the GO and the In powder are chemically transformed to In2O3 and then form In2O3/rGO hybrids. The In2O3/rGO hybrids are used as electrode materials and their electrochemical performance are studied using cyclic voltammetry and galvanostatic charge/discharge. The In2O3/rGO hybrids demonstrate excellent electrochemical performance and their highest specific capacitance is 178.8 F g-1 which is much higher than that of either In2O3 or rGO. In addition, the In2O3/rGO hybrids are also very stable.

Electrochemical Properties of RuO2 Electrodes as a Function of Thin Film Thickness

NASA Astrophysics Data System (ADS)

Li, Xiang; Xiong, Jian; Luo, Yuan; Luo, Yongmei

2018-01-01

A thin film RuO2 electrode was prepared by spin coating thermal decomposition methods. Precursor containing RuCl3·nH2O and isopropyl alcohol was coated on tantalum substrate and annealed at 250-260°C for 3 h to form a thin film RuO2 electrode of about 2.5 μm, 5.6 μm, 11.4 μm, and 14.5 μm in thickness. X-ray diffraction revealed that peak intensities of those electrodes were similar and close to each other. Scanning electron microscopy showed that thin film of 5.6 μm in thickness was dense and free of cracks. Electrochemical performances of electrodes were examined by cyclic voltammetry, galvanostatic charge/discharge as well as equivalent series resistance. The highest specific capacitance value of 725 F g-1 was registered for the electrode of 5.6 μm in thickness with good constant current charge/discharge and equivalent series resistance of 0.36 Ω as well as cyclic stability.

Synthesis of Ammonia-Assisted Porous Nickel Ferrite (NiFe₂O₄) Nanostructures as an Electrode Material for Supercapacitors.

PubMed

Bhojane, Prateek; Sharma, Alfa; Pusty, Manojit; Kumar, Yogendra; Sen, Somaditya; Shirage, Parasharam

2017-02-01

In this work, we report a low cost, facile synthesis method for Nickel ferrite (NiFe₂O₄) nanostructures obtained by chemical bath deposition method for alternate transition metal oxide electrode material as a solution for clean energy. We developed a template free ammonia assisted method for obtaining porous structure which offering better supercapacitive performance of NiFe₂O₄ electrode material than previously reported for pure NiFe₂O₄. Here we explore the physical characterizations X-ray diffraction, FESEM, HRTEM performed to under-stand its crystal structure and morphology as well as the electrochemical measurements was performed to understand the electrochemical behaviour of the material. Here ammonia plays an important role in governing the structure/morphology of the material and enhances the electrochemical performance. The specific capacitance of 541 Fg⁻¹ is achieved at 2 mVs⁻¹ scan rate which is highest for the pure NiFe₂O₄ electrode material without using any addition of carbon based material, heterostructure or template based method.

Great improvement in pseudocapacitor properties of nickel hydroxide via simple gold deposition

NASA Astrophysics Data System (ADS)

Kim, Sun-I.; Thiyagarajan, Pradheep; Jang, Ji-Hyun

2014-09-01

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data.In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02204a

Redox-Active Hydrogel Polymer Electrolytes with Different pH Values for Enhancing the Energy Density of the Hybrid Solid-State Supercapacitor.

PubMed

Tang, Xiaohui; Lui, Yu Hui; Merhi, Abdul Rahman; Chen, Bolin; Ding, Shaowei; Zhang, Bowei; Hu, Shan

2017-12-27

To enhance the energy density of solid-state supercapacitors, a novel solid-state cell, made of redox-active poly(vinyl alcohol) (PVA) hydrogel electrolytes and functionalized carbon nanotube-coated cellulose paper electrodes, was investigated in this work. Briefly, acidic PVA-[BMIM]Cl-lactic acid-LiBr and neutral PVA-[BMIM]Cl-sodium acetate-LiBr hydrogel polymer electrolytes are used as catholyte and anolyte, respectively. The acidic condition of the catholyte contributes to suppression of the undesired irreversible reaction of Br - and extension of the oxygen evolution reaction potential to a higher value than that of the redox potential of Br - /Br 3 - reaction. The observed Br - /Br 3 - redox activity at the cathode contributes to enhance the cathode capacitance. The neutral condition of the anolyte helps extend the operating voltage window of the supercapacitor by introducing hydrogen evolution reaction overpotential to the anode. The electrosorption of nascent H on the negative electrode also increases the anode capacitance. As a result, the prepared solid-state hybrid supercapacitor shows a broad voltage window of 1.6 V, with a high Coulombic efficiency of 97.6% and the highest energy density of 16.3 Wh/kg with power density of 932.6 W/kg at 2 A/g obtained. After 10 000 cycles of galvanostatic charge and discharge tests at the current density of 10 A/g, it exhibits great cyclic stability with 93.4% retention of the initial capacitance. In addition, a robust capacitive performance can also be observed from the solid-state supercapacitor at different bending angles, indicating its great potential as a flexible energy storage device.

Gaseous slip flow analysis of a micromachined flow sensor for ultra small flow applications

NASA Astrophysics Data System (ADS)

Jang, Jaesung; Wereley, Steven T.

2007-02-01

The velocity slip of a fluid at a wall is one of the most typical phenomena in microscale gas flows. This paper presents a flow analysis considering the velocity slip in a capacitive micro gas flow sensor based on pressure difference measurements along a microchannel. The tangential momentum accommodation coefficient (TMAC) measurements of a particular channel wall in planar microchannels will be presented while the previous micro gas flow studies have been based on the same TMACs on both walls. The sensors consist of a pair of capacitive pressure sensors, inlet/outlet and a microchannel. The main microchannel is 128.0 µm wide, 4.64 µm deep and 5680 µm long, and operated under nearly atmospheric conditions where the outlet Knudsen number is 0.0137. The sensor was fabricated using silicon wet etching, ultrasonic drilling, deep reactive ion etching (DRIE) and anodic bonding. The capacitance change of the sensor and the mass flow rate of nitrogen were measured as the inlet-to-outlet pressure ratio was varied from 1.00 to 1.24. The measured maximum mass flow rate was 3.86 × 10-10 kg s-1 (0.019 sccm) at the highest pressure ratio tested. As the pressure difference increased, both the capacitance of the differential pressure sensor and the flow rate through the main microchannel increased. The laminar friction constant f sdot Re, an important consideration in sensor design, varied from the incompressible no-slip case and the mass sensitivity and resolution of this sensor were discussed. Using the current slip flow formulae, a microchannel with much smaller mass flow rates can be designed at the same pressure ratios.

High performance supercapacitors based on three-dimensional ultralight flexible manganese oxide nanosheets/carbon foam composites

NASA Astrophysics Data System (ADS)

He, Shuijian; Chen, Wei

2014-09-01

The syntheses and capacitance performances of ultralight and flexible MnO2/carbon foam (MnO2/CF) hybrids are systematically studied. Flexible carbon foam with a low mass density of 6.2 mg cm-3 and high porosity of 99.66% is simply obtained by carbonization of commercially available and low-cost melamine resin foam. With the high porous carbon foam as framework, ultrathin MnO2 nanosheets are grown through in situ redox reaction between KMnO4 and carbon foam. The three-dimensional (3D) MnO2/CF networks exhibit highly ordered hierarchical pore structure. Attributed to the good flexibility and ultralight weight, the MnO2/CF nanomaterials can be directly fabricated into supercapacitor electrodes without any binder and conductive agents. Moreover, the pseudocapacitance of the MnO2 nanosheets is enhanced by the fast ion diffusion in the three-dimensional porous architecture and by the conductive carbon foam skeleton as well as good contact of carbon/oxide interfaces. Supercapacitor based on the MnO2/CF composite with 3.4% weight percent of MnO2 shows a high specific capacitance of 1270.5 F g-1 (92.7% of the theoretical specific capacitance of MnO2) and high energy density of 86.2 Wh kg-1. The excellent capacitance performance of the present 3D ultralight and flexible nanomaterials make them promising candidates as electrode materials for supercapacitors.

Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

NASA Astrophysics Data System (ADS)

Gobal, Fereydoon; Faraji, Masoud

2014-12-01

Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

NASA Astrophysics Data System (ADS)

Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

2015-12-01

Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

Mesoporous composite nickel cobalt oxide/graphene oxide synthesized via a template-assistant co-precipitation route as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Xu, Yanjie; Wang, Lincai; Cao, Peiqi; Cai, Chuanlin; Fu, Yanbao; Ma, Xiaohua

2016-02-01

A simple co-precipitation method utilizing SDS (sodium dodecyl sulfate) as template and ammonia as precipitant is successfully employed to synthesize nickel cobalt oxide/graphene oxide (NiCo2O4/GO) composite. The as-prepared composite (NCG-10) exhibits a high capacitance of 1211.25 F g-1, 687 F g-1 at the current density of 1 A g-1, 10 A g-1 and good cycling ability which renders NCG-10 as promising electrode material for supercapacitors. An asymmetric supercapacitor (ASC) (full button cell) has been constructed with NCG-10 as positive electrode and lab-made reduced graphene oxide (rGO) as negative electrode. The fabricated NCG-10//rGO with an extended stable operational voltage of 1.6 V can deliver a high specific capacitance of 144.45 F g-1 at a current density of 1 A g-1. The as-prepared NCG-10//rGO demonstrates remarkable energy density (51.36 W h kg-1 at 1 A g-1), high power density (50 kW kg-1 at 20 A g-1). The retention of capacitance is 88.6% at the current density of 8 A g-1 after 2000 cycles. The enhanced capacitive performance can be attributed to the improved specific surface area and 3D open area of NCG-10 generated by the pores and channels with the substantial function of SDS.

Synthesis and loading-dependent characteristics of nitrogen-doped graphene foam/carbon nanotube/manganese oxide ternary composite electrodes for high performance supercapacitors.

PubMed

Cheng, Tao; Yu, Baozhi; Cao, Linli; Tan, Huiyun; Li, Xinghua; Zheng, Xinliang; Li, Weilong; Ren, Zhaoyu; Bai, Jinbo

2017-09-01

The ternary composite electrodes, nitrogen-doped graphene foam/carbon nanotube/manganese dioxide (NGF/CNT/MnO 2 ), have been successfully fabricated via chemical vapor deposition (CVD) and facile hydrothermal method. The morphologies of the MnO 2 nanoflakes presented the loading-dependent characteristics and the nanoflake thickness could also be tuned by MnO 2 mass loading in the fabrication process. The correlation between their morphology and electrochemical performance was systematically investigated by controlling MnO 2 mass loading in the ternary composite electrodes. The electrochemical properties of the flexible ternary electrode (MnO 2 mass loading of 70%) exhibited a high areal capacitance of 3.03F/cm 2 and a high specific capacitance of 284F/g at the scan rate of 2mV/s. Moreover, it was interesting to find that the capacitance of the NGF/CNT/MnO 2 composite electrodes showed a 51.6% increase after 15,000 cycles. The gradual increase in specific capacitance was due to the formation of defective regions in the MnO 2 nanostructures during the electrochemical cycles of the electrodes, which further resulted in increased porosity, surface area, and consequently increased electrochemical capacity. This work demonstrates a rarely reported conclusion about loading-dependent characteristics for the NGF/CNT/MnO 2 ternary composite electrodes. It will bring new perspectives on designing novel ternary or multi-structure for various energy storage applications. Copyright © 2017 Elsevier Inc. All rights reserved.

ERGO grown on Ni-Cu foam frameworks by constant potential method as high performance electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Mirzaee, Majid; Dehghanian, Changiz; Sabet Bokati, Kazem

2018-04-01

This study presents composite electrode materials based on Electrochemically Reduced graphene oxide (ERGO) and Ni-Cu Foam for supercapacitor applications. Constant potential (CP) method was used to form reduced graphene oxide on Ni-Cu foam and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-Ray Photoelectron Spectra (XPS), Raman Spectroscopy and electrochemical measurements. ERGO improves the electrical conduction leading to decrease of the internal resistance of the heterostructure. The ERGO served as a conductive network to facilitate the collection and transportation of electrons during the cycling, improved the conductivity of Ni-Cu foam, and allowed for a larger specific surface area. The irregular porous structure allowed for the easy diffusion of the electrolyte into the inner region of the electrode. Moreover, the nanocomposite directly fabricated on Ni-Cu foam with a better adhesion and avoided the use of polymer binder. This method efficiently reduced ohmic polarization and enhanced the rate capability. As a result, the Ni-Cu foam/ERGO nanocomposite exhibited a specific capacitance of 1259.3 F g-1 at 2 A g-1and about 99.3% of the capacitance retained after 5000 cycles. The capacitance retention was about 3% when the current density increased from 2 A g-1 to 15 A g-1. This two-step process drop cast and GO reduction by potentiostatic method is nontoxic and scalable and holds promise for improved energy density from redox capacitance in comparison with the conventional double layer supercapacitors.

Vertically Aligned Carbon Nanotube Arrays as Efficient Supports for Faradaic Capacitive Electrodes

NASA Astrophysics Data System (ADS)

Oguntoye, Moses; Holleran, Mary-Kate; Roberts, Katherine; Pesika, Noshir

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for faradaic capacitive electrode materials. The objective is to develop electrodes functioning in an inexpensive aqueous environment with small potential windows, that store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NiCo2O4, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT arrays as supports is significantly more than that obtained by direct deposition onto current collectors or by using VACNT alone. The ease of VACNT growth and the degree of coating control achievable using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

2D nickel oxide nanosheets with highly porous structure for high performance capacitive energy storage

NASA Astrophysics Data System (ADS)

Li, Zijiong; Zhang, Weiyang; Liu, Yanyue; Guo, Jinjin; Yang, Baocheng

2018-01-01

Developing advanced electrochemical electrode materials with excellent performance is critical to their future energy storage devices. Herein, we design and synthesize two-dimensional (2D) porous structure nickel oxide (NiO) nanosheets via a facile and scalable hydrothermal approach, and further heating. The effects of heating time on the electrochemical performances are investigated. The results indicate that the maximum specific capacitance is achieved for NiO nanosheets when heating temperature and time are 300 °C and 3 h, respectively (namely NiO-3). The as-prepared NiO-3 nanosheet are grown uniform on the skeleton of reduced graphene oxide (rGO). The optimum NiO/rGO displays a reversible discharge capacity of 781.7 F g-1 at 1 A g-1, and shows an ultra-long life-span with over 94% capacitance retention after 4000 cycles. The enhanced electrochemical properties for NiO/rGO can be ascribed to a collaborative effect between NiO and rGO, which possess high capacitance storage ability and excellent conductivity, respectively.

MnO2/carbon nanowalls composite electrode for supercapacitor application

NASA Astrophysics Data System (ADS)

Hassan, Sameh; Suzuki, Masaaki; Mori, Shinsuke; El-Moneim, Ahmed Abd

2014-03-01

Amorphous MnO2/carbon nanowalls composite films are developed for the supercapacitor applications. Synthesis of carbon nanowalls template is performed by plasma-enhanced chemical vapor deposition in a CO/H2 microwave discharge system. A well dispersion of amorphous MnO2 domains throughout carbon nanowalls template is obtained by potentiostatic anodic deposition technique. Carbon nanowalls enable to improve the capacitive behavior and rate capability of MnO2, a specific capacitance of 851 F g-1 at a current density of 1 mA cm-2 and charge transfer resistance of 1.02 Ω are obtained. MnO2/carbon nanowalls composite film exhibits energy density of 118 wh kg-1, power density of 783 wh kg-1, and capacitance retention of 92% after long cycle life of 2000 cycles by charging and discharging at 3 mA cm-2. The high density of atomic scale graphitic edges and large surface area of carbon nanowalls in conjunction with the presence of amorphous MnO2 domains facilitate rapid electron and ion transport and hence offering the potential of the improved capacitive behavior.

"Egg-Box"-Assisted Fabrication of Porous Carbon with Small Mesopores for High-Rate Electric Double Layer Capacitors.

PubMed

Kang, Danmiao; Liu, Qinglei; Gu, Jiajun; Su, Yishi; Zhang, Wang; Zhang, Di

2015-11-24

Here we report a method to fabricate porous carbon with small mesopores around 2-4 nm by simple activation of charcoals derived from carbonization of seaweed consisting of microcrystalline domains formed by the "egg-box" model. The existence of mesopores in charcoals leads to a high specific surface area up to 3270 m(2) g(-1), with 95% surface area provided by small mesopores. This special pore structure shows high adaptability when used as electrode materials for an electric double layer capacitor, especially at high charge-discharge rate. The gravimetric capacitance values of the porous carbon are 425 and 210 F g(-1) and volumetric capacitance values are 242 and 120 F cm(-3) in 1 M H2SO4 and 1 M TEA BF4/AN, respectively. The capacitances even remain at 280 F g(-1) (160 F cm(-3)) at 100 A g(-1) and 156 F g(-1) (90 F cm(-3)) at 50 A g(-1) in the aqueous and organic electrolytes, demonstrating excellent high-rate capacitive performance.

Facile Synthesis of Mixed Metal Organic Frameworks: Electrode Materials for Supercapacitor with Excellent Areal Capacitance and Operational Stability.

PubMed

Kazemi, Sayed Habib; Hosseinzadeh, Batoul; Kazemi, Hojjat; Kiani, Mohammad Ali; Hajati, Shaaker

2018-06-08

Electrode materials with high surface area, tailored pore size and efficient capability for ion insertion and enhanced transport of electrons and ions are needed for advanced supercapacitors. In the present study, a mixed metal organic framework (cobalt and manganese based MOF) was synthesized through a simple one pot solvothermal method and employed as the electrode material for supercapacitor. Notably, Co-Mn MOF electrode displayed a large surface area and excellent cycling stability (over 95% capacitance retention after 1500 cycles). Also, superior pseudocapacitive behavior was observed for Co-Mn MOF electrode in KOH electrolyte with an exceptional areal capacitance of 1.318 F cm-2. Moreover, an asymmetric supercapacitor was assembled using Co-Mn MOF and activated carbon electrode as positive and negative electrodes, respectively. The fabricated supercapacitor showed specific capacitances of 106.7 F g-1 at a scan rate of 10 mV s-1 and delivered maximum energy density of 30 Wh kg-1 at 2285.7 W kg-1. Our studies suggest the Co-Mn MOF as promising electrode materials for supercapacitor applications.

A Novel Layered Sedimentary Rocks Structure of the Oxygen-Enriched Carbon for Ultrahigh-Rate-Performance Supercapacitors.

PubMed

Zhang, Lin-Lin; Li, Huan-Huan; Shi, Yan-Hong; Fan, Chao-Ying; Wu, Xing-Long; Wang, Hai-Feng; Sun, Hai-Zhu; Zhang, Jing-Ping

2016-02-17

In this paper, gelatin as a natural biomass was selected to successfully prepare an oxygen-enriched carbon with layered sedimentary rocks structure, which exhibited ultrahigh-rate performance and excellent cycling stability as supercapacitors. The specific capacitance reached 272.6 F g(-1) at 1 A g(-1) and still retained 197.0 F g(-1) even at 100 A g(-1) (with high capacitance retention of 72.3%). The outstanding electrochemical performance resulted from the special layered structure with large surface area (827.8 m(2) g(-1)) and high content of oxygen (16.215 wt %), which effectively realized the synergistic effects of the electrical double-layer capacitance and pseudocapacitance. Moreover, it delivered an energy density of 25.3 Wh kg(-1) even with a high power density of 34.7 kW kg(-1) and ultralong cycling stability (with no capacitance decay even over 10,000 cycles at 2 A g(-1)) in a symmetric supercapacitor, which are highly desirable for their practical application in energy storage devices and conversion.

Capacitive behaviour of MnF2 and CoF2 submicro/nanoparticles synthesized via a mild ionic liquid-assisted route

NASA Astrophysics Data System (ADS)

Ma, Ruguang; Zhou, Yao; Yao, Lin; Liu, Guanghui; Zhou, Zhenzhen; Lee, Jong-Min; Wang, Jiacheng; Liu, Qian

2016-01-01

Submicro-/nano-sized MnF2 rods and hierarchical CoF2 cuboids are respectively synthesized via a facile precipitation method assisted by ionic liquid under a mild condition. The as-prepared MF2 (M = Mn, Co) submicro/nanoparticles exhibit impressive specific capacitance in 1.0 M KOH aqueous solution, especially at relatively high current densities, e.g. 91.2, 68.7 and 56.4 F g-1 for MnF2, and 81.7, 70.6 and 63.0 F g-1 for CoF2 at 5, 8 and 10 A g-1, respectively. The mechanism of striking capacitance of MF2 is clarified on the basis of analysing the cycled electrodes by different characterization techniques. Such remarkable capacitance is ascribed to the redox reactions between MF2 and MOOH in aqueous alkaline electrolytes, which can not be obtained in aqueous neutral electrolytes. This study for the first time provides direct evidences on the pseudocapacitance mechanism of MF2 in alkaline electrolytes and paves the way of application of transition metal fluorides as electrodes in supercapacitors.

Free-standing porous manganese dioxide/graphene composite films for high performance supercapacitors.

PubMed

Guo, Wang-Huan; Liu, Teng-Jiao; Jiang, Peng; Zhang, Zhan-Jun

2015-01-01

A simple hard template method and hydrothermal process have been employed to fabricate a self-standing hierarchical porous MnO2/graphene film. Thus-constructed electrode materials for binder-free supercapacitors exhibit a high specific capacitance of 266.3 F g(-1) at the density of 0.2 A g(-1). Moreover, the two-electrode device demonstrates an excellent rate capability and cycling stability with capacitance retention of 85.1% after 2000 charge-discharge cycles at a current density of 1 A g(-1). The porous nanostructured design can effectively improve the specific surface areas and account for the shorter relaxation time for the electrodes, resulting in a high electrochemical performance. Copyright © 2014 Elsevier Inc. All rights reserved.

Facile synthesis of Mesoporouscobalt Hexacyanoferrate Nanocubes for High-Performance Supercapacitors

PubMed Central

2017-01-01

Mesoporous cobalt hexacyanoferrate nanocubes (meso–CoHCF) were prepared for the first time through a facile sacrificial template method. The CoHCF mesostructures possess a high specific surface area of 548.5 m2·g−1 and a large amount of mesopores, which enable fast mass transport of electrolyte and abundant energy storage sites. When evaluated as supercapacitor materials, the meso–CoHCF materials exhibit a high specific capacitance of 285 F·g−1, good rate capability and long cycle life with capacitance retention of 92.9% after 3000 cycles in Na2SO4 aqueous electrolyte. The excellent electrochemical properties demonstrate the rational preparation of mesoporous prussian blue and its analogues for energy storage applications. PMID:28825671

Amorphous V-O-C composite nanofibers electrospun from solution precursors as binder- and conductive additive-free electrodes for supercapacitors with outstanding performance.

PubMed

Chen, Xia; Zhao, Bote; Cai, Yong; Tadé, Moses O; Shao, Zongping

2013-12-21

Flexible V-O-C composite nanofibers were fabricated from solution precursors via electrospinning and were investigated as free-standing and additive-free film electrodes for supercapacitors. Specifically, composite nanofibers (V0, V5, V10 and V20) with different vanadyl acetylacetonate (VO(acac)2) contents of 0, 5, 10 and 20 wt% with respect to polyacrylonitrile (PAN) were prepared. The composite nanofibers were comparatively studied using XRD, Raman spectroscopy, XPS, N2 adsorption-desorption, FE-SEM, TEM and S-TEM. The vanadium element was found to be well-dispersed in the carbon nanofibers, free from the formation of an aggregated crystalline phase, even in the case of V20. A specific surface area of 587.9 m(2) g(-1) was reached for V10 after calcination, which is approximately twice that of the vanadium-free carbon nanofibers (V0, 300.9 m(2) g(-1)). To perform as an electrode for supercapacitors in an aqueous electrolyte, the V10 film delivered a specific capacitance of 463 F g(-1) at 1 A g(-1). V10 was also able to retain a specific capacitance of 380 F g(-1), even at a current density of 10 A g(-1). Additionally, very stable cycling stability was achieved, maintaining an outstanding specific capacitance of 400 F g(-1) at 5 A g(-1) after charge-discharge cycling 5000 times. Thus, V-O-C composite nanofibers are highly attractive electrode materials for flexible, high-power, thin film energy storage devices and applications.

PolyHIPE Derived Freestanding 3D Carbon Foam for Cobalt Hydroxide Nanorods Based High Performance Supercapacitor

PubMed Central

Patil, Umakant M.; Ghorpade, Ravindra V.; Nam, Min Sik; Nalawade, Archana C.; Lee, Sangrae; Han, Haksoo; Jun, Seong Chan

2016-01-01

The current paper describes enhanced electrochemical capacitive performance of chemically grown Cobalt hydroxide (Co(OH)2) nanorods (NRs) decorated porous three dimensional graphitic carbon foam (Co(OH)2/3D GCF) as a supercapacitor electrode. Freestanding 3D porous GCF is prepared by carbonizing, high internal phase emulsion (HIPE) polymerized styrene and divinylbenzene. The PolyHIPE was sulfonated and carbonized at temperature up to 850 °C to obtain graphitic 3D carbon foam with high surface area (389 m2 g−1) having open voids (14 μm) interconnected by windows (4 μm) in monolithic form. Moreover, entangled Co(OH)2 NRs are anchored on 3D GCF electrodes by using a facile chemical bath deposition (CBD) method. The wide porous structure with high specific surface area (520 m2 g−1) access offered by the interconnected 3D GCF along with Co(OH)2 NRs morphology, displays ultrahigh specific capacitance, specific energy and power. The Co(OH)2/3D GCF electrode exhibits maximum specific capacitance about ~1235 F g−1 at ~1 A g−1 charge-discharge current density, in 1 M aqueous KOH solution. These results endorse potential applicability of Co(OH)2/3D GCF electrode in supercapacitors and signifies that, the porous GCF is a proficient 3D freestanding framework for loading pseudocapacitive nanostructured materials. PMID:27762284

Fabrication of hybrid supercapacitor based on rod-like HKUST-1@polyaniline as cathode and reduced graphene oxide as anode

NASA Astrophysics Data System (ADS)

Jafari, Elnaz Abbasi; Moradi, Morteza; Borhani, Saeed; Bigdeli, Hadise; Hajati, Shaaker

2018-05-01

Rod-like HKUST-1 (MOF-199) was hydrothermally synthesized, and the electrochemical capacitance properties of this MOF composited with polyaniline (PANI) were studied. The electrode was characterized by X-ray diffraction technique (XRD), Brunauer, Emmett, and Teller (BET) and scanning electron microscopy (SEM). The electrochemical performance of the HKUST-1 and PANI, as well as HKUST-1/PANI (HP) composite was investigated by cyclic voltammetry and galvanostatic charge-discharge. Pure HKUST-1 showed a low specific capacitance at a current density of 1 A/g, because of its poor conductivity. However, due to the high surface area (190 m2/g) of the rod-like HKUST-1, its composite with PANI led to an improvement in electrochemical performance. The specific capacitance of HP was achieved to be 270 F/g at the current density of 1 A/g, which is much higher than that of HKUST-1 (70 F/g) and PANI (227 F/g). An asymmetric supercapacitor (ASC) was fabricated by using the HP as cathode and rGO nanosheets as anode. This ASC provided a maximum specific power of 7497 W/kg and a specific energy of 6.22 Wh/kg with a wide working potential of 1.5 V and 87% capacity retention after 2000 cycles. Two ASCs connected in series were applied, which without recharging, lightened green and red LEDs up for 3 and 5 min, respectively.

Carbon aerogel-based supercapacitors modified by hummers oxidation method.

PubMed

Xu, Yuelong; Ren, Bin; Wang, Shasha; Zhang, Lihui; Liu, Zhenfa

2018-05-14

Carbon aerogels of an inter-connected three-dimensional (3D) structure are a potential carbon material for supercapacitors. We report a new oxidation modification method to prepare a series of modified carbon aerogels (OM-CA) by Hummers oxidation method. Oxidation-modified carbon aerogels (OM-CA) are obtained from carbon aerogel powders oxidized by Hummers method. Sulfuric acid stoichiometry is studied in order to investigate the effect of the surface oxygen group on surface area and electrochemical performance. Additionally, heteroatoms are doped into carbon aerogels in the oxidation process. The effect of heteroatom doping on electrochemical performance as a supercapacitor electrode material is investigated. When the amount of sulfuric acid is 40 wt%, the dopping manganese content is 0.9 mol%, the specific surface area of OM-CA is 450 m 2 /g, and its specific capacitance is 151 F g -1 at 0.5 A g -1 , which is achieved by heteroatom doping and texture properties. In addition, OM-CA composite supercapacitors exhibit a stable cycle life at a current density of 0.5 A g -1 and retain 98.0% of initial capacitance over 500 cycles, and OM-CA-40% still presents a higher capacity, up to 148 F g -1 at 0.5 A g -1 . The high specific surface area and specific capacitance suggest the porous carbon material has potential applications in supercapacitors. Copyright © 2018 Elsevier Inc. All rights reserved.

Biomass derived nitrogen-doped hierarchical porous carbon sheets for supercapacitors with high performance.

PubMed

Wang, Cunjing; Wu, Dapeng; Wang, Hongju; Gao, Zhiyong; Xu, Fang; Jiang, Kai

2018-08-01

A facile potassium chloride salt-locking technique combined with hydrothermal treatment on precursors was explored to prepare nitrogen-doped hierarchical porous carbon sheets in air from biomass. Benefiting from the effective synthesis strategy, the as-obtained carbon possesses a unique nitrogen-doped thin carbon sheet structure with abundant hierarchical pores and large specific surface areas of 1459 m 2  g -1 . The doped nitrogen in carbon framework has a positive effect on the electrochemical properties of the electrode material, the thin carbon sheet structure benefits for fast ion transfer, the abundant meso-pores provide convenient channels for rapid charge transportation, large specific surface area and lots of micro-pores guarantee sufficient ion-storage sites. Therefore, applied for supercapacitors, the carbon electrode material exhibits an outstanding specific capacitance of 451 F g -1 at 0.5 A g -1 in a three-electrode system. Moreover, the assembled symmetric supercapacitor based on two identical carbon electrodes also displays high specific capacitance of 309 F g -1 at 0.5 A g -1 , excellent rate capacity and remarkable cycling stability with 99.3% of the initial capacitance retention after 10,000 cycles at 5 A -1 . The synthesis strategy avoids expensive inert gas protection and the use of corrosive KOH and toxic ZnCl 2 activated reagents, representing a promising green route to design advanced carbon electrode materials from biomass for high-capacity supercapacitors. Copyright © 2018. Published by Elsevier Inc.

Ultrafine MnO2 Nanowire Arrays Grown on Carbon Fibers for High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Jiyu; Qian, Feng; Song, Guosheng; Li, Wenyao; Wang, Linlin

2016-10-01

Large-area ultrafine MnO2 nanowire arrays (NWA) directly grew on a carbon fiber (CF, used as a substrate) by a simple electrochemical method, forming three-dimensional (3D) hierarchical heterostructures of a CF@MnO2 NWA composite. As an electrode for supercapacitors, the CF@MnO2 NWA composite exhibits excellent electrochemical performances including high specific capacitance (321.3 F g-1 at 1000 mA g-1) and good rate capability. Further, the overall capacitance retention is 99.7 % capacitance after 3000 cycles. These outstanding electrochemical performances attribute to a large number of transport channels for the penetration of electrolyte and the transportation of ions and electrons of electrodes. The as-prepared CF@MnO2 NWA composite may be a promising electrode material for high-performance supercapacitors.