The effect of dip time variations on electrochemical performance of polypyrrole (PPy)-copper hydroxide hybrid thin-film electrodes was studied well in depth. Synthesis was carried out using a successive ionic layer adsorption and reaction (SILAR) method via an aqueous route, using 0.1 M pyrrole, 0.1 M Cu(NO3)2, and H2O2. The electrochemical analysis was made by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) image of optimized electrode shows nanolamellae-like structures. The characteristic peak observed in Fourier transform infrared (FTIR) analysis at 1558 cm?1 validates the existence of PPy in hybrid electrode material, while the peaks observed at 21.5° and 44.5° in X-ray diffraction (XRD) patterns are evidence for triclinic Cu(OH)2. The observed maximum values of specific capacitance (SC), specific power (SP), specific energy (SE), and coulombic efficiency (η) of the optimized electrode are 56.05 F/g, 10.48 Wh/kg, 11.11 kW/kg, and 46.47%, respectively. For originality and value, the SILAR synthesis of PPy-Cu(OH)2 hybrid thin-film electrodes was carried out for the very first time. Synthesized electrodes showed improved surface structures and electrochemical stability than the pristine PPy electrodes which are necessary for the supercapacitive applications.
Electrochemical behavior of poly-3,4-ethylenedioxythiophene composites with manganese dioxide (PEDOT/MnO2) has been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance at various component ratios and in different electrolyte solutions. The electrochemical formation of PEDOT film on the electrode surface and PEDOT/MnO2 composite film during the electrochemical deposition of manganese dioxide into the polymer matrix was gravimetrically monitored. The mass of manganese dioxide deposited into PEDOT at different time of electrodeposition and apparent molar mass values of species involved into mass transfer during redox cycling of PEDOT/MnO2 composites were evaluated. It was found that during the redox cycling of PEDOT/MnO2 composite films with various MnO2 content, the oppositely directed fluxes of counterions (anions and cations) occur, resulting in a change of the slope of linear parts of the Δf–E plots with changing the mass fraction of MnO2 in the composite film.Rectangular shape of cyclic voltammograms of PEDOT/MnO2 composites with different loadings of manganese dioxide was observed, which is characteristic of the pseudocapacitive behavior of the composite material. Specific capacity values of PEDOT/MnO2 composites obtained from cyclic voltammograms were about 169 F g?1. The specific capacity, related to the contribution of manganese dioxide component, was about 240 F g?1. 相似文献
Herein, we introduce a facile, inexpensive and fast, and additive-/template-free method to fabricate highly stable nickel hydroxide nanofibers for supercapacitor applications. Ni(OH)2 nanofibers were electrodeposited on electro-etched carbon fiber paper by a potential step method (Ni(OH)2-ECFs) and characterized using scanning electron microscopy and X-ray diffraction analysis. Electrochemical performance of Ni(OH)2-ECF was studied in symmetric two-electrode assembly by cyclic voltammetry, galvanostatic charge–discharge method, and electrochemical impedance spectroscopy. A specific capacitance of 277.5 F g?1 was achieved for the symmetric supercapacitor based on two identical Ni(OH)2-ECFs. Our findings demonstrate high-rate capability with excellent stability (approximately 100 % capacitance retention) for Ni(OH)2-ECF supercapacitor, originated from the intimate contact between Ni(OH)2 and ECF. Our studies suggest the Ni(OH)2-ECF electrode as an excellent material for supercapacitor applications. 相似文献
Sn-doped Li-rich layered oxides of Li1.2Mn0.54-xNi0.13Co0.13SnxO2 have been synthesized via a sol-gel method, and their microstructure and electrochemical performance have been studied. The addition of Sn4+ ions has no distinct influence on the crystal structure of the materials. After doped with an appropriate amount of Sn4+, the electrochemical performance of Li1.2Mn0.54-xNi0.13Co0.13SnxO2 cathode materials is significantly enhanced. The optimal electrochemical performance is obtained at x = 0.01. The Li1.2Mn0.53Ni0.13Co0.13Sn0.01O2 electrode delivers a high initial discharge capacity of 268.9 mAh g?1 with an initial coulombic efficiency of 76.5% and a reversible capacity of 199.8 mAh g?1 at 0.1 C with capacity retention of 75.2% after 100 cycles. In addition, the Li1.2Mn0.53Ni0.13Co0.13Sn0.01O2 electrode exhibits the superior rate capability with discharge capacities of 239.8, 198.6, 164.4, 133.4, and 88.8 mAh g?1 at 0.2, 0.5, 1, 2, and 5 C, respectively, which are much higher than those of Li1.2Mn0.54Ni0.13Co0.13O2 (196.2, 153.5, 117.5, 92.7, and 43.8 mAh g?1 at 0.2, 0.5, 1, 2, and 5 C, respectively). The substitution of Sn4+ for Mn4+ enlarges the Li+ diffusion channels due to its larger ionic radius compared to Mn4+ and enhances the structural stability of Li-rich oxides, leading to the improved electrochemical performance in the Sn-doped Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials. 相似文献
Due to the high specific capacities and environmental benignity, lithium-sulfur (Li-S) batteries have shown fascinating potential to replace the currently dominant Li-ion batteries to power portable electronics and electric vehicles. However, the shuttling effect caused by the dissolution of polysulfides seriously degrades their electrochemical performance. In this paper, Mn2O3 microcubes are fabricated to serve as the sulfur host, on top of which Al2O3 layers of 2 nm in thickness are deposited via atomic layer deposition (ALD) to form Mn2O3/S (MOS) @Al2O3 composite electrodes. The MOS@Al2O3 electrode delivers an excellent initial capacity of 1012.1 mAh g?1 and a capacity retention of 78.6% after 200 cycles at 0.5 C, and its coulombic efficiency reaches nearly 99%, giving rise to much better performance than the neat MOS electrode. These findings demonstrate the double confinement effect of the composite electrode in that both the porous Mn2O3 structure and the atomic Al2O3 layer serve as the spacious host and the protection layer of sulfur active materials, respectively, for significantly improved electrochemical performance of the Li-S battery. 相似文献
Direct hydrocarbon type solid oxide fuel cells are attractive from simple gas feed process and also high energy conversion efficiency. In this study, La0.5Sr0.5MnO3 (LSM55) perovskite oxide was studied as oxide anode for direct hydrocarbon type solid oxide fuel cell (SOFC). Although reasonable power density like 1 W/cm2 and open circuit voltage (OCV) (1.1 V) at 1273 K was exhibited when H2 was used as fuel, the power density as well as OCV of the cell using LSM55 for anode was significantly decreased when dry C3H8 was used for fuel. After power generation measurement, LSM55 phase was decomposed to MnO and La2MnO4. Effects of various dopants to Mn site in LSM55 were studied and it was found that partial substitution of Mn in LSM55 with other cation, especially transition metal, is effective for increasing maximum power density. In particular, reasonable high power density can be achieved on the cell using Ni-doped LSM55 for anode. On the other hand, Al substitution is effective for increasing stability against reduction and so, dopant effects of Al were studied in more details for dry C3H8 fuel. The power density as well as OCV increased with increasing Al content and the highest power density was achieved at x = 0.4 in La0.5Sr0.5Mn1 ? xAlxO3. Among the examined composition, it was found that the cell using La0.5Sr0.5Mn0.6Al0.4O3 anode shows the largest power density (0.2 W/cm2) at 1173 K and high OCV (1.01 V) against dry C3H8 fuel. 相似文献
Two kinds of electrode materials Ni(OH)2 and Ni(OH)2@Zn(OH)2 composite are fabricated on nickel foam. Electrochemical experiments indicate Ni(OH)2@Zn(OH)2 composite deserves further study due to high specific capacitance and good cycle stability, so that it can achieve energy storage and conversion as much as possible. When the hydrothermal time is different, the electrochemical performance of the sample is also different. Accurately, samples can obtain better electrochemical performance at 15 h, and the maximum specific capacitance of Ni(OH)2@Zn(OH)2 is 7.87 F cm?2 compared to Ni(OH)2 (0.61 F cm?2) at 5 mA cm?2. Even at 50 mA cm?2, specific capacitance is 5.24 F cm?2 and rate capability is 66.6%. Furthermore, Ni(OH)2@Zn(OH)2-15 h loses 19.8% after 1000 cycles, revealing the composite has an outstanding stable cycle. These properties also indicate Ni(OH)2@Zn(OH)2-15 h is a promising electrode material. 相似文献
In-situ polymerization of pyrrole was carried out with strontium arsenate (ceramics) in the existence of oxidizing agent ammonium persulphate to synthesize polypyrrole/strontium arsenate composites by chemical oxidation method. The polypyrrole/strontium arsenate composites were synthesized with various compositions viz., 10 to 50 wt % of strontium arsenate was placed in polypyrrole. The surface morphologies of these composites were analyzed using Scanning Electron Microscopy (SEM) which confirmed the embedment of strontium arsenate particles in PPy chain. The Fourier Transform Infra-Red spectra (FTIR) revealed the shift of lengthens frequencies towards elevated frequency area. The powder X-ray diffraction patterns (XRD) disclosed the crystalline behavior exhibition of the composites. Thermographs of thermal analysis (TG/DTA) exposed the stronger stability of polypyrrole/strontium arsenate composites than PPy. D.C. conductivity reveals that, the strontium arsenate concentration in polypyrrole is accountable for the variant of conductivity of the composites. The results of the study signify the increment of D.C. conductivity for 40 wt % of strontium arsenate in polypyrrole. The temperature reliant conductivity dimension shows the thermally activated exponential behavior of PPy/Sr3(AsO4)2 composites. The reduction in electrical resistance was experienced, when the polymer composites were bare to the wide range of relative humidity (Rh) (from 30 to 95%). This reduce is due to enhance in surface electrical conductivity ensuing from humidity fascination and also due to capillary abridgment of water causing change in conductivity within the sensing materials. The composite shows sensitivity in the range 30 to 95% Rh, we also studied response and recovery time. 相似文献
The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide (LVP/N-RGO) composite was prepared by a facile one-pot hydrothermal method and evaluated as cathode material for lithium-ion batteries. It is clearly seen that the novel porous structure of the as-prepared LVP/N-RGO significantly facilitates electron transfer and lithium-ion diffusion, as well as markedly restrains the agglomeration of Li3V2(PO4)3 (LVP) nanoparticles. The introduction of N atom also has positive influence on the conductivity of RGO, which improves the kinetics of electrochemical reaction during the charge and discharge cycles. It can be found that the resultant LVP/N-RGO composite exhibits superior rate properties (92 mA h g?1 at 30 C) and outstanding cycle performance (122 mA h g?1 after 300 cycles at 5 C), indicating that nitrogen-doped RGO could be used to improve the electrochemical properties of LVP cathodes for high-power lithium-ion battery application.
Graphical abstract The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide composite with significantly accelerating electron transfer and lithium-ion diffusion exhibits superior rate property and outstanding cycle performance.
Nb-doped cathode materials with the formula Li(Ni0.7Mn0.3)1?xNbxO2 (x?=?0, 0.01, 0.02, 0.03, 0.04) have been prepared successfully by calcining the mixtures of LiOH·H2O, Nb2O5, and Ni0.7Mn0.3(OH)2 precursor formed through a simple continuous co-precipitation method. The effects of Nb substitution on the crystal structure and electrochemical properties of LiNi0.7Mn0.3O2 were studied systematically by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and various electrochemical measurements. The results show that the lattice parameters of the Nb substitution LiNi0.7Mn0.3O2 samples are slightly larger than that of pure LiNi0.7Mn0.3O2, and the basic α-NaFeO2 layered structure does not change with the Nb doping. What’s more, better morphology, lower resistance, and good cycle stability were obtained after Nb substitution. In addition, CV test exhibits that Nb doping results in lower electrode polarization and XPS results indicate that the valence of Mn kept constant but the component of Ni3+ decreased after doping. All the results indicate that Nb doping in LiNi0.7Mn0.3O2 is a promising method to improve the properties of Ni-rich lithium-ion batteries positive-electrode materials. 相似文献
A facile and green electrochemical method for the fabrication of three‐dimensional porous nitrogen‐doped graphene (3DNG) modified electrode was reported. This method embraces two consecutive steps: First, 3D graphene/polypyrrole (ERGO/PPy) composite was prepared by electrochemical co‐deposition of graphene and polypyrrole on a gold foil. Subsequently, the ERGO/PPy composite modified gold electrode was annealed at high temperature. Thus 3DNG modified electrode was obtained. Scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to characterize the structure and morphology of the electrode. The electrode exhibits excellent electroanalytical performance for the reduction of hydrogen peroxide (H2O2). By linear sweep voltammetric measurement, the cathodic peak current was linearly proportional to H2O2 concentration in the range from 0.6 μM to 2.1 mM with a sensitivity of 1.0 μA μM−1 cm−2. The detection limit was ascertained to be 0.3 μM. The anti‐interference ability, reproducibility and stability of the electrode were carried out and the electrode was applied to the detection of H2O2 in serum sample with recoveries from 98.4 % to 103.2 %. 相似文献
A porous, hollow, microspherical composite of Li2MnO3 and LiMn1/3Co1/3Ni1/3O2 (composition: Li1.2Mn0.53Ni0.13Co0.13O2) was prepared using hollow MnO2 as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g?1 at a specific current of 25 mA g?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g?1 was obtained for this composite at a specific current of 1000 mA g?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature.
Mn3O4 and Mn3O4 (140)/CNTs have been investigated as high-capacity anode materials for lithium-ion batteries (LIBs) applications. Nanoparticle Mn3O4 samples were synthesized by hydrothermal method using Mn(Ac)2 and NH3·H2O as the raw materials and characterized by XRD, TG, EA, TEM, and SEM. Its electrochemical performances, as anode materials, were evaluated by galvanostatic discharge-charge tests. The Mn3O4 (140)/CNTs displays outstanding electrochemical performances, such as high initial capacity (1942 mAh g?1), stable cycling performance (1088 mAh g?1 and coulombic efficiency remain at 97% after 60 cycles) and great rate performance (recover 823 mAh g?1 when return to initial current density after 44 cycles). Compared to pure Mn3O4 (140), the improving electrochemical performances can be attributed to the existence of very conductive CNTs. The Mn3O4 (140)/CNTs with excellent electrochemical properties might find applications as highly effective materials in electromagnetism, catalysis, microelectronic devices, etc. The process should also offer an effective and facile method to fabricate many other nanosized metallic oxide/CNTs nanocomposites for low-cost, high-capacity, and environmentally benign materials for LIBs. 相似文献
In this study, novel ternary synthesis of reduced graphene oxide (rGO) sheets via intercalation of Ag nanoparticles (Ag) and polypyrrole (PPy) was obtained for supercapacitor evaluations. The synthesis procedure of nanocomposite is simple, cheap, and ecologically friendly. The nanocomposites were analyzed by Fourier transform infrared-attenuated transmission reflectance (FTIR-ATR) and scanning electron microscopy-energy dispersion X-ray analysis (SEM-EDX). In addition, electrochemical performances of electrode active materials (rGO/Ag/PPy) of the samples were tested by means of galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The highest specific capacitance and energy density of rGO/Ag/PPy nanocomposite were obtained as Csp = 1085.22 F/g and E = 36.92 Wh/kg for [rGO]o/[Py]o = 1/5 at 4 mV/s in 1 M H2SO4 solution. Under the optimized preparation conditions in different initial feed ratios ([rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10) of rGO/Ag/PPy, nanocomposites acquired a high Coulombic efficiency, and a retention of 66% of its initial capacitance for [rGO]o/[Py]o = 1/10 after 1000 cycles. GCD and EIS measurements of rGO/Ag/PPy nanocomposite electrode active material allowed for supercapacitor applications. 相似文献
Lithium–sulfur (Li–S) battery is considered as a promising option for electrochemical energy storage applications because of its low-cost and high theoretical capacity. However, the practical application of Li–S battery is still hindered due to the poor electrical conductivity of S cathode and the high dissolution/shuttling of polysulfides in electrolyte. Herein, we report a novel physical and chemical entrapment strategy to address these two problems by designing a sulfur–MnO2@graphene (S–MnO2@GN) ternary hybrid material structure. The MnO2 particles with size of ~ 10 nm are anchored tightly on the wrinkled and twisted GN sheets to form a highly efficient sulfur host. Benefiting from the synergistic effects of GN and MnO2 in both improving the electronic conductivity and hindering polysulfides by physical and chemical adsorptions, this unique S–MnO2@GN composite exhibits excellent electrochemical performances. Reversible specific capacities of 1416, 1114, and 421 mA h g?1 are achieved at rates of 0.1, 0.2, and 3.2 C, respectively. After a 100 cycle stability test, S–MnO2@GN composite cathode could still maintain a reversible capacity of 825 mA h g?1. 相似文献
Porous network-like MnO2 thick films are successfully synthesized on a flexible stainless steel (SS) mesh using a simple and low-cost electrodeposition method followed by an electrochemical activation process. Morphology, chemical composition, and crystal structure of the prepared electrodes before and after the activation process are determined and compared by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The results show that the implementation of the electrochemical activation process does not change the chemical composition and crystal structure of the films, but it influences the surface morphology of the MnO2 thick layer to a flaky nanostructure. Based on the electrochemical data analysis, the maximum specific capacitance of 1400 mF (381 F g?1) and 3700 mF (352 F g?1) are measured for small (2.6 cm2) and large (10 cm2) surface area electrodes, respectively. In addition, a flexible symmetric MnO2//MnO2 solid-state supercapacitor shows a capacitance of 0.3 F with about 98% retention at different bending angles from 0 to 360°. 相似文献
The large internal surface areas and outstanding electrical and mechanical properties of graphene have prompted to blend graphene with NiCo2O4 to fabricate nanostructured NiCo2O4/graphene composites for supercapacitor applications. The use of graphene as blending with NiCo2O4 enhances the specific capacitance and rate capability and improves the cyclic performance when compared to the pristine NiCo2O4 material. Here, we synthesized two different nanostructured morphologies of NiCo2O4 on graphene sheets by solvothermal method. It has been suggested that the morphologies of oxides are greatly influenced by dielectric constant, thermal conductivity, and viscosity of solvents employed during the synthesis. In order to test this concept, we have synthesized nanostructured NiCo2O4 on graphene sheets by facile solvothermal method using N-methyl pyrrolidone and N,N-dimethylformamide solvents with water. We find that mixture of N-methyl pyrrolidone and water solvent favored the formation of nanonet-like NiCo2O4/graphene (NiCoO-net) whereas mixture of N,N-dimethylformamide and water solvent produced microsphere-like NiCo2O4/graphene (NiCoO-sphere). Electrochemical pseudocapacitance behavior of the two NiCo2O4/graphene electrode materials was studied by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy techniques. The supercapacitance measurements on NiCoO-net and NiCoO-sphere electrodes showed specific capacitance values of 1060 and 855 F g?1, respectively, at the current density of 1.5 A g?1. The capacitance retention of NiCoO-net electrode is 93 % while that of NiCoO-sphere electrode is 77 % after long-term 5000 charge-discharge cycles at high current density of 10 A g?1. 相似文献
A series of Ce–MnOx/TiO2 catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3 at temperatures ranging from 353 to 473 K. The 0.07Ce–MnOx/TiO2 catalyst showed the highest activity and best resistance to SO2 poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H2-temperature-programmed reduction (TPR), and NH3-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnOx/TiO2 catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO2 poisoning resistance of the 0.07Ce–MnOx/TiO2 catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnOx. In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH3 and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism. 相似文献
A polypyrrole/molybdenum trioxide/graphene nanoribbon (PPy/MoO3/GNR) ternary nanocomposite was successfully synthesized via an in situ method. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses show that MoO3 was successfully combined with the GNRs. The one-dimensional morphology was observed using field emission scanning electron microscopy and transmission electron microscopy. The electrochemical tests show that the PPy/MoO3/GNR ternary nanocomposite exhibits the highest specific capacitance (844 F g?1) among the investigated materials and exhibits good cycling stability for 1000 cycles. These results collectively demonstrate that the combination of each component can efficiently increase the specific capacitance and cycling stability. As such, the method reported herein represents a promising approach for fabricating supercapacitor electrode materials. 相似文献
The authors report on the fabrication of Co(OH)2-enfolded Cu2O nanocubes on reduced graphene oxide (rGO), and the use of this material in an electrochemical caffeine sensor. The rGO/Cu2O/Co(OH)2 composite was characterized by X-ray powder diffraction pattern analysis, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. A rotating disc glassy carbon electrode covered with the nanocomposite displays enhanced electrocatalytic activity towards the electro-oxidation of caffeine. The peak oxidation potential is at 1.4 V (vs. Ag/AgCl) and hence is strongly shifted to the negative side when compared to other modified electrodes. The calibration plot is linear in the 0.83 to 1200 μM concentration range, with a 0.4 μM detection limit (at a signal-to-noise ratio of 3). The modified electrode is sensitive, selective and stable. It was successfully applied to the determination of caffeine in (spiked) caffeine-containing beverages and coffee powder and gave recoveries that ranged from 95.7 to 98.3 %.
