Facile fabrication of mesoporous manganese oxides as advanced electrode materials for supercapacitors

Mesoporous manganese oxides (MnO₂) were synthesized via a facile chemical deposition strategy. Three kinds of basic precipitants including sodium carbonate (Na₂CO₃), sodium bicarbonate (NaHCO₃), and sodium hydroxide (NaOH) were employed to adjust the microstructures and surface morphologies of MnO₂ materials. The obtained MnO₂ materials display different microstructures. Great differences are observed in their specific surface area and porosity properties. The microstructures and surface morphologies characteristics of MnO₂ materials largely determine their pseudocapacitive behavior for supercapacitors. The MnO₂ prepared with Na₂CO₃ precipitant exhibits the optimal microstructures and surface morphologies compared with the other two samples, contributing to their best electrochemical performances for supercapacitors when conducted either in the single electrode tests or in the capacitor measurements. The optimal MnO₂ electrode exhibits a high specific capacitance (173 F g^–1 at 0.25 A g^?1), high-rate capability (123 F g^?1 at 4 A g^?1), and excellent cyclic stability (no capacitance loss after 5,000 cycles at 1 A g^?1). The optimal activated carbon//MnO₂ hybrid capacitor exhibits a wide working voltage (1.8 V), high-power and high-energy densities (1,734 W kg^?1 and 20.9 Wh kg^?1), and excellent cycling behavior (93.8 % capacitance retention after 10,000 cycles at 1 A g^?1), indicating the promising applications of the easily fabricated mesoporous MnO₂ for supercapacitors.     

Ultrafine manganese dioxide nanowire network for high-performance supercapacitors

Ultrafine MnO(2) nanowires with sub-10 nm diameters have been synthesized by a simple process of hydrothermal treatment with subsequent calcinations to form networks that exhibit an enhanced specific capacitance (279 F g(-1) at 1 A g(-1)), high rate capability (54.5% retention at 20 A g(-1)) and good cycling stability (1.7% loss after 1000 cycles).     

Copper doped manganese dioxide as counter electrode for dye-sensitized solar cells

Many materials have been tried as the counter electrode (CE) material as a substitute to the noble metal Pt in dye-sensitized solar cells (DSSCs). The CE property is critical to the operation of a DSSC as it catalyzes the reduction of I₃^- ions and retrieves the electrons from the photoanode. Here we have explored the application of manganese dioxide (MnO₂) and copper-doped manganese dioxide (Cu-MnO₂) nanoparticles as CE candidates for DSSCs mainly as low-cost alternatives to Pt. A simple hydrothermal method was followed to synthesize α-MnO2 and Cu-MnO2 nanoparticles at a temperature of 140 °C for 14 h. The nanoparticles were characterized to prove its electrocatalytic abilities for DSSCs. DSSC devices fabricated with 10 wt% Cu-MnO₂ as CE showed the best V_OC of 781 mV, I_SC of 3.69 mA/cm², FF of 0.50, and %PCE of 1.7 whereas Pt as CE showed V_OC of 780 mV, I_SC of 14.8 mA/cm², FF of 0.43, and %PCE of 5.83 under 0.85 Sun. The low-cost feature of using Cu-MnO₂ is encouraging to further study the factors that can improve the efficiency of DSSCs with alternative CEs to conventional Pt electrodes.     

Self-assembly preparation of mesoporous hollow nanospheric manganese dioxide and its application in zinc-air battery

In this work, mesoporous manganese dioxide with novel hollow nanospheric structure was prepared by a facile, template-free self-assembly process at room temperature in a short period of time. The product was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that the as-prepared material has a special mesoporous hollow nanospheric morphology and a typical composition of γ-MnO₂. Polarization curve, chronoamperometry and Tafel plot tests demonstrate that this nanostructured material has high electrocatalytic activity for the reduction of dioxygen compared to commercial electrolytic MnO₂ (EMD). Electrochemical impedance spectroscopy that was analyzed by equivalent circuit shows that as-prepared MnO₂-catalysted air electrode has a small contact resistance and ohmic resistance, a low value of electrochemical polarization resistance. An all solid-state zinc-air cell has been fabricated with this material as electrocatalyst for oxygen electrode and potassium salt of cross-linked poly(acrylic acid) as an alkaline polymer gel electrolyte. The cell has a better discharge characteristic than that of the cell employing EMD at room temperature.     

A review of electrode materials for electrochemical supercapacitors

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).     

Self-standing rationally functionalized graphene as high-performance electrode materials for supercapacitors

Supercapacitors（SCs） have attracted much attention as one of the alternative energy devices due to their high power performance,long cycle life,and low maintenance cost.Graphene is considered as an innovative and promising material due to its large theoretical specific surface area,high electrical conductivity,good mechanical properties and chemical stability.Herein,we report an effective strategy for elaborately constructing rationally functionalized self-standing graphene（SG） obtained from giant graphene oxide（GGO） paper followed by an ultrarapid thermal-processing.This treatment results in both the exfoliation of graphene sheets and the reduction of GGO by elimination of oxygencontaining groups.The as-prepared SG electrode materials without additive and conducting agent provide an excellent combination of the electrical double layer capacitor（EDLC） and pseudocapacitor（PC） functions and exhibit superior electrochemical performance,including high specific capacitance,good rate capability and excellent cycling stability when investigated in three-electrode electrochemical cells.     

Partially carbonized tungsten oxide as electrode material for asymmetric supercapacitors

Journal of Solid State Electrochemistry - Synthesis of partially carbonized tungsten oxide employing a simple, one-step, and scalable in-situ reduction/carbonization process is reported along with...     

Pomegranate rind-derived activated carbon as electrode material for high-performance supercapacitors

In this paper, activated carbon materials were synthesized from pomegranate rind through carbonization and alkaline activation processes. The effects of pyrolytic temperature on the textual properties and electrochemical performance were investigated. The surface area of the activated carbon can reach at least 2200 m² g^?1 at different pyrolytic temperatures. It was found that, at the range of 600–900 °C, decreasing the carbonization temperature leads to the increase of t-plot micropore area, t-plot micropore volume, and capacitance. Further decreasing the carbonization temperature to 500 °C also leads to the increase of t-plot micropore area and t-plot micropore volume, but the capacitance is slightly poorer. The activated carbon carbonized at 600 °C and activated at 800 °C possesses very high specific area (2931 m² g^?1) and exhibits very high capacitance (～268 F g^?1 at 0.1 A g^?1 and ～242 F g^?1 at 1 A g^?1). There is no capacitance fading after 2000th cycle.     

PANI-PMMA as cathodic electrode material and its application in cathodic polarization antifouling

Cathodic voltage applied to metal substrata has been proven to exhibit useful antifouling properties due to the generation of H₂O₂, where the metal substratum is used as a cathode in the process. However, most metals immersed in a marine environment are protected by insulating (anticorrosive) coatings, restricting the cathodic polarization that can be applied to the metal. In this work, polyaniline-polymethyl methacrylate was found to have good stability and low background current density, as measured by linear sweep voltammetry (LSV), chronoamperometry (CA) and cyclic voltammetry (CV), suggesting potential for use of PANI-PMMA as a cathode material. The antifouling effects of the PANI-PMMA coating on 24-h-old Escherichia coli bacteria (E. coli) were measured under different cathodic potentials and different polarization times; the outstanding antifouling effect was verified by fluorescence microscopy.     

A new selenite selective membrane electrode and its application

A new membrane ion selective electrode sensitive to selenite ion has been developed. The electrode consisted of 1,2-phenylenediamine selen complex PIS (piaselenol) as the active material, PVC or SR (silicon rubber) as membrane matrix and DBF (dibutylphtalate) as plasticizer. This electrode showed linear response for selenite ion in the 10(-5)-10(-1)M concentration range. The slope of the linear portion was 21 mV/10-fold change in selenite concentration. The effect of membrane composition and membrane thickness on electrode response was studied and the electrode which contains 2% PIS, 49% PVC and 49% DBF was found to be the most sensitive one to selenite. The slope of the electrode did not change for 2 months and the pH change did not affect the response of the electrode in pH range of 3-9. The interferences of SO(4)(2-), SO(3)(2-), S(2-), HPO4(2-), CI(-), Br(-), and I(-) are investigated and while no interference was observed for SO(4)(2-), SO(3)(2-), S(2-) and I(-), a very small interference was observed for CI(-) and Br(-). The selenium present in anodic slime is determined using this electrode.     

Nickel metal-organic framework nanoparticles as electrode materials for Li-ion batteries and supercapacitors

Journal of Solid State Electrochemistry - Nickel-based metal-organic framework ([Ni(4,4′-bpy)(tfbdc)(H2O)2], Ni-MOF) nanoparticles with the size of 45–250 nm were synthesized...     

PPy doped with different metal sulphate as electrode materials for supercapacitors

A facile approach has been established to prepare PPy via in situ polymerization with different metal sulfate as dopants. The morphology and structure of PPy and doped PPy were characterized by scanning electron microscopy (SEM) and fourier transform infrared (FT-IR). It was found that doped PPy has different morphology and a slight structure change. The electrochemical performance of the samples has been illustrated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and AC impedance measurements. Compared with the PPy, the specific capacitance of PPy/Cu²⁺ has been improved to 224 F g^–1 at the current density of 0.6 A g^–1. Also, the relationship between electrochemical properties of doped PPy and various parameters of metal ions has been investigated.     

Organic acid doped polythiophene nanoparticles as electrode material for redox supercapacitors

An organic acid doped electronically conducting polymer nanomaterial, polythiophene‐tartaric acid (PTh‐TA) nanoparticles, was prepared by cationic surfactant‐assisted dilute polymerization method. The physical properties of the synthesized polymer were characterized by FT‐IR, UV‐visible spectroscopy, X‐ray diffraction, SEM, and electrical conductivity studies. The symmetric type redox supercapacitor performances were studied in PVdF‐HFP in 1 M LiPF₆ containing EC&PC (1:1 v/v) based microporous polymer electrolyte. The specific capacitance of the capacitor was found to be 156 F g^?1. The energy and power densities were calculated as 14 Wh kg^?1 and 522 W kg^?1, respectively. The value of capacitance was found to be almost stable up to 1000 cycles and even more. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical performance of NaCo2O4 as electrode for supercapacitors

Sub-micron-scaled sodium cobalt oxide （NaCo2O4） powders are prepared by a solid-state reaction method. Characterization using X-ray diffraction indicates that the synthesized NaCo2O4 has a hexagonal layered structure. The electrochemical performance of the NaCo2O4 electrodes is investigated using cyclic voltarnmetry and galvanostatic charge/discharge in NaOH solution. The results show that the specific capacitance of the NaCo2O4 electrode reaches 337 F/g over the potential range of 0.15-0.65 V at a mass normalized current of 50 mA/g. Moreover, NaCo2O4 exhibits very good stability and cycling performance as a supercapacitor material.     

Carbon aerogels with modified pore structures as electrode materials for supercapacitors

Carbon aerogels (CA) with uniform pore structures were prepared by the polycondensation of phloroglucinol, resorcinol, and formaldehyde, using carboxylated chitosan as a soft template. The CA were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and surface area analysis. When carboxylated chitosan was added, the time for wet gel formation was reduced by 60%, and the CA showed a more uniform pore structures. The electrochemical performance of the CA was measured in a three-electrode electrochemical cell. The CA prepared with added carboxylated chitosan showed lower charge transfer resistance on the electrode surface, and the specific capacitances were also enhanced, showing a specific capacitance as high as 135 F/g at a resorcinol-to-carboxylated chitosan mass ratio of 250:1 at a current density of 0.5 A/g. This specific capacitance is much higher than that of the CA without carboxylated chitosan. The capacitance retention under increasing discharge current density was also enhanced by the addition of carboxylated chitosan. The electrochemical performance of the CA in different electrolytes (1 M LiOH, 1 M NaOH, 1 M KOH, 3 M KOH, 6 M KOH, and 9 M KOH) was investigated. The results show that the electrochemical performance in 6 M KOH was better than those in other electrolytes.     

3D石墨烯基气凝胶的制备及在超级电容器中的应用

超级电容器作为一种新型的能源存储装置,由于其较高的功率密度、优良的充放电特性、超长的循环寿命,使其在移动电源,新能源汽车等众多领域具有非常广泛的应用前景.3D石墨烯基气凝胶具有多孔结构、大的比表面积、高的导电率、优异的机械性能和电子传输能力,它一直被认为是超级电容器的理想电极材料.本文综述了3D石墨烯基气凝胶的制备方法...     

Microwave-assisted synthesis of Fe-doped NiMnO3 as electrode material for high-performance supercapacitors

Journal of Solid State Electrochemistry - Fe-doped NiMnO3 nanosheet electrode material was successfully synthesized by convenient and efficient microwave-assisted hydrothermal method. The crystal...     

Ni/Co-based metal-organic frameworks as electrode material for high performance supercapacitors

A novel bimetallic Ni/Co-based metal-organic framework (Ni/Co-MOF) was successfully synthesized via a simple solvothermal method, which used as electrode material for high performance supercapacitors.