Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.     

Preparation and electrochemical performance of activated carbon thin films with polyethylene oxide-salt addition for electrochemical capacitor applications

The effect of polymer–salt addition in the activated carbon electrode for electric double-layer capacitor (EDLC) has been investigated. A series of composite thin film electrode consisting of activated carbon, carbon black, polytetrafluoroethylene and polymer–salt complex (polyethyleneoxide–LiClO₄) with an appropriate weight ratio were prepared and examined their performance for EDLCs using 1 mol L⁻¹ LiClO₄ in ethylene carbonate:diethylcarbonate electrolyte solution. The electrochemical capacitance performances of these electrodes with different compositions were characterized by cyclic voltammetry, galvanostatic charge–discharge cycling, and AC impedance measurements. By comparison, the best results were obtained with a composite electrode rich in polymer–salt additive (132 F g⁻¹ at 100 mA g⁻¹ of galvanostatic experiment). In general, the polymer–salt-containing electrode had shown improved performance over activated carbon electrodes without polymer–salt at high current density.     

Synthesis and characterization of mesoporous nickel oxide for electrochemical capacitor

A mesoporous electrochemical active material NiO with face center cubic structure has been synthesized using supramolecular as template and urea as hydrolysis-controlling agent. The synthesized product was characterized physically by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller-specific surface area measurement. Electrochemical characterization was performed using cyclic voltammetry and chronopotentiometry in 6 mol/l KOH aqueous solution electrolyte. A specific capacitance of approximately 327 F/g was obtained by annealing the sample at 350 °C. To get a better understanding of the effect of supramolecular template on improving the structure property and electrochemical performance, a compared experiment was also carried out in this work.     

Electrolytic nickel sulfide in a model electrochemical capacitor

Operation of an electrode made of electrolytic nickel sulfide in a prototype electrochemical capacitor with potassium hydroxide solutions of various concentrations was studied by cyclic voltammetry.     

Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

With MnSO₄, NaOH and K₂S₂O₈ as the raw materials, the amorphous and δ-type manganese dioxide (MnO₂) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge–discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO₂ reaches to 301.2 F g⁻¹ at a current density of 200 mA g⁻¹ and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g⁻¹ and 71% of the δ-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO₂ should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi₂O₃ is coated on the amorphous MnO₂, its specific capacitance increases to 352.8 F g⁻¹ and the capacitance retention rate is 90% after 2000 cycles.     

Lithium manganese spinel materials for high-rate electrochemical applications

In order to successively compete with supercapacitors, an ability of fast discharge is a must for lithium-ion batteries. From this point of view, stoichiometric and substituted lithium manganese spinels as cathode materials are one of the most prospective candidates, especially in their nanosized form. In this article, an overview of the most recent data regarding physico-chemical and electrochemical properties of lithium manganese spinels, especially, LiMn2O4 and LiNi0.5Mn1.5O4, synthesized by means of various methods is presented, with special emphasis of their use in high-rate electrochemical applications. In particular, specific capacities and rate capabilities of spinel materials are analyzed. It is suggested that reduced specific capacity is determined primarily by the aggregation of material particles, whereas good high-rate capability is governed not only by the size of crystallites but also by the perfectness of crystals. The most technologically advantageous solutions are described, existing gaps in the knowledge of spinel materials are outlined, and the ways of their filling are suggested, in a hope to be helpful in keeping lithium batteries afloat in the struggle for a worthy place among electrochemical energy systems of the 21st century.     

Immunosensor based on carbon nanotube/manganese dioxide electrochemical tags

This article reports on carbon nanotube/manganese dioxide (CNT–MnO₂) composites as electrochemical tags for non-enzymatic signal amplification in immunosensing. The synthesized CNT–MnO₂ composites showed good electrochemical activity, electrical conductivity and stability. The electrochemical signal of CNT–MnO₂ composites coated glassy carbon electrode (GCE) increased by nearly two orders of magnitude compared to bare GCE in hydrogen peroxide (H₂O₂) environment. CNT–MnO₂ composite was subsequently validated as electrochemical tags for sensitive detection of α-fetoprotein (AFP), a tumor marker for diagnosing hepatocellular carcinoma. The electrochemical immunosensor demonstrated a linear response on a log-scale for AFP concentrations ranging from 0.2 to 100 ng mL⁻¹. The limit of detection (LOD) was estimated to be 40 pg mL⁻¹ (S/N = 3) in PBS buffer. Further measurements using AFP spiked plasma samples revealed the applicability of fabricated CNT–MnO₂ composites for clinical and diagnostic applications.     

Cathodic electrophoretic deposition of manganese dioxide films

Cathodic electrophoretic deposition (EPD) method has been developed for the deposition of manganese dioxide films. It was shown that phosphate ester (PE) is an effective charging additive, which provides stabilization of manganese dioxide nanoparticles in suspensions. The influence of PE concentration and deposition voltage on the deposition efficiency has been studied. EPD has been utilized for the fabrication of porous nanostructured films with thickness in the range of 0.5–20 μm for application in electrochemical supercapacitors (ES). Cyclic voltammetry and chronopotentiometry data for the films tested in the 0.1 M Na₂SO₄ solutions showed capacitive behavior in the voltage window of 1 V. The highest specific capacitance (SC) of 377 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹. The SC decreased with increasing film thickness and increasing scan rate in the range of 2–100 mV s⁻¹. The deposition mechanism, kinetics of deposition and charge storage properties of the films are discussed.     

Preparation of hexagonal nanoporous nickel hydroxide film and its application for electrochemical capacitor

Nanoporous nickel hydroxide film has been successfully electrodeposited on titanium substrate from nickel nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Low-angle X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies show that the film has a regular nanostructure consisting of a hexagonal array of cylindrical pores with a repeat center-to-center spacing of about 7 nm. Preliminary electrochemical studies are carried out using cyclic voltammetry (CV) and chronopotentiometry technology. A maximum specific capacitance of 578 F g⁻¹ could be achieved for the nanoporous Ni(OH)₂ film electrode, suggesting its potential application in electrochemical capacitors.     

Synthesis and electrochemical characterization of carbon nanotubes decorated with nickel nanoparticles for use as an electrochemical capacitor

Attachment of nickel nanoparticles on multiwalled carbon nanotubes (MWCNTs) was conducted to explore the influence of Ni loading on the electrochemical capacitance of MWCNT electrodes. A chemical impregnation leaded to homogeneously disperse Ni particles onto the surface of MWCNTs, and the Ni particles were found to be an average size of 30–50 nm. The capacitive behavior of the MWCNT electrodes was investigated in 6 M KOH, by using cyclic voltammetry (CV), charge–discharge cycling, and ac electrochemical impedance spectroscopy. CV measurements showed that the Faradaic current was found to increase with the Ni coverage, indicating that the presence of Ni would enhance the pseudocapacitance through the redox process. Equivalent circuit analysis indicated that both of electrical connection and charge transfer resistances accounted for the major proportion of the overall resistance and were found to decrease with the amount of nickel. A linearity relationship between the total capacitance and the Ni population reflected that each Ni particle exhibits an identical electrochemical activity in enhancing the electrochemical capacitance. The overall electrochemical capacitance (including double layer capacitance and pseudocapacitance) of Ni-MWCNT electrode can reach a maximum of 210 F/g over 500 cycles.     

Ultrathin CoNi-layered double hydroxide grown on nickel foam as high-performance current collector for lithium-sulfur batteries

Journal of Solid State Electrochemistry - This work designed and synthesized a novel cobalt-nickel-layered double hydroxide flake grown on nickel foam (CoNi LDH@NF) as a high-performance current...     

Lithium manganese oxide with excellent electrochemical performance prepared from chemical manganese dioxide for lithium ion batteries

Chemical manganese dioxide (CMD) is synthesized by the SEDEMA process and adopted as a precursor for lithium manganese oxide with a spinel structure (LMO). LMO is also prepared from electrolytic manganese dioxide (EMD) as a reference for comparison. X-ray diffraction (XRD) shows that CMD is composed of γ-MnO₂, and scanning electron microscopy (SEM) with transmission electron microscopy (TEM) shows that the nanorods cover a spherical core with a diameter < 1 μm. The LMO prepared from CMD shows a much better rate capability and cycle life performance than that from EMD at high temperatures and high current densities. The excellent electrochemical performance is attributed to the structural stability during charge and discharge and the morphology of the LMO, a loose aggregation of the octahedral particles with a uniform size (<1 μm) and shape, which originated from that of CMD.     

Porous cobalt hydroxide film electrodeposited on nickel foam with excellent electrochemical capacitive behavior

A new porous cobalt hydroxide film has been successfully electrodeposited on nickel foam from 0.1?M cobalt nitrate electrolyte at ?1.0?V vs. SCE without adding any surfactant. The microstructure and surface morphology of prepared cobalt hydroxide films were physically characterized by X-ray diffraction analysis and scanning electron microscopy. The results indicate that an interlaced network structure was obtained. The effects of electrodeposition time, deposition potential, and different substrates on the specific capacitance and microstructure of prepared porous ??-Co(OH)₂ thin film were systematically studied. The results indicate that the film deposited on nickel foam at ?1.0?V has excellent electrochemical properties. A maximum specific capacitance of 1473?F?g^?1 could be achieved at a current density of 2?A?g^?1.     

X-ray photoelectron spectroscopy of thermally grown silicon dioxide films on silicon

At various stages of in situ thermal oxidation of Si(111) monocrystals, X-ray photoelectron spectroscopy (XPS or ESCA) reveals a shift in the silicon core-level binding energies which varies continuously from 2.4 to 4.2 eV. From the oxygen and silicon ESCA peak intensities, these films can be said to have the silicon dioxide composition with an excess in oxygen concentration. By correlating the silicon 2p or 2s binding-energy shifts with oxygen KLL Auger energy and oxygen 1s binding-energy shifts, it is shown that a Fermi level shift and differential extra-atomic relaxation energy in the interfacial region must be invoked, in addition to chemical structure considerations, to interpret these data.     

Modification and characterization of thin polymer films for electrochemical applications

Proton-conducting polymer membranes are utilized as the solid electrolyte in low temperature polymer electrolyte fuel cells (PEFC), which are efficient energy converters. We have selected the process of radiation grafting and subsequent sulfonation to prepare novel membranes because of its feasibility as a low cost production method. Investigations of the two first preparations steps, i.e., irradiation and grafting, lead to insight concerning the optimization of these two steps and the dependence of the final membrane properties on the various preparation parameters.     

In situ template synthesis of SnO nanoparticles on nickel foam with high electrochemical performance

A solution strategy performed at room temperature was presented for the in situ synthesis of SnO nanoparticles. SnO nanoparticles were prepared through the following sequent procedure: (1) preparation of rod-like Cd(OH)Cl utilizing the reaction between Cd²⁺ ions and epoxide; (2) production of Sn₂₁Cl₁₆(OH)₁₄O₆ template through the cation exchange reaction between Cd(OH)Cl and Sn²⁺ ions; (3) formation of SnO nanoparticles on nickel foam by the in situ reaction in strong alkaline electrolyte solution before electrochemical measurement. The as-prepared SnO had very small particle size and ordered nanostructure of particulate sheet, therefore resulting in its excellent electrochemical performance including high specific capacitance and high electrochemical stability for the charge-discharge cycle. Hence, the SnO nanoparticles synthesized in this work could be considered as one promising metal oxide for the utilization as electrode material in supercapacitor.

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SnO nanoparticles were prepared by an in situ template strategy. The synthetic procedure included the production of rod-like Cd(OH)Cl precursor at room temperature, preparation of platelet-like Sn₂₁Cl₁₆(OH)₁₄O₆ template through a cation exchange reaction, and the in situ synthesis of SnO nanoparticles from the template on nickel foam. Due to the small particle size, SnO presented high electrochemical performance as electrode material for application in supercapacitor.

     

Asymmetric electrochemical capacitor microdevice designed with vanadium nitride and nickel oxide thin film electrodes

Vanadium nitride thin film has been coupled with electrodeposited nickel oxide in order to design an electrochemical capacitor microdevice. VN has been used as negative electrode while NiO was used as the positive one in 1 M KOH electrolyte. VN exhibits a pseudo-capacitive behavior while NiO shows a faradaic behavior. This asymmetric microdevice has been operated between 0.5 and up to 1.8 V in aqueous based electrolyte (1 M KOH). Long term cycling ability (10,000 charge/discharge cycles) has been demonstrated with interesting energy (1.0 μW h cm^− 2) and power (40 mW cm^− 2) densities.     

Electrochemical behavior of nickel in electrolytes based on 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid for capacitor applications

Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene glycol or of γ-butyrolactone with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The aim of the study was to evaluate the use of these systems in electrochemical double-layer capacitor. Cyclic voltammetry experiments showed a potential range at which the Ni electrode behaved as a polarizable electrode. Ni oxidizes at high anodic potentials. Inside the potential range without electrochemical activity, the capacitance and the solution resistance, which were evaluated by impedance electrochemical spectroscopy, were compared for the two solutions tested. Conductivity measurements of the electrolytes with different compositions were also acquired. The results of cyclic voltammetry indicated that the Ni has a wide electrochemical window and low current peak densities of oxidation in the γ-butyrolactone medium than in ethylene glycol medium. The γ-butyrolactone and 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions had the highest conductivity values. Decreased 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid content in different solvent mixtures resulted in an increase in the capacitance value at the Ni/electrolyte interface. The highest capacitance values were obtained for Ni in ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate medium.     

Spectral and electrochemical behavior of manganese dioxide nanodispersions prepared in reverse micelle

Nanodispersed aggregates of MnO₂ were prepared in the aqueous core of the H₂O/Aerosol OT (AOT)/heptane reverse micelle using the comproportionation reaction between and Mn²⁺ ions. The formed nanoparticles were characterized by transmission electron microscopy (TEM), UV–visible spectroscopy and cyclic voltammetry. The electro-oxidation of dextrose and fructose on platinum modified by reverse micellar MnO₂ deposits was studied. The oxidation of fructose was found to be much more facile than dextrose oxidation. There was a linear correlation between the steady state oxidation currents and the carbohydrate concentrations, which was shown to be useful for analytical application. The sensitivity for fructose detection was found to be about seven times higher than that of dextrose. The scope of developing an electroanalytical method for estimation of dextrose and fructose individually in their mixture was explored.