Papers by Keyword: Electrochemical Properties

Abstract: Contribution deals with evaluation of the electrodeposition process of octacalcium phosphate layer on the surface of Elektron 21 magnesium alloy. The octacalcium phosphate coating (OCP) was electrochemically deposited in a solution containing 0.167 M CaCl₂ and 0.1 M NH₄H₂PO₄. The formation of calcium phosphate was divided into several stages and described using light microscopy. The influence of octacalcium phosphate layer on the electrochemical characteristics of Elektron 21 magnesium alloy was evaluated by potentiodynamic measurements in 0.1 M NaCl solution at a temperature 22 ± 1°C. Evaluation of calcium phosphating process realized on the alloy surface after grinding was investigated by electrochemical tests supported by photodocumentation using stereomicroscope.

Abstract: The Ni+MoS₂ composite coatings were prepared by electrodeposition under galvanostatic conditions from the Ni-plating bath containing suspended MoS₂ powder (100 mesh). Investigations of hydrogen evolution reaction (HER) were carried out using steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) in 5 M KOH solution on the coatings obtained at 30, 40, and 50°C. It was found that the kinetics of the HER on the Ni+MoS₂ coatings decreases with the increase in the electrodeposition temperature of the coatings. This effect is attributed to decreasing content of MoS₂ (from 26.4 to 18.0 wt.%) embedded into the Ni matrix as composite crystalline component having the electrocatalytic properties towards the HER and/or surface development of the coatings. The higher amount of MoS₂ was embedded, the more porous electrodes containing pear-shape pores on the surface were produced what was detected by EIS.

Abstract: The precursor Ni (OH)₂ was synthesized by a simple hydrothermal method with hexamethylenetetramine ((CH₂)₆N₄) as precipitant and template, and then NiO was gained after calcination. The phase and morphology of the synthesized product were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the electrochemical capacitive characterization was performed using cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) in a 6mol/L KOH aqueous solution electrolyte. The result shows that spherical NiO without impurity was synthesized, the average diameter of the spheres is 5 um and these spheres were constructed by the interactive arrangement of many nanoflakes in three dimensions. This kind of NiO shows the typical electrochemical characteristics of pseudo capacitance with high specific capacity and excellent rate capability. The specific capacity can reach 515F/g at the current density of 1A/g

Abstract: The precursor nickel and manganese carbonates were synthesized by co-precipitation with sodium carbonate as precipitant, and then nickel and manganese oxides were gained after calcination. The phase and morphology of the synthesized product were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the electrochemical characterization was performed using cyclic voltammetry (CV), galvanostatic charge–discharge tests (GCD) and electrochemical impedance spectroscopy (EIS) in a 6mol/L KOH aqueous solution electrolyte. The result showed that the products were the mixture of nickel and manganese oxides and solid solution. nanoparticles and spherical particles were gained by controlling the molar ratio of nickel and manganese. All of the samples exhibited typical Faradic redox capacitance. The specific capacitance was different with the change of nickel and manganese molar ratio. The specific capacitance (Cs) reached 130F/g at 1A/g when the ratio was 2:1.

Abstract: In this paper the fractures appeared in the surface of nanoparticle silicon anode for lithium-ion batteries was explored. The changes of nanoparticle silicon anode before and after cycling were charactered using SEM, XRD,Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS). The result indicates that the electrode cracking occured in the cycling process , the CV, EIS and discharge specific capacity curves proved the fractures could lead to the degradation of the electrochemical performance.

Abstract: BCN nanoparticles sandwiched between carbon nanosheets were synthesized with the P123 and borate ammonium under nitrogen atmosphere. The samples were characterized by SEM, TEM, and EELS. The SEM and TEM images show BCN nanoparticles are attached on the carbon nanosheets. Cyclic voltammetry (CV) and galvanostatic charge-discharge measurements are used to evaluate electrochemical properties of the composites. The samples show the specific capacitance of 102 F/g at current density of 200mA/g and good durability.

Abstract: The effect of the substitution of La with Pr on the microstructure and some electrochemical properties of La_0.7-xPr_xMg_0.3Al_0.3Mn_0.4Co_0.5Ni_3.8 (x=0.0, 0.1, 0.3, 0.5, and 0.7) ingot alloys as powder electrode was studied in this paper. XDR and SEM (+EDX) analyses revealed that the as-cast alloys consist mainly of similar LaNi₅ and (La,Pr)Mg₂Ni₉ phases. With the increase in Pr content, both the relative abundance of the phases and microstructure changed. The electrochemical studies showed that the maximum discharge capacity decreased with the increase in Pr content. For the alloy without Pr, the self-discharge studies revealed a major stability of the hydride until the first 984 hours (41 days) of the charge/discharge cycles. The high-rate dischargeability of this alloy electrode showed the best result HRD=88% at a discharge current density of I_d=250 mA/g.

Abstract: Electrodeposition process of calcium phosphate (CaP) was performed on Elektron 21 magnesium alloy and the influence on corrosion resistance of the alloy covered by CaP was investigated by electrochemical tests. The electrodeposition treatment was performed by potential controlled method in water solution of Ca (NO₃)₂.4H₂O, NH₄H₂PO₄ and H₂O₂. Corrosion measurements were performed in 0.1M NaCl solution at laboratory temperature (22 ± 1 °C) using electrochemical impedance spectroscopy. Electrodeposited surfaces had higher polarization resistance than only ground surface after all exposition time in 0.1M NaCl.

Abstract: Two thiophene derivatives 4,4'-di (thiophen-2-yl) biphenyl and 4,4'-di (thiophen-2-yl) -2-nitrobiphenyl ,which were used as monomers for preparing poly (4,4'-di (thiophen-2-yl) biphenyl) (DPBT) and poly (4,4'-di (thiophen-2-yl)-2-nitrobiphenyl) (DPNT) by ferric chloride oxidation polymerization, were synthesized via Suzuki reaction with 4,4'-dibromobiphenyl as the raw material. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were recorded and used for calculating the band-gap (E_g), HOMO orbital energy (E_HOMO) and LUMO orbital energy (E_LUMO) of the polymers. The calculation results indicated that attaching an electron-withdrawing group such as-NO₂ to the main chain can lower band-gap and increase the maximum absorption wavelength.

Abstract: The nanoscale TiO₂ was synthesized and their electrochemical properties as the anode electrode materials for rechargeable Li-ion batteries were measured. The structure, morphology and electrochemical properties of the nanoscale TiO₂ composites synthesized were characterized in detail by X-ray (XRD), Transmission Electron Microscopy (TEM) and electrochemical measurement. The first discharge capacities were 126 mAh/g for the nanoscale TiO₂ at the current density of 100 mA/g at ambient temperatures. The specific capacities were stabilized at around 57mAh/g after 20 cycles.