A novel all-solid-state polymeric membrane Pb2+-selective electrode was developed by electrodepositing the CNTs films on the glassy carbon (GC) electrode, and characterized by electrochemical impedance spectroscopy (EIS), chronopotentiometry, and water layer test. The results showed that the electrodeposited CNTs films formed a well interconnected spaghetti-like structure on the GC substrates and increased the low-frequency capacitance of electrode from the EIS curves. The electrode has excellent ion-to-electron transducing ability, showing a Nernstian response of 29.0 mV per decade in the Pb2+ concentrations range of 10−3–10−8 M. No water film was observed on the surface of the electrode for long-term measurements. The research demonstrated a new strategy for the fabrication of robust potentiometric ion sensors.
The corrosion behavior of low alloy steel for cargo oil tanks (COT) is investigated by thermo mechanical control process (TMCP) at various cooling rates. The corrosion rate is estimated by accelerated corrosion test in strong acid sodium chloride solution. The corrosion mechanism is studied by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) measurements. It indicates that the acicular ferrite is refined as the cooling rate increases, the CR15 steel with higher cooling rate exhibits good corrosion resistance with a less weight loss, lower corrosion current density and bigger impedance modulus than steels CR10 and CR12.
Crystallographic and morphological data and the galvanostatic cycling and rate performance of the cobalt-substituted Li2Fe0.5Mn0.5SiO4/C compounds Li2FexMnxCo1−2xSiO4/C (x = 0.33, 0.40, 0.45) were evaluated and compared with those of unsubstituted Li2Fe0.5Mn0.5SiO4/C. The hydrothermally synthesized Li2FexMnxCo1−2xSiO4, consisting of uniform nanosized primary particles and no impurities, were indexed on the basis of the orthorhombic unit cell in space group Pmn21 and exhibited a solid solution at least beyond x = 0.33. The primary particle sizes of Li2FexMnxCo1−2xSiO4 decreased because of the substitution of cobalt for iron and manganese. In addition, although the capacity fades of Li2FexMnxCo1−2xSiO4/C were similar to those of Li2Fe0.5Mn0.5SiO4/C, the discharge capacity and rate capability of Li2Fe0.5Mn0.5SiO4/C were improved by the substitution of cobalt for iron and manganese. Li2FexMnxCo1−2xSiO4/C (x = 0.45) exhibited the best electrochemical performance with first discharge capacities of 242.5 and 163.6 mAh g−1 at current rates of 3.3 and 165 mA g−1, respectively. The good electrochemical performance of Li2FexMnxCo1−2xSiO4/C cathode materials is attributed to their smaller primary particle size compared with that of Li2Fe0.5Mn0.5SiO4/C.
SiO2/C composite as an anode material of lithium ion batteries was prepared by a facile synthesis method using raw materials of polyaniline and silicon dioxide. The SiO2/C composite shows the higher reversible capacity of 533.4 mAh g−1 after 100th cycles with good cycling stability. This improvement of electrochemical performance of the synthesized composite is benefit from the carbon coated on the SiO2 nanospheres, which improves the electrical conductivity and restrains the volume variation during the lithiation and delithiation process. Due to the superior electrochemical performance, the SiO2/C composite prepared via facile synthesis could be promising as anode materials with high capacity, low-cost for lithium-ion batteries.
Based on mathematical solutions of the impedances of one-dimensional transmission-line models, a variety of models of porous electrodes are made to cope with possible actual cases. In the examined models, ionic resistance in pores, faradaic impedance, and electronic resistance are considered. Numerical calculation of the impedance values of each model revealed the effects of each parameters on the behaviors of the Cole-Cole plots. In addition, effects of additional elements set at the both ends of the transmission-line model, which determine the boundary conditions, were also examined. Finally, possibility to extract the impedance at the interface only by reverse-estimation was investigated. Although this attempt has been achieved, it is also demonstrated that inaccuracies of the assumed parameters might deteriorate the estimated values.
An electrochemical sensor based on poly (guanine) modified glassy carbon electrode (PGA/GCE) was fabricated by electropolymerization of guanine on a bare GCE surface. Scanning electron microscope (SEM) was employed to characterized the electrode surface. This modified electrode exhibited a good electrocatalytic property towards the oxidation of epinephrine (EP) and uric acid (UC) in 0.1 M phosphate buffer solution (PBS) (pH 4.0) due to the enhanced peak currents and well-defined peak separations. Under optimum reaction conditions, the oxidation peak currents of EP and UA were proportional to their concentrations in the ranges of 1.0 × 10−5 to 1.0 × 10−3 M for both two compounds, and the detection limits were 1.8 × 10−6 and 5.0 × 10−7 M, respectively. Finally, this method was efficiently used for the determination of EP in EP injections.
The inhibitory effect of extract of Hibiscus Sabdariffa on corrosion of steel in aqueous 8 M H3PO4 was investigated by potentiodynamic polarization technique. The inhibition efficiency of Hibiscus extract on corrosion of steel in aqueous 8 M H3PO4 solution increases on increasing in concentration of the extract and decreases with a rise in temperature. Potentiodynamic polarization measurement indicates that Hibiscus acts as a corrosion inhibitor. Theoretical fitting of the different isotherms were tested to clarify the nature of adsorption. The increase in activation energy of corrosion process in the presence of the extract indicates that the extract retards the rate of corrosion of steel in 8 M H3PO4 solution. The structure and morphology of the extract were characterized by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) study confirmed the adsorption of inhibitor molecules on steel surface.
Silicon-alloys are candidates for anode materials of high capacity lithium-ion batteries. Here we report the mechanical milling (mechanical alloying) synthesis of various silicon-alloy samples. The samples have been characterized by X-ray diffraction, scanning electron and transmission electron microscopies, and electrochemical tests to investigate their electrochemical lithium insertion-extraction performance. The metallic elements added during alloying such as Ni, Co, Cu, and Zr are found to be effective for nanocrystallization or amorphization of silicon alloy. Especially Si-Sn-Cu alloy has high 1st lithium storage capacity of 2690 mAh g−1 with a coulombic efficiency of 85% and relatively long cycle life. The changes of Si-Sn-Cu alloy composite electrode in volume and structure were also investigated to obtain insights for practical electrode design.
Graphite-like layered materials composed of boron/carbon/nitrogen (B/C/N) and boron/carbon (B/C) have been prepared by CVD method using BCl3 and CH3CN or C2H4 as starting materials, respectively. Electrochemical behaviors of B/C/N and B/C materials as anodes of sodium ion batteries have been investigated. Their properties have been compared with those of carbon/nitrogen (C/N) material and carbons prepared by CVD method. B/C/N and B/C materials showed reversible intercalation and de-intercalation on their discharge and charge cycles. The formation of stage structures was observed during the discharge (electrochemical intercalation) in 1 M-NaPF6/EC+DEC (1:1) electrolyte solution, which was not clearly observed in the cases of C/N material and carbon. Potentials at the beginning of discharge (intercalation of Na+ ion) were higher than those of C/N material and carbons, and depended on the boron content in the material. B/C materials having larger boron content tended to show higher reversible capacity. B/C/N materials showed highest reversible capacity 190 mAh g−1 among the materials prepared in this study by using CVD method. These results could be explained by the electronic structure of the material in which electron deficient boron atom lowered the bottom of conduction band, and will provide useful information for designing materials as electrodes.
Proton conducting glasses were prepared from proton type zeolite materials by the spark plasma sintering technique in vacuum. TOF-SIMS analysis showed that the glass structure contains protons. The electrical conductivity was affected by proton content and probably by the pore structure of the starting zeolite material.