Chang-Soo Jin

Electropolymerization and spectroelectrochemical characterization of poly(1,5-diaminonaphthalene)

Abstract 1,5-Diaminonaphthalene has been polymerized at glassy carbon and platinum electrodes in 0.1 M HCL and acetonitrile solutions by potential cycling methods. The polymer film grown on the platinum electrode in an aqueous solution had a conductivity of ∼ 1 × 10 −5 S/cm. The number of electrons used for the polymerization reaction was found to be about 4 per mole of the monomer from coulometric experiments. The polymer structure, in which monomers are postulated to be linked to each other through 1- and 5- positions of naphthalene, was consistent with the infrared spectroscopic data of the polymer and coulometric data for the polymerization reaction. When the polymer film is oxidized in 0.10 M HCL, the band of 350 nm undergoes a blue shift to about 290 nm with its reduced absorption and a new band shows up at 580 nm with its absorption extending to wavelengths longer than 800 nm.

Carbide-derived carbon/sulfur composite cathode for multi-layer separator assembled Li-S battery

To improve the electrochemical performance of Li-S rechargeable batteries, tunable porous carbon materials, which are known as carbide-derived carbons (CDCs), are employed as adsorbents and conductive matrices for the cathodic sulfur materials. A new assembly for Li-S cells was developed by introducing multi-layer membranes as separators. The use of the multi-layer membranes enables the minimization of the shuttle effect by expanding the distance between the separators and blocking the penetration of the polysulfide. The best discharge capacity and cycle life were obtained with ten layers of PP membrane in a sulfur-CDC@1200 composite cathode, resulting in a discharge capacity of 670 mA h g−1 and a minimal gap in the charge-discharge capacity during cell cycling.

Effect of support for alcohol-hydrocarbon synthesis from syngas in Cu-based catalyst

Effects of a Cu-based catalyst on the catalytic performance in alcohol-hydrocarbon synthesis from syngas have been investigated, using various supports. Under the different porosities of three supports (zinc oxide, activation carbon, and titanium dioxide), whereas Cu/ZnO produces one liquid phase of major mixed alcohols, Cu/AC and Cu/TiO2 create two phases, alcohol (∼75%) and hydrocarbon (∼25%). X-ray diffraction shows that CuO impregnated on supports undergoes a complete reduction of metallic copper Cu0, which is the real active phase in the catalytic process. The Cu/TiO2 catalyst showed the highest ethanol composition in a mixed alcohol phase under GHSV 18,000 h−1, 30 bar, and 300 °C.

Effect of Preparation Parameters of Sulfur Cathodes on Electrochemical Properties of Lithium Sulfur Battery

Sulfur cathodes were prepared by ball milling method with different types of electronic conductors and binders in different ball milling time. The sulfur cell with a cathode prepared in 45 min ball milling time gave an initial discharge capacity of 794 mAh/g with Super-P as an electronic conductor and poly(vinylidene fluoride) as a binder. The cathode with multi-walled carbon nanotube as an electronic conductor showed an initial discharge capacity of 944 mAh/g and a discharge capacity of 300 mAh/g after 20 cycles. Cathodes with poly(ethylene oxide) and poly(vinylidene fluoride) as binders showed different cycle performance.

Effects of Electrolyte Concentration on Growth of Dendritic Zinc in Aqueous Solutions

In order to understand the nature of dendritic zinc growth, electrochemical zinc redox reaction on nickel plate was investigated in aqueous solutions containing different concentrations, 0.2, 0.1 and 0.02 (M), of zinc sulfate () or zinc chloride (). Zinc ion was efficiently reduced and oxidized on nickel in the high-concentration (0.2 M) solution, whereas relatively poor efficiency was obtained from the other low-concentration solutions (0,1 and 0.02 M). Cyclic voltammetry (CV) analysis revealed that the 0.2 M electrolyte solution decomposes at more positive potentials than the 0.1 and the 0.02 M solutions. These results suggested that the concentration of electrolyte solution and anion would be an important factor that suppresses the reaction of the zinc dendrite formation. Scanning Electron Microscopy (SEM) data revealed that the shape of dendritic zinc and its growing behavior were also influenced by electrolyte concentration.

Synthesis of Defective-Structure Li 4 Mn 5 O 12 by Combustion Method and Its Application to Hybrid Capacitor

was synthesized by combustion method using , and . was obtained over , however, the sample calcined at for any time was mixed phases of and . calcined at for 5 h had larger first discharge capacity (41.5mAh/g) at 1C-rate for 3.7~4.4V than other calcined samples. Moreover, applying to hybrid capacitor, it had good discharge capacity (24.74 mAh/g or 10.46 mAh/cc) at 100 mA/g for 1~2.5 V and higher energy density (39Wh/kg or 16.49Wh/cc) at same condition.

Economic feasibility of ethanol production from biomass and waste resources via catalytic reaction

An economic evaluation of ethanol (EtOH) production from a thermo-chemical process derived from biomass/waste feedstocks was conducted. The influence of feed amounts, catalytic conversions, and EtOH selling prices was examined as these are the major variables for the economic evaluation of biomass/wastes conversion to EtOH. Among the three feedstock systems of biomass, high-moisture municipal solid waste (MSW), and plastic waste, the plastic waste has far better economic feasibility, with a payback period of 2–5 years at maximum CO conversion (40%) from syngas to ethanol, due to its higher heating value in comparison with biomass and high-moisture MSW. The heating value of the feedstock is a key factor in determining the overall economic efficiency in a thermo-chemical EtOH production system. Furthermore, enhancement of the CO conversion (related to catalytic activity) from syngas to EtOH using a low cost catalyst is necessary to retain economic efficiency because the CO conversion and cost consideration of catalyst are crucial factors to reduce the payback period.

Synthesis of Li 2 Mn 3 O 7 and Application to Hybrid Capacitor

In order to apply hybrid capacitor, was synthesized by combustion method using , and . Spinel pattern was identified the samples calcined over in XRD. Intensity of peak increased as the calcination temperature increased. To decide n/p ratio and to investigate electrochemical properties, charge-discharge tests of Li/ and Li/AC half-cell were carried out. Applying to AC/ hybrid capacitor, it had high discharge capacitance of 32.8 F/cc at 100 mA/g.

Fabrication of Aluminum Powder Disk by a Template Method and Its Etching Condition for an Electrode of Hybrid Supercapacitor

Capacitance of a hybrid capacitor that has characteristics of both electrolyte capacitor and supercapacitor is determined by anode surface covered with oxide layer. In this study, optimal condition processes for anode to fabricate a high voltage hybrid capacitor was investigated. We mixed aluminum powder having mean particle size of with NaCl powders at weight ratio of 4 : 1 and prepared a disk type electrode after annealing at various temperature. After dissolving NaCl in distilled water, heat treatment, eletropolishing, chemical treatment, and the first and the second etching of Al disk were conducted. In each process, capacitances and resistances of the disk measured by ac-impedance analyzer were compared to find its optimum treatment condition. Also, the surface morphology of treated disks were observed and compared by SEM. After the second etching, the Al disk was anodized at 365V to make an anode of hybrid supercapacitor that can be operated at 300V, Capacitance and resistance of the anodized Al disk electrode was compared with those of commercialized conventional aluminum electrolytic capacitor at different frequencies.

Novel Preparation Method of Carbon Nano Fibers/DAAQ Electrode for Supercapacitor System

A new type of supercapacitor was constructed by using carbon nanofibers (CNFs) and DAAQ (1,5-diaminoanthraquinone) oligomer. DAAQ was deposited on the carbon nanofibers by chemical polymerization with ammonium peroxodisulfate ((NH4)2S2O8) as oxidant in the 0.1 M H2SO4. Polymerization reaction was carried out with constant sonication. From the analysis, it is clear that surface of carbon nanofibers was quite uniformly coated with DAAQ. The performance characteristics of the supercapacitors have been evaluated using cyclic voltammetry. CNFs/DAAQ based composite electrode showed relatively good electrochemical behaviors in acidic electrolyte system. CNFs/DAAQ composite electrode showed relatively good capacitance (7 Ah/kg) compared to conventional capacitors in the range of -0.4~0.4 V