Gab-Jin Hwang

Preparation of anion exchange membrane using polyvinyl chloride (PVC) for alkaline water electrolysis

An anion exchange membrane was prepared by the chloromethylation and the amination of polyvinyl chloride (PVC), as the base polymer. The membrane properties of the prepared anion exchange membrane, including ionic conductivity, ion exchange capacity, and water content were measured. The ionic conductivity of the prepared anion exchange membrane was in the range of 0.098×10−2-7.0×10−2S cm−1. The ranges of ion exchange capacity and water content were 1.9-3.7meq./g-dry-membrane and 35.1-63.1%, respectively. The chemical stability of the prepared anion exchange membrane was tested by soaking in 30 wt% KOH solution to determine its availability as a separator in the alkaline water electrolysis. The ionic conductivity during the chemical stability test largely did not change.

Study on the Electrode Characteristics for the Alkaline Water Electrolysis

Alkaline electrolysis needs the electrode having a low overvoltage and good corrosion resistance in alkaline solution such as KOH and NaOH, for the oxygen and hydrogen production. The commercial materials such as SUS(stainless steel)-316, Ni and NiFe were evaluated for the electrode in alkaline electrolysis. The test solution for the alkaline electrolysis used 1~9M NaOH and 1~9M KOH. The voltage increased with an increase of current density in each solution. As for the 15wt.% (about 5M) NaOH, the voltage of the tested electrode under the current density of 1.8A/ showed the almost same value. The voltage over the current density of 1.8A/ deceased in the order: NiNiFe showed the almost same value. The voltage over the current density of 1.8A/ deceased in the order: NiFeSUS-316. From the results, it was estimated that NiFe and Ni was suitable as the electrode for the alkaline water electrolysis using NaOH and KOH electrolyte.

Study on the Electrolyte for Zn-Br Redox Flow Battery

Four types of electrolyte were tested for the application as an electrolyte in the Zn-Br redox flow battery. Electrolyte was consist of ZnBr2 (electrolyte number 1), ZnBr2+KCl (electrolyte number 2), ZnBr2 +KCl+NH4Br (electrolyte number 3) and ZnBr2+KCl+EMPBr(C7H16BF4N) (electrolyte number 4). The each electrolyte property was measured by CV (cyclic voltammetry) method. The different between the potential of anodic and cathodic maximum current density in a CV experiment (△EP) was 0.89V, 0.89V, 1.06V and 0.61V for the electrolyte number 1, 2, 3 and 4, respectively. The electrolyte involved KCl increased conductivity which was appeared by anodic and cathodic maximum current density in a CV experiment. It was estimated that the electrolyte of number 3 (ZnBr2+KCl+NH4Br) and number 4 (ZnBr2+KCl+EMPBr) could be suitable as an electrolyte in the Zn-Br redox flow battery with non-appeared bubble, non-Br formation and high anodic-cathodic maximum current density.

An Analysis on Stainless Steel for Hydrogen Generator' Pipeline Interacting with Alkaline Solution

This study was performed to observe the change of stainless steel pipe interacting with alkaline solution. We used STS316L and STS304 as samples which were soaked in alkaline solution. We measured the samples by use of FE-SEM, EDX, SIMS to observe the surface and depth profile of both samples. The result showed that the precipitate appeared on the surface of both samples from 5 days. but the precipitate was confirmed to be decreased as time passes. but the quantitative change of precipitates at both samples was different as time passed. The EDX showed that the precipitate is Potassium from solution of Electrolysis. The result also showed that the primary elements of stainless steel pipeline and of Alkaline Solution were changed. The change of primary elements was severe between 5 days to 16 days and was stable around 40 days at both samples. The reaction of STS316L with alkaline solution was lower than STS304. We hoped that this study would be the foundation of developing the electrode of the alkaline hydrogen generator.

Research Review of Sodium and Sodium Ion Battery

The secondary battery using sodium is investigating as one of power storage system and power in electric vehicles. The secondary battery using sodium as a sodium battery and sodium ion battery had merits such as a abundant resources, high energy density and safety. Sodium battery (sodium molten salt battery) is operated at lower temperature (100℃) compared to NAS and ZEBRA battery (300~350℃). Sodium ion battery is investigating as one of the post lithium ion battery. In this paper, it is explained for the principle and recent research trends in sodium molten salt and sodium ion battery.

Multiple tube preparation characteristics of silica hydrogen permselective membrane

The multiple tube preparation of a silica membrane using a porous α-alumina tube as a support tube was carried out by chemical vapor deposition (CVD) to scale up the membrane reactor. A porous alumina tube with a pore size of 100 nm was modified by chemical vapor deposition using tetraethoxysilane as an Si source. The single-component permeance of H2 and N2 in the prepared silica membrane that was achieved by a multiple tube membrane preparation system was measured at 300–600 °C. Hydrogen permeance of the modified membrane at a permeation temperature of 600 °C was 5×10−8 mol·Pa−1·m−2·s−1. H2/N2 selectivity at 600 °C was about 32. It was confirmed that permeance of H2 and N2 and the selectivity for H2 to N2 in the prepared silica membrane by the multiple tube membrane preparation system had almost the same value compared to those of the silica membrane prepared by the single-tube system.

Electrochemical Characteristics of Supercapacitor Using Ionic Liquid Electrolyte

Supercapacitor has been studied actively as one of the most promising electrochemical energy storage system for a wide range of applications. To increase the energy density of super- capacitor, the introduction of ionic liquids is required. In this study, two types of EMI-BF4 based on quaternary imidazolium salt were prepared with quaternary reaction and anion exchange. The structural characterization and thermal stability were analyzed by nuclear magnetic reso- nance( 1 H-NMR) and thermogravimetric analysis(TGA), respectively. Thermal stability of the EMI-BF4 using TGA confirmed that, after heat treatment, the decomposition temperature of EMI-BF4 was increased. Supercapacitors were fabricated with synthesized and commercial ionic liquids, and charge/discharge characteristics were also investigated. The capacity of supercapacitor, for synthesized and commercial EMI-BF4 were determined to be 0.067 F and 0.073 F respectively, by means of charge/discharge test.

Study on the Electrolyte Added Chlorosulfuric Acid for All-vanadium Redox Flow Battery

>> The electrolyte added the chlorosulfuric acid (HSO3Cl) as an additive was tested for the electrolyte in all-vanadium redox flow battery (VRFB) to increase the thermal stability of electrolyte. The electrolyte property was measured by the CV (cyclic voltammetry) method. The maximum value of a voltage and current density in the electrolyte added HSO3Cl was higher than that in the electrolyte non-added HSO3Cl. The thermal stability of the pentavalent vanadium ion solution, which was tested at 40°C, increased by adding HSO3Cl. The performances of VRFB using the electrolyte added and non-added HSO3Cl were measured during 30 cycles of charge-discharge at the current density of 60 mA/cm 2 . An average energy efficiency of the VRFB was 72.5%, 82.4%, and 81.6% for the electrolyte non-added HSO3Cl, added 0.5 mol of HSO3Cl, and added 1.0 mol of HSO3Cl, respectively. VRFB using the electrolyte added HSO3Cl was showed the higher performance than that using the electrolyte non-added HSO3Cl.

Characteristics of the Zn-Br Redox Flow Battery using the Different Electrolyte and Membrane

>> Cell performance of the Zn-Br redox flow battery (ZBRFB) using two different type’s membrane (Nafion117 and SF-600) was evaluated at 20 mA/cm 2 of current density in 1M (mol/L) ZnBr2 + 2M KCl + 0.3M EMPBr(1-ethyl-1-methyl pyrrolidinium bromide) electrolyte. The average energy efficiencies of ZBRFB were 74.9% and 74.7% for Nafion117 and SF-600, respectively. The electrolyte added the 1-ethyl-3-methylimidazolium dicyanamide (EMICA) as an additive was tested for the electrolyte in ZBRFB using SF-600 at 30 mA/cm 2 of current density. An average energy efficiency of the ZBRFB was 74.5% and 77.4% for the electrolyte non-added EMICA and added 1wt% of EMICA, respectively. ZBRFB using the electrolyte added EMICA was showed the higher performance than that using the electrolyte non-added EMICA.

Study on the Electrochemical Characteristics of Lithium Ion Doping to Cathode for the Lithium Ion Capacitor

>> Lithium Ion capacitor (LIC) is a new storage device which combines high power density and high energy density compared to conventional supercapacitors. LIC is capable of storing approximately 5.10 times more energy than conventional EDLCs and also have the benefits of high power and long cycle-life. In this study, LICs are assembled with activated carbon (AC) cathode and pre-doped graphite anode. Cathode material of natural graphite and artificial graphite kinds of MAGE-E3 was selected as the experiment proceeds. Super-P as a conductive agent and PTFE was used as binder, with the graphite: conductive agent: binder of 85: 10: 5 ratio of the negative electrode was prepared. Lithium doping condition of current density of 2 mA/cm 2 to 1 mA/cm 2 , and was conducted by varying the doping. Results Analysis of Inductively Coupled Plasma Spectrometer (ICP) was used and a 1 mA/cm 2 current density, 2 mA/cm 2 , when more than 1.5% of lithium ions was confirmed that contained. In addition, lithium ion doping to 0.005 V at 10, 20 and 30°C temperature varying the voltage variation was confirmed, 20°C cell from the low internal resistance of 4.9 Ω was confirmed.