• Korean Chemical Engineering Research
• /
• v.59 no.1
• /
• pp.49-53
• /
• 2021

The Fenton reaction is often used to evaluate the chemical durability of polymer membranes of Proton Exchange Membrane Fuel Cells (PEMFC). However, due to the violent reaction between hydrogen peroxide and iron ions, it is difficult to compare experimental data because of low reproducibility. In this study, we tried to find the reaction conditions to improve the reproducibility of the durability test of the membrane by the Fenton reaction. The hydrogen peroxide concentration was fixed at 30%, the iron ion concentration, temperature, stirring speed, and sample size were varied, and the fluorine ion concentration of the Nafion polymer membrane deteriorated by radicals was measured. When the iron ion concentration was increased or the membrane sample size was increased, and the reaction temperature was increased to 80 ℃, the experimental deviation increased, so an iron ion concentration of 10 ppm, a temperature of 70 ℃, and a sample size of 0.5 ㎠ were suitable.

• Korean Chemical Engineering Research
• /
• v.60 no.1
• /
• pp.7-11
• /
• 2022

In the membrane forming process of a proton exchange membrane fuel cell (PEMFC), drying and annealing heat treatment processes are required for performance and durability. In this study, the optimal annealing temperature for improving the durability of the polymer membrane was studied. It was annealed in the temperature range of 125~175 ℃, and thermal stability and hydrogen permeability were measured as basic data of durability at each annealing temperature. The electrochemical durability was analyzed by Fenton reaction and open circuit voltage (OCV) holding. The annealing temperature of 165 ℃ was the optimal temperature in terms of thermal stability and hydrogen permeability. In the Fenton reaction, the fluorine emission rate of the membrane annealed at 165 ℃ was the lowest, and the lifespan of the membrane annealed at 165 ℃ was the longest in the OCV holding experiment, confirming that 165 ℃ was the optimal temperature for the durability of the polymer membrane.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.2
• /
• pp.164-175
• /
• 2022

In this work, sulfonated poly (ether ether ketone) (SPEEK) composite membranes including strontium zirconate (SrZrO₃) were fabricated by the electrospinning method. Fourier-transform infrared spectroscopic analysis and X-ray diffraction analysis were used to identify the chemical structure and the crystallinity of SrZrO₃ and electrospun composite membranes. The thermal stability of the pure SPEEK and SPEEK/SrZrO₃ electrospun composite membranes were investigated by using thermogravimetric analysis. The physicochemical properties and proton conductivity were enhanced with the addition of different weight ratio of SrZrO₃ nanofiller (2, 4 and 6 wt%) in SPEEK polymer. The optimized SPEEK/SrZrO₃-4 electrospun membrane containing 4 wt% of SrZrO₃ showed a high proton conductivity compared to other electrospun SPEEK/SrZrO₃ composite membranes. The results indicate that electrospun composite membranes incorporating these perovskite nanofillers should be explored as potential candidates for use in proton exchange membrane fuel cells.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.4
• /
• pp.283-289
• /
• 2010

A two-dimensional isothermal model has been employed for numerical simulations of a high temperature hydrogen fuel cell with proton exchange membrane. The model is validated with existing experimental data and used for examination on the effects of various operating conditions on the fuel cell performance. The present numerical results show that the cell performance increases with increasing exchange current density, ion conductivity of the membrane, inlet gas flow rate as well as operating pressure. Also, higher porosity of gas diffusion layer (GDL) results in higher cell performance due to enhancement of the diffusion through the GDL, where the cathode GDL porosity more influences on the performance as compared with the anode one.

• Journal of the Korean Chemical Society
• /
• v.31 no.2
• /
• pp.197-202
• /
• 1987

Sigmatropic rearrangement of cis and trans-2-methyl-N-phenyl-1,3-oxathiolane-2-acetamide (b) and (c) gave unisolable sulfenic acids (d) and (f), respectively. These sulfenic acids were confirmed by deuterium exchange reactions involving 2-methylene and 2-methyl groups. The reactions also showed that no isomerization between the cis and trans sulfoxides (b) and (c) occurred under neutral conditions. However, the isomerization took place in the presence of acid catalyst. Stereospecific recyclization of sulfenic acids to the sulfoxides is attributable to possible hydrogen bonding between sulfenyl oxygen and NH proton or it arises from the geometrical requirements of the reacting bond and atoms in the reverse sigmatropic rearrangement. In the oxidation of 1, 3-oxathiolane, cis sulfoxide (b) could be obtained selectively in high yield by using $H_2O_2$-benzene seleninic acid.

• Membrane Journal
• /
• v.26 no.6
• /
• pp.458-462
• /
• 2016

Saline water electrolysis, known as chlor-alkali (CA) membrane process, is an electrochemical process to generate valued chemicals such as chlorine, hydrogen and sodium hydroxide with high purities higher than 99%, using an electrolytic cell composed of cation exchange membrane, anode and cathode. It is necessary to reduce energy consumption per a unit chemical production. This issue can be solved by decreasing intrinsic resistance of the membrane and the electrodes and/or by reducing their interfacial resistance. In this study, the electron radiation grafting of a $Na^+$ ion-selective polymer was conducted onto a hydrocarbon sulfonated ionomer membrane with high chemical resistance. This approach was effective in improving electrochemical efficiency via the synergistic effect of relatively fast $Na^+$ ion conduction and reduced interfacial resistance.

• Journal of the Korean Ceramic Society
• /
• v.47 no.6
• /
• pp.627-632
• /
• 2010

In this paper the effect of the structure, particle size, morphology of nanofibers and nanoparticles for the electrochemical characteristics of $Li_4Ti_5O_{12}$ was investigated. The $H_2Ti_2O_5{\cdot}H_2O$ synthesized in hydrothermal treatment from a NaOH treatment on $TiO_2$ by ion exchange processing with HCl solutions. After the $Li_4Ti_5O_{12}$ nanofibers synthesized in hydrothermal treatment of $H_2Ti_2O_5{\cdot}H_2O$ and $LiOH{\cdot}H_2O$. The hydrogen titanate precursor prepared by ion exchange processing with 0.1~0.3M HCl solutions and the final products calcined at $350^{\circ}C{\sim}400^{\circ}C$. The $Li_4Ti_5O_{12}$ nanofibers showed well reversibility during the insertion and extraction of Li, good cycle performance, high capacity and low electrochemical reaction resistance than nanoparticles. also c-rate exhibited a discharge capacity of 172 mAh/g at 0.2C and 115mAh/g at 5C, which is the 77%, 67% of that obtained in the process charged, discharged at 0.2C.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.1 s.38
• /
• pp.57-61
• /
• 2006

Fuel cells are direct current (DC) power generators. They generate electricity through an electrochemical process that converts the energy stored in a fuel directly into electricity. Fuel cells have many benefits, which produce no particulate matter, nitrogen or sulfur oxides. And they have few moving parts and produce little or no noise. When fueled by hydrogen, they yield only heat and water as byproducts. Their wide application can reduce our dependence on fossil fuels and foreign sources of petroleum. This paper is studied on a high efficiency power conditioning system (PCS) applied to the proton exchange membrane fuel cell (PEMFC) generation system. This paper is designed to a novel PCS circuit topology of high efficiency. Some experimental results of the proposed PCS is confirmed to the validity of the analytical results.

• Applied Chemistry for Engineering
• /
• v.30 no.6
• /
• pp.659-666
• /
• 2019

Proton exchange membrane fuel cells (PEMFCs) generate electricity by electrochemical reactions of hydrogen and oxygen. PEMFCs are expected to alternate electric power generator using fossil fuels with various advantages of high power density, low operating temperature, and environmental-friendly products. PEMFCs have widely been used in a number of applications such as fuel cell vehicles (FCVs) and stationary fuel cell systems. However, there are remaining technical issues, particularly the long-term durability of each part of fuel cells. Degradation of a carbon supported-platinum catalyst in the anode and cathode follows various mechanistic origins in different fuel cell operating conditions, and thus accelerated stress test (AST) is suggested to evaluate the durability of electrocatalyst. In this article, comparable protocols of the AST durability test are intensively explained.

• Korean Chemical Engineering Research
• /
• v.58 no.2
• /
• pp.171-175
• /
• 2020

In the proton exchange membrane fuel cells (PEMFC), the development of a reinforced membrane with improved durability by a support is actively in progress in Korea. In this study, the initial performance and characteristics of four types of reinforced membranes were compared. Reinforced membranes with higher amounts of C-F chains in the polymer membrane showed lower water diffusion coefficients due to the hydrophobicity of the C-F chains. The thicker the polymer membrane, the more the hydrogen permeability decreased and the higher the OCV. Membrane with short resistance below 1.5 Ωcm² showed OCV below 0.9 V and the lowest performance, so short resistance should be above 3.0 Ωcm². Compared with the current standard membrane, there was a similar domestic membrane, which could confirm the possibility of localization of PEMFC polymer membrane.