• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.189-195
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• 2023

As a PEMFC (Polymer Exchange Membrane Fuel Cell) cathode catalyst, Pt-Co/C has recently been widely used because of its improved durability. In a fuel cell, electrodes and electrolytes have a close influence on each other in terms of performance and durability. The effect on the electrochemical durability of the electrolyte membrane when Pt-Co/C was replaced in the Pt/C electrode catalyst was studied. The durability of Pt-Co/C MEA (Membrane Electrode Assembly) was higher than that of Pt/C MEA in the electrochemical accelerated degradation process of PEMFC membrane. As a result of analyzing the FER (Fluorine Emission Rate) and hydrogen permeability, it was shown that the degradation rate of the membrane of Pt-Co/C MEA was lower than that of Pt/C MEA. In the OCV (Open Circuit Voltage) holding process, the rate of decrease of the active area of the Pt-Co/C electrode was lower than that of the Pt/C electrode, and the amount of Pt deposited on the membrane was smaller in Pt-Co/C MEA than in Pt/C MEA. Pt inside the polymer membrane deteriorates the membrane by generating radicals, so the degradation rate of the membrane of Pt/C MEA with a high Pt deposition rate was higher than Pt-Co/C MEA. When the Pt-Co/C catalyst was used, the electrode durability was improved, and the amount of Pt deposited on the membrane was also reduced, thereby improving the electrochemical durability of the membrane.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.524-529
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• 2020

To increase the mechanical durability of the proton exchange membrane fuel cells, a reinforced membrane in which a support is placed in the polymer membrane is used. The support mainly uses e-PTFE, which is hydrophobic and does not transfer ions, which may cause performance degradation. In this study, we investigated the effect of e-PTFE support on PEMFC performance and electrochemical durability. In this study, the reinforced membrane with the support was compared with the single membrane (non-reinforced membrane). Due to the hydrophobicity of the support, the water diffusion coefficient of the reinforced membrane was lower than that of the single membrane. The reinforced membrane had a lower water diffusion coefficient, resulting in higher HFR, which is the membrane migration resistance of ions, than that of a single membrane. Due to the low hydrogen permeability of the support, the OCV of the reinforced membrane was higher than that of the single membrane. The support was shown to reduce the hydrogen permeability, thereby reducing the rate of radical generation, thereby improving the electrochemical durability of the reinforced membrane.

• Journal of Environmental Science International
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• v.17 no.1
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• pp.107-112
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• 2008

A study on the enhancement of environmental durability of EPDM rubber materials for the aerator membrane was performed using a butyl rubber as a modifier. A conventional EPDM rubber formulation was evaluated as having about 26.0 wt% or more oil content from the chloroform immersion test. These oils would be gradually and continuously deleted from the aerator membrane when directly exposed to a waste-water or chemically corrosive fluids, making the membrane less flexible and the performance worse. To improve this, a butyl rubber (IIR) was utilized as the modifier for a low-ENB type of EPDM rubber formulation with low-oil content. The environmental durability of the IIR-modified EPDM rubber material was expected to be greatly enhanced compared to the conventional one. However, the mechanical and performance properties such as elongation, tensile strength, and air bubble size, etc. were still maintained as good as in the conventional one. Furthermore, TGA analysis of the IIR-modified EPDM material showed that there would be partially compatible between IIR and EPDM. It also showed that the initial degradation temperature of the IIR-modified EPDM could be somewhat increased, exhibiting the enhanced compatibility among the components and, thereby, more enhanced environmental durability.

• Journal of Hydrogen and New Energy
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• v.32 no.5
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• pp.308-314
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• 2021

Chemical durability issue in polymer electrolyte membranes has been a challenge for the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). In this study, we proposed a manufacturing method of Nafion composite membrane containing a stable polyimide antioxidant to improve the chemical durability of the membrane. The thermal casting of the Nafion solution with poly (amic acid) induced polyimide reaction. We evaluated proton conductivity, oxidative stability with ex-situ Fenton's test, and fluoride ion emission to analyze the effect of polyimide antioxidants. We confirmed that incorporating the polyimide antioxidant improves the chemical durability of the Nafion membrane while maintaining inherent proton conductivity.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.296-301
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• 2017

Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, sulfonated poly (ether ether ketone) (sPEEK) membrane reinforced with poly imide was made to enhance of membrane durability. In order to test durability of single (un-reinforced) membrane and reinforced membrane MEA (Membrane and Electrode Assembly), degradation accelerated stress test was used. Before and after degradation, I-V polarization curve, hydrogen crossover current, electrochemical surface area, membrane resistance and charge transfer resistance were measured. As a result of experiments, hydrogen crossover current of reinforced MEA was lower than that of single MEA, therefor durability of reinforced MEA was higher than that of single MEA. There was not especially short phenomena in reinforced MEA after degradation accelerated stress test.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.508-513
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• 2021

In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with ePTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.321-326
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• 2022

As the thickness of the polymer membrane of PEMFC(Proton Exchange Membrane Fuel Cells) is getting thinner for PEMFC performance and price reduction, research on improving durability has become more important. In the durability evaluation of membranes, the mechanical durability evaluation time is more than twice that of the chemical durability evaluation time, so it is necessary to select the durability evaluation conditions well. In this study, we tried to check how much the mechanical durability evaluation time changes when there is a difference in the inflow gas type and flow rate in the mechanical durability evaluation protocol (Wet/Dry). When nitrogen was used at a flow rate of 2,000 mL/min, the evaluation time increased by 1.25 times compared to when air was used. An increase in the degradation rate of the electrode Pt was the main factor when air was used. When the flow rate was reduced to 800 mL/min, the air and nitrogen evaluation times increased by 1.5 times and 1.2 times, respectively.

• Membrane Journal
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• v.25 no.5
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• pp.447-455
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• 2015

In this study, Polysulfone (PSf) and polyetherimide (PEI) as the anion exchange polymers were aminated in the different ratio whereas the polyether ether ketone (PEEK) as the cation exchange polymer was sulfonated. The bipolar membranes of SPEEK (sulfonated PEEK)/APSf (aminated PSf) and SPEEK/APEI (aminated PEI) were prepared by the double-casting method. The surfaces of bipolar membranes were fluorinated in accordance with the amination ratio and applied to produce the hypochlorite. As the amination increased, the hypochlorite concentration is also increased. Typically, for SPEEK/APSf 3 : 1 membrane, the produced hypochlorite concentration was 61.0 ppm and its durability was 220 min for the non-fluorinated membrane while for the fluorinated membrane, the concentration of 58.6 ppm and its durability lasted 570 min. Also for SPEEK/APEI 3 : 1 membrane, the hypochlorite concentrations of 60.1 ppm and 58.3 ppm for before- and after-fluorination, respectively were observed whereas the durability was remarkably developed from 150 min to 440 min. Therefore, the surface fluorination takes an important role for the development of the membrane durability.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.344-350
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• 2019

Durability is very important for the commercialization of membranes and electrode assemblies (MEA) developed for proton exchange membrane fuel cells (PEMFC). Durability evaluation of stationary PEMFC MEA has a problem that the voltage change rate should be measured for a long time over 1000 hours under constant current conditions. In this study, the electrochemical durability evaluation protocol of membranes (OCV holding method) using to vehicle MEAs was applied to the stationary MEA for the purpose of shortening the durability evaluation time. After operation of the stationary and automobile MEA for 168 hours under conditions of OCV, cathode oxygen, $90^{\circ}C$ and relative humidity of 30%, I-V, LSV, CV, impedance and FER were measured and compared. When the hydrogen permeability, OCV change, ionic conductivity, and fluorine flow rate, which represent the durability of the membrane after degradation, were all examined, it was shown that durability of stationary MEA membrane was better than that of vehicles MEA membrane. In addition, the electrode degradation of stationary MEA was smaller than that of vehicles MEA after degradation operation. It was possible to evaluate in a short time using automotive protocol that the durability of stationary MEA was superior that of vehicle MEA in terms of membrane and the electrode.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.26-31
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• 2023

For durability improvement of polymer electrolyte membrane fuel cell (PEMFC) polymer membrane, accelerated durability evaluation methods that can evaluate durability in a short time have been researched and developed. However, the lifespan of fuel cells for large commercial vehicles such as trucks and buses is more than three times that of passenger cars, and the chemical accelerated stress test (AST) time is also longer, reaching 1,500 hours or more. Therefore, in this study, as a method to evaluate the chemical durability of a membrane within a short time, it was examined whether the durability could be predicted by the pristine membrane characteristics. Hydrogen crossover current density (HCCD) and short resistance (SR) were estimated as initial characteristics, and AST time was predicted through the Fenton experiment, which was possible as an out-of-cell experiment for 3 hours. As the HCCD and fluoride ion emission concentration increased, the AST time tended to be linearly shortened, but there was a deviation (R² ≒0.65). When the SR decreased, the AST time showed a linear increase, and the accuracy was high (R² =0.93), so the AST time could be predicted with the initial SR of the membrane.