• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.315-319
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• 2018

Fenton reaction is widely used as a out of cell method for evaluating the membrane electrochemical durability of Proton Exchange Fuel Cell (PEMFC). In this study, we investigated the factors affecting the Fenton reaction. In order to estimate the degree of the reaction, it is necessary to analyze the radicals as a product in the Fenton reaction. However, since the radicals are difficult to analyze, the degree of the reaction was measured by analyzing the concentration of hydrogen peroxide. The activation energy was calculated from the rate of hydrogen peroxide change with temperature. The activation energy was 24.9 kJ/mol at 180 min. The Fenton reaction rate was affected by the iron ion concentration. At $80^{\circ}C$, 200 rpm, and $Fe^{2+}$ 80 ppm, the concentration of hydrogen peroxide was decreased more than 20% even for 1 hour, which shows that frequent solution replacement increases the membrane degradation rate.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.106-111
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• 1999

The effect of the MG on the electrochemical charge-discharge properties of $CaNi_5$ hydrogen storage alloys was investigated under Ar and $H_2$ atmosphere. $CaNi_5$ alloy was partially decomposed to CaO and Ni phase during the MG process. The decomposition of $CaNi_5$ alloy was enhanced by the MG process which leads to crash and reformation of oxide layer on the alloy surface. As the MG process time increased, initial discharge capacity of the electrode was reduced, but the decay rate of the capacity compared to $CaNi_5$ alloys was slower. It may be described that the degradation of $MG-CaNi_5$ electrode was caused by the reduction of the reversible hydrogen reaction sites and increasing polarization resistance of hydrogen adsorption resulted from phase decomposition and disorder during the MG process, and/or by hydroxide formation during the electrochemical charge-discharge cycles.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.50-60
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• 2013

High temperature proton exchange membrane fuel cells (PEMFCs) using phosphoric acid (PA) doped polybenzimidazole (PBI) membranes have been concentrated as one of solutions to the limits with traditional low temperature PEMFCs. However, the amount of reported experimental data is not enough to catch the operational characteristics correlated with cell performance and durability. In this study, design of experiments (DOE) based operational optimization method for high temperature PEMFCs has been proposed. Response surface method (RSM) is very useful to effectively analyze target system's characteristics and to optimize operating conditions for a short time. Thus RSM using central composite design (CCD) as one of methodologies for design of experiments (DOE) was adopted. For this work, the statistic models which predict the performance and degradation rate with respect to the operating conditions have been developed. The developed performance and degradation models exhibit a good agreement with experimental data. Compared to the existing arbitrary operation, the expected cell lifetime and average cell performance during whole operation could be improved by optimizing operating conditions. Furthermore, the proposed optimization method could find different new optimal solutions for operating conditions if the target lifetime of the fuel cell system is changed. It is expected that the proposed method is very useful to find optimal operating conditions and enhance performance and durability for many other types of fuel cell systems.

• 한국전기화학회:학술대회논문집
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• 1999.10a
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• pp.51-51
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• 1999

• Rapid Communication in Photoscience
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• v.1 no.2
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• pp.46-46
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• 2012

• Proceedings of the PSK Conference
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• 2001.04a
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• pp.172.2-172.2
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• 2001

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.536-540
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• 2020

The support of the PEMFC membrane plays a key role in improving mechanical durability. The e-PTFE used as a support is chemically stable, so electro-chemical degradation in the PEMFC driving process has been rarely studied. In this study, we investigated whether e-PTFE is chemically stable to radicals and hydrogen peroxide during Fenton reaction. After the Fenton reaction, the main chain of e-PTFE broke, resulting in a change in the chemical structure and morphology of the support, resulting in a decrease in tensile strength. The results of this study showed that electrochemical degradation of the membrane ionomer in the PEMFC process occurs inside the membrane by radicals and hydrogen peroxide, so that electrochemical degradation may also occur at the e-PTFE support in the cell.

• Microbiology and Biotechnology Letters
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• v.27 no.1
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• pp.62-69
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• 1999

Clostridium butyricum NCIB 9576 evolved hydrogen gas and produced various organic acids from glucose, lactose, starch, and glycerol. Total amount of hydrogen gas produced from 1 and 2% glucose were 630 and 950ml $H_2$/l-broth, respectively, for the first 24 hrs of incubation and the maximum hydrogen production rates were 42 and 94ml $H_2$/hr/1-broth, respectively. Teh initial pH 6.8 decreased to 4.2~4.5 during the first 12~16 hrs of fermentation when the pH was not controlled, resulting in ceasing the cell growth and hydrogen evolution and in degradation of 82 and 40% glucose after 24hrs of incubation from 1 and 2% glucose, respectively. When pH was controlled to 5.5, glucose was consumed completely and resulted in increasing hydrogen production approximately 38~50% compared to the experiments without the pH control. C. butyricum NCIB 9576 produced hydrogen gas approximately 644, 1,700 and 3,080 ml $H_2$/l-broth with 0.5, 1 and 2% lactose, respectively and the maximum hydrogen production rates were 41, 141 and 179ml $H_2$/hr/l-broth, respectively. All of the lactose added was degraded completely during fermentation even though pH was not controlled. C. butyricum NCIB 9576 produced 183 and 709ml $H_2$/l-broth with 0.1 and 0.5% starch for 48 hrs, respectively, when pH was not controlled. The maximum rates of hydrogen gas production were 43 and 186ml $H_2$/l-broth, respectively and 80~100% of starch added was fermented. Approximately 107ml $H_2$/l-broth was produced using 1% glycerol by C. butyricum NCIB 9576 and the pH was maintained higher than 6.1 during fermentation without pH control. The degradation of glucose, lactose, starch and glycerol by C. butyricum NCIB 9576 were affected by the pH of fermentation broth and the organic acids released during fermentation. The pH of feremtntation broth dropped to 4.2~4.6 after 12~14 hrs incubation when glucose was used as a substrate while pHs were maintained above pH 5 under the same experimental conditions when lactose, starch and glycerol were used. The organic solvents and acids produced during glucose fermentation were mainly ethanol, butyrate, acetate and a little of propionate, while butyrate was the main organic acids during the lactose, starch, and glycerol fermentation by C. butyricum NCIB 9576.

• KSBB Journal
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• v.20 no.6
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• pp.408-412
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• 2005

In a previous research, it has been found that it could be possible to increase the partial pressure of hydrogen and hydrogen yield by scavenging the $CO_2$ from the heads pace of reactor. In this research, the positive and negative effects of the $CO_2$ scavenging especially on the fate of by-products were investigated by a batch experiment. Production and conversion of by-products had critical relationships with hydrogen evolution and consumption. The maximum hydrogen fraction in the headspace was increased from 66.4 to 91.2% by removing the $CO_2$ in the headspace and the degradation rate of glucose was also enhanced. The removal of $CO_2$ effectively hindered the homoacetogenesis but caused several negative phenomena. The degradation of ethanol, one of the main products, was inhibited by the high partial pressure of hydrogen and/or the absence of $CO_2$. Also it was observed that other by-products such as propionate, propanol, acetone, etc. could not be degraded further after produced from glucose. On the other hand, solventogenesis was not observed in spite of the high hydrogen partial pressure apart from previous researches and it might hinder the excess production of acetate, which could cause overall inhibition. From this research, it could be implicated that the $CO_2$ scavenging method could be recommended if the fermentation was purposed to produce hydrogen and ethanol.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.68-72
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• 2013

Until a recent day, degradation of PEMFC MEA (membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. During simultaneous degradation, there was interaction between membrane degradation and electrode degradation. The effect of electrode degradation on membrane degradation was studied in this work. We compared membrane degradation after electrode degradation and membrane degradation without electrode degradation. I-V performance, hydrogen crossover current, fluoride emission rate (FER), impedance and TEM were measured after and before degradation of MEA. Electrode degradation reduced active area of Pt catalyst, and then radical/$H_2O_2$ evolution rate decreased on Pt. Decrease of radical/$H_2O_2$ reduced the velocity of membrane degradation.