• 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.

• Journal of Industrial Technology
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• v.35
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• pp.89-94
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• 2015

Graphene is a carbon-based two dimensional honeycomb lattice with monoatomic thickness and has attracted much attention due to its superior mechanical, electronic, and physical properties. Here, we present a synthesis of high quality graphene on Pt substrate using a chemical vapor deposition (CVD). We optimized synthesis condition with various parameters such as synthesis temperature, time, and cooling rate. Based on the results, we concluded that graphene synthesis is driven by mainly carbon adsorption on surface rather than precipitation of carbon which is dominant in other metal substrate. In addition, Pt substrate can be repeatedly used several times with high quality graphene.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.63-66
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• 2006

A long term deactivation study was carried out with commercial MEA provided by Hyundai Motor Co. The deactivation phenomena were observed only at high voltage region where there is no diffusion-limited reaction. A rapid deactivation was observed up to 40h owing to the sintering of Pt particles. This was followed a gradual increase in the activity up to 300 h, which is probably caused by improvement in the electrode properties in the presence of current during the reaction. After 300 h, monotonic decrease in the activity was observed owing to dissolution of Pt particles especially in the cathode. The presence oxygen is the cause of oxidation and dissolution of Pt. The dissolution rate can be somewhat retarded by generation of current, which reduces Pt ion back to Pt in the cathode.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.202-207
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• 2022

The study on electrode degradation of Proton Exchange Membrane Fuel Cell (PEMFC) was mainly studied on the particle growth and active area reduction of Pt on the electrode. The degradation of the electrode catalyst Pt in contact with the membrane affects the deterioration of the polymer membrane, but there are not many studies related to this. In this study, the phenomenon of the deposition of deteriorated Pt inside the polymer membrane during the accelerated electrode catalyst degradation test and its effects were studied. The voltage change (0.6 V ↔ 0.9 V) was repeated up to 30,000 cycles to accelerate the platinum degradation rate. When the voltage change cycle was repeated while oxygen was introduced into the cathode, the amount of Pt deposited inside the film was larger than when nitrogen was introduced. As the number of voltage change cycles increased, the amount of Pt deposited inside the membrane increased, and Pt dissolved in the cathode moved toward the anode, showing a uniform distribution throughout the membrane at 20,000 cycles. In the process of the accelerated electrode catalyst degradation test, the hydrogen crossover current density of the membrane did not change, and it was confirmed that the deposited Pt did not affect the durability of the membrane.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.325-329
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• 2013

The membrane and electrode were degraded coincidentally at real PEMFC(Proton Exchange Membrane Fuel Cells) operation condition. But the interaction membrane degradation between electrode degradation has not been studied. The effect of membrane degradation on electrode degradation was studied in this work. We compared electrode degradation after membrane degradation and electrode degradation without membrane degradation. I-V performance, hydrogen crossover current, impedance and TEM were measured after and before degradation of MEA. Membrane degradation enhanced hydrogen crossover, and then Pt particle growth rate was reduced. Increase of hydrogen crossover by membrane degradation reduced the electrode degradation rate.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.478-482
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• 2017

Humidity control of proton exchange membrane fuel cell(PEMFC) is very important control condition during driving. In terms of water management, low humidification conditions are advantageous, and high humidification is advantageous in terms of drainage utilization and energy efficiency. In this study, the characteristics of outlet water in low humidification and high humidification process were studied in terms of utilization of discharged water. Since the impurities in the effluent are generated during the degradation of the membrane and the electrode assembly(MEA), degradation of the MEA under low humidification and high humidification conditions was also studied. The rate of radical generation was high at low humidification condition of the anode RH 0%, which showed that it was the main cause of the degradation of the polymer membrane. Analysis of effluent showed low concentration of fluoride ion concentration of about 20 ppb at high humidification (both electrodes RH 100%) and 0.6 V, which was enough to be used as the feed water for electrolysis. Very low concentration of platinum below 0.2 ppb was detected in the condensate discharged from the high humidification condition.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.2
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• pp.103-110
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• 2008

The most failure mode of PEM fuel cell is gas crossover caused by pinhole formation in MEAs. The degradation phenomena of MEA with pinholes were evaluated in various accelerated operation condition, such as OCV, low humidity and high partial pressure of oxygen. The performances of MEA with pinholes were almost same before and after normal 144 hours operation($70^{\circ}C$, $640mA/cm^2$, 65%RH $H_2/air$). The results of accelerated operation showed that OCV and low humidity condition more deteriorated MEA than gas crossover owing to pinholes. When oxygen was used as cathode gas, the pinholes of MEA were enlarged due to heat of combustion reaction on Pt catalyst of electrodes. This combustion reaction occurred at pinholes near gas inlet and resulted in local MEA failure.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.277-282
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• 2010

Durability of automotive polymer electrolyte membrane fuel cell (PEMFC) strongly depends the startup/shutdown procedure. Formation of hydrogen/air boundary in the anode gas channel, so-called reverse current condition, particularly induces fast degradation of the cathode. Under the reverse current condition, high voltage is present at the cathode facing air in the anode gas channel and is a function of residual oxygen concentration in the gas channels, that increases with storage time and reaches 21% (air) eventually. In this study, effects of residual oxygen concentration in a PEMFC on degradation of the PEMFC.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.204-209
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• 1996

각종 전자부품에 이용되는 백금막의 밀착력과 응집화 현상에 대해 연구하였다. 온도저항계수(TCR)의 열화 없이 밀착력을 향상 시키기 위해서 AI, Si의 산화물을 adhesion promoting layer로 이용한 결과 매우 우수한 밀착력과 TCR을 보였다. 질소분위기 600-90$0^{\circ}C$의 온도범위에서 행한 열처리를 통해 응집화현상을 관찰한 결과 응집화는 기판거칠기에 따라 다른 양상을 보였다. Si3N4등의 기판거칠기가 작은 adhesion promoting layer를 이용한 시편의 경우 고온인 90$0^{\circ}C$에서 응집화 현상이 발생되었다. 표면거칠기가 큰 AI-Si 산화물을 adhesion promoting layer로 이용한 시편의 경우 비교적 저온인 $600^{\circ}C$에서 응집화 현상이 발생했으며 80$0^{\circ}C$이상의 열처리의 경우 중앙응집체와 응집체고갈지역이 형성되는 현상을 나타내었다.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.1-7
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• 2012

This study was performed to develop a low Pt content catalyst as a catalyst for HI decomposition in S-I process. Bimetallic catalysts added various amounts of Pt on a silica supported Ni catalyst were prepared by impregnation method. HI decomposition was carried out using a fixed bed reactor. As a result, Ni-Pt bimetallic catalyst showed enhanced catalytic activity compared with each monometallic catalyst. Deactivation of Ni-Pt catalyst was not observed while deactivation of Ni monometallic catalyst was rapidly occurred in HI decomposition. The HI conversion of Ni-Pt bimetallic catalyst was increased similar to Pt catalyst with increase of the reaction temperature over a temperature range 573K to 773K. From the TG analysis, it was shown that $NiI_2$ remained on the Ni(5.0)-Pt(0.5)/$SiO_2$ catalyst after the HI decomposition reaction was decomposed below 700K. It seems that small amount of Pt in bimetallic catalyst increase the decomposition of $NiI_2$ generated after the decomposition of HI. Consequently, it was considered that the activity of Ni-Pt bimetallic catalyst was kept during the HI decomposition reaction.