PEMFC에서 막 열화가 전극 열화에 미치는 영향

송진훈 ( Jin Hoon Song ),정재진 ( Jae Jin Jeong ),정재현 ( Jae Hyeun Jeong ),김세훈 ( Sae Hoon Kim ),안병기 ( Byung Ki Ahn ),고재준 ( Jai Joon Ko ),박권필 ( Kwon Pol Park ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.3

실제 고분자 전해질 연료전지(PEMFC) 운전조건에서는 전극과 전해질 막은 동시에 열화된다. 그런데 고분자전해질연료전지의 전극 열화와 전해질 열화의 상호 작용에 대해 연구되지 않았다. 본 연구에서는 전해질 막 열화가 전극 열화에 미치는 영향에 대해 연구하였다. 전해질 막 열화 후 전극을 열화시켜 전해질 막 열화없이 전극을 열화시켰을 때와 비교하였다. 열화전후의 I-V 성능, 수소투과전류, 순환 전압측정(CV), 임피던스, TEM 등을 측정하였다. 전해질 막열화에 의해 수소투과도가 증가하고, 이에 따라 백금 입자 성장속도가 감소함으로써 전극 열화속도가 감소함을 보였다. 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.

PEMFC에서 전극 열화가 전해질 막 열화에 미치는 영향

박권필 ( Kwon Pil Park ),송진훈 ( Jin Hoon Song ),김세훈 ( Sae Hoon Kim ),안병기 ( Byung Ki Ahn ),고재준 ( Jai Joon Ko ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.1

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/H2O2 evolution rate decreased on Pt. Decrease of radical/H2O2 reduced the velocity of membrane degradation.

PEMFC에서 전극과 전해질 막의 열화 가속 시험

송진훈 ( Jin Hoon Song ),김세훈 ( Sae Hoon Kim ),인병기 ( Byung Ki Ahn ),고재준 ( Jai Joon Ko ),박권필 ( Kwon Pil Park ) 한국화학공학회 2012 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.50 No.5

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. Therefore in this work, AST (Accelerated Stress Test) of MEA degradation was done at the condition that membrane and electrode were degraded simultaneously. There was interaction between membrane degradation and electrode degradation. Membrane degradation reduced the decrease range of catalyst active area by electrode degradation. Electrode degradation reduces increase range of the hydrogen crossover current and FER (Fluoride Emission Rate) by membrane degradation.

PEMFC 고분자 막의 전기화학적 가속 열화에 미치는 평가조건들의 영향

오소형,유동근,배석주,채선규,박권필,Sohyeong Oh,Donggeun Yoo,Suk Joo Bae,Sun Geu Chae,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

In order to improve the durability of the proton exchange membrane fuel cell (PEMFC), it is important to accurately evaluate the durability of the polymer membrane in a short time. The test conditions for chemically accelerated durability evaluation of membranes are high voltage, high temperature, low humidity, and high gas pressure. It can be said that the protocol is developed by changing these conditions. However, the relative influence of each test condition on the degradation of the membrane has not been studied. In chemical accelerated degradation experiment of the membrane, the influence of 4 factors (conditions) was examined through the factor experiment method. The degree of degradation of the membrane after accelerated degradation was determined by measuring the hydrogen permeability and effluent fluoride ion concentration, and it was possible to determine the degradation order of the polymer membrane under 8 conditions by the difference in fluoride ion concentration. It was shown that the influence of the membrane degradation factor was in the order of voltage > temperature > oxygen pressure > humidity. It was confirmed that the degradation of the electrode catalyst had an effect on the chemical degradation of the membrane.

PEMFC의 고분자막에서 지지체가 고분자전해질 막 성능 및 전기화학적 내구성에 미치는 영향

오소형 ( Sohyung Oh ),임대현 ( Dae Hyun Lim ),이대웅 ( Daewoong Lee ),박권필 ( Kwonpil Park ) 한국화학공학회 2020 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.58 No.4

고분자전해질 연료전지의 기계적 내구성을 높이기 위해 고분자막에 지지체를 넣은 강화막이 사용되고 있다. 지지체는 주로 e-PTFE를 사용하는데 소수성이고 이온전달이 안되므로 성능저하의 원인이 될 수 있다. 그래서 본 연구에서는 e-PTFE 지지체가 PEMFC 성능과 전기화학적 내구성 미치는 영향에 대해 연구하였다. 본연구에서는 지지체가 들어간 강화막과 들어가지 않은 단일막(비강화막)을 비교하였는데, 지지체의 소수성 때문에 강화막의 물 확산계수가 단일막보다 낮았다. 강화막은 물확산 계수가 낮아 이온의 막 이동 저항이 단일막보다 높았다. 지지체의 낮은 수소투과도 때문에 강화막의 OCV가 단일막보다 높았다. 지지체가 수소투과도를 감소시킴으로서 라디칼 발생속도를 감소시켜 강화막의 전기화학적 내구성도 향상시킴을 보였다. 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.

Pinhole formation in PEMFC membrane after electrochemical degradation and wet/dry cycling test

Ho Lee,박권필,Taehee Kim,Woojong Sim,Saehoon Kim,Byungki Ahn,Taewon Lim 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2

During the operation of a PEMFC, the polymer membrane is degraded by electrochemical reactions and mechanical stresses. We investigated the effects of repeated electrochemical and mechanical degradations in a membrane. For mechanical degradation, the membrane and MEA were repeatedly subjected to wet/dry cycles; for electrochemical degradation, the cell was operated under open-circuit voltage (OCV)/low-humidity conditions. The repeated wet/dry cycles led to a decrease in the mechanical strength of the membrane. When the MEA was degraded electrochemically, repeated wet/dry cycling resulted in the formation of pinholes in the membrane. In the case of different MEAs that were first degraded electrochemically, the extents of their hydrogen crossover currents increased due to repeated wet/dry cycling being different. Therefore, these results indicated that the membrane durability could be evaluated by these methods of repeated electrochemical degradation and wet/dry cycles.

고분자전해질 연료전지의 전극 열화 과정에서 고분자막에 석출된 백금에 관한 연구

오소형 ( Sohyeong Oh ),권혜진 ( Hyejin Gwon ),유동근 ( Donggeun Yoo ),박권필 ( Kwonpil Park ) 한국화학공학회 2022 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.60 No.2

고분자 전해질 연료전지(PEMFC)의 전극 열화에 대한 연구는 전극상에서 Pt의 입자 성장 및 활성면적 감소에 대한 연구가 대부분이다. 고분자막과 접해 있는 전극촉매 Pt의 열화는 고분자막 열화에 영향을 주는데, 이와 관련된 연구는 많지 않다. 본 연구에서는 전극촉매 열화 가속 시험 과정에서 열화된 Pt가 고분자막 내부에 석출되는 현상과 그 영향에 대해서 연구하였다. 백금 열화 속도를 가속화시키기 위해 전압 변화(0.6 V ↔ 0.9 V)를 30,000 사이클까지 반복했다. Cathode에 산소를 유입하면서 전압 변화 사이클을 반복했을 때 질소를 유입했을 때 보다 막 내부에 석출된 Pt의 양이 더 많았다. 전압 변화 사이클 횟수가 증가할수록 막 내부에 석출된 Pt의 양이 증가하였고, cathode에서 용해된 Pt가 anode 쪽으로 이동해 20,000 사이클에서는 막 내부에 전체적으로 균일한 분포를 보였다. 이와 같은 전극촉매 열화 가속 시험과정에서 고분자막의 수소투과 전류밀도는 거의 변하지 않아서, 석출된 Pt가 고분자막의 내구성에는 영향을 주지 않음을 확인하였다. 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.

Chemical stability enhancement of Nafion membrane by impregnation of a novel organic ·OH radical scavenger, 3,4-dihydroxy-cinnamic acid

Park, Yongman,Kim, Dukjoon Elsevier 2018 Journal of membrane science Vol.566 No.-

<P><B>Abstract</B></P> <P>In this contribution, the effect of a novel organic ·OH scavenger, 3,4-dihydroxy-cinnamic acid (CA), is investigated on the anti-oxidation of Nafion membranes, as the endurance of fuel cell performance is recently a critical issue in the development of proton exchange membrane. As this organic scavenger is possibly kept in the membrane without migration by water flow and does not diminish proton conductivity by ionic interaction with sulfonic acids, much more durable property of the membrane is expected than well-known cerium ion (CE) scavenger. CA contained Nafion membrane (CA-Nafion) were prepared to analyze the effect of CA on the fundamental structure and properties of membrane using a variety of instruments such as SAXs, FTIR, TGA, and UTM. CA and CE leaching out test result showed that CA can be preserved in composite membrane compared to CE. Cell performance and oxidation stability of pristine Nafion, CA-Nafion and CE-Nafion membrane were determined by ex-situ and in-situ method. As a result, both CA-Nafion membrane and CE-Nafion membrane have oxidation stability compare to pristine Nafion, but only CA-Nafion membrane maintained the cell performance of pristine Nafion membrane.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CA contained Nafion membrane (CA-Nafion) were prepared to analyze the effect of CA. </LI> <LI> The effect of CA on the fundamental structure and properties of membrane were analyzed. </LI> <LI> CA leaching out test result showed that CA can be preserved in composite membrane. </LI> <LI> CA-Nafion membrane and CE-Nafion membrane have oxidation stability. </LI> <LI> Only CA-Nafion membrane maintained the cell performance of pristine Nafion membrane. </LI> </UL> </P>

Acceleration of electrolyte membrane degradation by frequent activation in PEMFC electrochemical durability evaluation

Yoo Donggeun,Hwang Byungchan,Oh Sohyeong,박권필 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.8

During the durability tests for PEMFC membranes, performance characterization is conducted to determine the degree of degradation, the interval for which is different for each durability test protocol. Before performance characterization, activation is carried out to determine the reliability. Most activations are accompanied by voltage changes, which can lead to electrode degradation. However, this has largely been neglected because the activation time is shorter than the durability test time. In this study, activation was conducted at 24, 48, and 144 h intervals, during the membrane durability test of a PEMFC, and the effect of activation on the degradation of the membrane and electrode was investigated. For a shorter activation interval during the durability test, the lifetime of the membrane was reduced by up to 35%. For the same durability test time, more activations led to greater electrode and membrane degradation. Through scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS) analysis, it was found that for a shorter activation interval, more Pt was deposited into the membrane and then the membrane was thinner. During the durability test, frequent activation accelerated membrane and electrode degradation.

PEMFC에서 Pt-Co/C Cathode 촉매가 고분자막의 전기화학적 내구성에 미치는 영향

오소형,유동근,김명환,박지용,박권필 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.2

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.