Durability of high temperature polymer electrolyte membrane fuel cells in daily based start/stop operation mode using reformed gas

Kim, Jintae,Kim, Minjin,Lee, Bong-Gu,Sohn, Young-Jun Elsevier 2015 International journal of hydrogen energy Vol.40 No.24

<P><B>Abstract</B></P> <P>As the best substitute for traditional low-temperature proton exchange membrane (PEM) fuel cells, phosphoric acid-doped polybenzimidazole (PBI)-based high-temperature PEM fuel cells have been studied. However, it has been reported that the performance of PBI fuel cells decreases more rapidly than the performance of low-temperature PEM fuel cells. At first, it was determined the effect of the composition of the gas supplied to the anode on the performance characteristics of high-temperature PEM fuel cells. It was observed that CO<SUB>2</SUB> and CO reduced the cell voltage, while CH<SUB>4</SUB> had an insignificant effect. The second, to investigate the degradation of high-temperature PEM fuel cells according to the composition of the simulated reformate, daily based start-up and shut-down (DSS) tests were carried out at 0.2 A cm<SUP>−2</SUP> and 150 °C. Degradation rates with pure hydrogen, and two kinds of simulated reformate were 170, 160, and 270 μV h<SUP>−1</SUP>, respectively. Equivalent circuit (EC) modeling using electrochemical impedance spectroscopy (EIS) was performed to confirm the variations for certain resistances through the DSS tests. Electronic transfer resistance at the anode increased significantly during the DSS tests with reformed gas. Consequently, it was verified that reformed gas that included a small amount of CO did not significantly decrease the durability of high-temperature PEM fuel cells, but the cell voltage diminished when the CO concentration increased.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High temperature proton exchange membrane fuel cells (HT-PEMFCs). </LI> <LI> Experimental performance degrading data of HT-PEMFCs from daily based start and stop operations. </LI> <LI> Comparison of the performance and durability for HT-MEA at the various composition of the reformed gas. </LI> </UL> </P>

Temperature-dependent performance of the polymer electrolyte membrane fuel cell using short-side-chain perfluorosulfonic acid ionomer

Jeon, Y.,Hwang, H.k.,Park, J.,Hwang, H.,Shul, Y.G. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.22

We report on polymer electrolyte membrane fuel cells (PEMFCs) that function at high temperature and low humidity conditions based on short-side-chain perfluorosulfonic acid ionomer (SSC-PFSA). The PEMFCs fabricated with both SSC-PFSA membrane and ionomer exhibit higher performances than those with long-side-chain (LSC) PFSA at temperatures higher than 100 <SUP>o</SUP>C. The SSC-PFSA cell delivers 2.43 times higher current density (0.524 A cm<SUP>-1</SUP>) at a potential of 0.6 V than LSC-PFSA cell at 140 <SUP>o</SUP>C and 20% relative humidity (RH). Such a higher performance at the elevated temperature is confirmed from the better membrane properties that are effective for an operation of high temperature fuel cell. From the characterization technique of TGA, XRD, FT-IR, water uptake and tensile test, we found that the SSC-PFSA membrane shows thermal stability by higher crystallinity, and chemical/mechanical stability than the LSC-PFSA membrane at high temperature. These fine properties are found to be the factor for applying Aquivion(TM) E87-05S membrane rather than Nafion<SUP>®</SUP> 212 membrane for a high temperature fuel cell.

Developement of a PEFC electrodes under the high temperature and low humidified conditions

류성관(Ryu, Sung-Kwan),최영우(Choi, Young-Woo),박진수(Park, Jin-Soo),임성대(Yim, Sung-Dae),양태현(Yang, Tae-Hyun),김한성(Kim, Han-Sung),김창수(Kim, Chang-Soo) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.11

Generally, Nafion ionomer is used in the polymer electrolyte fuel cell (PEFC) electrodes to achieve high power density. At the high temperature operation of PEFC, however, ionic conductivity of Nafion remarkably decreased due to the evaporation of water in Nafion polymer. Recently, many researchers have focused on using the Ionic Liquids(ILs) instead of water in Nafion polymer. ILs have intrinsic properties such as good electrochemical stability, high ionic conductivity, and non-flammability. Especially, ILs play a crucial role in proton conduction by the Grottuss mechanism and act as water in water-free Nafion polymer. However, it was found that the ILs was leached out of the polymer matrix easily. In this study, we prepared membrane electrode assemblies with various contents of ILs. The effect of ILs in the electrode of each designed was investigated by a cyclic voltammetry measurement and the cell performance obtained through a single cell test using H2/Air gases. Electrodes with different contents of ILs in catalyst layer were examined at high temperature and low humidified condition.

Effect of operating conditions on carbon corrosion in High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs)

이진희(Lee, Jinhee),김한성(Kim, Hansung) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11

The influence of potential and humidity on the electrochemical carbon corrosion in high temperature polymer electrolyte membrane fuel cells(HT-PEMFCs) is investigated by measuring CO₂ emission at different potentials for 30 min using on-line mass spectrometry. These results are compared with low tempterature polymer electrolyte membrane fuel cells(LT-PEMFCs) operated at lower temperature and higher humidity condition. Although the HT-PEMFC is operated at non humidified condition, the emitted CO₂ in the condition of HT-PEMFC is more than LT-PEMFC at the same potential in carbon corrosion test. Thus, carbon corrosion shows a stronger positive correlation with the cell temperature. In addition, the presence of a little amount of water activate electrochemical carbon corrosion considerably in HT-PEMFC. With increased carbon corrosion, changes in fuel cell electrochemical characteristics become more noticeable and thereby indicate that such corrosion considerably affects fuel cell durability.

Accelerated life-time test protocols for polymer electrolyte membrane fuel cells operated at high temperature

Jeon, Y.,Na, H.,Hwang, H.,Park, J.,Hwang, H.,Shul, Y.g. Pergamon Press ; Elsevier Science Ltd 2015 International journal of hydrogen energy Vol.40 No.7

Durability of high temperature fuel cells with low humidity has been receiving attention for its commercialization into the automobile. Therefore, advanced durability protocols are designed to evaluate the membrane electrode assembly (MEA) composed of short-side-chain conducting polymer (Aquivion(TM)) at the high temperature of 120 <SUP>o</SUP>C and low humidity of 40%RH. Accelerated life time tests (ALTs) of on-off cycle test with the duration time of 10 min and load cycle test with a voltage sweep of 0.6 V-1.0 V and a duration of 4.25 min, are developed to induce different stresses. The different degradation behaviors of the MEAs are monitored and compared to the normal constant voltage mode of 0.6 V. The decay rate using the on-off cycle test is 0.113 mA/(cm<SUP>2</SUP> min) whereas a slightly slower decay rate of 0.096 mA/(cm<SUP>2</SUP> min) is obtained for the load cycle test. The electrochemical analyses of membrane electrode assembly (MEA) are confirmed periodically during the tests for each protocol using polarization curve, impedance spectroscopy and cyclic voltammetry. The characterizations of the MEA are carried out before and after the durability tests to verify the material degradation and failure mechanisms. Although both protocols show similar degradation on the MEA materials, the membrane degradation is more dominant after the on-off test while more catalyst degradation is observed after the load cycling test. Nafion<SUP>®</SUP> is also tested by the developed load cycle test to observe the difference between short-side-chain and long-side-chain conducting polymer.

HT-PEMFC/이중효용 흡수식 냉동기 하이브리드 시스템 개발

이용균(Yong Gyun Lee),김동규(Dong Kyu Kim) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6

이 연구에서는 고온 고분자 전해질 막 연료전지(High Temperature-Polymer Electrolyte Membran Fuel Cell, HT-PEMFC)의 폐열을 이용한 이중효용 흡수식 냉동기 모델 개발 연구가 실행되었다. 본 연구를 통해 개발된 하이브리드 모델은 HT-PEMFC의 운전 조건에 따른 성능과 폐열을 계산하는 모델과 발생된 폐열을 열원으로 하여 작동하는 이중효용 흡수식 냉동기의 냉방 효율을 계산하는 모델로 구성되어있다. 본 연구는 연료전지를 통한 전력생산과 폐열을 활용한 공기 조화 시스템을 제시함으로서 고온 연료전지의 낮은 효율을 극복해 상용화를 앞당기는 것에 기여할 것이다.

Synthesis and Characterization of H3PO4 Doped Poly(benzimidazole-co-benzoxazole) Membranes for High Temperature Polymer Electrolyte Fuel Cells

Hye Jin Lee,Dong Hoon Lee,Dirk Henkensmeier,장종현,조은애,김형준,김화용 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

Poly(benzimidazole-co-benzoxazole)s (PBI-co-PBO) are synthesized by polycondensation reaction with 3,3'- diaminobenzidine, terephthalic acid and 3,3'-dihydroxybenzidine or 4,6-diaminoresorcinol in polyphosphoric acid (PPA). All polymer membranes are prepared by the direct casting method (in-situ fabrication). The introduction of benzoxazole units (BO units) into a polymer backbone lowers the basic property and H3PO4 doping level of the copolymer membranes, resulting in the improvement of mechanical strength. The proton conductivity of H3PO4 doped PBI-co-PBO membranes decrease as a result of adding amounts of BO units. The maximum tensile strength reaches 4.1 MPa with a 10% molar ratio of BO units in the copolymer. As a result, the H3PO4 doped PBI-co-PBO membranes could be utilized as alternative proton exchange membranes in high temperature polymer electrolyte fuel cells.

Preparation and Characterization of Ionic Liquid-based Electrode for High Temperature Fuel Cells Using Cyclic Voltammetry

류성관,최영우,김창수,양태현,김한성,박진수 한국전기화학회 2013 한국전기화학회지 Vol.16 No.1

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deion-ized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under con-ditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different fea-tures. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

The Electrochemical Performance Evaluation of PBI-based MEA with Phosphoric Acid Doped Cathode for High Temperature Fuel Cell

이준기,이찬민,전유권,이홍연,박상선,김태영,김희선,송순호,박정옥,설용건 한국수소및신에너지학회 2017 한국수소 및 신에너지학회논문집 Vol.28 No.5

A proton exchange membrane fuel cell (PEMFC) operated at 150℃ was evaluated by a controlling different amount of phosphoric acid (PA) to a membrane-electrode assembly (MEA) without humidification of the cells. The effects on MEA performance of the amount of PA in the cathode are investigated. The PA content in the cathodes was optimized for higher catalyst utilization. The highest value of the active electrochemical area is achieved with the optimum amount of PA in the cathode confirmed by in-situ cyclic voltammetry. The current density-voltage experiments (I-V curve) also shows a transient response of cell voltage affected by the amount of PA in the electrodes. Furthermore, this information was compared with the production variables such as hot pressing and vacuum drying to investigate those effect to the electrochemical performances.

고온 고분자 전해질막 연료전지 수소극 전극에서 서로 다른 가스 확산층에 따른 최적 바인더 함량 결정

전현수,김도형,정현승,박찬호 한국수소및신에너지학회 2022 한국수소 및 신에너지학회논문집 Vol.33 No.1

Two different gas diffusion layers having noticeable differences in micro-porous layer’s (MPL’s) crack were studied as a substrate for the gas diffusion electrode (GDE) with different binder/carbon (B/C) ratios in high-temperature polymer electrolyte fuel cell (Ht-PEMFC). As a result, the performance defined as the voltage at 0.2 A/cm2 and maximum power density from the single cells using GDEs from H23 C2 and SGL38 BC with different B/C ratios were compared. GDEs from H23 C2 showed a proportional increase of the voltage with the binder content on the other hand GDEs from SGL38 BC displayed a proportional decline of the voltage to the binder content. It was revealed that MPL crack influences the structure of catalyst layer in GDEs as well as affects the RCathode which is in close connection with the Ht-PEMFC performance.