An electrode-supported fabrication of thin polybenzimidazole membrane-based polymer electrolyte membrane fuel cell

Yuk, Seongmin,Lee, Dong-Hyun,Choi, Sungyu,Doo, Gisu,Lee, Dong Wook,Kim, Hee-Tak Elsevier 2018 ELECTROCHIMICA ACTA Vol.270 No.-

<P><B>Abstract</B></P> <P>H<SUB>3</SUB>PO<SUB>4</SUB>-doped polybenzimidazole (PBI) membranes have been employed for high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Although a thinner PBI membrane is beneficial in enhancing power performance, the use of thin PBI membrane has been hindered by its poor mechanical property and consequent difficulty in membrane handling during membrane electrode assembly (MEA) fabrication. Here, novel fabrication route to realize a thin PBI membrane (∼35 μm)-based HT-MEA is presented. The key feature of the process is to fabricate thin blend membrane of PBI and poly(ethylene glycol) (PEG) and laminate the blend membrane to anode gas diffusion electrode (GDE) followed by H<SUB>3</SUB>PO<SUB>4</SUB> doping. The introduction of PEG to PBI film enables the tight bonding of the membrane to the GDE at a mild lamination temperature and mitigates the membrane expansion with the doping, preserving the tight interfacial bonding. Due to the lowered membrane thickness, the corresponding MEA exhibits a high power density of 264 mW cm<SUP>-2</SUP> at 0.6 V. Therefore, the new fabrication strategy based on the blend of PBI/PEG is highly effective in improving both process and power performance of HT-MEA.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

계면활성제가 도입된 이오노머를 함침시킨 ePTFE기반 강화복합막의 제작과 이들의 PEMFC 특성

한동헌(Dong-Heon Han),오승주(Seung-Ju Oh),이종인(Jong In Lee),배진우(Jin Woo Bae) 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.3

고분자 전해질막 연료전지(polymer electrolyte membrane fuel cell, PEMFC)용 ePTFE기반 강화복합막은 이오노머 막에 비해 낮은 가격과 우수한 내구성으로 인해 주목받고 있다. 그러나, 다공성 ePTFE 강화막의 소수성과 이오노머의 친수성 사이의 반발력으로 인해 강화복합막의 불완전한 함침 문제가 발생한다. 이는 ePTFE기반 강화복합막의 오믹 저항과 수소기체투과도를 증가시키기 때문에 PEMFC의 성능과 내구성을 감소시킨다. 본 연구에서는 친수성과 소수성의 반발력을 감소시킴으로써 함침을 개선시키기 위해서 Triton X-100와 Igepal CO-630 계면활성제를 각각 함량별로 이오노머에 도입시켜 용액을 제조하였다. 이를 활용하여 함침을 개선시킨 ePTFE기반 강화복합막을 제작하였으며, 막-전극 접합체(membrane electrode assembly, MEA)로 제작하여 PEMFC에 적용하였다. 계면활성제의 함량이 증가함에 따라서 ePTFE에서 대한 이오노머 용액의 젖음성을 증가되었기 때문에 ePTFE기반 강화복합막의 함침을 개선시켰다. 또한, PEMFC에서 ePTFE기반 강화복합막의 오믹 저항과 수소기체투과도를 감소시킨 것을 확인하였다. 더욱이, Triton X-100에 비해서 우수한 젖음성을 가지는 Igepal CO-630 계면활성제는 ePTFE에 대한 이오노머 용액의 함침을 더욱 개선할 수 있기 때문에 ePTFE기반 강화복합막의 PEMFC 성능과 내구성을 효과적으로 개선시킬 수 있었다. ePTFE-based reinforced composite membranes for polymer electrolyte membrane fuel cells (PEMFCs) have attracted attention because of their higher durability and lower cost than ionomer membranes. On the other hand, repulsion between the hydrophobic ePTFE membrane and hydrophilic ionomer causes incomplete impregnation. This problem deteriorates the performance and durability of PEMFCs owing to the increasing ohmic resistance and hydrogen crossover of the ePTFE-based reinforced composite membrane. This study developed ionomer solutions with Triton X-100 or Igepal CO-630 as surfactants, which can improve impregnation by reducing the repulsion between the hydrophobicity and hydrophilicity. The surfactant-introduced ionomer solutions were impregnated directly on the ePTFE membrane and applied to a membrane electrode assembly (MEA) for PEMFC. The presence of the surfactant improved the impregnation of the ePTFE-based reinforced composite membrane due to the increasing wetting properties of ionomer solutions on the ePTFE membrane and thus reduced the ohmic resistance and hydrogen crossover of PEMFC. In addition, the ionomer with the Igepal CO-630 surfactant showed better wetting properties than that with Triton X-100. Therefore, the introduction of a surfactant into the ePTFE-based reinforced composite membrane was expected to increase the performance and durability of PEMFC effectively.

Performance enhancement of membrane electrode assemblies with plasma etched polymer electrolyte membrane in PEM fuel cell

Cho, Yong-Hun,Bae, Jin Woo,Cho, Yoon-Hwan,Lim, Ju Wan,Ahn, Minjeh,Yoon, Won-Sub,Kwon, Nak-Hyun,Jho, Jae Young,Sung, Yung-Eun Elsevier 2010 International journal of hydrogen energy Vol.35 No.19

<P><B>Abstract</B></P><P>In this work, a surface modified Nafion 212 membrane was fabricated by plasma etching in order to enhance the performance of a membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Single-cell performance of MEA at 0.7V was increased by about 19% with membrane that was etched for 10min compared to that with untreated Nafion 212 membrane. The MEA with membrane etched for 20min exhibited a current density of 1700mAcm<SUP>−2</SUP> at 0.35V, which was 8% higher than that of MEA with untreated membrane (1580mAcm<SUP>−2</SUP>). The performances of MEAs containing etched membranes were affected by complex factors such as the thickness and surface morphology of the membrane related to etching time. The structural changes and electrochemical properties of the MEAs with etched membranes were characterized by field emission scanning electron microscopy, Fourier transform-infrared spectrometry, electrochemical impedance spectroscopy, and cyclic voltammetry.</P>

Gas diffusion layer/flow-field unified membrane-electrode assembly in fuel cell using graphene foam

Park, Ji Eun,Lim, Jongkoo,Lim, Myung Su,Kim, Sungjun,Kim, Ok-Hee,Lee, Dong Woog,Lee, Ji Hyun,Cho, Yong-Hun,Sung, Yung-Eun Pergamon Press 2019 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>The integration of a gas diffusion layer with a flow-field is essential for enhancing the polymer electrolyte membrane fuel cell performance. This is achieved by exploiting the ability of a gas diffusion layer-flow-field combination to decrease the size of the reactant pathway and the thickness of the membrane-electrode assembly, thereby reducing electrical and mass transport resistance. This study proposes a unified membrane-electrode assembly that incorporates graphene foam that functions as both a flow-field and a gas diffusion layer. The unified membrane-electrode assembly exhibits higher performance than conventional membrane-electrode assembly on overall current densities region, which is attributed to the increased the pressure drop. Furthermore, its estimated volume power density can be increased because of the 82% decrease in its thickness. Also, the simulation results show that this design enhances the exchange current density due to pressure drop in the graphene foam.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Unified MEA using graphene-foam that functions as flow-field and GDL is prepared. </LI> <LI> Unified MEA enhances cell performance and volume power density by 8.2 times. </LI> <LI> Simulation results exhibits that unified MEA improved exchange current density. </LI> <LI> This enhancement is attributed to the increased internal pressure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Performance of a MEA using patterned membrane with a directly coated electrode by the bar-coating method in a direct methanol fuel cell

Kang, Saetbyeol,Bae, Gyuna,Kim, Sang-Kyung,Jung, Doo-Hwan,Shul, Yong-Gun,Peck, Dong-Hyun Elsevier 2018 International journal of hydrogen energy Vol.43 No.24

<P><B>Abstract</B></P> <P>This study increased the surface area of a membrane by forming patterns on the Nafion resin membrane using a stainless steel mesh to enhance the performance of a direct methanol fuel cell (DMFC) because the triple-phase boundary is extended. Nafion resin (F-form (SO<SUB>3</SUB>F)) was used which has melt-moldability to form a stable surface pattern and to directly coat the catalyst layer by the bar-coating method. The performance (polarization and power density curves) and the resistance of the membrane-electrode assembly (MEA) were analyzed with a single cell and an impedance analyzer. The surface area of the patterned membranes was increased 1.99, 2.10, and 2.12 times compared to the flat membrane, and the power density also increased 12.9, 18.6, and 24.2% at 0.4 V, respectively. The performance of the MEA with the patterned membrane had a lower concentration polarization than that of the MEA with the flat membrane. The performance of the MEAs with the patterned membranes had a greater impact on the cathode side of the membrane than on the anode side. The results of these experiments offer a solution to the problem of a low performance of MEA, which is one of the disadvantages of DMFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The catalyst layer was directly coated onto the patterned membrane (F-form (SO<SUB>3</SUB>F)). </LI> <LI> The surface area of the patterned membranes was increased 2.12 times. </LI> <LI> The power density of the MEAs with the patterned membranes was also increased 24.2%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Role of the glass transition temperature of Nafion 117 membrane in the preparation of the membrane electrode assembly in a direct methanol fuel cell (DMFC)

Jung, H.Y.,Kim, J.W. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.17

The glass transition temperature (T<SUB>g</SUB>) of the Nafion 117 membrane was traced by DSC step by step during the preparation of the membrane electrode assembly (MEA). Wide-angle x-ray diffraction and frequency response analysis were used for the determination of the crystallinity and proton conductivity of the membrane. As-received Nafion 117 membrane showed two glass transition temperatures in the DSC thermogram. The first T<SUB>g</SUB>, caused by the mobility of the main chain in the polymer matrix, was 125 <SUP>o</SUP>C; the second T<SUB>g</SUB>, derived from the side chain due to the strong interaction between the sulfonic acid functional groups, was 195 <SUP>o</SUP>C. During the pretreatment of the membrane, the T<SUB>g</SUB> of the Nafion 117 membrane drastically decreased because of the plasticizer effect of water. In the hot-pressing process, the T<SUB>g</SUB> of the Nafion 117 membrane gradually increased due to the loss of water. When the Nafion 117 was completely dried, the T<SUB>g</SUB> of the membrane finally reached 132 <SUP>o</SUP>C. Thermal heat treatment was then applied to the MEA to obtain high interfacial stability; however, the membrane developed a crystalline morphology that led to reduced water uptake and proton conductivity. Therefore, the thermal heat treatment of the MEA should be carefully controlled in the region of the glass transition temperature (120-140 <SUP>o</SUP>C) of the Nafion 117 membrane to ensure the high performance of the MEA.

Bending-durable membrane-electrode assembly using metal nanowires for bendable polymer electrolyte membrane fuel cell

Kang, Yun Sik,Won, Phillip,Ko, Seung Hwan,Park, Taehyun,Yoo, Sung Jong Elsevier 2019 ENERGY Vol.172 No.-

<P><B>Abstract</B></P> <P>We herein report a simple and effective strategy to fabricate the bending-durable membrane-electrode assembly for bendable polymer electrolyte membrane fuel cells (PEMFCs) by simply coating conventional carbon papers with manually fabricated silver nanowires (Ag NWs). Due to the high stretchability and flexibility of Ag NWs, we expect that the introduction of Ag NWs to carbon fibers would relieve the increase of ohmic and charge transfer resistances derived from the disconnections between each carbon fiber and the resulting decrease of electrical conductivity by repeatedly bending the bendable PEMFCs. We find that by using Ag NWs as an added component to carbon paper, the performance of Ag NWs-applied PEMFC can be maintained after repetitive bending. Carbon papers with the Ag NWs also show higher performance than the PEMFC without Ag NWs in the previous research. From the electrochemical impedance spectra of Ag NWs-coated PEMFC, it is clearly demonstrated that the coated Ag NWs effectively connect between carbon fibers and thereby play a role as a good buffer medium when carbon fibers are disconnected by mechanical bending.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bending-durable polymer electrolyte membrane fuel cell was realized. </LI> <LI> Gas-diffusion layer was simply coated with percolated silver nanowires. </LI> <LI> Fuel cell with silver nanowires showed high durability after repetitive bending. </LI> <LI> Silver nanowires maintained electric connection between disconnected carbon fibers. </LI> </UL> </P>

Effect of Nafion⁽R) gradient in dual catalyst layer on proton exchange membrane fuel cell performance

Kim, K.-H.,Kim, H.-J.,Lee, K.-Y.,Jang, J.H.,Lee, S.-Y.,Cho, E.,Oh, I.-H.,Lim, T.-H. Pergamon Press ; Elsevier Science Ltd 2008 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.33 No.11

The role of Nafion<SUP>(</SUP>R) binder in the electrodes was evaluated by changing its content for the membrane electrode assembly (MEA) fabrication. In the study, we prepared MEAs that have two different compositions of catalyst layers in electrodes. One layer which is close to the electrolyte membrane has the higher Nafion<SUP>(</SUP>R) content. The other which is near the gas diffusion media (GDM) has the lower one. Also, we changed the thickness of two layers to find the ideal composition of the binder and Pt/C in the electrode. The dual catalyst layer coated MEA showed higher cell performance at high current density region than the pristine MEA.

Use of Inner Ionomer Solution in Preparing Membrane-Electrode Assembly (MEA) for Fuel Cells and Its Characterization

Seo, Seok-Jun,Woo, Jung-Je,Yun, Sung-Hyun,Park, Jin-Soo,Moon, Seung-Hyeon The Membrane Society of Korea 2008 Korean Membrane Journal Vol.10 No.1

Optimization of ionomer solution was conducted in order to improve the performance of MEAs in PEMPC. The interface between membrane and electrodes in MEAs is crucial region determining fuel cell performance as well as ORR reaction at cathode. Through the modification of Nafion ionomer content at the interface between membrane and electrodes, an optimal content was obtained with Nafion 115 membranes. Two times higher current density was obtained with the outer Nafion sprayed MEA compared with the non-sprayed one. In addition, the symmetrical impedance spectroscopy mode (SM) exhibited that the resistances of membrane area, proton hydration, and charge transfer decreased as the outer Nafion is sprayed. From the polarization curves and SM, the highest current density and the lowest resistance was obtained at the outer ionomer content of $0.15\;mg\;cm^{-2}$.

Effects of membranes thickness on performance of DMFCs under freeze-thaw cycles

Oh, Y.,Kim, S.K.,Peck, D.H.,Jung, D.H.,Shul, Y. Pergamon Press ; Elsevier Science Ltd 2014 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.39 No.28

The effect of membrane thickness on the performance degradation of DMFCs was investigated during freeze-thaw cycling across temperatures ranging from -32 <SUP>o</SUP>C to 60 <SUP>o</SUP>C. Three cells with Nafion membranes of varying thickness were prepared: Nafion 112, Nafion 115 and Nafion 117. Performance degradation was evaluated by comparing the changes to electrode polarization, electrochemical impedance and cyclic voltammetry over a range of freeze-thaw cycles. It was determined that freeze-thaw cycling affected the performance of the three membrane electrode assemblies (MEA). A cell with a Nafion 112 membrane showed a more significant increase in cathode overpotential than cells with either a Nafion 115 or Nafion 117 membrane. The charge transfer resistance of the cell with a thin membrane was more affected by freeze-thaw cycles than the cells with thicker membranes. All three cells showed a significant decrease in ECSA after freeze-thaw cycles. Freeze-thaw cycles damaged the triple phase boundary region and decreased the ECSA of cells with thinner membranes, which cause rapid performance degradation. The use of thick membranes in MEAs was determined to be the effective method for reducing performance degradation during freeze-thaw cycling.