• Membrane Journal
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• v.33 no.3
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• pp.127-136
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• 2023

In this study, the electrochemical performance of a 5-layer fuel cell stack using silica composite membranes as polymer electrolyte membranes was evaluated. It was observed that the flow rate of the fuel gases plays a crucial role in stack performance, particularly being mainly dependent on the flow rate of hydrogen. Increasing the flow rate of oxygen resulted in negligible changes in performance, whereas an increase in the flow rate of hydrogen demonstrated performance improvements. However, this led to an imbalance in the ratio of hydrogen to oxygen flow rates, causing significant degradation in stack performance and durability. A decline in stack performance was also observed over time due to the degradation of stack components. This phenomenon was consistently observed in individual unit cells. Based on these findings, it was emphasized that, in addition to optimizing the performance of each component during stack operation, it is important to optimize design and operating conditions for uniform flow rate control. Lastly, the developed silica composite membrane was assessed to have sufficient performance for application in actual fuel cell systems, exhibiting a performance of over 25 W based on maximum power.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.99-105
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• 2023

Recently, 2D materials greatly impact in the various applications especially in the energy conversion and storage devices. Among the 2D materials, nowadays researchers are showing their propensity towards the MXenes due to their potential structural and physical properties as well as their use in various applications. Recently, MXenes have been used as filler in polymer electrolytes membranes and as catalytic support to increase the performance of fuel cells (FCs). But this review covers only recent progress and application of MXenes in proton and anion exchange membranes for FCs. Also, this review will provide a significant guidance and broad overview for future research in MXenes based polymer electrolyte membrane for FCs.

• Membrane Journal
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• v.27 no.1
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• pp.53-59
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• 2017

In this study, the composite membranes prepared by sulfonated graphene oxide (sGO) and Nafion were developed as proton exchange membranes (PEMs) for polymer electrolyte membrane fuel cells (PEMFCs). The sGO/Nafion composite membranes were prepared by mixing Nafion solution with the sGO dispersed in a binary solvent system to improve dispersity of sGO. The composite membranes were investigated in terms of ionic conductivity, ion exchange capacity (IEC), FT-IR, TGA and SEM, etc. As a result, the binary solvent system, i.e., ortho-dichlorobenzene (ODB) and N,N-dimethylacetamide (DMAc), were used to obtain high dispersion of sGO particles in Nafion solution, and the ionic conductivity of the sGO/Nafion composite membrane showed $0.06Scm^{-1}$ similar to other research results at lower water uptake, 11 wt%.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.4
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• pp.331-338
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• 2018

In this study, sulfonated PAES block copolymers have been synthesized via nucleophilic substitution reaction. Hydrophobic oligomer was prepared using 2,6-dihydroxynaphthalene and bis(4-chlorophenyl) sulfone, whereas hydrophilic oligomer was prepared using sulfonated bis(4-chlorophenyl) sulfone and bis(4-hydroxyphenyl) sulfone. The chemical structure of polymers was analyzed by $^1H$ NMR, FT-IR and GPC. The thermal properties of polymers were measured by TGA and DSC. The oxidative stability of membranes was investigated by Fenton's test. Furthermore, the proton conductivity of membrane was found to be 26 mS/cm at $90^{\circ}C$. All physiochemical properties suggest that fabricated membrane have a great potential for applications in PEMFC.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.789-798
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• 2018

The role of empirical equation to predict the performance of polymer electrolyte membrane fuel cell is important. The activation, ohmic and mass transfer losses were separated in a polarization curve, and the curve fitting according to each region was performed using Kim's model and Hao's model. Changes of each loss were compared according to operation variables of the temperature, pressure, oxygen concentration and membrane thickness. The existing model showed a good fitting convergence, but less fitting accuracy in the separated loss region. A new model using the convergence coefficient was suggested to improve the accuracy of performance prediction of fuel cells of which results were demonstrated.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.7-14
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• 2017

This study aims to examine the influences of substrates/diffusion layers (DL) and oxygen reduction reaction catalysts ($M_{ORR}$) on the performance of $M_{ORR}/IrO_2$/DL-type bifunctional oxygen electrodes for use in polymer electrolyte membrane (PEM)-type unitized regenerative fuel cells (URFC). The $M_{ORR}/IrO_2$/DL electrodes were prepared via two sequential steps: anodic electrodeposition of $IrO_2$ on various DLs and fabrication of $M_{ORR}$ layers (Pt, Pd, and Pt-Ru) by spraying on $IrO_2/DL$. Experiments using different DLs, with Pt as the $M_{ORR}$, revealed that the roughness factor of the DL mainly determined the electrode performance for both water electrolyzer (WE) and fuel cell (FC) operations, while the contributions of porosity and substrate material were insignificant. When Pt-Ru was utilized as the $M_{ORR}$ instead of Pt, WE performance was enhanced and the electrode performance was assessed by analyzing round-trip efficiencies (${\varepsilon}_{RT}$) at current densities of 0.2 and $0.4A/cm^2$. As a result, using Pt-Ru instead of Pt alone provided better ${\varepsilon}_{RT}$ at both current densities, while Pd resulted in very low ${\varepsilon}_{RT}$. Improved efficiency was related to the additional catalytic action by Ru toward ORR during WE operation.

• Membrane Journal
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• v.19 no.4
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• pp.291-301
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• 2009

Double-layered polymer electrolyte membranes were prepared from two different sulfonated poly(aryl ether sulfone) copolymers by the two-step solution casting method for direct methanol fuel cells (DMFC). Sulfonation degrees were adjusted 10% (SPAES-10) and 50% (SPAES-50) by controlling monomer ratios, and the weight ratios of SPAES-10 copolymer were varied in the range of 5~20% to investigate the effect of thickness of coating layers on the membranes. Proton conducting layers were fabricated from SPAES-50 solutions of N-methyl-2-pyrrolidone (NMP) by a solution casting technique, and coating layers formed on the semiliquid surface of the conducting layer by pouring of SPAES-10-NMP solutions onto. It was found that double-layered polymer electrolyte membrane could significantly reduce the methanol crossover through the membrane and maintain high proton conductivities being comparable to single-layered SPAES-50 membrane. The maximum power density of membrane-electrolyte assembly (MEA) at the condition of $60^{\circ}C$ and 2 M methanol-air was $134.01\;mW/cm^2$ for the membrane prepared in the 5 wt-% of SPAES-10 copolymer, and it was corresponding to the 105.5% of the performance of the commercial Nafion 115 membrane.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.307-312
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• 2005

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.85-92
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• 2009

Polymer electrolyte membrane (PEM) fuel cells are a promising technology for short-term power generation required in residential and automobile applications. Proper management of water has been found to be essential for improving the performance and durability of PEM fuel cells. This study investigated the liquid water exhaust capabilities of various flow channels having different geometries and surface properties. Three-pass serpentine flow fields were prepared by patterning channels of 1 mm or 2 mm width onto hydrophilic Acrylic plates or hydrophobic Teflon plates, and the behaviors of liquid water in those flow channels were experimentally visualized. Computational fluid dynamics (CFD) simulations were also conducted to quantitatively assess the liquid water exhaust capabilities of flow channels for PEM fuel cells. Numerical results showed that hydrophobic flow channels have better liquid water exhaust capabilities than hydrophilic flow channels. Flow channels with curved corners showed less droplet stagnation than the channels with sharp corners. It was also found that a smaller width is desirable for hydrophobic flow channels while a larger width is desirable for hydrophilic ones. The above results were explained as being due to the different droplet morphologies in hydrophobic and hydrophilic channels.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.554-559
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• 2015

Single cell of PEMFC (polymer electrolyte membrane fuel cell) is composed of bipolar plates, gasket, GDL and the MEA. Bipolar plate's function is the collecting electricity, helping oxygen/hydrogen gas diffuse evenly and draining the water and heat. In this work, we have conducted experiments to low contact resistance and improve the performance of a $25cm^2$ single cell by using metal forms. We have following experimental cases: 1) Conventional graphite serpentine channel bipolar plate; 2) Channel-less bipolar plate with nickel(Ni) based metal foam which coated by various materials. We focused the difference in contact resistance and performance of the single cell with metal foam depending on various coating materials. The experimental results show the similar performance of single cells between with serpentine channel bipolar plates and with channel-less bipolar plate using metal foams. In addition, single cell with metal foam shows potential to higher performance than conventional channel.