• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.413-422
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• 2015

Proton exchange membrane (PEM), which transfers proton from the anode to the cathode, is the key component of the proton exchange membrane fuel cell (PEMFC). Nafion is widely used as PEM due to its high proton conductivity as well as excellent chemical and physical stabilities. However, its high cost and the environmental hazards limit the commercial application in PEMFCs. To overcome these disadvantages, various alternative polymer electrolytes have been investigated for fuel cell applications. We used densely sulfonated polymers to maximize the ion conductivity of the corresponding membrane. To overcome high swelling, dipole-dipole interaction was used by introducing nitrile groups into the polymer backbone. As a result, physically-crosslinked membranes showed improved swelling ratio despite of high water uptake. All the membranes with different hydrophilic-hydrophobic compositions showed higher conductivity, despite their lower IEC, than that of Nafion-117.

• Membrane Journal
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• v.29 no.3
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• pp.173-182
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• 2019

Much research has been made for finding new and eco-friendly alternative sources of energy to solve the problems related with the pollution caused by emissions of greenhouse gases such as carbon dioxide as the use of fossil fuels increases worldwide. Among them, fuel cells draws particular interests as an eco-friendly energy generator because only water is obtained as a by-product. Anion exchange membrane-based alkaline fuel cell (AEMFC) that uses anion exchange membrane as an electrolyte is of increased interest recently because of its advantages in using low-cost metal catalyst unlike the PEMFC (potton exchange membrane fuel cell) due to the high-catalyst activity in alkaline conditions. The main properties required as an anion exchange membrane are high hydroxide conductivity and chemical stability at high pH. Recently we reported a chemically crosslinked poly(2-dimethyl-1,4-phenylene oxide) (PPO) by reacting PPO with N,N,N',N'-tetramethyl-1,6-hexanediamine as novel anion exchange membranes. In the current work, we further developed the same crosslinked polymer but having enhanced physicochemical properties, including higher conductivity, increased mechanical and dimensional stabilities by using the PPO with a higher molecular weight and also by increasing the crosslinking density. The obtained polymer membrane also showed a good cell performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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• pp.91-101
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• 2012

A 200 W portable polymer electrolyte membrane fuel cell (PEMFC) system is developed. The PEMFC system consists of an air-cooled fuel cell stack module, a fuel supply subsystem, a power management subsystem, and a control electronics subsystem. The control logic is designed for the stable system operation. The system-level performance evaluation discloses that the present PEMFC system provides a rated power output of 200.5 W at 13.4 V with the maximum balance-of-plant (BOP) efficiency of 72%, and maximum system efficiency based on lower heating value (LHV) is 37% at 120.7 W system power output.

• Macromolecular Research
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• v.14 no.2
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• pp.214-219
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• 2006

Cast Nafion-based composite membranes containing different amounts of organic, nanorod-shaped polyrotaxane were prepared and characterized, with the aim of improving the properties of polymer electrolyte membranes for direct methanol fuel cell applications. Polyrotaxane was prepared using the inclusion-complex reaction between ${\alpha}$-cyclodextrin and poly(ethylene glycol) (PEG) of different molecular weights. The addition of polyrotaxane to Nafion changed the morphology and reduced the crystallinity. The conductivity of the composite membranes increased with increasing polyrotaxane content up to 5 wt%, but then decreased at higher polyrotaxane contents. Well-dispersed, organic polyrotaxane inside the membrane can provide a tortuous path for the transport of methanol, as the methanol permeability depends on the aspect ratio of polyrotaxane, which is controlled by the molecular weight of PEG. All of the Nafion-based, polyrotaxane composite membranes showed a higher selectivity parameter than the commercial Nafion films did.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.37-40
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• 2003

Mesoporous zeolite - heteropolyacid-polymer hybrid membrane was prepared by sol-gel processes to make a proton conducting membrane. The crystallinity of mesoporous zeolite in composite membrane was increased with contents of heteropolyacid. Proton conductivity obtained from impedance measurements increases with contents of heteropolyacid, about 10$^{-3}$ S/cm in ca. 1.5 Wt% heteropolyacid.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.687-693
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• 2019

As the hydrogen fuel cell market is expanded starting from hydrogen electric vehicle and power generation field, the demand for fuel cells and hydrogen increases recently. Therefore, research works on fuel cell durability and fuel efficiency are required in order to activate the fuel cell market and commercialization. A dead-ended anode system was used in this study to optimize the fuel cell performance and fuel efficiency. The effect of purge condition according to the applied current and hydrogen supply pressure on the fuel cell performance were evaluated. In addition, the influence of water back diffusion on the different electrolyte membrane thickness was analyzed. The accumulated water was purged with a solenoid valve in the case of 3% voltage decrease in the dead-ended anode system. The experiment was performed with the hydrogen supply pressure of 0.1~0.5 bar and purge duration of 0.1~1 second. A maximum fuel efficiency of 98.9% was achieved under the purge duration of 0.1 s and hydrogen supply pressure of 0.1 bar with a NR 211 (25.4 um) membrane. However, the fuel cell performance decreased in a long-term operation due to some frequent flooding. The fuel efficiency and purge interval increased due to decreased back diffusion rates of the water and nitrogen with a NR 212 (50.8 um) membrane.

• Membrane Journal
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• v.33 no.6
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• pp.325-343
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• 2023

Direct methanol fuel cells (DMFCs) have been attracting attention as energy conversion devices that can directly supply methanol liquid fuel without a fuel reforming process. The commercial polymer electrolyte membranes (PEMs) currently applied to DMFC are perfluorosulfonic acid ionomer-based PEMs, which exhibit high proton conductivity and physicochemical stability during the operation. However, problems such as high methanol permeability and environmental pollutants generated during decomposition require the development of PEMs for DMFCs using novel ionomers. Recently, studies have been reported to develop PEMs using hydrocarbon-based ionomers that exhibit low fuel permeability and high physicochemical stability. This review introduces the following studies on hydrocarbon-based PEMs for DMFC applications: 1) synthesis of grafting copolymers that exhibit distinct hydrophilic/hydrophobic phase-separated structure to improve both proton conductivity and methanol selectivity, 2) introduction of cross-linked structure during PEM fabrication to reduce the methanol permeability and improve dimensional stability, and 3) incorporation of organic/inorganic composites or reinforcing substrates to develop reinforced composite membranes showing improved PEM performances and durability.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.3
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• pp.271-279
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• 2014

A 25kW-class polymer electrolyte membrane (PEM) fuel cell system has been developed for the propulsion of a leisure boat. The fuel cell system was designed to satisfy various performance requirements, such as resistance to shock, stability under rolling and pitching oscillations, and durability under salinity condition, for its marine applications. Then, the major components including a 30kW-class PEM fuel cell stack, a DC-DC converter, a seawater cooling system, secondary battery packs, and balance of plants were developed for the fuel cell system. The PEM fuel cell stack employs a unique design structure called an anodic cascade-type stack design in which the anodic cells are divided into several blocks to maximize the fuel utilization without hydrogen recirculation devices. The performance evaluation results showed that the stack generated a maximum power of 31.0kW while maintaining a higher fuel utilization of 99.5% and an electrical efficiency of 56.1%. Combining the 30-kW stack with other components, the 25kW-class fuel cell system boat was fabricated for a leisure. As a result of testing, the fuel cell system reached an electrical efficiency of 48.0% at the maximum power of 25.6kW with stable operability. In the near future, two PEM fuel cell systems will be installed in a 20-m long leisure boat to supply electrical power up to 50kW for propelling the boat and for powering the auxiliary equipments.

• Ceramist
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• v.21 no.4
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• pp.331-348
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• 2018

With the expectation to overcome the problem of increasing energy consumption, polymer electrolyte membrane fuel cells are getting more attention as a promising environmentally friendly and sustainable next-generation energy conversion system. In spite of the rapid improvement of polymer electrolyte membrane fuel cells(PEMFCs), there are several critical issues still need to be resolved for practical commercialization. Out of the many issues, the main hurdle comes from oxygen reduction reaction(ORR), thus development of efficient ORR electrocatalysts is the main key for enhancing PEMFC performance. Among various catalysts, 1D nanostructured catalyst is a promising candidate because it holds many advantages that come from nanostructuring while supplementing the disadvantages of other nanostructures such as nanoparticles(0D) or gyroids(3D). This review focused on diverse 1D nanostructures and talks about their advantages as catalyst for ORR. Different 1D nanostructures will be introduced while applying the structures to different materials system showing the prospects of 1D nanostructures for improving PEMFC.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.667-673
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• 2009

The electrocatalytic characteristics of oxygen reduction reaction of the $PtxM_{(1-x)}$ (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The $Pt_xM_{(1-x)}$/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the $Pt_xM_{(1-x)}$ particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and $Pt_xM_{(1-x)}$/MWNTs catalysts are seen as FCC, and synthesized $Pt_xM_{(1-x)}$ crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, $Pt_{0.77}Co_{0.23}$/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or $Pt_xM_{(1-x)}$/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and $Pt_xM_{(1-x)}$ (M = Co, Cu, Ni) catalysts, the $Pt_{0.77}Co_{0.23}$/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.