• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.370-375
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• 2013

We analyze the effects of CO poisoning and air bleeding on the performance of a PEM (polymer electrolyte membrane) fuel cell stack fabricated using commercial MEA (membrane electrode assembly). Dynamic response data from the experiments on the performance of a stack are identified by obtaining steady-state gains and time-constants of the first-order system model expressed as a first-order differential equation. It is found that the cell voltage of the stack decreases by 1.3-1.6 mV as the CO concentration rises by 1 ppm. The time elapsed to reach a new steady state after a change in the CO concentration is shortened as the magnitude of the change in the CO concentration increases. In general, the steady-state gain becomes bigger and the time-constant gets smaller with increasing the air concentration (air-bleeding level) in the reformate gas to restore the cell voltage. However, it is possible to recover 87%-96% of the original cell voltages, which are measured with free of CO, within 1-30 min by introducing the bleed air as much as 1% of the reformate gas into the stack.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.149-157
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• 2006

Hydrogen as new energy sources is highly efficient and have very low environmental emissions. The proton exchange membrane fuel cell (PEMFC) is an emerging technology that can meet these demands. Therefore, the preparation of stable polymeric membranes with good proton conductivity and durability are very important for hydrogen production via water electrolysis with PEM at medium temperature above $80^{\circ}C$. Currently Nafion of Dupont and Aciflex of Asahi, etc., solid polymer electrolytes of perfluorosulfonic acid membrane, are the best performing commercially available polymer electrolytes. However, these membrane have several flaws including its high cost, and its limited operational temperature above $80^{\circ}C$. Because of this, significant research efforts have been devoted to the development of newer and cheaper membranes. In order to make up for the weak points and to improve the mechanical characteristics with cross -linking, acid-base complexes were prepared by the combination PSf-co-PPSS-$NH_2$ with PEEK-$SO_3H$. The results showed that the proton conductivity decreased in 17.6% and 40% but tensile strength increased in 78% and 98%, about $20.65\;{\times}\;10^6N/m^2$, in comparison with SBPSf/HPA and SPEEK/HPA complex membrane.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.673-681
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• 2023

Hydrocarbon-based polymer membranes to replace perfluorinated polymer membranes are being continuously researched. However, hydrocarbon-based membranes have a problem in that they are less durable than fluorine-based membranes. In this study, we sought to compare the annealing effect to improve the durability of sulfonated poly(ether ether ketone) (SPEEK). After membranes formation, thermogravimetric analysis and tensile strength were measured to compare changes in membranes properties due to annealing. After manufacturing the membrane and electrode assembly (MEA), the initial performance and chemical durability was compared with unit cell operation. During the 24-hour annealing process, the strength increased due to the increase in-S-O-S-crosslinking, and the sulfonic acid group decreased, leading to a decrease in I-V performance. By annealing, the hydrogen permeability was reduced to less than 1/10 of that of the nafion membrane, and as a result, open circuit voltage (OCV) and durability was improved. The SPEEK membranes annealed for 24 hours showed higher durability than the nafion 211 membranes of the same thickness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.487-490
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• 2011

We used X-ray tomography to carry out an experimental study to visualize the effect of freeze and thaw cycles on the gas diffusion layer (GDL) in a polymer electrolyte membrane fuel cell (PEMFC). A PEMFC has freeze and thaw cycles if the fuel cell is operating at a below-freezing ambient temperature. The cycle permanently deforms the fuel-cell capillary structures and reduces the ability of the cell to generate electric power and also reduces its service life. The GDL is the thickest capillary layer in the fuel cell, so it experiences the most deformation. The X-ray tomography facility at the Pohang Accelerator Laboratory was used to observe the structural changes in GDLs induced by a freeze and thaw cycle. We discuss the effects of these structural changes on the power production and service life of PEMFCs.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.1
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• pp.49-56
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• 2020

Epoxy/carbon composite was used to prepare a bipolar plate for polymer electrolyte membrane fuel cell (PEMFC). Phenol novolac-type epoxy and diglycidyl ether of bisphenol A (DGEBA)-type epoxy mixture was used as a matrix and graphite powder, carbon fiber (CF) and graphite fiber (GF) were used as carbon materials. In order to improve the mechanical properties of the bipolar plate, surface-modified CF was incorporated into the epoxy/carbon composite. To determine the cure temperature of the epoxy mixture, differential scanning calorimetry (DSC) analysis was performed and the data were introduced to Kissinger equation in order to get reaction activation energy and pre-exponential factor. Tensile and flexural strength was obtained by using universal testing machine (UTM). The surface morphology of the fractured specimen and the interfacial morphology between epoxy matrix and CF or GF were observed by a scanning electron microscopy (SEM).

• New & Renewable Energy
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• v.1 no.1 s.1
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• pp.72-78
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• 2005

Optimal design and proper operation are important to get aimed output power of a polymer electrolyte membrane fuel cell (PEMFC) stack. An air cooling fuel cell stack is widely used in sub kW PEMFC systems. The purpose of this study is to analyze operating conditions affecting the performance of the air cooling PEMFC which is designed for portable application. In portable applications, air cooling stack is difficult to maintain well balanced operating conditions. The importart parameters are the relative humidity, the temperature of the stack, the utilization of reactant gas and so on. in this study, a 500W air cooling PEMFC was fabricated and tested to evaluate the design performance and to determine optimal operating conditions. Moreover, basic modeling also is carried out. These results can be used 3s design criteria and optimal operating conditions for portable PEMFCs

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.849-855
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• 2008

The paper addresses modeling and analysis of the part load performance of a hybrid fuel cell system integrating a polymer electrolyte membrane fuel cell(PEMFC) and a gas turbine(GT). The system is a pressurized one where the working pressure of the PEMFC is higher than the ambient pressure. In addition to the two major components, the system also includes auxiliary parts such as a steam reformer, a humidifier, and afterburner and so on. Based on design analysis, component off-design models are incorporated in the analysis program and part load operation is simulated. The mode for the part load operation of the PEMFC/GT hybrid system is a variable rotational speed operation. The operating characteristics and variations in the system efficiency and component performance parameters at part load are analyzed.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.817-822
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• 2008

Metal matrix composite (MMC) materials having low electrical contact resistance based on 316L stainless steel (STS) matrix alloy with $ZrB_2$ particles were fabricated for PEMFC (Polymer Electrolyte Membrane Fuel Cell) separator by powder metallurgy (PM). The effects of the boride particle addition into the matrix alloy on microstructure, surface morphology, and interfacial contact resistance (ICR) between the samples and gas diffusion layer (GDL) were investigated. Both conventional and PM 316L STS samples showed high ICR due to the existence of non-conductive passive film on the alloy surface. The addition of the boride particles, however, remarkably reduced ICR of the samples. SEM observation revealed that the boride particles were protruded out of the matrix surface and particle density existing on the surface increased with increasing the boride content, causing increase of the total contact area between the conductive particles and GDL. ICR of the samples also decreased with increasing the boride content resulted from the increased contact area.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.435-450
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• 2021

The interest in eco-friendly energy is increasing, and polymer electrolyte membrane fuel cell (PEMFC) is attracting attention as alternative power sources. Research on metallic bipolar plates, a fuel cell component, is being actively conducted. However, since the operating conditions of PEMFC, in which sulfuric acid (H₂SO₄) and hydrofluoric acid (HF) are mixed, are strong acidity, the durability of the metallic bipolar plate is very important. In this research, the electrochemical characteristics and corrosion damage behavior of 316L stainless steel, a material for metallic bipolar plates, were analyzed through potentiostatic corrosion tests with test times and chloride concentrations. As the test times and chloride concentrations increased, the current density and corrosion damage increased. As a result of observation with scanning electron microscope(SEM) and 3D microscope, both the depth and width of pitting corrosion increased with increases in test times and chloride concentrations. In particular, the pitting corrosion damage depth at test conditions of 6 hours and 1000 ppm chloride increased the most. The growth of the pitting corrosion damage was not directly proportional to time and increased significantly after a certain period.

• Prospectives of Industrial Chemistry
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• v.24 no.3
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• pp.14-27
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• 2021

수소 에너지는 환경 문제를 최소화하고 고갈되는 화석연료를 대체할 수 있는 에너지원으로 각광을 받고 있다. 수소연료전지는 이러한 수소를 에너지원으로 사용하고 수소를 전기에너지로 전환하여 그 부산물로 물을 만드는 대표적인 친환경 전기화학 장치이다. 고분자 전해질막 연료전지는 수소이온교환 특성을 갖는 고분자막을 전해질로 사용하는 연료전지로 막전극집합체의 전극층은 촉매가 포함된 고분자 전해질막 연료전지의 주요 요소 중의 하나이다. 소재개발 측면에서 고분자 전해질막 연료전지 전극층 핵심 소재의 물성 발현 원리 등을 이해하고 최적화된 소재 설계를 위해서는 원자레벨에서의 소재 설계 접근법이 필요하다. 따라서 실험적인 연구가 어려운 부분과 원자단위에서의 물질 현상에 대한 이해 그리고 연구 개발의 효율성 증진을 위해 전산재료과학(computational materials science) 기술이 광범위하게 활용될 수 있다. 본 기고문에서는 고분자 전해질막 연료전지에서의 전극층 소재에 대한 분자동역학 기반의 전산모사 활용과 연구동향에 대하여 소개하고자 한다.