• Title/Summary/Keyword: Fuel cell performance

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Improvement of Oxidative Stability for Non-fluorinated Membranes Prepared by Substituted Styrene Monomers (스티렌 유도체를 이용한 비불소계 고분자 전해질막의 산화적 안정성 개선)

  • Moon, Seung-Hyeon;Woo, Jung-Je;Fu, Rong-Qiang;Seo, Seok-Jun;Yun, Sung-Hyun
    • Membrane Journal
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    • v.17 no.4
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    • pp.294-301
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    • 2007
  • To improve oxidative stability of non-fluorinated styrene-based polymer electrolyte membranes, copolymerized membranes were prepared using styrene derivatives such as p-methylstyrene, t-butylstyrene, and ${\alpha}-methylstyrene$ by monomer sorption method. Prepared membrane was characterized by measurement of weight gain ratio, water content, ion-exchange capacity, proton conductivity, and oxidative stability under the accelerated condition. It was found that each step of monomer sorption method including sorption, polymerization and sulfonation could be affected by the properties and the structures of styrenederivatives. Due to difficulty of polymerization, ${\alpha}$-methylstyrene was copolymerized with styrene or p-methylstyrene. Prepared membrane using ${\alpha}-methylstyrene$ and styrene showed higher performance and stability comparing to copolymerized membrane with styrene. However, copolymerized membranes with ${\alpha}-methylstyrene$ did not showed much improved oxidative stability comparing to styrene membrane due to their lower molecular weight. The t-butylstyrene membrane showed a low performance due to substituted bulky-butyl group which prevents sorption and sulfonation reaction. However, copolymerized t-butylstyrene membranes with p-methylstyrene showed good performance and much improved stability than the styrene membranes.

Experimental Study on Autothermal Reformation of Methanol with Various Oxygen to Methanol Ratios for Fuel Cell Applications (연료전지용 메탄올 자열 개질기의 산소-메탄올 비율에 따른 성능 실험)

  • Hwang, Ha-Na;Shin, Gi-Soo;Jang, Sang-Hoon;Choi, Kap-Seung;Kim, Hyung-Man
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.4
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    • pp.391-397
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    • 2011
  • The use of Hydrogen as a fuel is receiving considerable attention and as a result, research on novel methods of hydrogen production is necessary so that the hydrogen demands in the future can be satisfied. This study presents experimental data on methanol Autothermal Reformation that quantifies the relationship between the oxygen-to-methanol ratio ($O_2/CH_3OH$) and reformer efficiency. For each catalyst configuration, the $O_2/CH_3OH$ was varied from 0.1 to 0.4, with an increment of 0.05, to investigate the effects of $O_2/CH_3OH$ on the reactor performance, including temperature profile, conversion, and efficiency. $O_2/CH_3OH$ was increased from 0.15 to 0.20, and the catalyst bed temperature increased by $235^{\circ}C$ to approximately $550^{\circ}C$. The catalyst bed temperature increased with increasing $O_2/CH_3OH$ as the reaction shifted from endothermic to exothermic reaction and as a result, excess heat, which raised the reactor temperature, was generated. The reactor performance was shown to be highly dependent on $O_2/CH_3OH$. The optimum $O_2/CH_3OH$ = 0.30 found in the experimental tests is 30% higher than the theoretical optimum of 0.23. This is attributed to a combination of factors such as the concentrations of the $O_2$ and $CH_3OH$ gas, reaction rate, catalyst effects, heat loss from the reactor, and the difference between the actual amounts of reaction products formed and the theoretical amounts of the reaction products.

Synthesis and Electrochemical Properties of (La0.6Sr0.4)(Co0.2Fe0.8)O3 cathode for SOFC on pH Control Using Modified Oxalate Method (Modified Oxalate Method 의해 합성한 SOFC용(La0.6Sr0.4)(Co0.2Fe0.8)O3 Cathode의 pH 변화에 따른 특성)

  • Lee, Mi-Jai;Choi, Byung-Hyun;Kim, Sei-Ki;Park, Sang-Sun;Lee, Kyung-Hee
    • Journal of the Korean Electrochemical Society
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    • v.10 no.4
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    • pp.288-294
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    • 2007
  • The LSCF cathode far Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolytes and different pH. The LSCF powders employed La, Sr, Co and Fe oxides, oxalic acid, ethanol and $NH_4OH$ solution were synthesized with pH controlled as 2, 6, 7, 8, 9 and 10 at $80^{\circ}C$ Single crystalline phase was obtained from pH $2{\sim}9$. on the other hand, $La_2O_3$ appeared from pH 10. Very fine powder with particle size of 50 nm was obtained at calcination temperature of $800^{\circ}C$ for 4 hours. LSCF cathode synthesized at pH 7 showed the highest electric conductivity in the temperature range of $600^{\circ}C$ to $900^{\circ}C$ its value was 950 S/cm at $900^{\circ}C$ Under same synthesis conditions, polarization resistance of each LSCF cathode was changed with different calcination temperatures. As-prepared powder presented 2.52, 1.54 and $2.58\;{\Omega}$ at $600^{\circ}C$ with ScSZ, 8Y-YSZ and GDC as its electrolyte respectively after calcination at $800^{\circ}C$ for 4 hours.

Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

Improvement of Performance of Anti-reflective Coating Film Using Methyltrimethoxysilane (Methyltrimethoxysilane을 이용한 반사방지 코팅막의 성능 향상)

  • Keum, Young-Sub;Kim, Hyo-Sub;Park, Chu-Sik;Kim, Young-Ho
    • Applied Chemistry for Engineering
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    • v.26 no.4
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    • pp.400-405
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    • 2015
  • Traditional anti-reflective (AR) coating films prepared using tetraethylorthosilicate (TEOS) as a precursor absorbs water easily in addition to having a weak abrasion resistance. To improve the transmittance, hydrophobicity and abrasion resistance of AR coating film, various AR coating films were prepared using methyltrimethoxysilane (MTMS) as a precursor in addition to introducing a fluoroalkylsilane, acid catalyst, base catalyst and acid-base two step catalyst. The prepared AR coating films were then characterized by UV-Vis spectroscopy, contact angle analyzer, atomic force microscope (AFM), pencil scratch hardness test and cross-cut test. As a result, the transmittance of bare glass was 90.5%, while that of AR coating glass increased to 94.8% at curing temperature of $300^{\circ}C$. When the fluoroalkylsilane was added, the water contact angle of AR coating film increased from $96.3^{\circ}$ to $108^{\circ}$, indicating that the hydrophobicity of the film was greatly improved. The abrasion resistance of AR coating film was also improved by the acid catalyst, whereas the transmittance increased by the base catalyst. In the case of AR coating film prepared using an acid-base two step catalyzed reaction, both the transmittance and abrasion resistance of the film was synergistically enhanced as compared with those of AR coating films prepared without introduction of a catalyst.

Preparations of SPE Electrocatalysts Modified with Polypyrrole and Its Application for PEMFC (폴리피롤로 개질된 SPE 전극촉매의 제조 및 PEMFC로의 응용)

  • Kim, Jung-Hoon;Oh, Seung-Duck;Kim, Han-Sung;Park, Jong-Ho;Han, Jung-Woo;Lee, Kang Taek;Joe, Yung-Il
    • Korean Chemical Engineering Research
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    • v.43 no.1
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    • pp.118-124
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    • 2005
  • In this study, a novel deposition method of Pt catalysts onto Nafion membranes modified with polypyrrole (PPy) has been proposed for PEMFC application. The PPy/Nafion composite membranes were fabricated by chemical polymerization of pyrrole using $FeCl_3$ and $Na_2S_2O_8$ as initiator. The proton conductivity and water uptake of the chemically prepared PPy/Nafion composites were investigated. The ionic conductivity and water uptake of PPy/Nafion composite membrane prepared with $Na_2S_2O_8$ were decreased with polymerization time of pyrrole. In the case of $FeCl_3$, the ionic conductivity was almost retained and the water uptake was decreased with polymerization time of pyrrole. When the Pt particle was deposited on PPy/Nafion composites membrane by chemical reduction of $H_2PtCl_6$, the Pt loading on Nafion membrane was enhanced by polypyrrole due to electronic conduction property. The performance evaluation with membrane electrode assembly composed of Pt/PPy/Nafion composite and diffusion electrode was carried out using a single cell. As a result of fuel cell test, current density of $569mA/cm^2$ at 0.3 V has been obtained for MEA contained with Pt/PPy/Nafion composite. This study shows that direct deposition of Pt catalysts on Nafion impregnated polypyrrole is a promising method to prepare thin catalyst layer for the PEMFC.

Fabrication of Silane-crosslinked Proton Exchange Membranes by Radiation and Evaluation of Fuel Cell Performance (방사선을 이용한 실란 가교구조의 유/무기 복합 수소이온 교환막 제조 및 연료전지 성능 평가)

  • Lee, Ji-Hong;Sohn, Joon-Yong;Shin, Dong-Won;Song, Ju-Myung;Lee, Young-Moo;Nho, Young-Chang;Shin, Jun-Hwa
    • Polymer(Korea)
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    • v.36 no.4
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    • pp.525-530
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    • 2012
  • In this study, silane-crosslinked organic/inorganic composite membranes were prepared by simultaneous irradiation grafting of binary monomer mixtures (styrene and 3-(trimethoxysilyl)propyl methacrylate (TMSPM)) with various compositions onto a poly(ethylene-alt-tetraethylene) (ETFE) film and followed by sol-gel processing and sulfonation to provide a silane-crosslinked structure and a proton conducting ability, respectively. The Fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analysis (TGA) were utilized to confirm the crosslinking of ETFE-g-PS/PTMSPM films. The prepared membranes with similar ion exchange capacity but a different TMSPM content were selected and their membrane properties were compared. The ETFE-g-PSSA/PTMSPM membranes were characterized by water uptake, dimensional stability, and proton conductivity after sulfonation. The membrane electrode assemblies (MEA) of the prepared membranes were fabricated and their single cell performances were measured.

Evaluation of Biogas Production Rate by using Various Electrodes Materials in a Combined Anaerobic Digester and Microbial Electrochemical Technology (MET) (미생물 전기화학 기술이 적용된 단일 혐기성소화조에서 전극재질에 따른 바이오가스 생성 효율 평가)

  • Shin, Wonbeom;Park, Jungyu;Lee, Beom;Kim, Yonggeun;Jun, Hangbae
    • Journal of Korean Society of Environmental Engineers
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    • v.39 no.2
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    • pp.82-88
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    • 2017
  • MET (Microbial Electrochemical Technology), such as MFC (Microbial Fuel Cell) and MEC (Microbial Electrolysis Cell), is a promising technology for producing sustainable biogas from an anaerobic digester (AD). At current stage, however, the most likely limiting factors, large internal resistances, should be overcome for successful scale up of this technology. Various researchers reported that application of electrode materials containing high current density, increase of ion strength and conductivity, configuration of electrode are good methods for minimizing internal resistances. Recently, stainless steel is receiving great attention because of not only high performance and durability but also low cost. Therefore, in this study, we evaluate electrochemical characteristics and biogas production rate using various electrode materials and configuration (graphite carbon coated with catalysts ($GC-C_M$) or not (GC), stainless steel mesh (SUS-M) and plate (SUS-P)). As the results, current densities of $GC-C_M$, GC, SUS-P, SUS-M were 2.03, 1.36, 1.04, $1.13A/m^2$, respectively. Methane yields of $GC-C_M$, GC, SUS-P, SUS-M were 0.27, 0.14, 0.19, 0.21 $L-CH_4/g-COD_{rem}$., respectively. Stainless steel shows high current density and methane yield, which are similar as graphite carbon coated with catalysts.

Eelectrochemical Performance of Perovskite Materials coated Cathode for MCFC (perovskite 물질이 코팅된 MCFC용 공기극의 전기화학적 성능 고찰)

  • Song, Shin Ae;Kang, Min Gu;Yoon, Sung Pil;Han, Jong Hee;Oh, In Hwan
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.133.2-133.2
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    • 2010
  • 현재 융융탄산염 연료전지의 공기극으로 다공성의 lithiated NiO를 사용하고 있는데 이 재료의 경우 크게 두 가지의 문제점을 안고 있다. 첫 번째는 Ni이 전해질 내로 용해하는 것이고, 두 번째는 낮은 활성으로 인한 높은 공기극의 분극이다. Ni이 전해질로 용해되는 문제는 Co나 Fe를 코팅하여 공기극 표면에 $Li_x(Ni_yCo_{1-y})1-xO_2$$Li_x(Ni_yFe_{1-y})_{1-x}O_2$를 형성시켜 NiO의 전해질 내로 용해되는 것을 억제하는 방법이나 ZnO, MgO, $La_2O_3$ 등의 산화물을 NiO 표면에 코팅하여 전해질과 접촉을 막는 방식으로 해결하는 등 많은 연구가 이루어져 왔다. 하지만 연료극의 비해 상당히 높은 공기극의 분극으로 인해 큰 전압손실이 일어나 용융탄산염 연료전지 성능이 낮아지는 문제의 경우 이를 해결하고자 하는 연구는 상대적으로 많이 진행되지 못한 상태이다. 특히 현재 용융탄산염 연료전지의 장기수명화를 위해 기존의 작동온도인 $650^{\circ}C$ 보다 다소 낮은 온도인 $600{\sim}620^{\circ}C$에서 작동하려는 움직임이 있다. 작동 온도가 내려가면 전해질이 휘발되는 속도가 낮아져 전해질 부족에 따른 운전시간이 줄어드는 문제를 해결할 수 있어 장기 수명화를 위해서는 작동온도를 낮추는 것이 매우 유리하다. 하지만 작동 온도가 내려가면서 양 전극에서 일어나는 전기화학 반응 속도가 느려지기 때문에 각 전극에서의 활성화 분극으로 인한 전압손실은 더욱 커질 수밖에 없다. 특히 연료극의 수소산화반응 속도는 공기극의 산소환원반응에 비해 매우 빠르기 때문에 작동 온도가 내려감에 따라 연료극의 분극이 커지는 것에 비해 공기극의 분극이 급격히 커지게 된다. 따라서 운전온도가 낮아지는 상황에서는 낮은 작동온도에서도 성능감소가 적게 일어나 0.8V 이상 운전(150mA/$cm^2$, 단위전지 기준)이 가능한 공기극의 개발이 매우 필요한 실정이다. 이를 해결하고자 본 연구에서는 고체 산화물 연료전지의 공기극의 재료로 많이 연구되고 있는 혼합전도성 물질의 페로브스카이트 구조의 물질을 기존 NiO 전극에 코팅하여 새로운 공기극을 개발하였다. 페로브스카이트 구조의 물질로 대표적인 LSCF 물질을 사용하였으며 LSCF를 코팅한 공기극을 이용한 단위전지에서 150mA/$cm^2$의 전류를 흘려주었을 때 0.84V의 성능을 1000hr 유지하였다. 이는 기존의 NiO 전극을 사용했을 때보다 15~20mV 높은 값이다. 낮은 작동온도에서도 좋은 성능을 보였는데, 기존의 NiO 전극의 경우 $630^{\circ}C$에서 0.79V의 성능을 보인 반면 LSCF가 코팅된 공기극의 경우 $620^{\circ}C$에서 0.811V의 매우 좋은 성능을 보였다. 이는 LSCF의 산소이온전도성 및 전기전도성이 공기극에서의 분극을 낮추어 성능을 증가시키는 것으로 보인다.

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Effects of Acid Treatment of SAPO-34 on the Catalytic Lifetime and Light Olefin Selectivity during DTO Reaction (DTO 반응에서 촉매수명과 경질 올레핀 선택도에 미치는 SAPO-34의 산 처리 효과)

  • Choi, Ki-Hwan;Lee, Dong-Hee;Kim, Hyo-Sub;Park, Chu-Sik;Kim, Young-Ho
    • Applied Chemistry for Engineering
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    • v.26 no.2
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    • pp.217-223
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    • 2015
  • Effects of the post-acid treatment of SAPO-34 sample by hydrochloric acid were investigated to enhance the catalytic performance in DTO reaction. Uniformly sized SAPO-34 samples with cubic-like morphology were prepared by hydrothermal method using TEAOH and DEA as the structure directing agents. It was modified in terms of the HCl concentration and treating time. As a result, the total surface area and micropore volume for the well modified samples increased and the total acid site was somewhat decreased along with the erosion of the external surface. Especially, the catalytic lifetime and light olefins selectivity for acid treated SAPO-0.2 M (3 h) samples were considerably enhanced compared with those of untreated SAPO-34 samples. It indicates that the deactivation by coke formation proceeds mainly at the pore entrance on the external surface. Therefore, the acid treatment was confirmed to be a simple method which can significantly improve the catalytic performance by modifying the external surface of SAPO-34 catalyst.