• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.88-93
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• 2005

Anode-supported solid oxide fuel cell (SOFC) was investigated to increase the cell power density at intermediate temperature through control of the cathode structure. The anode-supported SOFC cell were fabricated by wet process, in which the electrolyte of $8mol\%\;Y_2O_3-stabilized\;ZrO_2 (YSZ)$ was coated on the surface of anode support of Ni/YSA and then the cathode was coated. The cathode has two- or three- layered structure composed of $(La_{0.85}Sr_{0.15})_{0.9}MnO_{3-x}(LSM),\;LSM/YS$ composite (LY), and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3{LSCF)$ with different thickness. Their single cells with different cathode structures were characterized by measuring the cell performance and ac impedance in the temperature range of 600 to $800^{\circ}C$ in humidified hydrogen with $3\%$ water and air. The cell with $LY\;9{\mu}m/LSM\;9{\mu}m/LSCF\;17{\mu}m$ showed best performance of $590mW/cm^2$, which was attributed to low polarization resistance due to LY and to low interfacial resistance due to LSCF.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.127.1-127.1
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• 2010

고체산화물연료전지는 고효율 및 무공해의 전기화학 에너지 변환장치로서, 최근 국내외에서 활발한 연구개발이 수행되고 있다. 특히, 고체산화물 연료전지 시스템의 조기 상용화를 위해 시스템의 작동온도를 약 $800^{\circ}C$ 이하로 낮추고 저가로 생산 할 수 있는 제조공정 개발에 대한 연구를 적극적으로 수행하고 있다. 본 연구에서는 고체산화물연료전지의 단위셀를 구성하는 연료극지지체 및 박막 전해질에 대해서 저가 양산의 테이프케스팅법 및 동시소성 공정, 그리고 연료극 지지체 전해질(anode-supported electrolyte)에 대한 공기극 페이스트 프린팅 제조공정에 대해 소개한다. 또한 고체산 화물연료전지의 제조공정 및 시간을 단축하기 위해 방전플라즈마 소결공법(SPS)에 의한 연료극 지지체 제조 공정, 단위셀의 성능 최적화를 위한 나노 스케일의 고성능 전해질 소재 분말합성 공정(crystallite size: 5~10nm, surface area : $100m^2/g$ 이상) 그리고 테이프케스팅에 의한 박막 전해질 제조 공정(thin film : $10{\mu}m$ 이하) 등 주요 단위셀 소재 및 부품의 제조공정 특성 그리고 단위셀의 전기화학적 특성(max. power density : 1.0 W/$cm^2$)에 대해 소개하며, 최종적으로 평판형 대면적 고체산화물연료전지(max. $20cm{\times}15cm$)의 단위셀 상용화 제조 기술 및 성능평가 기술에 대해서도 소개 할 예정이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.86-86
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• 2012

The new approaches for silicon solar cell of new concept have been actively conducted. Especially, solar cells with wire array structured radial p-n junctions has attracted considerable attention due to the unique advantages of orthogonalizing the direction of light absorption and charge separation while allowing for improved light scattering and trapping. One-dimenstional semiconductor nano/micro structures should be fabricated for radial p-n junction solar cell. Most of silicon wire and/or pillar arrays have been fabricated by vapour-liquid-solid (VLS) growth because of its simple and cheap process. In the case of the VLS method has some weak points, that is, the incorporation of heavy metal catalysts into the growing silicon wire, the high temperature procedure. We have tried new approaches; one is electrochemical etching, the other is noble metal catalytic etching method to overcome those problems. In this talk, the silicon pillar formation will be characterized by investigating the parameters of the electrochemical etching process such as HF concentration ratio of electrolyte, current density, back contact material, temperature of the solution, and large pre-pattern size and pitch. In the noble metal catalytic etching processes, the effect of solution composition and thickness of metal catalyst on the etching rate and morphologies of silicon was investigated. Finally, radial p-n junction wire arrays were fabricated by spin on doping (phosphor), starting from chemical etched p-Si wire arrays. In/Ga eutectic metal was used for contact metal. The energy conversion efficiency of radial p-n junction solar cell is discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.345-350
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• 2018

Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and $CH_4$ fuel running. Using Pd-doped perovskite, $La(Sr)Fe(Mn,Pd)O_3$, as an anode, fairly high maximum power densities of 0.5 and $0.2cm^{-2}$ were achieved at 1,073 K in $H_2$ and $CH_4$ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in $CH_4$ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.145-150
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• 1998

The electrical and mechanical properties of the 8 mol% yittria-stabilized zirconia and alumina composites have been examined as a function of the alumina content. The 3-point bending strength and fracture toughness of the composites increased with increasing alumina content up to 20 wt%. The average grain size of the composites decreased with increasing alumina content up to 20 wt%. The composite with 5 wt% $Al_2O_3$ showed a 3-point bending strength of 310 MPa and fracture toughness about $7.8MPa\cdot\textrm m^{1/2}$. The electrical conductivity of the composites at $1000^{\circ}C$ increased slightly with increasing alumina content up to 10 wt% and decreased monotonically with alumina content. The conductivity of the TZ-8YS with 5 wt% alumina was 0.4 S/cm at $1000^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.4
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• pp.440-447
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• 2006

Solid polymer electrolyte(SPE) membrane with electrodes embedded on both faces offer unique possibilities for the electrochemical cells like water electrolyzer with fuel cell. The Nafion 117 membrane was used as the SPE, and $Pt(NH_3)_4Cl_2$ and $NaBH_4$ as the electrocatalysts and reducing agent, respectively. The 'impregnation-reduction(I-R) method' has been investigated as a tool for the preparation of electrocatalysts for water electrolyzer by varying the concentration of reducing agent and reduction time at fixed concentration of platinum salt, 5 mmol/L. Pt-SPE electrocatalysts prepared by non-equilibrium I-R method showed the lowest cell voltage of 2.17 V at reduction time, 90 min and with concentration of reducing agent 0.8 mol/L and the cell voltage with those by equilibrium I-R method was 2.42 V at reduction time, 60 min and with concentration of reducing agent 0.8 mol/L. The cell voltage were obtained at a current density $1\;A/cm^2$ and $80^{\circ}C$. In water electrolysis, hydrogen production efficiency by Pt-SPE electrocatalyst is 68.2% in case of non-equilibrium I-R method and 61.2% at equilibrium I-R method.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.6
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• pp.533-539
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• 2010

Ni-YSZ supported button cells were prepared by spray-coating YSZ and screen-printing YSZ-LSM powder as an electrolyte and oxygen electrode on Ni-YSZ cermet disks. In order to identify the polarization loss mechanism in high temperature electrolysis current-voltage characteristics coupled with electrochemical impedance spectroscopy were investigated as a function of temperature, current load, and the humidity. The effects of the different current collectors of platinum and silver for oxygen electrodes were compared. With Ag current collector two polarization losses were distinguished. The high frequency component was attributed to the Ni-YSZ cermet which was less susceptible to temperature variation but increasing in loss with humidity. The lower frequency component was attributed to the LSM electrode. Platinum current collector led to a much lower polarization loss.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.214-214
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• 2003

고체 고분자 전해질에 대한 연구는 1979년 wright와 Armand에 처음 시작된 이래로 지난 20여년간 연구가 계속적으로 지속되고 있다. 전지의 적용되기 위해 전해질이 갖추어야 할 조건중에 이온전도도가 상온에서 10-4 S/cm 이상의 전도도를 나타내야 하지만 지금까지 연구되고 있는 여러 고체 고분자 전해질은 이런 조건을 만족시키지 못하고 있는 실정이다. 본 연구에서는 이런 상온에서의 이온 전도성을 향상시키기 위해 여러 종류의 실리카와 세라믹 계열의 첨가제를 첨가하여 이온전도성의 향상을 꾀하고자 하였다. 본 연구에서는 고체 고분자 전해질의 host polymer로써 분자량 400,000 의 Polyethylene oxide를 사용하였으며 Lithuim salt로는 Lithium (bisperfluroethylsulfonyl)imide(3M)를 기본적으로 사용하였다. 여기에 가소제의 역활로써 (3-cyanopropyl)methylsiloxane cyclics를 첨가하였고 표면그룹이 CH3와 OH기로 이루어진 기능성 나노 실리카를(<11nm)이용하여 함량별 전기 화학적 특성 및 기본 물성을 측정하였다. 기본적으로 이 네 가지 물질을 유기용매 Acetonitril에 잘 용해하여 Solid Casting방법으로 80-100 마이크로의 복합고분자 전해질을 제조하였다. Homogeneous하고 uniform한 필름 제조하기 위해 9$0^{\circ}C$에서 열처리를 24h 동안 실시하였다. 제조되어진 복합고분자전해질은 XRD를 통하여 결정성을 조사하였고 DSC를 이용하여 유리 전이온도 및 결정화도를 조사하였다. 복합고체고분자의 전기화학적 성질을 평가하기 위해 blocking electrode를 제작하여 임피던스 스펙트로 스코피를 이용하여 이온전도성을 측정하였다. 또한 복합 고분자 전해질의 온도의존성에 대해서도 조사하였다. 또한 실제 전지의 작동구간에서의 전해질의 안정성을 확인하기 위해 LSV를 측정하였고. Li metal을 사용하여 non-blocking electrode를 제작하여 복합고분자 전해질과의 계면저항을 측정하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.414-420
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• 2011

Thermal stress analysis of a planar anode-supported SOFC considering electrochemical reactions has been performed under operating conditions where average current density varies from 0 to 2000 $A/m^2$. For the case of the 2000 $A/m^2$ operating condition, Structural stress analysis based on the temperature distributions obtained from the CFD analysis of the unit cell has also been done. From this one way Fluid-Structure Interaction(FSI) analysis, Maximum Von-Mises stress under negligible temperature gradient fields occurs when cell components are perfectly bonded. The maximum stress of the electrolyte, cathode and anode in a unit cell SOFC is 262.58MPa, 28.55MPa and 15.1MPa respectively. The maximum thermal stress is critically dependent on static friction coefficient.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.373-373
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• 2009

Relative humidity, membrane conductivity and water activity are critical parameters of polymer electrolyte membrane fuel cells (PEMFC) for high performance and reliability. These parameters are closely related with temperature. Moreover, the ideal values of these parameters are not always identical along the channels. Therefore, the cooling channel design and its operating condition should be well optimized along the all location of the channels. In the present study, we have performed a numerical investigation on the effects of cooling channels on performance of a PEMFC. Three-dimensional Navier-Stokes equations are solved with the energy equation including heat generated by the electrochemical reactions in the fuel cell. The present numerical model includes the gas diffusion layers (GDL) and serpentine channels for both anode and cathode gas flows, as well as cooling channels. To accurately predict the water transport across the membrane, the distribution of water content in the membrane is calculated by solving a nonlinear differential equation with a nonlinear coefficient, i.e., the water diffusivity which is a function of water content as well as temperature. Main emphasis is placed on the heat transfer between the solid bipolar plate and coolant flow. The present results show that local current density is affected by cooling channels due to the change of the oxygen concentration and the membrane conductivity as well as the water content. It is also found that the relative humidity is influenced by the generated water and the gas temperature and thus it affects the distribution of fuel concentration and the conductivity of the membrane, ultimately fuel cell performance. Unit-cell experiments are also carried out to validate the numerical models. The performance curves between the models and experiments show reasonable results.