• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.514-517
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• 2008

Water gas shift(WGS) is an important step in fuel process for fuel cells, and improperness of commercial WGS catalysts for use in fuel cell systems has prompted numerous researches on noble metal catalysts. A selected noble metal catalyst for water gas shift reaction(WGS) was prepared with various metal loadings. The prepared catalysts were tested under two feeding conditions. At moderate residence time, carbon monoxide conversion was much higher on the noble metal catalysts as compared to commercial high-temperature shift catalyst. Effects of metal loading were examined by activity tests at short residence time. Higher metal loading effected higher reaction rate. The kinetic data was fitted to simple reaction equations and effectiveness factor was estimated. The results suggest the necessity of a structural design for the highly active noble metal catalysts.

• 한국수소및신에너지학회논문집
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• 제29권4호
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• pp.317-323
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• 2018

Solid oxide fuel cell (SOFC) operates at high temperature, therefor has the advantage of higher power generation and using exhaust heat than other fuel cells. In particular, the reforming reaction can be performed inside the SOFC stack to reduce the cooling of the stack and the burden on the reformer reactor. In this study, the reformer structure, operating characteristics, and thermal efficiency were evaluated for the optimization design of a heat exchanger type reformer of a 1 kW SOFC system.

• 대한기계학회논문집B
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• 제32권9호
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• pp.683-694
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• 2008

The performance and durability of Polymer Electrolyte Fuel Cells (PEFCs) are strongly influenced by the uniformity of current density, temperature, species distributions inside a cell In order to obtain uniform distributions in them, the optimal design of flowfield must be a key factor. In this paper, the numerical study of land/channel flowfield optimizations is performed, using a multi-dimensional, multi-phase, non-isothermal PEFC model. Numerical simulations reveal more uniform current density and HFR(High Frequency Resistance) distributions and thus better PEFC performance with narrower land/channel width where the less severe oxygen depletion effect near the land region and more uniform contact resistance variation along the in-plane direction are achieved. The present study elucidates detailed effects of land/channel width and assist in identifying optimal flow-field design strategies for the operation of PEFCs.

• 한국가스학회지
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• 제21권6호
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• pp.81-87
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• 2017

SOFC(Solid Oxide Fuel Cell)는 고온 연료전지 중 하나이며, SOFC 시스템과 스택은 고온 운전 특성을 가지고 있다. 이러한 특성 때문에 시스템 설계 및 재료의 선택, 내구성 확보, 안전성능 확보에 많은 어려움을 가지고 있다. 따라서 SOFC 연료전지의 상용화와 보급을 위해서는 안전성능 평가기술과 평가시스템의 개발이 병행되어야 한다. 본 연구에서는 스택 안전성능 평가시스템의 제작을 위하여 국내 외 SOFC 관련규격 및 스택의 위험요소를 분석하였다. 분석한 자료를 바탕으로 스택 안전성능 평가 시스템의 제작을 위한 평가항목을 도출하였다. 본 연구 결과를 통해 SOFC 연료전지의 보급 활성화와 안전한 사용 환경에 기여할 수 있기를 기대한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1870-1872
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• 1999

Performance of 20-cell stack for direct methanol fuel cell (DMFC) was tested at constant temperature. Electrode evaluation used to the stack was tested by the performance of a single cell. A new composite electrode prepared from active carbon cloth and high porous active carbon was developed for hydrophilic layer of the cell. Characteristics of a single cell using the composite electrode showed the current density of $500mA/cm^2$ at the cell voltage of 0.4V at $120^{\circ}C$. For the operating of 20 days. the cell voltage at constant cell current densty of $100mA/cm^2$ was slightly reduced from 0.62V to 0.53V with the cell voltage decay rate of 14.5%. Power of 20-cell stack at 5.3V, $100^{\circ}C$ was about 180W.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.627-631
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• 2012

휴대용 고분자전해질 연료전지의 수소발생용으로써 $NaBH_4$는 많은 장점을 갖고 있다. 본 연구에서는 $NaBH_4$ 가수분해 반응용 Co-P-B/Cu 촉매의 내구성에 대해 연구하였다. Co-P-B/Cu 촉매의 내구성 미치는 반응 온도, $NaBH_4$ 농도, NaOH 농도, 촉매 소성온도 등의 영향에 대해 실험하였다. 촉매의 내구성은 가수분해 반응 중에 발생하는 gel 형성에 영향을 받았다. 즉 gel 형성에 의해 촉매 손실률이 증가하였다. $NaBH_4$ 농도가 고농도일 때는 $60^{\circ}C$ 이상에서는 gel 형성이 안 되어 촉매 손실률이 낮았다. 그러나 $40^{\circ}C$ 이하에서는 gel이 형성되어 촉매 손실률이 증가했다. $NaBH_4$ 20 wt%, $40^{\circ}C$에서 NaOH 농도증가에 따라 겔이 형성되어 촉매 손실률이 증가함을 보였다. Co-P-B/Cu 촉매의 높은 온도에서 소성은 내구성을 향상시켰지만 촉매 활성을 감소시켰다.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.114-121
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• 2003

Hydrogen generation system using aqueous $NaBH_4$ solution was developed for feeding small polymer electrolyte membrane fuel cells (PEMFCs). Ru was selected as a catalyst with its high activity for the hydrogen generation reaction. Hydrogen generation rate was measured with changing the solution temperature, amount of catalyst loading, $NaBH_4$ concentration, and NaOH (a base-stabilizer) concentration. A passive air-breathing 2 W PEMFC stack was operated on hydrogen generated using $20wt%\;NaBH_4+5wt%$ NaOH solution and Ru catalyst.

• 한국재료학회지
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• 제28권5호
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• pp.308-314
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• 2018

Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

• 한국세라믹학회지
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• 제49권5호
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• pp.404-411
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• 2012

The reliability of solid oxide fuel cells (SOFCs) particularly depends on the high quality of solid oxide electrolytes. The application of thinner electrolytes and multi electrolyte layers requires a more reliable characterization method. Most of the investigations on thin film solid electrolytes have been made for the parallel transport along the interface, which is not however directly related to the fuel cell performance of those electrolytes. In this work an array of ion-blocking metallic Ti/Au microelectrodes with about a $160{\mu}m$ diameter was applied on top of an ultrathin ($1{\mu}m$) yttria-stabilized-zirconia/gadolinium-doped-ceria (YSZ/GDC) heterolayer solid electrolyte in a micro-SOFC prepared by PLD as well as an 8-${\mu}m$ thick YSZ layer by screen printing, to study the transport characteristics in the perpendicular direction relevant for fuel cell operation. While the capacitance variation in the electrode area supported the working principle of the measurement technique, other local variations could be related to the quality of the electrolyte layers and deposited electrode points. While the small electrode size and low temperature measurements increaseed the electrolyte resistances enough for the reliable estimation, the impedance spectra appeared to consist of only a large electrode polarization. Modulus representation distinguished two high frequency responses with resistance magnitude differing by orders of magnitude, which can be ascribed to the gadolinium-doped ceria buffer electrolyte layer with a 200 nm thickness and yttria-stabilized zirconia layer of about $1{\mu}m$. The major impedance response was attributed to the resistance due to electron hole conduction in GDC due to the ion-blocking top electrodes with activation energy of 0.7 eV. The respective conductivity values were obtained by model analysis using empirical Havriliak-Negami elements and by temperature adjustments with respect to the conductivity of the YSZ layers.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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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.