• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.299-302
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• 2005

Direct Borohydride Fuel Cell은 알칼리 붕소 수소화물의 수용액을 이용하는 연료전지로 연료의 직접 산화반응을 통해 기존의 DMFC(직접 메탄을 연료전지)보다 높은 전류밀도와 OUV(Open Circuit Voltage)를 나타낸다. 또한 액체 연료를 사용하므로 장치 구성이 간단하며, 사용하는 연료가 반응성이 높은 알칼리 붕소 수소화물로 이루어져 있기 때문에 탄화수소 계열의 액체 연료와 달리 전기화학 반응이 비귀금속 전극에서도 쉽게 이루어질 수 있다는 장점을 가지고 있다 하지만 강알칼리 조건에서 전기화학 반응이 진행되므로 이에 적합한 재료로 장치를 구성해야 하며, 액체 상태의 연료가 전해질을 투과하는 현상인 크로스오버 문제를 해결해야 하고, 생성물인 $BO_2$-가 침적되어 전지효율을 떨어뜨리는 것을 방지해야 하는 문제점이 있다. 또한 알칼리 붕소 수소화물이 물과 반응하여 수소를 발생시키는 hydrolysis 반응을 억제하여야 하고 직접 산화반응만이 진행될 수 있도록 전지를 구성해야 연료효율을 높일 수 있다. 따라서 본 연구에서는 수소 생성반응일 hydrolysis 반응은 억제하고 연료의 직접 산화반응만을 진행시키기 위한 전극촉매에 대하여 연구하였다. 일반적인 저온형 연료전지의 전극촉매로 사용하는 Pt등의 귀금속 촉매와, 귀금속 촉매를 대체할 수 있는 Ni등의 비귀금속 촉매를 그 연구 대상으로 하였으며, 평가 방법으로는 unit cell station을 이용한 단위전지 성능측정 실험과 Potentiostat/Galvanostat을 이용한 half cell 실험을 병행하여 수행하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.361-370
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• 2009

Ni-PTFE composite plated on graphite (C/Ni-PTFE) and PTFE (PTFE/Ni-PTFE) particles were prepared uniformly by electroless composite plating. The conductivity of C/Ni-PTFE particles was 280 S/m higher than 95 S/m of PTFE/Ni-PTFE particles at same composite plating condition (Ni:35~36 wt%, PTFE:8 wt%). The C/Ni-PTFE particles were formed into the C/Ni-PTFE plate using heat treatment at $350^{\circ}C$ under 10~$1000\;kg/cm^2$. The C/Ni-PTFE plate showed 1) high conductivity of $5.7\;{\times}\;10^4\;S/m$ due to the existence of graphite as conducting aid and the formation of 3-dimensional Ni network 2) good gas diffusion caused by various pore volumes (0.01~$100\;{\mu}m$) in the plate. The plate could be useful for an electrode in an alkaline fuel cell (AFC). The current density of C/Ni-PTFE electrode indicated $84\;mA/cm^2$ at 0.3V and it was 3.0 times higher than that of PTFE/Ni-PTFE electrode.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.4
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• pp.291-299
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• 2009

Ni-plated polytetrafluoroethylene(Ni-PTFE) particles($25{\mu}m$, $500{\mu}m$) were prepared by using nickel electroless plating. The Ni content in Ni-PTFE particles increased with increasing the amount of reduction agent. At about 53 wt% Ni content, $25{\mu}m$ Ni-PTFE particles showed conductivity of 320S/m. The Ni-PTFE particles were formed into the Ni-PTFE plate using heat treatment at $350^{\circ}C$ under $10{\sim}1000kg/cm^2$. The Ni-PTFE plate displayed the high conductivity of 5100S/m due to the formation of 3-dimentional Ni network. The plate was used as an electrode in an alkaline fuel cell(AFC). In terms of the current density, the Ni-PTFE electrode having higher Ni content(53 wt%) showed improved performance.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.543-553
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• 1996

Oxygen reduction in an alkaline fuel cell was studied by using perovskite type oxides as an oxygen electrode catalyst. The high surface area catalysts were prepared by malic acid method and had a formula of $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$(x=0.00, 0.01, 0.10, 0.20, 0.35 and 0.50). From the result of XRD pattern and specific surface area due to the amount of Fe substitution and the consumption of ammonia-water, the complex formation of Fe ion with $NH_3$ was the main factor for both the phase stability of perovskite and the increase of specific surface area. Multi-step calcination was necessary to give a single phase of perovskite in catalyst precursor. The crystal structure of the catalysts was simple cubic perovskite, which was verified from the XRD patterns of the catalysts. The activity of oxygen reduction was monitored by the techniques of cyclic voltammetry, static voltage-current method, and current interruption method. The activity(current density) of oxygen reduction showed its minimum at x=0.01 and its maximum between 0.20 and 0.35 of x-value in $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$. This tendency was independent of the change of surface area.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.230-239
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• 1992

Nickel was used as a catalyst for the hydrogen electrode in alkaline fuel cell. The optimum electrolyte concentration and recommendable operating temperature identified from polarization curves were 6N KOH and $80^{\circ}C$, respectively. Comparing the conductivity, apparent porosity and current density at porous hydrogen electrode manufactured with various PTFE additions, the proper content of PTFE was 10wt%. Chemisorption was carried out to define the appropriate surface area. The electrode produced with 10wt% of PTFE and sintered at $340^{\circ}C$ showed more than $200mA/cm^2$ of current density. The morphology of electrode surface was investigated with SEM. Cold pressing, hot pressing, rolling and calendering methods were carried out for manufacturing the electrode, and electrochemical characteristics for each method was studied.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.373-380
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• 1993

The preparation method of Raney nickel catalyst and the effect of promotor for the hydrogen electrode in alkaline fuel cell were investigated with electrochemical methods. The best electrode performance was observed with the Raney nickel which was obtained at $700^{\circ}C$ of sintering temperature and 60:40 of nickel:aluminum. As titanium was added for promotor, the activity of catalyst and characteristic of electrode was improved. Especially, the electrode containing 2w/o of titanium showed the maximum mass activity of 2.4A/g and its mean particle size was $5.7{\mu}m$. The resistance and capacitance of the electrode containing 2w/o of titanium, measured with AC impedance spectroscopy, were calculated to the $0.3{\Omega}cm^2$ and $0.42F/cm^2$, respectively.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.701-709
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• 1992

Silver particles were impregnated on carbon black with colloidal method and used as catalyst for oxygen electrode in alkaline fuel cell. With the addition of sodium dodecylbenzenesulfonate in $AgNO_3$ and $NaBH_4$solution, colloidal solution was made and confirmed with electrophoresis test. Effects of particle size on electrode performance were studied and $200{\AA}$ of silver particle size shown the highest value of mass activity. The aggromeration of silver particle was Influenced with surfactant amount, stirring time and heat treatment. Considering the increase of particle size caused of operating temperature, recommendable particle size of silver catalyst for manufacturing the electrode was $100{\AA}$. Dispersity of carbon black was investigated and reagglomeration was appeared after homogenizing 30 sec.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.927-933
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• 1997

The effects of carbon black on the electrodes performance and on the structure of the catalyst layer in Raney nickel hydrogen electrodes for alkaline fuel cells were investigated by using electrochemical and nitrogen adsorption methods. The optimum content of carbon black in the catalyst layer of Raney nickel hydrogen electrode was 2wt%. The limiting current density was increased by the addition of carbon black due to the enlargement of gas-liquid interface area. The rate determining step at the limiting current density was supposed to be a step where hydrogen dissolves at gas-liquid interfaces.

• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.150-155
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• 1999

The Electrochemical stabilities of the Brewer-Engel type intermetallic compounds of Co-Mo $(35 wt\%)$ and Ni-Mo$(35 wt\%)$ manufactured by the arc-melting method for the hydrogen electrode of $H_2-O_2$ alkaline fuel cell were investigated. Effects of temperature and concentration on the electrochemical behavior of the electrodes in the $80^{\circ}C$ 6 N KOH solution deaerated with $N_2$ gas were studied by electrochemical methods. The effect of overpotential on the electrochemical stabilities of Co-Mo and Ni-Mo intermetallic compounds was also discussed under the normal operation condition of AFC. It was shown that Co-Mo electrode had lower electrochemical stability as compared to Ni-Mo. In the case of Co-Mo electrode, a simultaneous dissolution of cobalt and molybdenum has occurred at low anodic overpotential form equilibrium hydrogen electrode potential, but the dissolution of cobalt was serious, and Co(OH)l layer on the electrode surface formed at the high anodic overpotential. In contrast the Ni-Mo electrode had high electrochemical stability because formation of the dense and thin protective $Ni(OH)_2$ layer prevented the dissolution of molybdenum.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.527-534
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• 1992

Raney nickel was used as catalyst in the hydrogen electrode for an alkaline fuel cell. The hydrogen electrode manufactured with the Raney nickel catalyst which was sintered at $700^{\circ}C$ was found to have the highest electrode performance. Using the Raney nickel powder of average particle size $90{\AA}$ for the electrode, the current density which had been measured was $450mA/cm^2$ at $80^{\circ}C$ using 6N KOH solution as an electrolyte. The effects of PTFE addition were investigated with CO-chemisorption, polarization curves and Tafel slope. CO-chemisorption had shown the optimum value when the Raney nickel was mixed with 5wt% of PTFE, but from the current density and Tafel slope at porous Raney nickel electrode, the appropriate value of PTFE addition was 10wt%. Recommendable Ni and Al portion for Raney nickel was 60 : 40 and loading amount was $0.25g/cm^2$. Also the influence of pressing pressure for manufacturing catalytic layer and for junction with gas diffusion layer was examined. The morphology of catalyst surface was investigated with SEM. The influence of reactivation time and heat-treatment temperature were also studied.