• 한국표면공학회지
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• 제43권6호
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• pp.297-303
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• 2010

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of electroreduction of trivalent chromium ions and solution stability. It was found that solution acidity controlled at pH 2.5 showed the widest current range for bright electrodeposits in the presence of PEG additives, which reduced the local current intensification at high current densities. Through complex interaction between PEG additives and hydrogen ion, that is, solution acidity, electrode potential was moved in the negative direction in the bulk solution, while it shifted in the positive when electric potential was scanned. In conjunction with electrochemical quartz crystal microbalance (EQCM), it was found that PEG additives had a role in promoting the electron transfer to trivalent chromium ion complexes in bulk solution and their adsorption at the electrode surface as well as interfering with hydrogen ion reduction process below pH 2.5. The PEG additives developed the nodular morphology during electroreduction of trivalent chromium ions with the increase of solution acidity and enhanced its current efficiency by maintaining the consumption of complexant, formic acid, at low speed.

• 한국전기전자재료학회논문지
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• 제31권2호
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• pp.102-106
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• 2018

Recently, there has been an increasing interest in the use of graphene as electrode materials for supercapacitors. In this regard, graphene oxide (GO) films were prepared using GO slurry obtained by dispersing GO powder in deionized (DI) water. The degree of dispersion of GO powder in DI water depends on the concentration of GO slurry, pH, impurity content, GO particle size, types of functional groups contained in GO, and manufacturing method of GO powder. In this study, the dispersivity of the GO powder was improved by adjusting the pH using only DI water (without additives), and a uniform GO film was obtained. The GO film was reduced by exposure to xenon intense pulsed light for a few milliseconds, and the reduced GO film was used as electrodes of a supercapacitor. The supercapacitor was characterized using cyclic voltammetry (CV), charge-discharge cycle, and electrochemical impedance spectroscopy measurements, and the specific capacitance of the supercapacitor was found to be ~140 F/g from the CV data.

• 한국가스학회지
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• 제4권1호
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• pp.40-48
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• 2000

연료전지는 일정하게 유지되는 전극-전해질계의 공정에 의해 연료와 산화제의 화학에너지를 전기에너지로 끊임없이 전환시킬 수 있는 전기화학장치이다. 인산형 연료전지는 전해질로 진한 인산염을 사용한다. 연료전지 시스템에서 가장 중요한 부분인 스택은 연료의 산화가 일어나는 anode, 산화물의 환원이 일어나는 cathode, 그리고 anode와 cathode를 분리시키고 이온을 전도시키는 전해질로 이루어져 있다. 연료전지의 성능은 시스템의 환경에 따른 작동 및 디자인 변수들에 의해 좌우된다. 따라서 연료전지의 핵심부분이라 할 수 있는 스택의 성능향상을 위하여 전산유체역학 코드를 이용한 스택에 대한 3차원적 모델링 및 전기화학반응이 포함된 모사를 수행하였다. 이로부터 산화제의 유량변화에 따른 스택 내부에서의 연료, 산화제 및 생성물의 농도, 그리고 반응에 의해 생성된 열의 전달에 의한 스택의 온도 분포 및 변화를 전산유체 코드인 FLUENT를 이용하여 계산하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.99-99
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• 2011

Fuel cell systems are a completely different form of electricity source that has been used so far and is an aggregation of multiple technologies with multidisciplinary features that can be operated safely only when gas and electrical safety are being considered. Since fuel cells generate through electrochemical reactions there are difficulties in ensuring electricity safety, power quality assessment, effective control and reliability standards for system faults using conventional inspection techniques and even though they are necessary as a primary means for reduction of CO2 owing to the Climate Convention, electrical safety assessment and measures are required for the prevention of faults in residential facilities. Although small-scaled distributed power supplies can be utilized as important means of peak control and energy management measures, research is required for observing the effects on the system and the development of inspection technology to ensure stable operation, and the electrical safety of residential fuel cell systems need to be assessed and the problems derived for establishing electrical safety standards. From the year 2002, Japan has established laws on technical safety standards and development and rules on the product specifications and standards for the industrialization of hydrogen fuel cells. Also, a lot of effort have been made for the commercialization of fuel cells by building one-stop certification services. Internationally, the IEC TC 105 has established international standards based on fuel cells. In order to protect the national interest, the country should be able to respond accordingly meet global standards. In fact, in Korea, to comply with the international trend, Korea Energy Management Corporation is establishing a certified agenda for fuel cells and Korean Agency for Technology and Standards is enacting technical standards for fuel cells. The current terms of fuel cells are that research has been focused more on the quality and performance of manufactured products rather than stable power operation and maintenance over time. In this paper, by considering the household fuel cell as a power device, the safety standards of the fuel cell system for a reliable operation with the existing power system is being proposed.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.598-602
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• 2018

석유정제공장에서 사용된 폐촉매의 특성을 조사하여 바나듐 레독스 흐름전지용 소재인 전해액의 제조에 대하여 연구하였다. 석유정제공정에서 사용된 폐촉매의 총공극 부피, 비표면적 및 평균 기공크기는 BET법과 BJH법으로 계산하여 각각 3.96cc/g, 13.81m2/g, 1.15A 구하여 폐촉매에서 바나듐을 회수하여 전해액으로 제조 할 수 있음을 확인하였다. 폐촉매를 TG-DTA분석결과, $25^{\circ}C$부터 $700^{\circ}C$ 범위에서 중량손실이 약 23wt%였다. 폐촉매의 성분을 ICP 장비를 분석하여 황, 바나듐, 니켈, 알루미늄, 망간 철 구리 등의 원소를 확인하였다. 또한 TEM 장비로 측정한 결과 바나듐 외 다른 원소들이 결정성 클러스터가 밝은 점으로 명백하게 드러남을 알 수 있었다. 액액 추출법을 사용하여 폐촉매로 부터 바나듐을 99.25%로 분리하여 추출한 바나듐용액의 전기화학적 특성분석을 위해 CV(cyclic votammetry)측정한 결과, 산화/환원피크가 나타남으로서 전해질 용액으로서의 가능성을 보여주고 있다. 또한 폐촉매로 부터 추출된 바나듐 용액의 순도를 더욱 높여 전해질 용액을 제조하면 기존 상용화된 전해질 성능과 같은 것을 제조 할 것으로 사료된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.116-117
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• 2006

We investigated selective emitter effect of Porous Silicon (PSI) as antireflection coatings (ARC). The thin PSi layer, less than 100nm, was electrochemically formed by electrochemical method in about $3{\mu}m$ thick $n^+$ emitter on single crystalline silicon wafer (sc-Si). The appropriate PSi formations for selective emitter effect were carried out a two steps. A first set of samples allowed to be etched after metal-contact processing and a second one to evaporate Ag front-side metallization on PSi layer, by evaluating the I-V features The PSi has reflectance less than 20% in wavelength for 450-1000nm and porosity is about 60%. The cell made after front-contact has improved cell efficiency of about in comparison with the one made after PSi. The observed increase of efficiency for samples with PSi coating could be explained not only by the reduction of the reflection loss and surface recombination but also by the increased short-circuit current (Isc) within selective emitter. The assumption was confirmed by numerical modeling. The obtained results point out that it would be possible to prepare a solar cell over 15% efficiency by the proposed simple technology.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
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• pp.177-180
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• 2003

A glassy carbon electrode(GCE) modified with nafion-DTPA-glycerol was used for the highly selective and sensitive determination of a trace amount of Cu$\^$2+/. Various experimental parameters, which influenced the response of nafion-DTPA-glycerol modified electrode to Cu$\^$2+/, were optimized. The copper(II) was accumulated on the electrode surface by the formation of the complex in an open circuit, and the resulting surface was characterized by medium exchange, electrochemical reduction, and differential pulse voltammetry, A linear range was obtained in the concentration range 1.0${\times}$10$\^$-8/M∼1.0${\times}$10$\^$-6/M Cu(II) with 7 min preconcentration. Further, when an approximate amount of lead(II) is added to the test solution, nafion-DTPA-glycerol modified glassy carbon electrode has a dynamic range of 2 orders magnitude(1.0${\times}$10$\^$-9/M∼1.0${\times}$10$\^$-7/M). The detection limit(3 $\sigma$) was as low as 5.0${\times}$10$\^$-6/M(0.032ppb). The interferences from other metal ions could be reduced by adding KCN into the sample solutions. This method was applied to the determination of coppe,(II) in certified reference material(3.23${\times}$10$\^$-7/M, 21ppb), sea water(9.50${\times}$10/sup-7/M, 60ppb). The result agrees satisfactorily with the value measured by Korea Research Institute of Standard and Science.

• Carbon letters
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• 제6권1호
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• pp.41-46
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• 2005

Plasma carbon blacks of 20~30 nm diameter were synthesized by direct decomposition of natural gas using a hybrid plasma torch system with 50 kW direct current and 4 MHz of radio frequency. The insulating rector which inside diameter of 400 mm and length of 1500 mm, respectively was kept at 300~$400^{\circ}C$ during the preparation. The ultimate analysis of plasma carbon blacks reveals that the raw plasma carbon blacks contains a large quantity of volatile which is mainly consist of hydrogen. Therefore devolatilization of raw plasma carbon blacks were carried out at $900^{\circ}C$ for one hour under nitrogen atmosphere. The devolatilization leads to the decrease in electrical resistivity and surface oxygen functional groups of plasma carbon black significantly. In order to investigate the plasma carbon as a catalyst support, devolatilized plasma black at $900^{\circ}C$ (DPB) supported PtAu catalyst was synthesized by sodium boronhydride reduction method. Electrochemical measurements and direct formic acid fuel cell test indicated that catalytic activity of DPB supported PtAu catalyst for formic acid oxidation was similar to that of Vulcan XC-72 of commercial carbon black supported one.

• 한국세라믹학회지
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• 제47권1호
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• pp.26-38
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• 2010

Degradation in Solid Oxide Fuel Cell performance can be ascribed to the following fundamental processes from the materials chemical point of view; that is, diffusion in solids and reaction with gaseous impurities. For SOFC materials, diffusion in solids is usually slow in operation temperatures $800\sim1000^{\circ}C$. Even at $800^{\circ}C$, however, a few processes are rapid enough to lead to some degradations; namely, Sr diffusion in doped ceria, cation diffusion in cathode materials, diffusion related with metal corrosion, and sintering of nickel anodes. For gaseous impurities, chromium containing vapors are important to know how the chemical stability of cathode materials is related with degradation of performance. For LSM as the most stable cathode among the perovskite-type cathodes, electrochemical reduction reaction of $CrO_3$(g) at the electrochemically active sites is crucial, whereas the rest of the cathodes have the $SrCrO_4$ formation at the point where cathodes meet with the gases, leading to rather complicated processes to the degradations, depending on the amount and distribution of reacted Cr component. These features can be easily generalized to other impurities in air or to the reaction of nickel anodes with gaseous impurities in anode atmosphere.

• 대한화학회지
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• 제56권5호
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• pp.571-576
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• 2012

Horseradish peroxidase (HRP), alkoxysilane인 TEOS의 겔 용액과 graphite를 혼합하여, 전기전도성을 나타내고 재사용이 가능하며 안정성을 향상시킨 carbon composite electrodes (CCEs) 바이오센서를 제작하였다. TEOS의 졸-겔 전이반응을 이용하여 HRP를 silicate gel network포획시킨 바이오센서는 -0.2 V에서 $H_2O_2$의 환원이 시작되었으며, HRP의 함량과 pH를 변화시켜 최적 분석 조건을 구하였다. 분석 최적 조건에서 검량선 및 검출한계를 구한 결과, 0.2~2.2 mM의 $H_2O_2$ 농도 범위에서 직선적인 감응을 나타내며 검출한계는 0.035 mM이었다. ascorbic acid, acetaminophene, uric acid의 방해작용을 조사한 결과 $H_2O_2$의 전기화학적 분석에 영향을 주지 않았다.