• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1137-1144
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• 2013

$TiO_2$ composites with seven different carbon materials (activated carbons, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene oxides, and reduced graphene oxides) that are virgin or treated with nitric acid are prepared through an evaporation method. The photocatalytic activities of the as-prepared samples are evaluated in terms of $H_2$ production from aqueous methanol solution (photo-catalytic reduction: PCR) and degradation of aqueous pollutants (phenol, methylene blue, and rhodamine B) (photocatalytic oxidation: PCO) under AM 1.5-light irradiation. Despite varying effects depending on the kinds of carbon materials and their surface treatment, composites typically show enhanced PCR activity with maximum 50 times higher $H_2$ production as compared to bare $TiO_2$. Conversely, the carbon-induced synergy effects on PCO activities are insignificant for all three substrates. Colorimetric quantification of hydroxyl radicals supports the absence of carbon effects. However, platinum deposition on the binary composites displays the enhanced effect on both PCR and PCO reactions. These differing effects of carbon materials on PCR and PCO reactions of $TiO_2$ are discussed in terms of physicochemical properties of carbon materials, coupling states of $TiO_2$/carbon composites, interfacial charge transfers. Various surface characterizations of composites (UV-Vis diffuse reflectance, SEM, FTIR, surface area, electrical conductivity, and photoluminescence) are performed to gain insight on their photocatalytic redox behaviors.

• 한국수소및신에너지학회논문집
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• 제25권4호
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• 공업화학
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• 제22권6호
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• pp.658-663
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• 2011

SNCR-SCR hybrid system은 SNCR에서 NOx를 제거한 뒤, SCR로 NOx를 추가 제거하는 시스템으로 NOx 제거 효율을 향상시키는 경제적인 시스템이다. 본 연구에서는 SNCR-SCR hybrid system에서 운전 변수가 질소산화물 저감 효율에 미치는 영향을 고찰하였다. SNCR을 optimum temperature ($900{\sim}950^{\circ}C$)보다 낮은 온도에서 운전할 경우, 추가적인 암모니아 주입 없이도 $NH_3$ slip을 이용한 NO의 추가적인 제거의 효과가 있었으나 $NH_3$ slip이 높은 것으로 나타났다. 그러나 그 이상의 온도에서는 고온에 의한 암모니아의 분해로 SCR에 의한 추가 제거의 효과를 얻지 못했다. 따라서 SNCR 공정을 optimum temperature에서 운전하는 것이 NO 제거 효율과 $NH_3$ slip 농도를 고찰하였을 때 가장 적절하였으며, $SR_{RES}$가 적정 수준으로 유지되도록 NSR을 조절하는 것이 중요한 운전 변수인 것으로 나타났다.

• 플랜트 저널
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• 제18권3호
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• pp.52-61
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• 2022

본 연구는 실제 운영중인 영동에코발전본부 1호기 125 MW 우드펠릿 발전소를 대상으로 탈질설비 운전조건이 NOx 발생량에 미치는 영향을 시험하였다. SNCR 요소 유량 증가에 따라 NOx 농도는 점차 감소하였으나 SCR 후단 암모니아 슬립은 상승하였다. 시험대상 보일러는 고온의 내부온도로 인해 SNCR 운영에 불리한 구조이며 노즐의 최적위치 검토가 필요할 것이다. SCR 희석공기 온도변화는 NOx 발생량에 영향을 미치지 않았다. SCR 암모니아 유량 증가는 SCR 후단 NOx 농도를 감소시켰고 NOx 제거효율도 증가시켰다. 다만 암모니아 슬립 자체 기준치를 초과하지 않는 암모니아 유량 111 kg/h가 최대 운전기준으로 추정된다. SCR 믹서 압력 상승은 NOx 농도를 감소시키고 제거효율도 최대로 측정되어 NOx 생성을 가장 효과적으로 억제하는 변수로 파악되었다.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2019년도 정기학술대회 발표논문집
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• pp.83-83
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• 2019

Increasing the CO₂ concentration in the atmosphere induce high temperature and rising sea levels. So the technology that capture and reuse of the CO₂ have been recently become popular. Among other methods, CRR(CO2₂ reduction reaction) is typical method of CO₂ reusing. Electrocatalyst can show more higher efficiencies in CRR than photocatalyst because it doesn't use nature source. Nowadays, finding high efficient electrocatalyst by controlling electronic (affected by stoichiometry) and geometric (affected by atomic arrangement) factors are very important issues. Mono-atomic electro-catalyst has limitations on controlling binding energy because each intermediate has own binding energy range. So the Multi-metallic electro-catalyst is important to stabilize intermediate at the same time. Carbon monoxide(CO) which is our target product and important feedstock of useful products. Au is known for the most high CO production metal. With copper, Not only gold/copper has advantages which is they have FCC packing for easily forming solid solution regardless of stoichiometry but also presence of adsorbed CO on Cu promotes the desorption of CO on Au because of strong repulsion. And gold/copper bi-metal catalyst can show high catalytic activity(mass activity) although it has low selectivity relatively Gold. Actually, multi-metallic catalyst structure control method is limited in the solution method which is takes a lot of time. In here, we introduce CTS(carbo thermal shock) method which is using heat to make MMNP in a few seconds for making gold-copper system. This method is very simple and efficient in terms of time(very short reaction time and using carbon substrate as a direct working electrode) and increasing reaction sites(highly dispersed and mixing alloy structures). Last one is easy to control degree of mixing and it can induce 5 or more metals in one alloy system. Gold/copper by CTS can show higher catalytic activity depending on metal ratio which is altered easily by changing simple variables. The ultimate goals are making CO₂ test system by CTS which can check the selectivity depending on metal types in a very short time.

• 공업화학전망
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• 제22권5호
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• pp.25-40
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• 2019

전 세계적으로 환경문제를 해결하기 위한 방안으로 환경규제를 강화시키며 특히 다양한 대기오염 물질 중 최근 큰 이슈인 초미세먼지 저감을 위해 전구물질로 알려진 질소산화물을 제어하기 위한 다양한 기술개발이 가속화되고 있다. 특히, 다양한 처리기술 중에 기술적·경제적인 이점을 갖춘 선택적 촉매환원법(selective catalytic reduction, SCR) 기술을 통하여 질소산화물 제거를 위해 암모니아를 환원제로 반응에 참여시켜 인체에 무해한 H₂O, N₂로 전환하는 기술이 대표적이다. 최근 전 세계적으로 다양한 산업군에서 질소산화물이 배출되고 있으며, 점오염원뿐만이 아니라 비점오염원(mobile sources)에 대한 규제가 강화되고 있다. 디젤엔진이 장착된 선박 배가스 처리장치 내 SCR 기술이 주목을 받고 있으며, NH₃-SCR에 사용되는 촉매는 주로 VO_x/TiO₂, VO_x/W/TiO₂ 촉매가 대표적이다. 한편 선박 디젤엔진에 사용되는 연료에 따라 연소배가스 특성이 다르다. 이러한 연료가 연소됨에 따라 SO₂, SO₃가 발생되고 환원제인 NH₃와 결합하여 황산암모늄염((NH₄)₂SO₄), ABS (ammonium bisulfate, NH₄HSO₄)과 같은 염을 형성시켜 탈질촉매의 비활성화 문제가 발생된다. 이러한 비활성화 물질이 침적된 탈질촉매를 재활성화 시키기 위하여 열 산화를 통해 재생시키고 있다. 이처럼 선박용 SCR 촉매는 강화되는 배출규제 및 엔진기술의 발달로 저감되는 운전 온도에 대비하여 저온 활성 재생이 가능한 고활성, 고내구성 촉매기술 개발이 필요하다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.278-278
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• 2009

A photovoltaic device consisting of arrays of radial p-n junction wires enables a decoupling of the requirements for light absorption and carrier extraction into orthogonal spatial directions. Each individual p-n junction wire in the cell is long in the direction of incident light, allowing for effective light absorption, but thin in orthogonal direction, allowing for effective carrier collection. To fabricate radial p-n junction solar cells, p or n-type vertical Si wire cores need to be produced. The majority of Si wires are produced by the vapor-liquid-solid (VLS) method. But contamination of the Si wires by metallic impurities such as Au, which is used for metal catalyst in the VLS technique, results in reduction of conversion efficiency of solar cells. To overcome impurity issue, top-down methods like noble metal catalytic etching is an excellent candidate. We used noble metal catalytic etching methods to make Si wire arrays. The used noble metal is two; Au and Pt. The method is noble metal deposition on photolithographycally defined Si surface by sputtering and then etching in various BOE and $H_2O_2$ solutions. The Si substrates were p-type ($10{\sim}20ohm{\cdot}cm$). The areas that noble metal was not deposited due to photo resist covering were not etched in noble metal catalytic etching. The Si wires of several tens of ${\mu}m$ in height were formed in uncovered areas by photo resist. The side surface of Si wires was very rough. When the distance of Si wires is longer than diameter of that Si nanowires are formed between Si wires. Theses Si nanowires can be removed by immersing the specimen in KOH solution. The optimum noble metal thickness exists for Si wires fabrication. The thicker or the thinner noble metal than the optimum thickness could not show well defined Si wire arrays. The solution composition observed in the highest etching rate was BOE(16.3ml)/$H_2O_2$(0.44M) in Au assisted chemical etching method. The morphology difference was compared between Au and Pt metal assisted chemical etching. The efficiencies of radial p-n junction solar Cells made of the Si wire arrays were also measured.

• Korean Chemical Engineering Research
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• 제54권1호
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• pp.64-69
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• 2016

바이오디젤 공정에서 비균일상 촉매는 생성물의 회수를 쉽게 하며 촉매를 재사용하는 장점이 있기 때문에 최근 연구가 활발히 진행되고 있다. 본 연구에서는 $K_2CO_3/{\gamma}-Al_2O_3$ 촉매를 이용한 바이오디젤 생성 반응에서 촉매의 소성온도가 반응활성에 미치는 영향을 살펴보았다. 소성온도가 $600^{\circ}C$까지 높아짐에 따라 촉매의 활성이 높아졌으며, 그 이상의 온도에서는 촉매의 활성이 급격히 감소하여 소성온도가 촉매의 활성에 매우 중요한 영향을 주는 것을 확인하였다. 고온에서 이와 같은 활성감소는 Al-O-K와 $Al-O_2-K$인 활성자리의 감소가 원인이었던 것으로 추정되었다.

• 센서학회지
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• 제16권1호
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• pp.7-10
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• 2007

A thick film catalytic gas sensors which can be operated at $142^{\circ}C$ in presence of ultra violet-light emitting diode has been developed to measure hydrogen concentration in 0-5 % range. The sensing material as a combustion catalyst consists of $TiO_{2}$ (5 wt%) and Pd/Pt (20 wt%) supported on $Al_{2}O_{3}$ powder and the reference material to compensate the heat capacity of it in a bridge circuit was an catalyst free $Al_{2}O_{3}$ powder. Platinum heater and sensor materials were formed on the alumina plate by screen printing method and heat treatment. The effect of UV radiation in the presence of photo catalyst $TiO_{2}$ on the sensor sensitivity, response and recovery time has been investigated. The reduction of operating temperature from $192^{\circ}C$ to $142^{\circ}C$ for hydrogen gas sensing property in presence of UV radiation is attributed to the hydroxy radical and superoxide which was formed at the surface of $TiO_{2}$ under UV radiation.

• 공업화학
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• 제2권1호
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• pp.38-46
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• 1991

탄소 침적과 황피독된 수소 첨가용 Ni 촉매의 재생에 관하여 연구하였다. 탄소 침적된 촉매를 수소로 재생할 경우, 재생율은 높았으나 재생 시간이 길었으며 침적된 탄소가 완전히 제거되지 않았다. 산소로 재생할 경우에는 재생시간이 단축되었고 대부분의 침적된 탄소를 제거시킬 수 있었으나 반드시 환원과정이 뒤따라야 한다는 문제점이 있었다. 황에 완전히 피독된 촉매를 수소와 수증기만으로 재생 처리할 경우 활성의 회복을 기대할 수 없었으나, 산소가 포함된 재생처리에는 $650^{\circ}C$에서 활성이 60 %까지 회복되었으며, HCl이 첨가된 경우에는 특히 저온에서 활성이 45 %정도까지 회복되었다. 수증기는 촉매의 소결현상을 촉진시키나, 산소 또는 염소는 소결억제 효과가 있는 것으로 나타났다.