A facile one-pot wet chemical process to prepare pure anatase TiO2 hollow structures using ammonium hexafluorotitanate as a precursor is developed. By defining the formic acid ratio, we fabricate TiO2 hollow structures containing fluorine on the surface. The TiO2 hollow sphere is composed of an anatase phase containing fluorine by various analytical techniques. A possible formation mechanism for the obtained hollow samples by self-transformation and Ostwald ripening is proposed. The TiO2 hollow structures containing fluorine exhibits 1.2 - 2.7 times higher performance than their counterparts in photocatalytic activity. The enhanced photocatalytic activity of the TiO2 hollow structures is attributed to the combined effects of high crystallinity, specific surface area (62 m2g-1), and the advantage of surface fluorine ions (at 8%) having strong electron-withdrawing ability of the surface ≡ Ti-F groups reduces the recombination of photogenerated electrons and holes.

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of TiO2, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile TiO2 because these coupled TiO2 powders can retain the benefits of TiO2, one of the best photocatalysts. In this study, anatase TiO2 nanoparticles are synthesized and coupled on the surface of rutile TiO2 powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase TiO2 nanoparticles and disperse anatase TiO2 nanoparticles uniformly on the surface of rutile TiO2 powders. Rutile TiO2 powders coupled with anatase TiO2 nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled TiO2 powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

본 연구에서는 질소산화물 제거용 환원제로 사용하는 요소 수용액을 암모니아로 전환하는데 있어 SCR 상용촉매의 활용가능성을 확인하기위해 촉매조성에 따른 반응온도, 공간속도의 영향에 대한 연구를 수행하였다. 연구결과 SCR 촉매로 널리 사용되는 V2O5/TiO2 촉매는 TiO2 및 WO3-V2O5/TiO2 촉매에 비해 암모니아 생성이 우수함을 보였다. 활성금속을 담지하지 않은 TiO2 촉매는 V2O5 혹은 WO3-V2O5를 담지 한 촉매에 비해 공간속도에 따른 암모니아 전환에 영향을 받지 않는 것으로 나타났으며, 활성금속을 담지 한 촉매는 공간속도가 증가함에 따라 암모니아 생성 농도가 감소됨을 확인하였다.

RuO2 is a common active component of Dimensionally Stable Anodes (DSAs) for chlorine evolution that can be used in wastewater treatment systems. The recent improvement of chlorine evolution using nanostructures of RuO2 electrodes to increase the treatment efficiency and reduce the energy consumption of this process has received much attention. In this study, RuO2 nanorod and nanosheet electrodes were simply fabricated using the sol-gel method with organic surfactants as the templates. The obtained RuO2 nanorod and nanosheet electrodes exhibit enhanced electrocatalytic activities for chlorine evolution possibly due to the active surface areas, especially the outer active surface areas, which are attributed to the increase in mass transfers compared with a conventional nanograin electrode. The electrocatalytic activities for chlorine evolution were increased up to 20 % in the case of the nanorod electrode and 35% in the case of the nanosheet electrode compared with the nanograin electrode. The RuO2 nanorod 80 nm in length and 20-30 nm in width and the RuO2 nanosheet 40-60 nm in length and 40 nm in width are formed on the surface of Ti substrates. These results support that the templated RuO2 nanorod and nanosheet electrodes are promising anode materials for chlorine evolution in future applications.

금속산화물 반도체 중 하나인 산화아연은 인체에 무해하고 친환경적이며, 우수한 화학적, 열 적 안정성의 특성을 지니며 3.37 eV의 넓은 밴드갭 에너지와 60 meV의 높은 엑시톤 바인딩 에너지로 인해 태양전지, 염료페기물의 분해, 가스센서 등 다양한 분야에 응용이 가능한 물질이다. 산화아연은 입 자 형상 및 결정성의 변화에 따라 광촉매 활성이 변하게 된다. 따라서, 다양한 실험변수와 첨가제를 사 용하여 입자를 합성하는 것이 매우 중요하다. 본 논문에서는 마이크로파 수열합성법을 사용하여 산화아연을 합성하였다. 전구체로는 질산아연을 사 용하였고, 수산화나트륨을 사용하여 용액의 pH를 11로 조정하였다. 첨가제로는 계면활성제인 에탄올아 민, 세틸트리메틸암모늄브로마이드, 소듐도데실설페이트, 솔비탄모노올레이트를 첨가하였다. 합성된 입자 는 별모양, 원추형, 씨드형태, 박막형태의 구형의 형상을 보였다. 합성된 산화아연의 물리・화학적 특성 은 XRD, SEM, TGA을 통하여 확인하였고, 광학적 특성은 UV-vis spectroscopy, PL spectroscopy, Raman spectroscopy으로 확인하였다.

국내 대기오염물질 중 도로공간에서 발생하는 오염원은 약 34.4%로 다소 많은 비중을 차지하고 있다. 이러한 대기오염을 정화하는 방법의 한 예로는 TiO2의 광촉매 작용을 이용하여 도로공간에서 발생하는 오염물질 제거방법이 있다. 현재 국내･외의 다양한 분야에서 광촉매를 활용한 연구가 활발히 진행 중이 며, 그 중 토목분야에서는 배기가스에 인한 도로 오염물질 배출을 저감하기 위한 연구가 진행되고 있다. TiO2는 빛을 이용하여 광화학 반응을 촉진시키는 물질로서 활성도가 높고 화학적으로 안정적이며, 인체 에 무해하여 대기정화, 수질정화, 셀프클리닝(self-cleaning), 초 친수성 제품 등 다양한 활용분야에 사 용되고 있다. 하지만 TiO2는 백색 분말로 이루어진 특성이 있어, 바람에 흩어지거나 물에 혼합되면 회수 가 어렵고 손실의 우려가 크다. 이에 대해 광촉매 분말의 고정화가 필요한 동시에 활성에 영향을 주는 비 표면적 확보와 바인더의 내구성 및 무해성이 요구된다. 따라서 본 연구에서는 1액형 광촉매를 도포한 아 스팔트 포장체의 광활성 거동을 파악하기 위한 기초연구를 수행하였으며, 광촉매 시료는 국내 B사의 광 촉매 물질을 수용액 중에서 마이셀화 시키는 음전하성 계면활성제와 무기질 바인더가 혼합된 1액형 TiO2 혼합물을 사용하였다. 본 실험에서는 수용성 미디움에서 표면의 광촉매 활성 시험 – 메틸렌 블루 분해법(KS L ISO 10678)과 노면의 미끄럼저항성 시험방법(KS F 2375)를 진행하였다. 메틸렌 블루 분해법을 통해 아스팔트 시편에 도포된 TiO2의 용량에 따른 광분해율의 변화를 파악 할 수 있었으며, 약 400g/m2 의 적정 도포량을 도출 하였다. 또한 광촉매 수용액이 도포된 아스팔트 표층의 미끄럼 저항성 측정 결과, 광촉매가 도포되지 않 은 시편과 비교하여 미끄럼 저항성이 1~2% 감소하는 것으로 나타났다. 이는 광촉매가 아스팔트 포장체의 미끄럼 저항성에 미치는 영향이 미비하다는 것을 의미한다.

10 wt.% and 20 wt.%Li-TiO2 composite powders are synthesized by a sol-gel method using titanium isopropoxide and Li2CO3 as precursors. The as-received amorphous 10 wt.%Li-TiO2 composite powders crystallize into the anatase-type crystal structure upon calcination at 450oC, which then changes to the rutile phase at 750oC. The asreceived 20 wt%Li-TiO2 composite powders, on the other hand, crystallize into the anatase-type structure. As the calcination temperature increases, the anatase TiO2 phase gets transformed to the LiTiO2 phase. The peaks for the samples obtained after calcination at 900oC mainly exhibit the LiTiO2 and Li2TiO3 phases. For a comparison of the photocatalytic activity, 10 wt.% and 20 wt.% Li-TiO2 composite powders calcined at 450oC, 600oC, and 750oC are used. The 20 wt.%Li-TiO2 composite powders calcined at 600oC show excellent efficiency for the removal of methylorange

The most general photocatalyst, TiO2 and WO3, are acknowledged to be ineffective in range of visible light. Therefore, many efforts have been directed at improving their activity such as: band-gap narrowing with non-metal element doping and making composites with high specific surface area to effectively separate electrons and holes. In this paper, the method was introduced to prepare a photo-active catalyst to visible irradiation by making a mixture with TiO2 and WO3. In the TiO2-WO3 composite, WO3 absorbs visible light creating excited electrons and holes while some of the excited electrons move to TiO2 and the holes remain in WO3. This charge separation reduces electron-hole recombination resulting in an enhancement of photocatalytic activity. Added Ag plays the role of electron acceptor, retarding the recombination rate of excited electrons and holes. In making a mixture of TiO2-WO3 composite, the mixing route affects the photocatalytic activity. The planetary ball-mill method is more effective than magnetic stirring route, owing to a more effective dispersion of aggregated powders. The volume ratio of TiO2(4) and WO3(6) shows the most effective photocatalytic activity in the range of visible light in the view point of effective separation of electrons and holes.

In order to improve the selective oxidation reaction of gaseous ammonia at a low temperature, various types of metal-impregnated activated alumina were prepared, and also physical and chemical properties of the conversion of ammonia were determined. Both types of metal (Cu, Ag) impregnated activated alumina show high conversion rate of ammonia at high temperature (over 300℃). However, at lower temperature (200 ℃), Ag-impregnated catalyst shows the highest conversion rate (93%). In addition, the effects of lattice oxygen of the developed catalyst was studied. Ce-impregnated catalyst showed higher conversion rate than commercial alumina, but also showed lower conversion rate than Ag-impregnated sample. Moreover, 5 vol.% of Ag activation under hydrogen shows the highest conversion rate result. Finally, through high conversion at low temperature, it was considered that the production of NO and NO2, toxic by-products, were effectively inhibited.

가시광선에 감응하는 광촉매를 제조하기 위하여 TiO2에 질소(N)를 도핑하여 N-TiO2를 제조하였다. 제조한 광촉매의 결정성, 입자 형상 및 도핑 상태는 XRD, FE-SEM 및 XPS를 이용하여 조사하였다. 제조한 광촉매의 활성 평가는 메틸렌블루의 광분해로 조사하였다. 제조한 광촉매는 anatase type이었으며, pH가 높을수록 결정화도가 향상되었다. 제조한 광촉매의 입자 크기는 pH 2.0에서 5.42 nm, pH 4.7에서 5.99 nm, pH 9.0에서 7.58 nm로, 입자 크기는 pH가 증가 할수록 약간씩 증가하였다. 광촉매의 활성은 결정화도에 비례하였다. TiO2에 N를 도핑하여 제조한 N-TiO2가 가시광선 하에서도 활성을 나타냈다. TiO2에 도핑한 N는 격자 속에 존재하는 것이 아니라 표면에 존재하였다.

To compare the photocatalytic performances of titania for purification of waste water according to applied voltages and doping, TiO2 films were prepared in a 1.0 M H2SO4 solution containing NH4F at different anodic voltages. Chemical bonding states of F-N-codoped TiO2 were analyzed using surface X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the co-doped TiO2 films was analyzed by the degradation of aniline blue solution. Nanotubes were formed with thicknesses of 200-300 nm for the films anodized at 30 V, but porous morphology was generated with pores of 1-2 μm for the TiO2 anodized at 180 V. The phenomenon of spark discharge was initiated at about 98 V due to the breakdown of the oxide films in both solutions. XPS analysis revealed the spectra of F1s at 684.3 eV and N1s at 399.8 eV for the TiO2 anodized in the H2SO4-NH4F solution at 180 V, suggesting the incorporation of F and N species during anodization. Dye removal rates for the pure TiO2 anodized at 30 V and 180 V were found to be 14.0% and 38.9%, respectively, in the photocatalytic degradation test of the aniline blue solution for 200 min irradiation; the rates for the F-N-codoped TiO2 anodized at 30 V and 180 V were found to be 21.2% and 65.6%, respectively. From the results of diffuse reflectance absorption spectroscopy (DRS), it was found that the absorption edge of the F-N-codoped TiO2 films shifted toward the visible light region up to 412 nm, indicating that the photocatalytic activity of TiO2 is improved by appropriate doping of F and N by the addition of NH4F.

본 연구는 VOC 배출원 중 도장, 인쇄 공정에서 주요 발생물질인 톨루엔을 저온 분해할 수 있는 귀금속 팔라듐촉매 개발에 목적을 두고 있다. 팔라듐은 톨루엔 제거에서 활성이 우수하지만 비용이 높다. 따라서 실용성의 방안으로 Pd 담지량의 최소화 비율(0.1~1.0wt%)로 제조한 촉매의 활성을 측정하였다. 그 결과 1.0wt% Pd(R) 촉매가 모든 조건에서 가장 높은 활성을 나타내었다. 이는 SEM 촬영과 XRD 분석을 통해 촉매 제조과정에서 Pd의 담지량 및 소성 분위기에 따른 분산 형태와 연관이 있는 것으로 사료된다.

This study shows that catalytic activity of bimetallic RhPt nanoparticle arrays under CO oxidation can be tuned by varying the size and composition of nanoparticles. The tuning of size of RhPt nanoparticles was achieved by changing concentration of rhodium and platinum precursors in one-step polyol synthesis. Two-dimensional RhPt bimetallic nanoparticle arrays in different size and composition were prepared through Langmuir-Blodgett thin film technique. CO oxidation was carried out on these two-dimensional nanoparticle arrays, revealing higher activity on the smaller nanoparticles compared to the bigger nanoparticles. X-ray photoelectron spectroscopy (XPS) results indicate the preferential surface segregation of Rh compared to Pt on the smaller nanoparticles, which is consistent with the thermodynamic analysis. Because the catalytic activity is associated with differences in the rates of dissociative adsorption between Pt and Rh, this paper suppose that the surface segregation of Rh on the smaller bimetallic nanoparticles is responsible for the higher catalytic activity in CO oxidation. This result suggests a control mechanism of catalytic activity via synthetic approaches of colloid nanoparticles, with possible application in rational design of nanocatalysts.

In this study, the used DOCs, which could remove the air pollutants such as CO and HC in the exhaust gas from diesel vehicle, were remanufactured by various conditions. Their catalytic performances and characterization were also investigated. The remanufacturing process of the deactivated DOCs includes high temperature cleaning of incineration, ultrasonic cleaning for washing with acid/base solutions to remove deactivating materials deposited to the surface of the catalysts, and active component reimpregnation for reactivating catalytic activity of them. The catalytic performance tests of the remanufactured DOCs were carried out by the diesel engine dynamo systems and chassi dynamo systems in CVS-75 mode. All prepared catalysts were characterized by the optical microscopes, SEM, EDX, porosimeter and BET to investigate correlations between catalytic reactivity and surface characteristics of them. The remanufactured DOCs at various conditions showed the improved catalytic performances reaching to 90% of fresh DOC, which is attributed to remove the deactivating materials from the surface of the used DOC through the analysis of catalytic performance test and their characterization.

A carbon doped (C-) photocatalyst, which shows good photocatalytic activity to Ultraviolet irradiation and visible irradiation, was successfully prepared by co-grinding of with ethanol or Activated Carbon(C), followed by heat treatment at in air for 60 min. Ethanol and C were used as a representative agent of liquid and solid for carbon doping. Their influence on improving photocatalytic ability and carbon doping degree was studied with degradation of methyl orange and XPS analysis. The product prepared by co-grinding of with Ethanol had Ti-C and C-O chemical bonds and showed higher photocatalytic activity than the product prepared by co-grinding of with C, where just C-O chemical bond existed. As a result, mechanochemical route is useful to prepare a carbon doped photocatalyst activating to visible irradiation, where the solid-liquid operation is more effective than solid-solid operation to obtain a carbon doped .

Esterification reaction between succinic acid and 1,4-butanediol was kinetically investigated in the presence of nontoxic organometallic compound catalyst(ESCAT-100E) at 150-190℃. The reaction rates measured by the amount of distilled water from the reaction vessel. The Esterification reaction was carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd. The linear relationship was shown between apparent reaction rate constant and reciprocal absolute temperature. By the Arrhenius plot the activation energy have been calculated as 376.13 kJ/mol under nontoxic organometallic compound catalyst and also apparent reaction rate constant, k' was found to obey first kinetics with respect to the concentration of catalyst.

A visible-light photoactive photocatalyst was synthesized successfully by means of cogrinding of anatase- in ambient, followed by heat-treatment at in air environment. In general, it is well known that the grinding-operation induces phase transformation of a- to rutile . This study investigates the influence of the amount of gas on the phase transformation rate of a- and enhancement of visible-light photocatalytic activity, and also examines the relation between the photocatalytic activity and the period of grinding time. The phase transformation rate of a- to rutile is retarded with the amount of NH3 injected. And the visible-light photocatalytic activity of samples, was more closely related to the period of grinding time than amount injected, which means that the doping amount of nitrogen into more effective to mechanical energy than amount injected. XRD, XPS, FT-IR, UV-vis, Specific surface area (SSA), NOx decomposition techniques are employed to verify above results more clearly.

Pt-loaded carbon black for the catalyst of a PEM fuel cell was synthesized with different molar ratios of polyvinylpyrrolidone and H2PtCl6 solution to improve the dispersion of Pt nanoparticles on carbon black and decrease the size of Pt nanoparticles. From transmission electron microscopy results, Pt nanoparticles of a size of approximately 2 nm were highly dispersed when the polyvinylpyrrolidone concentration was 10mM. The electrochemical activity of the synthesized Pt/C catalysts was investigated by cyclic voltammetry, showing that the as-synthesized Pt-loaded carbon black catalyst had the best activity at a polyvinylpyrrolidone concentration of 10 mM.

Nano-sized TiO2-60 wt% SrO composite powders were synthesized by a sol-gel method using titanium isopropoxide and Sr(OH)2 · 8H2O as precursors. 3, -5, -7 wt%Ag spot-coated TiO2-60 wt% SrO composite powders were synthesized by a Ag electroless deposition method using TiO2-60 wt% SrO composite powders calcined at 1050˚C, which mainly exhibited the SrTiO3phase. However, a small number of rutile TiO2, Sr2TiO4 and SrO2 phases were also detected. In the Ag spot-coated powders synthesized by electroless deposition, nano-sized particles about 5-25 nm in diameter adhered to the TiO2-60 wt% SrO composite powders. The photocatalytic activity of Ag spot-coated TiO2-SrO and TiO2-SrO composite powders for degradation of phenol showed that all of TiO2-SrO composite powders were highly active under UV light irradiation. 7 wt%Ag spot-coated TiO2-60wt.%SrO composite powders had a relatively higher photocatalytic activity than did TiO2-SrO composite powders under visible light.