We use vdW-corrected density functional theory (DFT) calculations with additional electron distribution correction to study the water binding chemistry of an Au nanoparticle supported on CeO2(111) with a linear step-edge. The initial structural model of Au/CeO2 used for DFT calculations is constructed by stabilizing a Au9 nanoparticle at the linear step-edge on a CeO2(111) slab. The calculated binding energy of a water molecule clearly shows that the interfacial site between Au and CeO2 binds water more strongly than the binding sites at the surface of Au nanoparticle. Subsequent water dissociation calculation result shows that the interface-bound water can be relatively easily dissociated into–OH and –H, providing a hydroxyl group that can be utilized as an oxygen source for CO oxidation. Based on the low dissociation energy of the interface bound water molecule, we suggest that the water at the Au-CeO2 interface can facilitate further oxidation of Au-bound CO. Our results point out that Au-CeO2 interface-bound water is beneficial for low-temperature oxidation reactions such as the water-gas shift reaction or preferential CO oxidation reaction.

CeO2 nanoparticles, employed in a lot of fields due to their excellent oxidation and reduction properties, are synthesized through a solvothermal process, and a high specific surface area is shown by controlling, among various process parameters in the solvothermal process, the type of solvent. The synthesized CeO2 nanoparticles are about 11~13 nm in the crystallite size and their specific surface area is about 65.38~84.65 m2/g, depending on the amount of ethanol contained in the solvent for the solvothermal process; all synthesized CeO2 nanoparticles shows a fluorite structure. The dispersibility and microstructure of the synthesized CeO2 nanoparticles are investigated according to the species of dispersant and the pH value of the solution; an improvement in dispersibility is shown with the addition of dispersants and control of the pH. Various dispersing properties appear according to the dispersant species and pH in the solution with the synthesized CeO2 nanoparticles, indicating that improved dispersing properties in the synthesized CeO2 nanoparticles can be secured by applying dispersant and pH control simultaneously.

세리아 입자의 합성을 위하여 분무열분해 시 유기 첨가제인 EG(ethylene glycol)과 CA(citric acid)를 첨가하여 중공성 및 다공성을 갖는 CeO2 마이크로 크기의 입자를 제조하였으며 첨가량에 따른 특성을 비교하였다. 분무열분해과정, 후소성 및 볼밀링 과정을 적절히 조합하여 만든 6가지 경로에 의해 나노 크기의 세리아 입자를 합성하였다. 6가지 경로 중 EG 및 CA가 0.05M 첨가된 Ce(III)가 전구체 수용액을 이용하여 분무열분해→후소성→볼밀링→후소성의 경로에 의해 얻어진 CeO2 입자에 대해 TEM 분석으로 측정한 입자의 평균 크기 24 nm(편차=3.8 nm)는 Debye-Scherrer식에 의해 계산된 1차 입자의 크기(20 nm)와 가장 유사한 크기를 나타내었다. 제조된 나노입자분말의 형태적 및 구조적 특성을 알아보기 위하여 SEM(Scanning Electron Microscopy), XRD(X-Ray Diffractometer) 및 TEM(Transmission Electron Microscopy)을 통하여 특성을 분석하였다.

Much research into fuel cells operating at a temperature below 800℃. is being performed. There are sig-nificant efforts to replace the yttria-stabilized zirconia electrolyte with a doped ceria electrolyte that has high ionic con-ductivity even at a lower temperature. Even if the doped ceria electrolyte has high ionic conductivity, it also shows highelectronic conductivity in a reducing environment, therefore, when used as a solid electrolyte of a fuel cell, the power-generation efficiency and mechanical properties of the fuel cell may be degraded. In this study, gadolinium-doped ceriananopowder with Al2O3 and Mn2O3 as a reinforcing and electron trapping agents were synthesized by ultrasonic pyrol-ysis process. After firing, their microstructure and mechanical and electrical properties were investigated and comparedwith those of pure gadolinium-doped ceria specimen.

The usual ceramic process of mixing and milling in state of oxides ZrO2 and CeO2 was adopted in this study in a wet process to manufacture Ce-TZP. CeO2-ZrO2 ceramics containing 8~20 mol% CeO2 were made by heat treatment at 1250~1500˚C for 5hr. The maximum dispersion point of every slurry manufactured with a mixture of ZrO2 and CeO2 was neat at pH10. A stable slurry with average particle size of 90 nm can be manufactured when it is dispersed with the use of ammonia water and polycarboxylic acid ammonium. The sintered Ce-TZP ceramics manufactured with the addition of CeO2 in a concentration of less than 10 mol% progressed to the fracture of the specimen due to the existence of a monoclinic phase of more than 30% at room temperature. More than 99% of the tetragonal phase was created for the sintered body with the addition of CeO2 beyond 18 mol%, but the degradation of the mechanical properties on the entire specimen was brought about due to the CeO2 existing in a percentage above 3%. Consequently, the optimal Ce-TZP level combined in the oxide state was identified to be 16 mol% of CeO2 contents.

Composites of gadolinium-doped ceria/magnesia(CGO/MgO) were synthesized and characterized for the electrolytes of intermediate temperature solid oxide fuel cells. XRD and SEM results revealed that composite electrolytes consisted of their own phases after sintering at 1400˚C without noticeable solid solution of Mg into CGO. As the MgO content increased, the total electrical conductivity decreased, which might be attributed to the decrease of grain boundary conductivity, possibly due to the lowering of the continuity of the CGO grains and blocking effects of the insulating MgO phase. The space charge effect may not be a significant factor to affect the electrical conductivity of the CGO/MgO composites.

The nanostructured cerium oxide powders were synthesized by spray thermal decomposition process for the use as the raw materials of resistive oxygen sensor. The synthesis routes consisted of 1) spray drying of water based organic solution made from cerium nitrate hydrate () and 2) heat treatment of spray dried precursor powders at in air atmosphere to remove the volatile components and identically to oxidize the cerium component. The produced powders have shown the loose structure agglomerated with extremely fine cerium oxide particles with about 15 nm and very high specific surface area (). The oxygen sensitivity, n ( and the response time, measured at in the sample sintered at , were about 0.25 and 3 seconds, respectively, which had much higher performances than those known in micron or sized sensors.

Nanostructured ceria powder was synthesized by a thermochemical process and investigated its applicability for an oxygen gas sensor. An amorphous precursor powders prepared by spray drying a cerium-nitrate solution were transformed successfully into nanostructured ceria by heat-treatment in air atmosphere. The powders were a loose agglomerated structure with extremely fine particles about 15 nm in size, resulting in a very high specific surface area . The oxygen sensitivity and the response time measured at sintered sample at was about -0.25 and very short, i.e., seconds, respectively.

세리아 안정화 지르코니아 성형체내에 이트리아를 침적법으로 도핑시켜 미세구조를 관철하였다. 도핑된 이트리아의 양과 열처리 조건을 제어하여 입계가 변형된 불규칙 입자형상의 미세구조를 형성시켰으며, 이때 입자형상의 불규칙 정도는 첨가된 이트리아의 양에 비례하였다. 0.2M 농도의 Y(NO3)3.6H2O의 수용액에 재침적하여 1650˚C에서 2시간 열처리한 시편의 미세구조는 표면부와 내부 모두에서 불규칙 입자형상을 나타내었으며, 입자의 불규칙도도 가장 큰 것으로 나타났다. 가압소결을 행한 결과 입계가 불규칙하게 변화된 미세구조가 창출됨과 동시에 평균입자 크기가 0.3μm 가량인 미세한 소결체를 제조할 수 있었으며, 상분석 결과 대부분 정방정상을 유지하고 있었다. 불규칙 입자형상의 미세구조를 가진 시편의 파괴인성값은, 정상적인 입자형상을 갖는 시편에서의 압흔 균열 크기로부터 비교 유추한 결과 17.6MPa.m(sup)1/2 이상인 것으로 나타났다.

Metal oxide promoted ceria-zirconia (Ce/Zr = 6/4) catalysts was applied to deoxygenation (DO) of oleic acid in batch mode at 300℃ under 1 bar of 20% H2/N2 condition. Metal oxide promoted ceria-zirconia catalysts were prepared by a co-precipitation method. As a result, Ni-Ce0.6Zr0.4O2 catalyst exhibited much higher oleic acid conversion, selectivity to C9 ~ C17 compounds (diesel fuel range), and oxygen removal efficiency than the others. This is due to the presence of free NiO species, synergy effect of nickel and Ce0.6Zr0.4O2, highest BET surface area, and the strong metal to support interaction (SMSI).