In this investigation, we synthesized a novel quaternary nanocomposite, denoted as RGO-Ba(OH)2/CeO2/TiO2, through a straightforward and cost-effective solid-state synthesis approach. The as-prepared composites underwent a series of comprehensive characterizations, including XRD, FTIR, TGA-DTA, XPS, SEM, EDAX, and TEM analyses, affirming the successful synthesis of a quaternary nanocomposite with well-interconnected nanoparticles, nanorods, and sheet-like structures. Further, our electrochemical performance evaluations demonstrated that the electrochemical capacitance of the RGO-Ba(OH)2/CeO2/ TiO2 nanocomposite achieved an impressive value of 445 F g− 1 at a current density of 1.0 A g− 1, particularly when the mass ratio of CeO2 and TiO2 was maintained at 90:10. Furthermore, the specific capacitance retained a remarkable 65% even after 2000 cycles at a current density of 6 A g− 1 in a 3 mol KOH electrolyte. Comparatively, this outstanding electrochemical performance of the RGO-Ba(OH)2/CeO2/TiO2 (90:10) nanocomposite can be attributed to several factors. These include the favorable electrical conductivity and large specific surface area provided by graphene, TiO2, and Ba(OH)2, the enhanced energy density and extended cycle life resulting from the presence of CeO2, and the synergistic contributions among all four components. Therefore, the RGO-Ba(OH)2/CeO2/TiO2 nanocomposite emerges as a highly promising electrode material for supercapacitors.

Pentachlorophenol (PCP), as one of the common pesticide and preservatives, is easily accumulated in living organisms. Considering the high toxicity of PCP, the development of an effective and sensitive inspection method to determine the residual trace amounts of PCP continues to be a significant challenge. Herein, a convenient and sensitive electrochemical sensor is constructed by modifying glassy carbon electrode with cerium dioxide ( CeO2) nanoparticles anchored graphene ( CeO2-GR) to detect trace PCP. Benefiting from the two-dimensional lamellar structural advantages, the extraordinary electron-transfer properties, as well as the intensive coupling effect between CeO2 nanoparticles and graphene, the afforded CeO2- GR electrode nanomaterial possesses excellent electrocatalytic activity for the oxidation of PCP. Under the optimum synthetic conditions, the PCP oxidation peak currents of developed CeO2– GR sample exhibit a wide linear range of 5–150 μM. Moreover, the corresponding detection limit of PCP on the CeO2– GR electrode is as low as 0.5 μM. Apart from providing a promising electrochemical sensor, this work, most importantly, promotes an efficient route for the construction of highly active sensing electrode materials.

To evaluate the chemical properties of the epsilon particle present as a precipitate in the high-level radioactive waste, we performed the experiments for the samples fabricated by CeO2 containing 1, 3, and 5wt%Mo, where CeO2 is used as the simulated high-level radioactive waste to replace the real one, using X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEMEDS). Moreover, to evaluate the chemical behavior of Mo epsilon particle in CeO2 at high temperature, the manufactured CeO2-1wt%Mo, CeO2-3wt%Mo, and CeO2-5wt%Mo samples were heated at 100, 300, 500, 700 and 900ºC for 7 h in a tube furnace under Ar atmosphere. In this study, the results of comprehensive analysis including the crystal structure, chemical state, and elemental distribution will be presented to verify the chemical properties for CeO2 samples containing Mo epsilon particle, depending on the Mo content and heating temperature.

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.

Cerium oxide (ceria, CeO2) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O2 2CO2). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H2O → H2 + CO2). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO2(111) surfaces. A stoichiometric CeO2(111) and a defected CeO2(111) surface showed different water adsorption chemistry, suggesting that defected CeO2 surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.

고분자 전해질 연료전지의 연료에 포함된 일산화탄소의 선택적 산화를 위하여, 귀금속 촉매를 대체하기 위한 CuO-CeO2 복합 산화물 촉매를 졸-겔법과 공침법으로 제조하였다. 졸-겔법으로 촉매 제조 시 Cu/Ce의 비와 가수분해 비를 변화시켰다. 제조한 촉매의 활성은 귀금속 촉매(Pt/γ-Al2O3)와 비교하였다. Cu/Ce의 비를 변화시키면서 제조한 촉매 중 Cu/Ce의 비가 4:16인 촉매가 가장 높은 CO 전환율(90%)과 선택도(60%)를 나타내었다. 촉매의 제조에서 가수분해 비가 증가할수록 촉매 표면적이 증가하였고, 아울러 촉매 활성 또한 증가하였다. 공침법으로 제조한 촉매와 1wt% Pt/γ-Al2O3 촉매의 가장 높은 CO 전환율은 각각 82% 및 81%인 반면, 졸-겔법으로 제조한 촉매의 경우는 90%가 얻어졌다. 이는 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매나 귀금속 촉매보다 더 높은 촉매활성을 보임을 의미한다. CO-TPD 실험을 통하여, 낮은 온도(140℃)에서 CO를 탈착하는 촉매가 본 반응에서 더 높은 촉매활성을 보임을 알 수 있었다.

본 연구에서는 CeO2 표면에 Ti(SO4)2의 가수 분해를 이용하여 TiO2를 성장시켜 코어-쉘 구조를 가지는 세라믹 나노입자를 합성 하였다. CeO2/TiO2 코어-쉘 합성에서는 CeO2:TiO2의 몰비, 반응 시간, 반응 온도, CeO2 슬러리 농도, Ti(SO4)2의 pH 조절을 통하여 코어-쉘 구조를 가지는 최적의 합성 조건을 찾았다. CeO2:TiO2의 최적의 몰비는 1:0.2~1.1, 최적의 반응 시간은 24 시간, 최적의 CeO2 슬러리 농도는 1%, 최적의 반응 온도는 50℃임을 알 수 있었다. NH4OH 수용액을 이용하여 Ti(SO4)2 의 pH를 1로 맞추어 CeO2 슬러리에 적하하면 10%의 농도를 가지는 CeO2 슬러리에서도 CeO2/TiO2 코어-쉘 나노 입자를 합성할 수 있었다. 80℃이상의 높은 온도에서 반응을 시키면 CeO2/TiO2 코어-쉘 구조가 아닌 독립된 TiO2 나노 입자를 형성함을 알 수 있었다. 최적의 반응 온도는 50℃로서 가장 좋은 구조의 CeO2/TiO2 코어-쉘이 합성되었다.

Cubic mesocrystal CeO2 was synthesized via a hydrothermal method with glutamic acid (C5H9NO4) as a template. The XRD pattern of a calcined sample shows the face-centered cubic fluorite structure of ceria. Transmission electron microscopy (TEM) and the selected-area electron diffraction (SAED) pattern revealed that the submicron cubic mesocrystals were composed of many small crystals attached to each other with the same orientation. The UV-visible adsorption spectrum exhibited the red-shift phenomenon of mesocrystal CeO2 compared to commercial CeO2 particles; thus, the prepared materials show tremendous potential to degrade organic dyes under visible light illumination . With a concentration of a rhodamine B solution of 20 mg/L and a catalyst amount of 0.1 g/L, the reaction showed higher photocatalytic performance following irradiation with a xenon lamp (≥ 380 nm). The decoloring rate can exceed 100% after 300 min.

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. SiO2-CuO-CeO2 multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. SiO2-CuO-CeO2 composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was 371.4m2/g. This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.

The preparation of Sm2O3 doped CeO2 in Igepal CO-520/cyclohexane reverse micelle solutions has been studied. In the present work, we synthesized nanosized Sm2O3 doped CeO2 powders by reverse micelle process using aqueous ammonia as the precipitant; hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase, and poly (xoyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by Thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), and Transmission electron microscopy (TEM). The crystallite size was found to increase with increase in water to surfactant (R) molar ratio. Average particle size and distribution of the synthesized Sm2O3 doped CeO2 were below 10 nm and narrow, respectively. TG-DTA analysis shows that phase of Sm2O3 doped CeO2 nanoparticles changed from monoclinic to tetragonal at approximately 560˚C. The phase of the synthesized Sm2O3 doped CeO2 with heating to 600˚C for 30 min was tetragonal CeO2. This study revealed that the particle formation process in reverse micelles is based on a two step model. The rapid first step is the complete reduction of the metal to the zero valence state. The second step is growth, via reagent exchanges between micelles through the inter-micellar exchange.

Nanosized Pt, Pt-Ru and Pt-CeO2 electrocatalysts supported on acid-treated carbon nanotube (CNT) were synthesized by microwave-assisted heating of polyol process using H2Cl6Pt·6H2O, RuCl3, CeCl3 precursors, respectively, and were characterized by XRD and TEM. And then the electrochemical activity of methanol oxidation for catalyst/CNT nanocomposite electrodes was investigated. The microwave assisted polyol process produced the nano-sized crystalline catalysts particles on CNT. The size of Pt supported on CNT was 7~12 nm but it decreased to 3~5 nm in which 10wt% sodium acetate was added as a stabilizer during the polyol process. This fine Pt catalyst particles resulted in a higher current density for Pt/CNT electrode. It was also found that 10 nm size of PtRu alloys were formed by polyol process and the onset potential decreased with Ru addition. Cyclic voltammetry analysis revealed that the Pt75Ru25/CNT electrode had the highest electrochemical activity owing to a higher ratio of the forward to reverse anodic peak current. And the chronoamperemetry test showed that Pt75Ru25 catalyst had a good catalyst stability. The activity of Pt was also found to be improved with the addition of CeO2.