One-pot hydrothermal synthesis and high temperature thermal stability of CexZr1−xO2 nanocrystals

Abstract

We report a facile one-pot synthesis of Ce x Zr 12x O 2 (0 ¡ x ¡ 1) solid solution nanocrystals using hydrothermal reactions. A direct formation of oxide solid solutions in aqueous solution under pressure at low temperatures was clearly revealed by X-ray diffraction, Raman spectroscopy, and chemical composition analysis of individual nanocrystals using energy dispersive X-ray spectroscopy in scanning transmission electron microscopy mode. Chemisorption behavior of the synthesized nanocrystals was characterized using a hydrogen temperature programmed reduction, which showed a superior lowtemperature activity in Ce x Zr 12x O 2 (0 , x , 1) compared to pure CeO 2 . Furthermore, we investigated the thermal stability of the prepared Ce 0.5 Zr 0.5 O 2 at high temperatures (900 uC-1400 uC) under oxidation and reduction atmosphere. The effect of varying conditions of heat-treatment has given information on the phase transformation in Ce 0.5 Zr 0.5 O 2 from pseudocubic to tetragonal structure under oxidation atmosphere, and to pyrochlore structure under reduction atmosphere.High surface area Ce x Zr 12x O 2 (0 ¡ x ¡ 1) samples were synthesized using a hydrothermal method. Typically, 0.1 M Ce(NO 3 ) 3 ?6H 2 O (Alfa Aesa, 99.99%) and 0.1 M ZrO(NO 3 ) 2 ?xH 2 O

Effect of preparation procedure on the formation of nanostructured ceria–zirconia mixed oxide catalysts for ethyl acetate oxidation: Homogeneous precipitation with urea vs template-assisted hydrothermal synthesis

“…Suguira et al [28] attributed the enhanced OSC of CeO 2 -ZrO 2 mixed oxides to the formation of k-CeZrO 4 phase, where Ce 4+ and Zr 4+ ions are regularly arranged. The incorporation of considerably smaller Zr 4+ ion in ceria lattice, which also prefers a 7-fold coordination, in contrast to the 8-fold coordination of the fluorite cation, leads to formation of oxygen vacancies associated with structural relaxation through reduction of Ce 4+ to the larger Ce 3+ ions [13,15,[29][30][31]. For most of the catalytic processes the importance of oxygen vacancies (tetrahedral holes normally occupied with oxide ions) and oxygen ions (at octahedral sites) mobility from the surface to the bulk and vice versa was assumed.…”

“…Transition of cubic to tetragonal fluorite phase occurs with increasing the zirconium content [35] and the degree of distortion of the cubic fluorite structure strongly depends on the synthesis method, particle size and thermal treatment [36]. Several methods, such as precipitation, microemulsion, microwave, hydrothermal synthesis including also supercritical water, flame spray, sol-gel, high temperature solid state reaction, high energy ball milling, and combustion synthesis have been applied to synthesize mixed oxide CeO 2 -ZrO 2 materials [ [8,16,30,[37][38][39][40] and Refs. therein].…”

Effect of Reduction Treatment on CO Oxidation with CeO2 Nanorod‐Supported CuOx Catalysts

“…Compared with the pure CeO 2 sample (Figure 6a), an evidentp eak shifting for the F 2g band was observed for both the CuO x -CeO 2 and CuO-CeO 2 samples, which is typicallye xplained by the formation of solid solutions in cerium-basedo xides or oxygen vacancy creation. [30,31] In Au-CeO 2 ,i tw as reported that this firstorder CeO 2 F 2g peak shift correlates with the reactivity for CO oxidation. [30] The most possible location of these oxygen-containingc opper speciess houldb ea tt he CuO x -CeO 2 interface for the reduced 10 wt %C uO x -CeO 2 nanorods sample, probably owing to the abundance of surface oxygen and defects located on the CeO 2 nanorods.…”

Surface Crystal Plane Determination and Strong Metal-Support Interactions in CeO 2 Nanorod-Supported CuOx Catalysts

“…The redox functionality of both catalyst and support are vital components for gas adsorption, oxygen migration at the metal-support interface and in the catalytic reactions mentioned above. To further understand CuOx-CeO2 interfacial effect, we report a comparative study on CeO2 nanorod-supported CuO and Cu catalysts for CO oxidation.CeO2 nanorods were prepared using a hydrothermal method [2][3][4]. Typically 0.1M Ce(NO3)36H2O and 6M NaOH mixtures were heated to 90~130 °C and held for 48 hrs in a sealed 200 mL Teflon-lined autoclave (~50 % fill).…”

“…CeO2 nanorods were prepared using a hydrothermal method [2][3][4]. Typically 0.1M Ce(NO3)36H2O and 6M NaOH mixtures were heated to 90~130 °C and held for 48 hrs in a sealed 200 mL Teflon-lined autoclave (~50 % fill).…”