Properties and Reactivity of Nanostructured CeO₂ Powders:  Comparison among Two Synthesis Procedures

Abstract

Three nanostructured cerium(IV) oxide powders were synthesized by two different synthetic routes: two samples were obtained by precipitation from a basic solution of cerium nitrate and treated at 523 and 923 K, respectively, and the third one was prepared by a microwave-assisted heating hydrolysis method and treated at 523 K. The obtained samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron (XPS), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic techniques, thermal analysis, and Brunauer-Emmett-Teller (BET) surface area. A broad particle size distribution is observed for CeO 2 obtained by precipitation (8.0-15.0 nm). Smaller particles (sizes around 3.3-4.0 nm) with a narrow particle size distribution characterize the ceria obtained by microwave irradiation. XPS and DRIFT outcomes show that (i) the CeO 2 prepared by microwave-assisted heating hydrolysis method is more reduced than that obtained by precipitation and treated at the same temperature; (ii) the CeO 2 obtained by precipitation and treated at 923 K is more reduced than that prepared by microwave irradiation. A higher amount of basic and acidic sites were noticed on the CeO 2 obtained by microwave irradiation. Methanol interacts mainly dissociatively with the CeO 2 surface regardless of the preparation procedure and reduction degree of surface; however, on the CeO 2 prepared by microwave irradiation the interaction is quantitative: all the methanol introduced in the reaction chamber reacts with the surface. The CeO 2 obtained by precipitation and treated at 523 K does not oxidize methanol, even at higher temperature, while traces of oxidation products are noted on the sample treated at 923 K. Methanol oxidation is favored on the CeO 2 prepared by microwave irradiation: the main oxidation products are formate species and inorganic carboxylate. Moreover, the oxidation capability increases with increasing temperature.

Ru–Pd Bimetallic Catalysts Supported on CeO2-MnOX Oxides as Efficient Systems for H2 Purification through CO Preferential Oxidation

“…On the basis of the literature, the signal at 3470 cm −1 can be assigned to the O-H stretching of H-bonded water [45]. The bands at 1585 and 1346 cm −1 are due to the O-C-O stretching vibrations whereas the features at 1057 and 852 cm −1 can be assigned to the C-O stretching, thus pointing to the presence of carbonate species on the oxide sample.…”

Investigation of the Synthesis and Properties of Ternary V–Cu–Ce Oxides of Composition VxCuxCe1 – 2xO2

“…All the mixed oxides investigated exhibited high surface areas. The BET areas of the samples decreased with increased vanadium and copper content, which may be due to blockage of the pore mouths (Radhika and Sugunan 2006;Gu et al 2006;Reddy et al 2003). The specific surface area of sample A1 (285 m 2 /g) was much larger than those of samples A8 (122 m 2 /g) and A9 (133 m 2 /g).…”

“…(Tschöpe et al 1999;Chen and Chang 2005;Chang and Chen 2005). The efficiency of ceria is based on its capacity to store or release oxygen because of lattice defects in CeO 2 -x (Matta et al 2002;Radhika and Sugunan 2006;Cousin et al 2001). Several metal-doped cerium oxides exhibit high oxygen ionic conductivity which makes them interesting materials for many applications (Zhao and Gorte 2003).…”

“…(Matta et al 2002;Shyue and De Guire 2005;Gu et al 2006). The presence of vanadia on ceria brings about interesting effects in catalyst performances for oxidative dehydrogenation (ODH) reactions, for the oxidative conversion of propane to propylene and ethylene, the preferential oxidation of CO to CO 2 , and other processes (Reddy et al 2003). In addition, Ce-V mixed oxides have been shown to be a good combination for transparency and ion-storage capacity.…”

Mg Doping Induced Effects on Structural, Optical, and Electrical Properties as Well as Cytotoxicity of CeO2 Nanostructures

“…CeO 2 nanostructures have received much attention due to their changed and enhanced characteristics as compared to their bulk counterparts. [12][13][14][15] In recent years, several synthetic methods have been used to explore CeO 2 nanostructures fabrication such as the surfactant-assisted approach, [16] micro-emulsion, [17] spray pyrolysis, pyrolysis (low temperature or spray), [18] thermodecomposition, [19] reflex method, [20] hexamethylenetetramine, [21] microwave-assisted heating, [22] chemical co-precipitation, [23] organometallic decomposition, [20] solution and solid combustion methods, [24] sol-gel methods, [25] flow method, [26] hydrothermal synthesis, [27] microwave heating, [28] and gas and sonochemical methods. [29] The chemical co-precipitation technique has several advantages, such as low cost, high reproducibility, versatility, and control over particle sizes and shapes.…”