Synthesis and characterization of ceria-coated silica nanospheres: their application in heterogeneous catalysis of organic pollutants

Abstract

Τhe present work investigates the parameters for the successful coating of silicon oxide nanoparticles surface with a homogeneous cerium oxide shell in an effort to develop core-shell nanostructures. For this, spherical silica nanoparticles (~ 300 nm) were developed by a biomimetic approach and their coating with ceria was performed through a precipitation method. Several processing conditions, such as the precipitation pH, the cerium precursor concentration and the treatment of silica cores (i.e., their use either as-received after their biomimetic formation, or after their calcination followed by surface modification), were examined and optimized. The as-obtained powder material was characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, N 2 adsorption and UV-Vis reflectance spectroscopy. The analysis revealed the formation of spherical core-shell nanostructures bearing a uniform shell layer of crystalline cerium oxide around each silica core which after calcination at 600 °C was comprised of cubic CeO 2 nanocrystals with sizes ranging between 2 and 6 nm. The material with the optimum core-shell structure and pure cerium dioxide were studied in terms of their catalytic reduction activity over 4-nitrophenol to 4-aminophenol.

Catalytic Neutralization of Water Pollutants Mediated by Dendritic Polymers

“…Apart from the photooxidation of NO the nanospheres carried out 4-nitrophenol reduction [156]. Replacing the external TiO2 overlay by a shell of CeO2 cubic nanocrystals with sizes ranging between 2 and 6 nm produced similar result [157]. A further occasion where templating by a dendritic polymer plays a substantial role to catalytic properties is the synthesis of CuFe2O4 nanoscale-confined precursor via coprecipitation of Fe +3 and Mn 3+ nitrates with a hyperbranched polyamide.…”

Catalytic Neutralization of Water Pollutants Mediated by Dendritic Polymers

“…Apart from the photooxidation of NO the nanospheres carried out 4-nitrophenol reduction [168]. Replacing the external TiO 2 overlay by a shell of CeO 2 cubic nanocrystals with sizes ranging between 2 and 6 nm produced a similar result [169]. A further example where templating by a dendritic polymer plays a substantial role in catalytic properties is the synthesis of CuFe 2 O 4 nanoscale-confined precursor via coprecipitation of Fe +3 and Mn 3+ nitrates with a hyperbranched polyamide.…”

Dendritic Polymers as Promising Additives for the Manufacturing of Hybrid Organoceramic Nanocomposites with Ameliorated Properties Suitable for an Extensive Diversity of Applications

“…Moreover, these metal organoceramic nanocomposites are noteworthy candidates for catalysis reactions [ 171 , 172 , 173 ] ( Table 2 ). They are particularly useful when gas phases are involved in reactions such as low molecular hydrocarbon hydrogenation and epoxidation.…”