TiO₂-CeO_x-Pt Hollow Nanosphere Catalyst for Low-Temperature CO Oxidation

TiO2-CeO2-Pt hollow nanospheres (1 wt-% Pt) are realized using a liquid-phase strategy using NaCl as a template. The NaCl template is first coated with TiO2 and thereafter with CeO2 via the hydrolyzation of TiCl(OiPr)(3) and Ce(OiPr)(4) as suitable alkoxides. Finally, the NaCl template is removed by washing with water. The resulting @TiO2-CeO2 hollow nanospheres (: inner cavity) exhibit an outer diameter of 140-180 nm, a wall thickness of 30-40 nm, an inner cavity of 80-100 nm, a specific surface area of 210 m(2)/g, a pore volume and area of 0.08 cm(3)/g and 191 m(2)/g, mainly with micropores >= 5 angstrom and <= 14 angstrom. The hollow nanosphere support is impregnated with Pt nanoparticles, using two different methods - a wet-chemical deposition (Pt(ac)(2), acetone, 25(degrees)C) and a supercritical fluid reactive deposition (SFRD) process ([Pt(COD)Me-2], supercritical CO2, 80 C-degrees, 15.6 MPa) resulting in an uniform size distribution with Pt nanoparticles 2.5 +/- 0.1 nm (TiO2-CeO2-PtWCD) and 2.3 +/- 0.1 nm (TiO2-CeO2-PtSFRD) in size. The catalytic properties of the TiO2-CeO2-Pt hollow nanospheres are evaluated for CO oxidation between 50 and 500 C-degrees. A promising catalytic activity and stable light-out/light-off temperatures are observed especially for the TiO2-CeO2-PtSFRD sample, indicating the suitability of hollow nanospheres as high-porosity catalyst material.