Template-free synthesis of sphere, rod and prism morphologies of CeO ₂ oxidation catalysts

Ceria materials with sphere, rod, and prism morphologies were synthesized via the hydrolysis of solutions containing Ce(NO₃)₃ and urea under hydrothermal conditions. By carefully adjusting the synthesis conditions (salt concentration, temperature and synthesis time), spheres with a diameter of about 200 nm, rods of about 6 nm in width and 60 nm in length and prisms with an edge length of about 600 nm were synthesized. XRD and TEM indicate that the grain size of these samples is in the range of 7-10 nm after calcination at 450 °C. These ceria materials exhibit a higher catalytic activity in the oxidation of CO than conventionally prepared CeO₂.