Highly Monodisperse Zirconia-Coated Silica Spheres and Zirconia/Silica Hollow Spheres with Remarkable Textural Properties

High surface area zirconia is an interesting material for many applications. In this contribution, we describe the synthesis of SiO2@ZrO2 and @ZrO2 (Liz-Marzan, L. M.; Correa-Duarte, M. A.; Pastoriza-Santos, I.; Mulvaney, P.; Ung, T.; Giersig, M.; Kotov, N. A. In Handbook of Surfaces and Interfaces of Materials; Nalwa, H. S., Ed.; Academic Press:  San Diego, 2001; Vol. 3) of high surface area zirconia. The synthesis consists of (1) preparing monodisperse silica spheres; (2) coating the spheres with hydrated zirconia; (3) aging the composites; (4) calcining the composite at 1173 K; and (5) leaching the silica with NaOH solution. This process results in the formation of hollow zirconia spheres with a surface area of around 300 m2 g-1. The zirconia is present in the tetragonal polymorph. The final material still contains silicon and sodium. However, it is present in a phase of which the nature could not be fully ascertained.