Novel hydrothermal preparation of pure brookite-type titanium(IV) oxide nanocrystal under strong acidic conditions

Titanium(IV) oxide (TiO2) nanocrystal with brookite phase was prepared by hydrothermal treatment of titanate nanotubes under strong acidic conditions (perchloric acid, hydrochloric acid and nitric acid). The relative fractions of crystal phases (anatase, rutile and brookite) were strongly dependent on hydrothermal treatment duration and the kind of strong acid used. A high brookite-type TiO2 content was obtained by hydrothermal treatment under perchloric acidic solution. Single-phase brookite TiO2 particles were extracted from as-prepared TiO2 by a centrifugal separation procedure, and they exhibited higher photocatalytic activity for acetaldehyde decomposition than TiO2 prepared without the separation procedure.