Characterization of H2Ti4O9 with high specific surface area prepared by a delamination/reassembling process

H2Ti4O9 nanocrystals with high specific surface areas were prepared by delamination and reassembly process through a way of ball milling combined with ion exchange reaction. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, chemical analysis, thermal analysis, N2 adsorption-desorption isotherm, and absorption spectrum. The crystallites of Ti4O9^2- in the form of titania nanosheets has lateral size less than 50 nm. The specific surface area of H2Ti4O9 nanocrystals depends on pH value of reassembling solution and ball milling time. H2Ti4O9 nanocrystals prepared by ball-milling of K2Ti4O9 for 2 h and suspending in 1 M HCl followed by precipitation at pH 8 had the specific surface area of 328.4 m^2 g^-1 which was about 16 times larger than the fibrous H2Ti4O9 prepared by treating original K2Ti4O9 without ball-milling in 1 M HCl.