Study of preparation of mesoporous TiO 2-B nanofibers from mesoporous anatase TiO 2 and interaction between CH 3I and TiO 2-B

Abstract

Anisotropically grown TiO 2-B with a textural porosity and a high specific surface area has been prepared, characterized, and used to catalyze the thermal and photochemical decomposition of CH 3I. The fibrous TiO 2-B is fabricated by the reaction of mesoporous anatase TiO 2 at 90 °C, followed by addition of 0.1 M HCl solution into the reaction precipitate to reach pH 1. Addition of 0.1 M HCl solution for other pH values of 6, 9, and 12 is also carried out to investigate the pH effect on the elemental composition and morphology of the reaction products, which provides some mechanistic clues for the formation of the TiO 2-B nanofibers. XRD patterns, Raman and reflectance UV–Vis spectra, and SEM and TEM images are used to characterize the material. The TiO 2-B fibers, ∼10 nm in width and several hundred nanometers in length, grow along the [ 1 2 0 1 ] direction of the monoclinic structure, as suggested by the observation of the (2 0 1) fringes which are normal to the axial direction and have a neighboring distance of 0.37 nm in the TEM images. The TiO 2-B nanofibers aggregate into cotton-like particles with a size similar to that of the original anatase particles, forming mesopores with an average diameter of 4.5 nm and a high BET area as much as ∼600 m 2/g which is much larger than those reported previously for titanates and TiO 2-B with morphologies of tube or fiber. The TiO 2-B material has an experimentally-determined bandgap energy of 3.3 eV. Its thermal and photochemical reactivities toward CH 3I decomposition are demonstrated by infrared spectroscopic investigation in a gas–solid system.