Chlorinated Nanocrystalline TiO₂ Powders via One-Step Ar/O₂ Radio Frequency Thermal Plasma Oxidizing Mists of TiCl₃ Solution:  Phase Structure and Photocatalytic Performance

Abstract

Chlorinated TiO 2 powders of high crystallinity and good dispersion have been synthesized via one-step Ar/O 2 radio frequency thermal plasma oxidation of atomized aqueous solutions of TiCl 3 . The resultant powders are anatase/rutile mixtures (∼66−72 wt % of anatase), with particle sizes ranging from ∼5 nm to 5 μm. Detailed studies via X-ray diffraction and Raman spectroscopy on the nanometric (<100 nm) and the coarser particles revealed weak dependence of the phase constituent and chemical stoichiometry on the size distribution or the O 2 input (5−90 L/min). Simultaneous incorporation of chlorine into the TiO 2 lattice was confirmed by thermal desorption and UV−vis spectroscopies. The chlorinated TiO 2 powders exhibit narrowed indirect band gaps of ∼2.65 eV and enhanced UV absorption and, thus, show substantially higher photocatalytic activities than Degussa P25 in the degradation of methyl orange solutions under both visible-light and UV illumination.