Isocyanate-modified TiO2 visible-light-activated photocatalyst

Visible-activated TiO2 photocatalysts were prepared by surface modification to TiO2 with different isocyanates, including conjugated structured Tolylene-2,4-diisocyanate (TDI) and unconjugated structured m-Xylylene diisocyanate (m-XDI). These two isocyanates could be anchored on the TiO2 surface via pi-conjugated chemical bonds of -NHCOOTi, which were formed through the reaction between -NCO groups of isocyanates and the hydroxyl groups of TiO2, and confirmed by FT-IR, XPS and UV-Vis spectra. As a result, donor-acceptor type pi-conjugated systems came into being between isocyanate and TiO2. Because the TDI molecules were conjugated themselves, perfect pi-conjugated systems were produced in TDI-modified TiO2 samples. Nevertheless, m-XDI-modified TiO2 Samples showed poor pi-conjugation due to the lack of conjugation of m-XDI. Therefore, TDI-modified TiO2 materials exhibited stronger visible absorption than m-XDI-modified TiO2 in the range from 400 to 600 nm. Methylene blue, as a photodegradation target, was used to evaluate the photocatalytic performance, TDI-modified TiO2 materials exhibited higher photocatalytic activity than m-XDI-modified TiO2 and unmodified TiO2, Moreover, the higher dosage of isocyanate would lead to the better photocatalytic activity. (C) 2008 Elsevier B.V. All rights reserved.