Pore-Wall Chemistry and Photocatalytic Activity of Mesoporous Titania Molecular Sieve Films

Abstract

Transparent zeolite-like mesoporous TiO2 nanocrystalline thin films with high photocatalytic activity were synthesized via a surfactant-templated method. The films were characterized by TGA−DTA, XRD, nitrogen adsorption, SEM, TEM, UV/vis, and FT-IR spectroscopy. The photocatalytic activity of the films was evaluated by photodecomposition of acetone in air at ambient conditions. It was found that thermal treatment resulted in surfactant elimination, framework solidification, as well as pore-wall crystallization of the mesoporous TiO2. The resulting zeolite-like mesoporous TiO2 nanocrystalline films had large specific surface areas (∼100 m2/g), high porosity (∼40%), extended band gap energy (∼3.3 eV), tri-directional communicating pore systems, and enhanced photocatalytic activity. The optimum calcination temperature was found to be 500 °C, at which the film possessed a cubic ordered mesoporous structure and exhibited the highest photocatalytic activity. A comparison with a conventional TiO2 film (prepared from a sol−gel method) showed that the ordered mesoporous TiO2 nanocrystalline film (calcined at 500 °C) had over 2 times the specific photocatalytic activity as the conventional film. The high photocatalytic activity of zeolite-like mesoporous TiO2 thin films can be explained by the large specific surface area and the three-dimensionally connected mesoporous architecture.