Preparation of Titanium-Containing Mesoporous SBA-15 and Evaluation of its Photocatalytic Properties
Titanium-containing mesoporous SBA-15 (Ti-SBA-15) with various titanium contents were synthesized by one-step method. The synthesized Ti-SBA-15 materials were characterized by means of N2 adsorption, inductively coupled plasma (ICP) -atomic emission spectroscopy (AES), X-ray diffraction (XRD), UV-Vis diffusion reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), 29Si magic-angle spinning nuclear magnetic resonance (29Si MAS NMR), and transmission electron microscope (TEM) in combination with energy dispersive X-ray analysis (EDX) techniques. The materials were also examined in terms of photocatalytic properties of photodecomposition of orange II in liquid phase. It was observed that limited content of titanium can be incorporated into the framework of SBA-15 without provoking structure changes and titanium in silicate framework possessed photocatalytic activity. Anatase phase was observed on the external surface of the solid particles at high titanium loadings. In addition, the particle size of TiO2 increased with increasing the titanium loading. The anatase TiO2 showed better photocatalytic activity comparing with titanium in framework of SBA-15, which indicated that the external surface was more essential in photocatalytic reaction due to easy accessibility to light and less mass transfer resistance to reactant. The highest activity was observed on the sample with a Ti/Si ratio of about 0.09. The excessive titanium in synthesis gel resulted in the agglomeration of TiO2 nanoparticles on external surface, which induced the decrease of photocatalytic activity.