Effects of templates on the structure, stability and photocatalytic activity of mesostructured TiO₂

Using long-chain alkylphosphate and alkylamine surfactants as templates, two kinds of purely mesoporous TiO₂ molecular sieves (Ti-TMS) were prepared by hydrolysis of titanium isopropoxide under completely different conditions. The templates can be successfully removed by refluxing the samples in an EtOH/H₂O/HN0₃ solution. Properties of the samples were characterized by means of SEM, FT-IR, DR-UV, TEM, XRD and TG-DTA techniques. XRD patterns and TEM images confirm that the uniformity and stability of Ti-TMS1 synthesized with dodecylphosphate, hexadecylphosphate, or octadecylphosphate as templates is superior to that of Ti-TMS2 prepared with dodecylamine. Furthermore, after the removal of the templates, the stability and the structure of the mesoporous Ti-TMS1 are better than that of Ti-TMS2. Effects of other factors on the structure and stability of Ti-TMS are discussed. The photocatalytic activities of Ti-TMS were also investigated by using polychlorophenol (TCP) and reactive red dye (X-3B) solutions as model pollutants. It was found that the amount of the templates greatly affects the photoactivity of these kind of mesoporous materials.