Synthesis of Mesoporous TiO₂ with a Template Free One Step Reaction of Acid-Catalyzed TiC

Abstract

Mesoporoustitania (TiO₂) having high specific surface areas of 163 to 306 m²/g was prepared by a template-free one step reaction between TiC precursor and aqueous nitric acid (HNO₃) solution. The effects of reaction parameters including acid concentration, reaction time and temperature were investigated. The properties of the prepared TiO₂ induced by those parameters were characterized by various techniques such as thermal gravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD). It was found that the TiC was completely oxidized to TiO₂ at reaction time of 8 h, 70°C with 5 M HNO₃. At this condition, the obtained TiO₂ composed a mixed phase of 45% anatase and 55% rutile and showed the highest pore volume of 0.239 cm³/g with specific surface area of 306 m²/g. Moreover, all the anatase was transformed into the rutile when the reaction time reached 48 h. The rates of the rutile transformation increased with increasing the acid concentrations but decreased with increasing the reaction temperatures. The pore volumes and the specific surface areas were reduced by increasing the acid concentrations or the reaction temperatures. It is possibly because at the conditions of the high acid concentrations or the high temperatures, the mesoporous framework of TiO₂ was collapsed. Based on the acid conditions, a peptization process was adopted to describe the effects of all investigated parameters.