Mesoporous Monocrystalline TiO2 and Its Solid-State Electrochemical Properties

Mesoporous monocrystalline rutile TiO2 has been fabricated at low temperature using mesoporous silicas SBA-15 and KIT-6 as hard templates. The key step of the synthetic process was introducing titanium nitrate complex into the template pores and allowing it to dry, dehydrate, decompose, and finally, form TiO2 crystals in the pores. It was found that the reaction temperature and concentration of HNO3 in the used precursor had great effects to the crystallization of TiO2. Removal of the silica templates after the TiO2 crystallization has been investigated. Crystallization of TiO2 in cage-containing mesoporous silicas, FDU-12 and SBA-16 was not successful, further confirming the previous speculation about strong interaction between the crystals and the wall of silica cages. The porous titanium oxide specimens were characterized by using various techniques, including XRD, HRTEM, and nitrogen adsorption/desorption. Proton conductivity and Li-ion insertion property of the samples were also examined. The highest conductivity, 8 x 10(-3) S cm(-1), was obtained at 50 degrees C under 100% RH and 1 Li+ could be accommodated per TiO2 unit (335 mA h/g) for the first discharge.