Surfactant-assisted mesoporous TiO2 synthesis and its photocatalytic activity

In this thesis work, the effects of the presence and the amount of a surfactant and calcination temperatures on the structural, surface and photocatalytic properties of TiO2 were investigated. Titanium (IV) n-butoxide was utilized as a precursor for the synthesis of TiO2 catalysts. Starting with a reaction mixture containing titanium (IV) n-butoxide and Tween 80 surfactant as a pore promoter, the catalysts were synthesized by a sol-gel process followed by a hydrothermal treatment. TiO2 nanoparticles with different pore size were obtained by expelling the surfactant from the structure by means of calcinations at five different temperatures. For a comparison the entire process was repeated without using a surfactant. Structural, surface and optical properties of the prepared catalysts were determined by XRD, BET, FTIR, SEM, zeta potential and light absorption measurements. The results showed that BET surface areas and total pore volumes decrease while crystallite sizes and average pore sizes of the catalysts increase, upon increasing the calcination temperatures. On the other hand, catalysts calcinated at 600oC and 700oC contain anatase/rutile mixed phase whereas those calcinated below 600oC consist merely of an anatase phase. It was observed that the use of surfactant neither changed the crystallite phase nor prevented crystal growth. The presence of the surfactant also gives rise to increases in BET surface areas and to decreases in the average pore sizes. Photocatalytic activities of the catalysts were studied for degradation of aqueous Rhodamine B (RhB) under UV irradiation. Among uncalcinated catalysts, high catalytic activities of 0.02S+TiO2 upon UV irradiation for 2 hours can be attributed to its greater surface area. High activities of the catalysts calcinated at 600oC and 700oC, on the other hand, can be ascribed to the synergetic effect developed by the dual-phased structure.