Post-synthesis of TiO2 Dispersed Inside the Pore Channels of SBA-15 and its Photocatalytic Activity for the Degradation of Methylene Blue

Abstract

TiO2-SBA-15 mesoporous materials in which titanium oxide species were dispersed inside the pore channels of SBA-15 were prepared by a novel post-synthesis method. In this method, cetyltrimethylammonium bromide surfactant molecules were incorporated inside the channels of the mesopores of SBA-15 followed by the addition of titanium tetraethoxide. Effect of hydrolysis conditions of titanium tetraethoxide on the formation and properties of Ti oxides in TiO2-SBA-15 materials was investigated. Physico-chemical properties of TiO2-SBA-15 materials were characterized by XRD, N2 adsorption, SEM and UV-vis. Size and morphology of Ti oxide species in TiO2-SBA-15 materials were dependent on the hydrolysis conditions of titanium tetraethoxide, i.e., H2O/Ti molar ratio. Dispersed titanium oxide species were mainly formed on the internal surface of SBA-15, i.e., on the surface of mesopore walls of the TiO2-SBA-15 samples when synthesized at low H2O/Ti ratios of 2 and 4, whereas large TiO2 anatase particles were predominantly formed on the external surface of SBA-15 when the samples were prepared at high H2O/Ti molar ratios. The photocatalytic activity of the TiO2-SBA-15 samples was investigated for the degradation of methylene blue, MB, and compared with that of pure TiO2, P25. The TiO2-SBA-15 samples, in which titanium oxide species were dispersed on the internal surface of SBA-15, showed higher and more stable photocatalytic activity in the degradation and/or decolorization of MB than P25 and TiO2-SBA-15 which has TiO2 particles on the outer surface of SBA-15.