Ligand-Assisted Assembly Approach to Synthesize Large-Pore Ordered Mesoporous Titania with Thermally Stable and Crystalline Framework

A novel ligand-assisted assembly approach is demonstrated for the synthesis of thermally stable and large-pore ordered mesoporous titanium dioxide with a highly crystalline framework by using diblock copolymer poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template and titanium isopropoxide (TIPO) as a precursor. Small-angle X-ray scattering, X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution scanning electron microscopy, and N-2-sorption measurements indicate that the obtained TiO2 materials possess an ordered primary cubic mesostructure with large, uniform pore diameters of about 16.0 nm, and high Brunauer-Emmett-Teller surface areas of -112 m(2) g(-1), as well as high thermal stability (similar to 700 degrees C). High resolution TEM and wide-angle XRD measurements clearly illustrate the high crystallinity of the mesoporous titania with an anatase structure in the pore walls. It is worth mentioning that, in this process, in addition to tetrahydrofuran as a solvent, acetylacetone was employed as a coordination agent to avoid rapid hydrolysis of the titanium precursor. Additionally, stepped evaporation and heating processes were adopted to control the condensation rate and facilitate the assembly of the ordered mesostructure, and ensure the formation of fully polycrystalline anatase titania frameworks without collapse of the mesostructure. By employing the obtained mesoporous and crystallized TiO2 as the photoanode in a dye-sensitized solar cell, a high power-conversion efficiency (5.45%) can be achieved in combination with the N719 dye, which shows that this mesoprous titania is a great potential candidate as a catalyst support for photonic-conversion applications.