Prepareration And Application In Photoelectrochemistry Of Porous Matel Oxides （TiO_x,SnO₂）

Three dimensionally ordered macropores (3DOM) or inverse opals are an orderly photonic crystal structure. They not only have characteristics of traditional porous materials, such as large specific surface area and high porosity, but also unique properties:(1) the periodically arranged pores lead to the band structure of electron energy levels with band gap;(2) narrow pore distribution;(3) uniformly tuned pore diameters. Therefore, nowadays3DOM materials is cutting edge research field in the world. Transition metal oxides (such as SnO2, TiO2) are important semiconducting photocatalyst and photoanode materials of dye-sensitized solar cells (DSSCs). Their non-stoichiometric oxides, for example, TiOx, possess better conductivity (Ti4O7:1500s.cm-1), narrower electronic band gap, same high refractive index as stoichiometric oxides. Hence, non-stoichiometric suboxides with three dimensionally ordered macroporous structure have the following characteristics:(1) intensive absorption to visible and near-infrared light;(2) fast carriers and holes transportation;(3) high surface areas which bring about the large amount absorption of some of chemicals on the surface, thus fast chemical reaction proceeded on the surface of materials. Therefore, non-stoichiometric oxides can be applied into photocatalytic degradation of organic contaminants and DSSCs, etc.This thesis focuses on following works:1. Monodisperse PMMA microspheres with diameters of350nm,400nm,450nm, and510nm were synthesized by microemulsion polymerization process. PMMA and TiO2gel/PS composite colloidal crystal templates were prepared by centrifugation and water bath drying at constant temperature. TiO2sol was synthesized by sol-gel process, infiltrated into the PMMA templates by immersion technique. After drying and heating, the TiO2with3DOM structure was obtained. Next the coral-like porous Ti4O7materials was achieved by H2reduction. The samples were characterized by XRD and SEM techniques. The results show that the two factors are key to quality of3DOM structures:(1) uniformity of PMMA micspheres size;(2) ordering of PMMA micspheres packing.2. Porous TiOx compounds were prepared by reduction process using TiO23DOM materials as precursor, sodium borohydride powder and aqueous solution as reducers. The samples were measured with SEM and XRD tools. The1h degradation efficiency of methylene blue with TiOx compounds photocatalyst prepared by the sodium borohydride aqueous solution as reducer is79%,hower prepared by the sodium as reducer is only77%.3. Mesoporous SnO2precursors were synthesized by spray reaction route and mesoporous SnO2spheres were attained after microwave-drying under "low-fire" condition and calcinations. The anode of DSSCs were fabricated with nanostructured TiO2layer and mesoporous SnO2spheres as scattering layer. DSSCs were assembled using two-layer anodes and FTO glass with deposited platinum film as counter electrode, which possess highest photoelectronic conversion efficiency of3.11%so far.