Preparation, Structuer And Phocatalytic Activities Of Nanostructured TiO₂Films Photocatalyst

After pioneering work of intriguing “water photolysis effect” over rutile TiO₂singlecrystal electrode reported by Fujishima and Honda in1972and photocatalytic degradation oforganic pollutants over semiconductor particles proposed by Bard et al. in1977, TiO₂thinfilm have attracted extensive attention of researchers in basic research and practicalapplications, demonstrating their enormous scientific value and marketing value in the fieldof environmental purification and energy conversion. Therein, preparation andimmobilization technology of TiO₂film become core technology toward practical application.Up until now, method including anodic oxidation and alkali chemical etching of titaniumsubstrate has become popular, due to the following advantages:（1） simple operation, mildconditions;（2） strong attachment of film to the substrate;（3） good electrical properties;（4）controllable structure and morphology. In this dissertation, the work is around TiO₂/Tifunctional films, mainly including exploring the effect of a series of preparation conditionsand external environment on the structure of TiO₂nanostructures and studies the relationshipbetween the structure and photocatalytic properties of TiO₂thin films. It can be summarizedas following two aspects:（1） A simple approach was employed to fabricate TiO₂nanosheet array film on Ti foil byemploying Ti foil as both reactant and substrate. By simply tuning the time of hydrothermaltreatment, perpendicular sodium trititanate nanosheet array could be facily prepared on Ti foildipped in NaOH solution. By further ion exchange of Na+with H+and thereafter annealingtreatment, the perpendicular layered titanate nanosheet array was topotactically transformedinto TiO₂phases. Structural analysis of the TiO₂nanosheet array proved the formation of anovel anatase/TiO₂（B） heterostructure with coherent interface between the two phases, whichexhibited superior photocatalytic efficiency under UV illumination as compared with therelevant commercial products-P25and anode oxidized TiO₂nanotube film of the samethickness but with greater mass of photocatalyst. The high photocatalytic activity of the TiO₂nanosheet array film can be ascribed to the synergistic effect of large surface area, highcrystallinity as well as heterojunction between TiO₂（B） and anatase phase.（2） By adopting hydrogen trititanate nanosheet as precursor, along with the assistance ofsodium chlorine solution in the reaction system, TiO₂nanorods with large percentage of {100}facet exposure have been successfully prepared. The structural characteristics and formationmechanism of the anatase TiO₂nanorods was deduced from XRD, SEM and TEMcharacterizations, which revealed that formation of TiO₂nanorods were derived from acombined effect of phase transition retard from hydrogen tiantate to anatase TiO₂induced by Na ion and selective adsorption of Cl ion on the{100} facets of anatase TiO₂crystals.Photocatalytic performance indicated that the TiO₂nanorods with high-energy {100} facetexposure exhibit much higher activities than that of rhombic nanoparticles with low-energy{101} facet exposure for the degradation of organic contaminants.