Preparation And Application Of TiO₂ Materials With Different Morphology

In this study,tapered tetragonal TiO₂ nanorods with exposed crystal facets and spherical TiO₂ nanomaterials were prepared.Firstly,anatase tapered tetragonal TiO₂nanorods with exposed high-energy{100}and{001}facets and low-energy{101}facets were fabricated in the presence of surfactants cetyltrimethylammonium bromide,didecyldimethylammonium bromide,and ammonia via a facile hydrothermal method.The structure and composition of the samples were characterized by a wariety of test methods.The results showed that the particle size and morphology were mainly tuned by regulating the hydrothermal temperature.When the temperature was increased from 150? to 180? and 200?,the length of the nanorods decreased from 700-1000 nm to 400-500 nm and 100-200 nm,respectively.Concurrently,the edges and tops of the truncated tetragonal pyramid of the TiO₂ nanorods became blurry and flattened.Through the research on the formation mechanism of tapered tetragonal TiO₂ nanorods,we found that the surfactants were employed as shape-controlling and capping reagents in the synthesis of TiO₂ materials with exposed facets.Ammonia was utilized to provide a basic environment for the reaction and facilitate the oriented growth of TiO₂ nanorods.The synthesized typical TiO₂ nanorods were then used as photocatalysts,and their performance during the direct generation of H₂ from water was evaluated.The TiO₂ nanorods obtained at150? successfully produced high amounts of H₂ evolution in the presence of methanol as a sacrificial agent under ultraviolet light irradiation for 4 h?281.36?mol?.The outstanding photocatalytic activity of the nanorods can be mainly ascribed to two points:?1?the oxidation and reduction reactions during the catalytic process were separated by exposed high-energy{100}and{001}facets and low-energy{101}facets of tapered tetragonal TiO₂ nanorods,reducing the recombination of electron-hole pairs,thereby improving the catalytic performance.?2?The formation of surface heterojunctions in the edges and corners between adjacent high-energy{001}or{100}facets and low-energy{101}facets.The formed heterojunctions could facilitate charge separation through preferential carrier flow toward the specific facets,which was conducive to the catalytic process.Spherical TiO₂ nanomaterials formed by stacking TiO₂ nanoparticles with different particle sizes were prepared by solvothermal method by using surfactant poly?ethylene-glycol?-block-poly?propy-glycol?-poly?ethylene-glycol?assoft templates and Titanium oxysulfate-sulfuric acid hydrate as the titanium source under acidic conditions.The sizes of the spherical TiO₂ nanomaterials obtained at 150? and 180? hydrothermal temperatures are between 400-600 nm and 200-300 nm,respectively,and the size of the TiO₂ nanoparticles are about 5-10 nm and 10-20 nm.The two samples prepared at different hydrothermal temperatures were used for photocatalytic degradation of methyl orange and all of them exhibit outstanding catalytic performance.However,the spherical TiO₂ nanomaterials obtained at the temperature of 150? need about 1 h for completely photocatalytic degradation of methyl orange in the dispersion and the spherical TiO₂ nanomaterial prepared at the temperature of 180? requires about 1.5 h.In this way,we know that the spherical TiO₂ nanomaterials prepared at the temperature of 150? have excellent photocatalytic activity.