Green Synthesis And Modification Of Anatase TiO₂ Mesocrystals And Their Applications In Photocatalysis

TiO₂semiconductor materials were widely used in the field of photocatalysis due to their advantages such as non-toxicity,harmlessness,and availability.Mesocrystal originally originated from biomineralization,which is a superstructure formed by the orientation and aggregation of nanocrystals,and it has the characteristics of high porosity and high crystallinity.In recent years,TiO₂mesocrystals have gradually become a research hotspot because of their unique structures and excellent properties.However,using green methods to prepare TiO₂mesocrystals still faces great difficulties and challenges,at the same time,the fast photo-generated carrier recombination rate and large band gap width of TiO₂mesocrystals have limited their further development and application.Herein,spindle-shaped and spherical anatase TiO₂mesocrystals were synthesized by simple hydrothermal methods using green ethyl formate and polyethylene glycol 400 as solvents,respectively.The prepared TiO₂mesocrystals were further modified to improve their photocatalytic performance.The main research contents are follows:?1?The spindle-shaped anatase TiO₂mesocrystals were synthesized by solvothermal method using green ethyl formate as the sole solvent and tetrabutyl titanate as the titanium source.It is worth noting that the solvent ethyl formate was re-used three times,and the precipitated product still retained the mesocrystal structures,which could minimize the impact of organic solvents on the environment during the synthesis process.The morphology,structure and growth mechanism of the spindle-shaped anatase TiO₂mesocrystals were investigated through a series of characterizations.In order to further improve the photocatalytic performance,the materials were calcined in air for carbonate doping,and the obtained carbonate-doped anatase Ti O_2-xmesocrystals were applied to photocatalytic degradation of sulfathiazole and reducing heavy metal pollutant Cr?VI?fields.The carbonate-doped anatase Ti O_2-xmesocrystals exhibited excellent photocatalytic performance under visible light irradiation,and the mechanism of photocatalytic reaction has been thoroughly explored.?2?Spherical anatase TiO₂mesocrytals were synthesized by hydrothermal method using green polyethylene glycol 400 as solvent and Ti₂?SO₄?₃as titanium source.The synthesized spherical anatase TiO₂mesocrystals were used as a template and reactant,and they were compounded with Sr Ti O₃by a simple one-step hydrothermal method to obtain Sr Ti O₃/spherical TiO₂mesocrystal composites with different ratios.TEM and XPS characterization results showed that the spherical anatase TiO₂mesocrystals and Sr Ti O₃were successfully combined to form a heterostructure.And the photoelectrochemical characterizations showed that composites could effectively promote the separation of electrons and holes,and improve quantum efficiency.Compared with single spherical TiO₂mesocrystals and Sr Ti O₃nanoparticles,the photocatalytic performance of the composites was greatly improved.Under the irradiation of simulated sunlight with a light intensity of 100 m W/cm²,the composites exhibited efficient photocatalytic performance for degradation of the dye methyl orange and reduced heavy metal Cr?VI?.Moreover,the mechanism of photocatalytic reaction has been thoroughly explored.