Study On Fabrication And Properties Of Hierarchically Porous Structure Ni,La-SrTiO₃ Photocatalyst

As one of functional materials,SrTiO₃ has been widely used as photo-catalyst due to its excellently physical and chemical properties.However,the disadvantages of the wide band gap?3.2 ev?,which makes them have no visible-light responsibility,and the low surface area have become the bottleneck problems for further improving the photocatalytic activities.Hierarchical pore structure not only enlarges the specific surface area but also improves the ability of light trapping via multiple reflection and scattering of light in hierarchical pores,thus improving its photocatalytic activities.Therefore,it is absolutely significant both theoretically and practically to synthesize visible-light responsive SrTiO₃ with high surface area for solving the problem of energy and pollution.The effect of organic and inorganic template on the structure of obtained materials was investigated in this thesis.And the results reveal that the optimal conditions are as follows:CaCO₃ is the better inorganic template and its optimal dosage is 50%,CTAB is the better organic template.Hierarchically porous Ni,La-SrTiO₃ has been synthesized successfully with three methods,including Two-step method?Hydrothermal aging and Solid phase crystallization?,Hydrothermal crystallization and Hard template method with coprecipitation in this thesis.And the effect of methods and parameters of synthesis system on the structure of the synthesized materials were discussed.The results reveal that?1?the materials obtained by Two-step method possess coral like with hierarchical structure and with a specific surface area of lager than 180 m²/g.?2?the materials of Ni,La-SrTiO₃ synthesized through hydrothermal crystallization present a cube shape with depressed six surfaces or flower-like.Furthermore,the amount of water in synthesis system has significant effect on morphology of as-synthesized samples,and the nano-size Ni,La-SrTiO₃ with a surface area of more than 117 m²/g is easily formed in the system with high water content.?3?In the process of preparing hierarchical strontium titanate with hard template produced by coprecipitation method,it was found that the alkalinity of synthesis system displays a key role in the critical crystallization temperature of forming Ni,La-SrTiO₃,and the temperature increases with the increasing of pH when the pH value is less than 11.The lowest critical crystallization temperature is 420?when the pH value of system is 8,and the as-synthesized sample prepared under the optimal conditions at that temperature has hierarchically porous structure and a surface area of more than 160 m²/g.In summary,the hierarchical structure can be fabricated by the above mentioned three method,and the degradation rate of malachite green is up to 91.1%by using the prepared materials as photocatlysts under UV-light irradiation.