Fabrication And Photocatalytic Performance Of SrTiO₃ Materials With Specific Morphologies

The semiconductor photocatalysis,as one of the most significant green technologies to utilize solar energy,has attracted much attention due to environmental friendliness and energy sustainability.Strontium titanate?SrTiO₃?,a typical ternary cubic-perovskite-type oxide with large nonlinear optical coefficient,is regarded as one of the most attractive n-type semiconductor photocatalyst due to low cost,high efficiency,durable photostability and corrosion resistance,which exhibits the great potential in water splitting for hydrogen production and organic compound degradation.Currently,due to low light-harvesting capacity and easy recombination of photogenerated charge carriers,the solar energy conversion efficiency of pristine SrTiO₃ is still low.In order to solve these two key issues restricting the SrTiO₃ application,a series of SrTiO₃ materials with specific morphologies and efficient photocatalytic performance have been synthesized in this dissertation.First,one-dimensional?1D?SrTiO₃ nanotubes?STNTs?have been fabricated via a facile isomorphic conversion strategy using the protonated titanate nanotube as both precursor and template under the hydrothermal treatment.The as-prepared STNTs consist of uniform and continuous multilayers,having inner and outer diameters about8.0 and 13.0 nm.The STNTs formation involves the exchange of Sr²⁺ions with H⁺ions in HTNTs,and then in situ growth of cubic SrTiO₃ crystals by the templating of HTNT frameworks.It is found that the concentration of Sr²⁺ions plays a critical role in controlling the nanotube morphology of SrTiO₃ crystals.In addition,the SrTiO₃nanotubes exhibit high photocatalytic activity for the Cr???reduction,which can reduce nearly 100%Cr???within 6 h under simulated sunlight irradiation.Second,two-dimensional?2D?Cr-doped SrTiO₃ nanoplates?CrSTO?have been synthesized by a mild hydrothermal process using ethylene glycol as the capping agent.The plane length and thickness of as-synthesized CrSTO nanoplates are about100 and 20 nm,respectively.The absorption edge of CrSTO samples shifts toward the visible light region,leading to higher photocatalytic activity for the Cr???reduction under visible light.Among all CrSTO samples,CrSTO-0.9(the Cr³⁺doping content is0.9 wt.%)exhibits the highest visible–light photocatalytic activity,which can reduce92.0%Cr???within 3.5 h.Such improvements are also attributed to the enhancement in light scattering due to the pseudo-square-shaped 2D plate-like morphology,the increase in electron lifetime and the decrease in electron-hole recombination.Finally,three-dimensional?3D?porous SrTiO₃ microspheres?PSTO?have been prepared by using the flower-like titanate as the template.The as-prepared PSTO microspheres are uniform and about 5.0?m in diameter,which are composed of SrTiO₃ nanocrystals.There are many worm-like pores on their surface and in their interior.The 3D porous microsphere structure facilitates the adsorption and diffusion process during the photocatalytic reaction and simplifies the recycling of photocatalysts.Therefore,the porous SrTiO₃ microspheres exhibit the outstanding photocatalytic performance for the Cr???reduction,which can reduce nearly 98.8%Cr???within 4 h under simulated sunlight irradiation.Hopefully,the above studies could not only provide the reference for the synthesis of SrTiO₃ materials with specific morphologies,but also offer the reference for the rational design of photocatalytic materials with high catalytic activity and stability.