Study On The Synthesis And Photocatalytic Activity Of Strontium Titanate Nanostructures

Strontium titanate (SrTiO3), a prototypical perovskite oxide, with a band gap of 3.2 ev, has been considered to be a promising alternative to TiO2 as semiconductor photocatalyst. In this paper, in attempt to improve the photocatalytic activity of this oxide, SrTiO3 mesporous spheres have been synthesized via a facile hydrothermal route in the presence of sodium metasilicate (Na2SiO3·9H2O), SrTiO3 nanosheets and size-controlled nanospheres have also been synthesized by using ethylene glycol (EG) and neovaricaine as solvents, repectively. Furthermore, the formation mechanism and photocatalytic activity were discussed and studied. The main results are included as follows:SrTiO3 mesporous spheres have been synthesized via hydrothermal route by adding Na2SiO3·9H2O. Na2SiO3·9H2O could develope silicate species in the solution, which adsorb on the precursor particles to form a semipermeable membrane.thus inhibiting the Ostwald ripening process and resulting in the formation of nanocrystallites assembled SrTiO3 mesporous spheres. The size of the mesporous spheres and primary particles, mesoporous structure could be tuned by adjusting the concentration of KOH solution, because the polymerization degree of silicate species was affected by OH" ions concentration. The samples with KOH concentration of 1.0 M have the largest BET surface area and pore volume, which are 195.45 m2/g and 0.342cm3/g, respectively.Nanoparticles-assembled SrTiO3 nanosheets have been synthesized by solvothermal method with EG as solvent. EG has strong viscosity and can selectively absorb onto the surface of crystals, which leads to the formation of a few of SrTiO3 nanosheets and a large number of nanoparticles. The SrTiO3 nanosheets induce nanoparticles to assemble to SrTiO3 nanosheets. The photocatalytic activity of the SrTiO3 nanosheets synthesized by solvothermal method with EG as solvent was 3 times as high as that of SrTiO3 cubic nanoparticles.SrTiO3 nanospheres have been synthesized via solvothermal method with neovaricaine as solvent. The size of the SrTiO3 nanospheres could be tuned by varying the kind of solvents or introducing PVA. When using neovaricaine, diethanolameine, triethanolamine as solvents, respectively, the size of SrTiO3 nanospheres was ranged from 112.5 nm to 41.9 nm、36.2 nm. By adding PVA, the size of SrTiO3 nanospheres can be tuned from 112.5nm to 45.4 nm. Furthermore, the introduction of PVA improved the photocatalytic activity.