Synthesis,Rare Metals Modification And Photocatalytic Properties Of Hexahydroxy Strontium Stannate Nanorods

Hexahydroxy strontium stannate（Sr Sn（OH）₆）nanoscale materials exhibit great application potential in the photocatalytic treatment field of the organic pollutants owing to good catalytic,optical and electronic properties.Sr Sn（OH）₆ nanorods,La doped and Nd doped Sr Sn（OH）₆ were synthesized by a facile hydrothermal method.Nd modified Sr Sn（OH）₆ nanorods were prepared by the photo-deposition method.The structure,morphology,size,composition,optical and electrochemical performance of the products were analyzed by X-ray diffraction（XRD）,electron microscopy analysis,X-ray photoelectron spectroscopy（XPS）,solid ultraviolet-visible（UV-vis）diffuse reflectance spectroscopy,photoluminescence（PL）spectroscopy and electrochemical impedance spectroscopy（EIS）.The photocatalytic performance and photocatalytic reaction process for gentian violet（GV）degradation using the Sr Sn（OH）₆ nanorods,rare metals doped Sr Sn（OH）₆ and Nd modified Sr Sn（OH）₆ nanorods were investigated sysmatically.The present research provides necessary experimental and theoretical basis for the photocatalyic application of the Sr Sn（OH）₆ nanoscale materials which is of great significance for the sewage treatment.Sr Sn（OH）₆ nanorods were synthesized using sodium stannate and strontium chloride as raw material from 180℃for 24 h.The obtained nanorods are composed of hexagonal Sr Sn（OH）₆ phase with smooth surface and flat tip.The length is less than 10μm and the diameter is 50-150 nm.The formation and growth of the Sr Sn（OH）₆ nanorods can be explained by the nucleation and crystalline growth process.The band gap of Sr Sn（OH）₆ nanorods is 3.72 e V.Sr Sn（OH）₆ nanorods show good photocatalytic activity for the GV degradation under UV light irradiation.The GV degradation rate increases obviously with increasing the amount of the Sr Sn（OH）₆ nanorods.10 m L GV solution(10 mg·L^-1)can be degraded totally using10 mg Sr Sn（OH）₆ nanorods under the light irradiation for 6 h.The reaction rate constant for the GV degradation is 0.005 min^-1.La doped Sr Sn（OH）₆ nanorods（La-Sr Sn（OH）₆）and Nd doped Sr Sn（OH）₆nanorods（Nd-Sr Sn（OH）₆）were synthesized by hydrothermal method using La acetate and Nd nitrate as the La and Nd source materials,respectively.2 wt.%rare metals doped Sr Sn（OH）₆ contains hexagonal Sr Sn（OH）₆ and tetragonal Sn O₂ phases.La and Nd in 5 wt.%and 8 wt.%rare metals doped Sr Sn（OH）₆ exist in the form of cubic La Sn₂O₇ and cubic Nd Sn₂O₇ phases.The morphology of the La doped Sr Sn（OH）₆ is transformed from nanorods to nanosheets with increasing the La doping mass ratio.The morphology of the Nd doped Sr Sn（OH）₆ is transformed from nanorods to nanoscale particles with increasing the Nd doping mass ratio.The band gap of L La-Sr Sn（OH）₆ and Nd-Sr Sn（OH）₆ is 3.26 e V and 3.25 e V,respectively when the doped content of the rare metals is 2 wt.%.10 m L 10 mg·L^-1GV solution can be degraded totally using 10 mg 2 wt.%rare metals doped Sr Sn（OH）₆ nanorods under the light irradiation for 120 min.The reaction rate constant for the GV degradation is0.005 min^-1.The reaction rate constant of the 2wt.%La-Sr Sn（OH）₆ and 2wt.%Nd-Sr Sn（OH）₆ is 0.015 min^-1 and 0.017 min^-1,respectively,which is 3 times of that(0.005 min^-1)of the Sr Sn（OH）₆ nanorods.Nd modified Sr Sn（OH）₆ nanorods were prepared via the photo-deposition method using Sr Sn（OH）₆ nanorods and Nd nitrate as the raw materials.Nd nanoscale particles attach to the surface of the Sr Sn（OH）₆ nanorods.XPS spectra confirm that the Nd modified Sr Sn（OH）₆ nanorods contain Sr,Sn,O and Nd elements.Solid UV-vis diffuse reflectance spectra show that the band gap of the Sr Sn（OH）₆ nanorods with Nd content of 0.08 mmol（0.08-Nd Sr Sn OHNRs）is 3.33 e V.10 m L 10 mg·L^-1GV solution can be degraded totally using 10 mg 0.08-Nd Sr Sn OHNRs under the light irradiation for 150 min.The reaction rate constant of the 0.08-Nd Sr Sn OHNRs is0.014 min^-1,which is 2.8 times of that of the Sr Sn（OH）₆ nanorods.GV degradation ratio increases obviously with the increase of the amount of the Nd modified Sr Sn（OH）₆ nanorods.Radical scavengers photocatalytic results show that the superoxide radical（·O₂^-）,holes（h⁺）and hydroxyl radical（·OH）are the reactive active species for the GV degradation.EIS and PL spectra show that the La doping,Nd doping and Nd surface modification of the Sr Sn（OH）₆ nanorods can inhibit efficiently the recombination of the electron/hole（e^-/h⁺）pairs,increase the amount of the charge carriers of the surface of the rare metals doped Sr Sn（OH）₆and Nd modified Sr Sn（OH）₆ nanorods for the photocatalytic reaction,and enhance the photocatalytic activity of the Sr Sn（OH）₆nanorods toward GV.Sr Sn（OH）₆ nanorods,rare metals doped and Nd modified Sr Sn（OH）₆ nanorods are recoverable and show good photocatalytic stability for GV degradation.