Preparation And Characterization And Photocatalytic Properties Of Coupling Semiconductors SnO₂ And TiO₂ And Inverse Doping-Ion Structural Materials

In this paper,four series of semiconductors SnO₂-TiO₂ coupling and inverse doping-ion nanostructured materials were prepared via solvothermal-calcination two-step method by respectively using defatted cotton fiber?CF?and pomelo peel?PP?as template.XRD,SEM and BET were used to characterize the target samples.The decolorization behavior of the dye methylene blue?MB?solution on the samples under a 300 W high pressure mercury lamp?HPHL?at a dominant wavelength of 365 nm were also carried out.The factors,such as calcination conditions-temperature and time,inverse doping-ion amount and depth,and the amount of coupling semiconductors were investigate and affect the phase composition,inverse doping-ion amount and depth,and photocatalytic properties of the composites.The specific research content will carried from the following two aspects.1.Two series of semiconductors SnO₂-TiO₂ coupling and inverse doping-ion nanofiber structured materials,in which SnO₂ and TiO₂ were respectively used as “core”,were prepared via solvothermal-calcination two-step method by using CF as template and labeled as CF-Ti⁴⁺/SnO₂ @ Sn⁴⁺/TiO₂ and CF-Sn⁴⁺/TiO₂ @ Ti⁴⁺/SnO₂,respectively.Some factors,calcining temperature?T = 400,450,500,550,600 ??and time?t_s/t_c = 20/100?40/80?60/60?80/40?100/20;t_s: calcination time of target material,t_c: calcination time of core?,amount?2.50 25.0 %?of coupling semiconductors were investigated.Characterizing results showed:A series of the samples CF-Ti⁴⁺/SnO₂ @ Sn⁴⁺/TiO₂:a.Under calcining temperature T ? 600 ?,the conversion of anatase to rutile TiO₂ occurs,so the calcining temperature T was determined to be 550 ? to ensure relatively simple phase component and good photocatalytic property of the as-prepared samples.b.Under t_s + t_c = 120 min,characteristic diffraction peak?at about 25.30°?of TiO₂ phase shifted to the lower diffraction angle?2??with the prolongation of calcination time t_s.The shift of the diffraction peak to the lower 2? indicates the size increase of the unit cell.Introducing Sn⁴⁺ ions into TiO₂ lattice leads to the expansion of TiO₂ unit cell because the radius of Sn⁴⁺?0.0690 nm?is larger than that of Ti⁴⁺?0.0605 nm?.So the shift of characteristic diffraction peak of TiO₂ phase to low 2? proves that Sn⁴⁺ ion of guest SnO₂ phase enters to the lattice of the main phase TiO₂ and the main phase TiO₂ is really Sn⁴⁺-dopped TiO₂(Sn⁴⁺/TiO₂).And photocatalytic results show that under t_s/t_c = 40/80 condition,as-prepared sample has the best photocatalytic performance,indicating that a proper amount of counter doping-ion is beneficial to the improvement of the photocatalytic performance.c.Coupling amount of CF-Ti⁴⁺/SnO₂ @ Sn⁴⁺/TiO₂?2.50 10.00?mol?%?affects the photocatalytic properties and the photocatalytic performance of the sample was the best when the amount was about 5.00 %,for example,the activity of the sample CF-Ti⁴⁺/SnO₂ @ Sn⁴⁺/TiO₂-A-5.00 is 2.0 times as pure TiO₂ and 2.8 times as pure SnO₂,respectively.A series of the samples CF-Sn⁴⁺/TiO₂ @ Ti⁴⁺/SnO₂:a.In the calcination temperature range of 600 700 °C,the photocatalytic performances of the samples lighly changed.Therefore,the temperature was set to 600 °C.b.Similar to the result of above-described series,XRD results of as-prepared samples under different t_s/t_c condition?20/100?40/80?60/60?80/40?100/20?showed that the characteristic diffraction peak?at about 26.60°?of main SnO₂ shifted to higher diffraction angle?2??,indicating the entering of Ti⁴⁺ ion of the guest phase TiO₂ into the lattice of the main SnO₂ and the decrease of the SnO₂ unit cell.So herein the main phase is really Ti⁴⁺ dopped SnO₂(Ti⁴⁺/SnO₂).And the photocatalytic results showed that the sample CF-Sn⁴⁺/TiO₂ @ Ti⁴⁺/SnO₂-t_s/t_c-60/60 has the best photocatalytic performance.c.The photocatalytic performance of the samples CF-Sn⁴⁺/TiO₂ @ Ti⁴⁺/SnO₂ was also affected by the amount of coupling semicondutors and when the amount was about 17.5 %,the as-obtained sample showed the best photocatalytic performance,and it_s activity was about 1.66 times as pure TiO₂ and 2.35 times as pure SnO₂,respectively.Other two series of semiconductors SnO₂-TiO₂ coupling and inverse doping-ion nanosheets structured materials,in which SnO₂ and TiO₂ were respectively used as “core”,were also prepared via solvothermal-calcination two-step method by using PP as template and labeled as PP-Ti⁴⁺/SnO₂ @ Sn⁴⁺/TiO₂ and PP-Sn⁴⁺/TiO₂ @ Ti⁴⁺/SnO₂,respectively.Some factors,calcining temperature?T = 400,450,500,550,600 ??and time?t_s/t_c = 20/100?40/80?60/60?80/40?100/20;t_s: calcination time of target material,t_c: calcination time of core?,amount?2.50 25.0 %?of coupling semiconductors were also investigated.The results were similar to that of the above-described two series and showed that for the series of the samples,the effects of the calcining temperature and time and the amount of coupling semiconductors on the phases component and ions dopping of guest phases into main phases and photocatlytic performance were similar to that of the prepared samples by using CF as the template.The results demonstrated: a.the conversion of TiO₂ anatase to rutile occurred under some high calcining temperature,prolonging the calcining time t_s would bring about the dopping of the more guest ions into main phase,called as inverse dopping of the ions.b.their photocatalytic performance were also affected by the amounts of inverse doppng ion and coupling semiconductors and proper amount of inverse dopping ions and coupling semiconductors were advantageous to ensuring good photocatalytic performance of the samples.In fact,entering of main phases ions into guest phases are certainly possible although herein XRD results of four series of the samples have demonstrated the entering of guest phases ions into main phases because in main phase,the intensity of diffraction peaks is enough strong to give reliable informations.So during the process of realizing semiconductors couple under some preparing conditions,ion doppings from guest phase to main phase and from main phase into guest phase are possible and in semiconductors-coupled materials,the inverse dopping of ions exists and affects their photocatalytic property.