Preparation And Photocatalytic Properties Of SrSn（OH）₆

Photocatalytic technology is a promising solution for energy crisis and environmental problems.After 40 years of development,the photocatalytic basic and applied research has been considerable progressed.However,titanium dioxide,as a typical photocatalyst,still has its shortcoming such as low quantum efficiency and underutilization of solar energy.Based on the above two points,to explore the new photocatalyst for efficient removal of organic pollutants is still necessary.Much progress has been made in photocatalytic decomposition of benzene.Some photocatalysts(such as CaSn(OH)6,ZnSn(OH)6,CdSnO3·3H2O,etc.)have been proved to have high photocatalytic activities.Recently,our group also found a photocatalyst of strontium antimonate(Sr1.21 H4.36Sb2O6.18)for effective degradation of benzene.The central Sn atom and Sb atom are both variable valency ions and easy to form d10 electronic configuration,which is favorable for the separation of photo-generated electron/hole pairs.Since strontium antimonite have good photocatalytic activity,we presume that the SrSn(OH)6 may have good photocatalytic activity as well.In this paper,a novel photocatalyst SrSn(OH)6 was successfully synthesized via a facile homogeneous precipitation method.First,we investigated the photocatalytic effects of SrSn(OH)6 that prepared by different reaction conditions on the degradation of benzene.Second,through a variety of characterization methods,we found that the important factors to the high photocatalytic activity are the specific surface area and the energy band gap.Finally,according to the ESR and the experimental study with various scavengers,we found out the main active species during the degradation reaction and preliminary speculated its reaction mechanism.The results are as follows:(1)SrSn(OH)6 with hexagonal structure was prepared by homogeneous precipitation method.The BET surface area of the sample that has the best photocatalytic activity is 72.81m2/g.The absorption edge of SrSn(OH)6 located at 321.2 nm,corresponding to the band gap of 3.86eV.(2)This kind of SrSn(OH)6 with excellent photocatalytic activity was prepared for the first time.During 32 h of photocatalytic process,the conversion ratio of benzene over SrSn(OH)6 and TiO2(P25)were 31%and 11%,and the mineralization ratio were about 55%and 16%,respectively.(3)According to the ESR and the experimental study with various scavengers,the hydroxyl radical is the most important species for the degradation.It can be concluded that the degradation was driven by the order of ·OH>O2·->h+.(4)SrSn(OH)6 has the photocatalytic activity of photo-induced H2 from a CH3OH-H2O solution.The quantum efficiency of SrSn(OH)6 is 22 times higher than that of P25 under the irradiation of 254 nm UV light using methanol as the sacrificial agent.Features and innovations of paper:(1)SrSn(OH)6 with hexagonal structure was synthesized without template,catalyst,surfactant and high temperature.(2)It is the first time to explore SrSn(OH)6’s photocatalytic activity of degradation of benenze and photo-induced H2 from a CH3OH-H2O solution.(3)With the decrease of the pH value in catalyst preparation process,the photocatalytic activities of the prepared samples increase.The high photocatalytic activity of SrSn(OH)6 with low pH value can attribute to a larger surface area and a broader band gap.