Preparation Of Stannous Sulfide-based Materials And Their Photocatalytic Properties

Recently,the macromolecular organic pollutants have become one of the hot research topics in the environmental chemistry remediation.Among them,the typcial organic pollutants are dyes,which are toxicity and visibility(even if the concentration<1 ppm),and are considered as the first pollutants in wastewater.As an effective advanced treatment technology,heterogeneous phototcatalysis is a promising and innovative green purification technology.Currently,photocatlaysis technology based on TiO2 has provided an effective and promising means for remediation of environmental pollutants in air and water.However,the widespread technological used of TiO2 is impaired by its wide band gap,which can only be activated under UV light.Therefore,to finding an appropriate catalyst that is capable of utilizing the visible light(or solar energy)is a task in photocatalysis field.In order to efficiently utilize visible light,tin(Ⅱ)sulfide(SnS)with narrow band gap,non-toxic and rich material characteristics was chosen as photocatalyst and used it for the degradation of methyl orange(MO)and rhodamine B(Rh B)pollutants.This dissertation are divided into three parts,three sections are contained as follows:(1)The effects of preparation conditions on the catalytic properties had been investigated.The suitable conditions were obtained:sulful source was thioace tamide,reaction time was 24 h,reaction temperature was 200℃,solvent was ethlene glycol.Meanwhile,choosing two different morphology of SnS catalysts for degradation of MO and Rh B to analysis the influence of morphology on photocatalytic properties.The photocatalytic degradation process conditions of SnS were also investigated by single factor experiments,the optimum reaction conditions were obtained:MO had the better photocatalytic degradation activity,catalyst dosage was 15 mg,concentration of MO was 30 mg/L.(2)The different conposition of SnS/SnS2-A-D p-n heterojunction photocatalysts were successfully synthesized by a one-step solvothermal method through adjusting the quality percentage of Sn4+ in raw material,SnS was a p-type semiconductor and SnS2 was a n-type semiconductor.Among these samples,SnS/SnS2-B showed the better photocatalytic activity.The degradation rate of MO was 83.25%in illuminate 60 min,and degradation reaction were calculated by adopting the pseudo-first-order reaction kinetics,the k value was 3.351×1O-2 min-1 which higher than pure SnS and pure SrnS2.Under these conditions,reproducibility experiments were conducted,the results showed that the degradation rate was 76.68%,only 6.6%reduction compared with the original result after fourth cycling.The experiment results demonstrated that the active species in photocatalytic degradation of MO of SnS/SnS2-B heterojunction sample was:·O2-radical was the main active species,and OH radical was the secondary active species and it should be generated via the ·O2-→H2O2→·OH route.For the degradation process of MO,we preliminary think the MO degradation on the SnS/SnS2-B photocatalyst may firstly occurred a reduction mechanism in which the photoelectrons directly reduced the N=N double to generate as intermediates of 4-aminobenzene sulfonic acid solution,then followed by the subsequent oxidation by the main active species·O2-and OH to be mineralized into CO2 and H2O.(3)We first synthesised the SnS and conducting polymer polyaniline organic-inorganic hybrid materials,and obtained a series of SnS/PANI composite materials through a proton doped in-situ polymerization technique.And explained photocatalytic improvement and photocorrosion inhibition of PANI modified SnS composites in photocatalytic degradation reaction of MO.The results indicated that c-PANI/SnS-2 and c-PANI/SnS-0.5 samples had a 83.39%and 58.27%degradation rate of MO,respectively,which were better than SnS/SnS2-B sample with 55.98%in illuminate 40 min.The reasons could be owing to photo-generated holes migrating from VB of SnS to HOMO of PANI,photo-generated electron migrating from LUMO of PANI to CB of SnS,significantly separated photogenerated electrons and holes and improved the efficiency of light absorption.In the meantime,the newly formed N-Sn bond between PANI and SnS resulting in efficient photocorrosion amelioration.