Study On Preparation And Catalytic Mechanism Of Visible-Light-Responsive In_2.77S₄-Based Composite Photocatalytic System

In recent years,semiconductor photocatalytic degradation technology has received wide attention becasue it has many special advantages and been deemed as an advanced technology to solve the problems of water pollution and energy shortage.In_2.77S₄nanosheets,with the band gap of about 1.75 e V,has excellent photocatalytic activity and been reported in our research group.It can effectly degrade some organic pollutants such as the organic dye methyl?MO?and antibiotic tetracycline?TC?under visible light illumination.However,it still have some shortcomings such as poor cycle stability and low separation efficiency of the photo-generated carries,which limit it further application.Aiming at solve them,in this work,some strategies such as doping ions,changing morphology and constructing the semiconductor composites,have been used to change the micro-structure and then improve its photocatalytic performance.Many In_2.77S₄-based photocatalysts with excellent photocatalytic performance have been developed and the proper photocatalytic degradation mechanism of the samples has also been discussed.This work contains the following three parts.?1?Stdudy on the preparation,performance and mechanism of Sn-doped In_2.77S₄photocatalysts.The Sn-doped In_2.77S₄ photocatalysts were synthesized by one-step hydrothermal method.The structure,microstructure,optical properties,chemical valence,and electrochemical properties of Sn-doped In_2.77S₄ were analyzed by using X-ray diffraction?XRD?,transmission electron microscope?TEM?,ultraviolet-visible diffuse reflection spectrum?UV-vis DRS?,X-ray photoelectron spectroscopy?XPS?and electrochemical workstation,respectively.Moreover,the possible photocatalytic mechanism of the as-prepared composites was discussed.The experimental results exhibit that the morphology of In_2.77S₄ has not been changed significantly after doping Sn.Under the visible light irradiation,the photocatalytic degradation efficiency of as-developed composites for TC solution is obviously affected by the doping content of Sn.As it increased,the photocatalytic degradation efficiency of the samples is firstly increasing and then decreasing.When the theoretical molar ratio of Sn to In is 0.04:1,the photocatalytic efficiency of the as-prepared Sn-In_2.77S₄photocatalyst shows the maxium of 87.4%in 20 min,which is 48.2%higher than that of pure In_2.77S₄.The possible reason for this improvement is that the separation efficiency of the photo-generated carries of the hybrids has been improved.In addition,the holes are the main active species in the photocatalytic reaction process,and followed with superoxide radicals and hydroxyl radicals.?2?Stdudy on the the preparation,performance and mechanism of flower-like In_2.77S₄/BiVO₄ composite photocatalysts.The flower-shaped In_2.77S₄ was prepared by using polyvinylpyrrolidone?PVP?as the surfactant during a hydrothermal process.Basing on this,the flower-like In_2.77S₄/BiVO₄ composite photocatalyst was constructed.The influences of the ratio of raw materials on the physical and chemical properties of the composite photocatalyst were discussed.And the photocatalytic performance of the samples was assessed by using TC dilute solution.The experimental results show that the degradation efficiency of as-prepared composite photocatalysts for TC solution is higher than that of In_2.77S₄ and BiVO₄.As the countent of BiVO₄ increased,the photocatalytic performance of the as-synthysized composite is firstly increased and then decreased.Among the samples,In_2.77S₄/BiVO₄-15 has the best photocatalytic efficiency,which can degrade 88%TC solution in 90 min.Compared with pure In_2.77S₄ and BiVO₄,it enhances by 26.9%and 37.3%,respectively.In addition,the cyclic stability of the sample is also improved obviously.After degradation for 5 cycles,the photocatalytic degradation efficiency of the as-prepared hybrids is 86.9%.The enhancing photocatalytic performance of as-prepared composite photocatalyst is attributed to the matching band structure of In_2.77S₄ and BiVO₄,which can improve the separation efficiency of photogenerated carriers.The holes are the main active species during the photocatalytic reaction process.?3?Study on regulating the morphology and photocatalytic performance of In_2.77S₄.The flower-spherical-like,band-like and fold-like In_2.77S₄photocatalysts were prepared by using PVP and hexamethylene tetramine?HMTA?as the surfactant during a hydrothermal process.The structure and properties of as-prepared In_2.77S₄with different morphology were then characterized with using XRD and TEM.The photocatalytic degradation efficiency of the as-prepared flower-spherical-like In_2.77S₄was evaluated by using TC,oxytetracycline hydrochloride?OTC?,norfloxacin?NOR?,levofloxacin?LEV?and potassium dichromate?Cr?VI??dilute solution.The experimental results exhibites that the as-prepared flower-spherical-like In_2.77S₄has obvious photocatalytic activity for above mentioned pollutants.For example,it can respectively degrade 61.1%,46.7%,50%,55.3%and 86.6%for TC,OTC,NOR,LEV and Cr?VI?ions in 90 min,which show a low selectivity to pollutants.