Study On Preparation And Photocatalytic Degradation Of Organic Pollutants Of ZnO Composite Materials

The traditional n-type semiconductor Zn O has a good application prospect in the field of photocatalysis due to its excellent photoelectric performance and low cost.However,the Zn O band gap width is 3.37 e V,which can only be excited in the UV light band（λ<400 nm）to get electrons and holes,while UV light only accounts for less 5%of the total solar energy,which greatly reduces the efficiency of solar energy utilization.In addition,Zn O photogenerated electron-hole recombination easily occurs during the migration process,which greatly limits the photocatalytic activity of Zn O.Therefore,in order to improve the photocatalytic efficiency of Zn O,Ag₂O/Zn O,Ag/AgCl/Zn O and Zn O/ACF composites were prepared in this paper.The effects of different reaction systems on the structure,morphology,optical properties and photocatalytic performance of the materials were studied.The main work of this article is as follows:1.The Ag₂O/Zn O heterostructure was prepared by a simple hydrothermal method,and the compounding of wide bandgap semiconductors and narrow bandgap semiconductors was achieved.The control of the reaction concentration and temperature was used to study its effect on structure,morphology,optical properties,and photocatalytic performance.The mechanism of photocatalytic degradation of Ag₂O/Zn O heterostructure was studied.The experimental results show that when the reaction temperature is fixed at 120℃and the Ag⁺/Zn²⁺molar ratio is 2:8,the S3 sample has the best photocatalytic activity under UV light,the degradation rate of the MO solution can reach 98.4%under UV light irradiation 100 min.Simultaneously,the photocatalytic degradation efficiency of single-phase Zn O is only 18.3%under the same experimental conditions.The S4 sample with Ag⁺/Zn²⁺molar ratio of 4:8 has the best photocatalytic activity under visible light,it can degrade 97.1%of MO molecules under 200min visible light irradiation.After 5 cycles of degradation experiments,its phase structure and photocatalytic activity did not change significantly,and the degradation rate of MO solution could reach 88.3%,indicating that Ag₂O/Zn O has good stability under visible light.By exploring the photocatalytic degradation mechanism of Ag₂O/Zn O heterostructure,it was found that hydroxyl radicals（.OH）and superoxide radicals（.O₂^-）are the main active groups in photocatalytic reactions.2.Ag/AgCl/Zn O three-way catalyst with visible light response was prepared by photoreduction using Zn O as the carrier,silver nitrate as the silver source and dilute hydrochloric acid as the precipitant.The effects of different photoreduction times on its photocatalytic performance were studied and its photocatalytic mechanism was analyzed.The experimental results show that based on the plasmon resonance effect of Ag,the photoresponse range of the catalyst is extended to the visible light region,and with the increase of the photoreduction time,the amount of Ag generated by photoreduction of the sample increases continuously and the catalytic efficiency tends to increase first and then decrease.When the light reduction time was 15 min,the catalyst had the best degradation efficiency.The decolorization rate of the MO solution was 99.4%under the visible light irradiated 200 min.3.Zn O/ACF composite material integrating photocatalysis and adsorption was prepared by using an acidified ACF as a carrier by a dipping-water bath method,and the influence of the growth solution temperature on the properties of the composite was investigated.The results show that ACF successfully introduced groups such as hydroxyl and carboxyl groups after acid-treated,which improved the hydrophilicity of the ACF matrix and did not significantly change the micromorphology and structure of the ACF.The introduction of ACF greatly improved the light absorption capacity of Zn O and inhibited the photoelectron-hole fast recombination.The removal rate of Zn O/ACF to toluene is significantly higher than ACF matrix,and the photocatalytic activity first increased and then decreased with the increase of the temperature of the growing liquid.The Zn O/ACF（S3）composite prepared with a growth solution temperature of 80℃has the best photocatalytic efficiency.The degradation efficiency of toluene can reach 70.5%when exposed to visible light for 6 h,and the photocatalytic activity of benzene and ethylbenzene is relatively high.