Design Of Bismuth Subcarbonate-based Materials For Enhanced Photocatalytic Activity

It is crucially important to create environmentally-friendly technologies for the sustainable development of society.Sunlight is seen as a highly clean and sustainable energy resource,and it is one of the direct ways to tackle energy and environment issues.Photocatalysis,which could directly use sunlight,has attracted people's attention.It can be utilized in many environmental and energy processes,among which,photodegradation receives a lot of attention of scientists.Recently,bismuth-containing photocatalysts have been widely employed in the field of environmental photocatalysis,among which,?BiO?₂CO₃ is used to drive photocatalytic NO and organic pollutants removal because of layered structure,good stability and non-toxic nature.Similar to many photocatalysts,?BiO?₂CO₃ cannot absorb light with longer wavelength and separate charge carriers easily,so it is of great importance to find some proper ways to enhance the photoactivity of?BiO?₂CO₃,thus being good for theories and applications.We mainly use S,N:GQDs to modify the?BiO?₂CO₃ and post modification methods to improve the photocatalytic property.This thesis mainly deals with the following three parts:1.The performance of composite photocatalysts?S,N:GQDs/?BiO?₂CO₃?can be tuned by changing the amount of the S,N:GQDs.The structure,optical and electrical property of the composite material can be determined by a series of characterization methods.According to photo?electro?chemical tests,S,N:GQDs can be used to separate the carriers.Since S,N:GQDs have peroxidase mimetic property,it can transform the H₂O₂ generated in the photocatalytic processes to strong oxidant?^·OH?.Because of these fantastic properties,S,N:GQDs/?BiO?₂CO₃ material can produce more ROS to degrade RhB,TC and BPA.Degradation experiments demonstrate that the optimal S,N:GQDs/?BiO?₂CO₃ catalyst can remove 81.7%of RhB,85.2%of TC within 2 hours and 86.8%of BPA within 2 hours.2.We use metal chloride,such as SnCl₂,to partially etch?BiO?₂CO₃,resulting in heterojunction and cation doping.Compared with the sample produced by HCl etching method,this novel method could improve light absorption and separation of electron-hole pairs simultaneously,which is better for activating molecular oxygen and ROS production.From the results of H₂O₂,^·O₂^-production and RDE experiments,this unique etching method could improve the one-electron and two-electron reaction.Owing to the formation of heterostructure,the e^--h+pairs could be effectively separated,thus resulting in the one-electron reaction to^·O₂^-;doping could induce the formation of Sn²⁺/Sn⁴⁺redox couple,which promotes the two-electron reaction to H₂O₂.The partially etched?BiO?₂CO₃?Sn:BiOCl/?BiO?₂CO₃?has better performance for RhB,TC and BPA removal under visible and UV light thanks to the increased ROS generation.Degradation experiments demonstrate that the Sn:BiOCl/?BiO?₂CO₃catalyst can remove 98.2%of RhB,81.8%of TC within 2 hours and 81.6%of BPA within 5 hours under visible light;it can also remove more than 90%of RhB,TC and BPA under UV light.3.Since?BiO?₂CO₃ is very sensitive to high temperature,we could introduce narrow bandgap semiconductor Bi₂O₃ by calcining itself to improve light absorption and separation of electron-hole pairs.RhB degradation experiments demonstrate that the sample prepared at 350°C is Bi₂O₃/?BiO?₂CO₃.The Bi₂O₃/?BiO?₂CO₃ sample has the best activity,displaying that it can degrade 53.4%of RhB.According to XRD,the sample prepared at 400°C is Bi₂O₃.The Bi₂O₃/?BiO?₂CO₃ sample could generate more superoxide ion by^·O₂^-measurements experiments,demonstrating that heterostructure formation could induce more ROS.