Synthesis Of Bismuth Oxychloride Supported Single-atom Iron And Its Photocatalytic Degradation Performance Of Organic Pollutants

The development of human society and the process of industrialization often comes at the cost of environmental destruction and pollution.Water pollution is one of the most serious environmental problems facing human sustainable development.Organic pollutants are important parts of water environmental pollution.Most organic pollutants have the "three causes" effects of "carcinogenic","teratogenic",and "mutagenic",after entering the water body,it will be enriched with the food chain and seriously threaten the health of organisms.Therefore,it is urgent to explore the technologies with high-efficiency organic pollutant treatment in water bodies.As one of the advanced oxidation methods(AOPs),semiconductor photocatalysis technology can use clean solar energy to generate high-energy free radicals to effectively degrade a variety of common organic pollutants in water bodies.And compared to other advanced oxidation technologies,photocatalysis has the advantages of high efficiency,low energy consumption,low pollution,green and environmental protection mild,reaction conditions and wide application range.However,the common semiconductor photocatalysts still have problem of low catalytic efficiency,among them,the recombination of photo-generated carriers is an important factor that restricts it’s reaction efficiency.Therefore,it is very significant to design and synthesize photocatalytic system which with high photo-generated charges separation efficiency for the effective degradation of organic pollutants in water.This study starts with single-atom catalysts and surface oxygen vacancies of semiconductor.We loaded single-atom iron on the different exposed surface of BiOCl,and created surface oxygen vacancies.The aim is to study the effect of single-atom iron for oxygen vacancies produced of BiOCl and its role in degradation of pollutants.Experiments found that the single-atom iron can improve photocatalytic degradation pollutants performance of BiOCl in water,and further explored the path,possible mechanism of photocatalytic degradation of organic pollutants after the introduction of single-atom iron.This article provides ideas for the design of new high-efficiency photocatalytic system.It mainly includes the following two parts:1.To study the formation of oxygen vacancies,the photochemical activation of molecular oxygen and photocatalytic degradation of p-chlorophenol(4-CP)after the introduction of single-atom iron on the surface of BiOCl(001).BiOCl has the advantages of low toxicity,wide distribution of constituent elements,stable optical and chemical properties,but the wide band gap(about 3.2 eV)and narrow spectral response range,which directly affect its photocatalytic activity and application.In order to improve the photocatalytic performance of BiOCl,we designed to load single-atom iron on the BiOCl(001)surface and create surface oxygen vacancies(denoted as:Fe/BOC-001-OV).We used it for the photocatalytic degradation of p-chlorophenol,a common chlorophenol organic pollutant in water.Experiments found that the performance of photocatalytic degradation of 4-CP after loading single-atom iron is improved.We explored the stability of catalysts,the active species during reaction process,adsorption and activation of molecular oxygen,the possible intermediate products of 4-CP degradation,and separation efficiency of photo-generated carriers.The results showed that the introduction of single-atom iron improved the catalysts stability,the ability of adsorption and activation molecular oxygen and the separation efficiency of photo-generated charges.To figure out the relationship between catalyst performance and structure of catalysts,we used DFT and multiple material characterization methods to investigate the catalyst structure.The results showed that the Fe/BOC-001-OV is easier to produce surface oxygen vacancies,and oxygen vacancies are the main molecular oxygen adsorption and activation centers.The higher oxygen vacancies concentration on the surface of Fe/BOC-001-OV enhanced its ability to activate molecular oxygen,which improved its ability of photocatalytic degradation of 4-CP.2.The study in the first part showed that the single-atom iron on the BiOCl(001)surface improved the surface oxygen vacancies formation capacity and photo-generated carriers separation efficiency,which enhanced its ability of photochemical activation molecular oxygen for degradation of 4-CP.According to literature reports,BiOCl possesses surface structure-dependent photochemical molecular oxygen activation properties under light.The key scientific problem of this research is exploring the photochemical molecular oxygen activation after loading single-atom iron on different exposed surface of BiOCl.Therefore,in the second work,we supported single-atom iron on the BiOCl(010)surface and created oxygen vacancies(denoted as:Fe/BOC-010-OV).We used it for photocatalytic degradation of sulfa antibiotics sulfamethazine(SM2)in water.Experiments found that the performance of photocatalytic degradation of SM2 after loading single-atom iron was significantly improved.We explored the stability of catalysts,the active species of reaction process,the activation of molecular oxygen,the possible intermediate products of SM2 degradation,and the separation efficiency of photo-generated carries.The results showed that the introduction of single-atom iron improved the stability of catalysts,the ability to adsorb and activate molecular oxygen and photo-generated charges separation efficiency.The study of mechanism showed that these promotion effects are because of the catalysts is easier to produce surface oxygen vacancies after loading single-atom iron,and oxygen vacancies are the main molecular oxygen adsorption and activation centers.This study clarified the interaction between oxygen vacancies and single-atom iron,and provided new ideas for the application of single-atom catalysts and the design of high-efficiency photocatalysts.