| Semiconductor photocatalysis is an advanced technology that converts solar energy into chemical energy.The technology can be used in the degradation of organic pollutants,CO2 reduction,and production of fuels.It is expected to solve the problems of environmental pollution and energy shortage.However,the main problem restricting the development and application of photocatalytic technology is the lower photocatalytic efficiency.Therefore,it is urgent to improve the photocatalytic efficiency.In recent years,many studies have reported the photocatalytic performance of layered perovskite ferroelectric materials,which has attracted extensive attention.The general formula of Aurivillius layered perovskite oxide is(Bi2O2)2+(An-1BnO3n+1)2-,where n refers to the numbers of perovskite units.Such materials behave spontaneous polarization that can effectively separate free carriers.Meanwhile,the layered perovskite oxide has good visible light absorption.We chose SrBi4Ti4O15(SBTO)as the research object,and regulated its microstructure and fabricated composite materials to improve the photocatalytic performance.Applying electric field to pole the catalysts to strength ferroelectric polarization.Furthermore,esternal fields such as ultrasonic and thermal field,were utilized to suppress the shielding of static spontaneous polarization field.In a word,the effect of the built-in electric field on the photocatalytic performance has been investigated,and its mechanism has been discussed.The work are divided into the following chapters:Chapter 1:Firstly,photocatalysis and the optimization methods were introduced.Then,we described the basic characteristics and the research status of ferroelectric materials.The influence of spontaneous polarization and the external field on photocatalytic performance were discussed.Secondly,the structure and the recent research of layered perovskite materials were introduced.Chapter 2:This chapter introduced the chemical reagents,instruments and equipment involved in this paper,as well as the preparation methods of materials,the characterization methods and the photocatalytic analysis experiments.Chapter 3:We prepared the four-layer layered perovskite SBTO nanomaterials by the hydrothermal method.The effects of mineralizer concentration and hydrothermal reaction time on the morphology of samples were investigated,the optimal preparation process for SBTO was determined:the concentration of NaOH was 1.5M,and the hydrothermal reaction time was 36h.The UV-vis absorption spectra of SBTO samples were measured,and their band gap were calculated.Chapter 4:We used the post annealing treatment to regulate the oxygen vacancy concentration of the prepared samples.The result showed that the sample annealed at 650℃(650-SBTO)has the highest photocatalytic efficiency,and the degradation efficiency reached 100%within 35min.We applied the external electric field to strengthen the ferroelectric polarization.It was found that the external electric field had a positive effect on the photocatalytic reaction.In addition,the ultrasonic field was applied to inhibit the shielding effect of static spontaneous polarization.Comparing the photocatalytic performance of all samples with different oxygen vacancy concentrations,we found that the ultrasonic field can effectively improved the photocatalytic activity.We discussed the mechanism of enhancement of photocatalytic efficiency with the synergy of ultrasonic field.What’s more,the photocatalytic degradation performance of SBTO under thermal and magnetic field was also explored.Chapter 5:Ag2O particles were loaded on SBTO nanoplates by chemical precipitation to form Ag2O/SrBi4Ti4O15(A/SBTO)composites.The result showed that 15%-A/SBTO sample has the best photocatalytic effect.The photocatalytic activity of the 15%-A/SBTO was effectively improved by introducing the ultrasonic field,and its internal mechanism was discussed.The 15%-A/SBTO sample was also utilized to photo sterilization of acinetobacter baumannii(AB).Conclusion:The photocatalytic properties of SBTO was summarized. |
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