Element-Doping-Mediated Regulation Of Photogenerated Charge Carrier Behaviors In Layered Bismuth Oxide Based Photocatalysts

In the 21st century,as the economy grows and productivity increases,the consumption of fossil fuels is increasing day by day.However,the exploration and use of renewable energy sources has drawn much attention and research since the nonrenewable nature of fossil fuels has caused a significant energy dilemma.Solar energy,as a clean energy source,is the most economical and cleanest infinite energy source.Using solar energy to drive the selective synthesis of organic compounds with added value can reduce the consumption of non-renewable fossil energy,which is important to solve the global energy crisis,and therefore has been the focus of scientists’ research.In order to realize the above reactions,it is of utmost importance to design efficient photocatalysts to improve the photocatalytic reaction activity and achieve the conversion of solar energy to chemical energy under relatively mild conditions.It is well known that the photocatalytic activity of semiconductor photocatalysts is strongly related to the carrier behavior,and therefore the behavior modulation of carriers can directly affect the catalyst activity.Based on this,this paper uses elemental doping to modulate the semiconductor energy band structure to obtain a higher concentration of photogenerated carriers and further enhance the photocatalytic activity.The purpose of this thesis is to study bismuth oxy-semiconductor materials and to modulate the photogenerated carrier behavior in semiconductors by affecting the energy band structure of semiconductors through elemental doping.It is demonstrated that vanadium doping can effectively suppress the capture of surface-state mediated carriers in the system and copper doping can effectively suppress the recombination of photogenerated electron-hole pairs in the semiconductor by various testing and characterization methods.Thanks to these results,higher photogenerated carrier concentrations were obtained,and therefore higher photocatalytic activity in selective aerobic oxidation was also achieved.The main research of this thesis is as follows:1.Elemental doping inhibits surface-state-mediated charge carrier trapping for promoting photocatalytic selective oxidation:The surface-state-mediated capture process is the main depletion pathway of photocatalytic carriers and sometimes plays a detrimental role in obtaining efficient photocatalytic solar energy utilization.In this paper,we use Bi2O2CO3 as a typical prototype and highlight that vanadium doping can effectively suppress the surface-state-mediated carrier capture in the system.Based on spectroscopic analysis and theoretical calculations,we attribute this suppression to the presence of shallow trap states near the band edge caused by vanadium doping.Compared to the surface states,these vanadium-doped induced states can trap photoinduced carriers,while their shallow character favors carrier untrapping.Thanks to these properties,vanadium-doped Bi2O2CO3(V-Bi2O2CO3)exhibits good performance in photocatalytic molecular oxygen activation and selective aerobic oxidation of organic compounds.This work provides an effective method for suppressing surface-state mediated deleterious carrier capture in semiconductor photocatalysis.2.Regulation of Bi2WO6 energy band by Cu doping and activation of oxygen molecules:excitation and transfer of carriers in the photocatalytic process is a key factor to promote the photocatalytic reaction.In this paper,we take Bi2WO6 as a prototype and emphasize that copper doping can modulate the semiconductor energy band structure to effectively reduce the compounding efficiency and increase the concentration of photogenerated carriers.Based on the spectral analysis,we find that copper doping tends to p-type doping,and the defective attitude induced by doping can increase the carrier separation efficiency and reduce the complex efficiency of photogenerated electron-hole pairs to obtain a higher carrier concentration under light conditions.Thanks to these properties,copper-doped Bi2WO6(Cu-Bi2WO6)shows good performance in photocatalytic selective aerobic oxidation.This work provides an effective method for suppressing photogenerated electron-hole pair complexation.