Establishing A New Hot Electrons Transfer Channel By Ion Doping In Plasmonic Metal/Semiconductor Photocatalyst

In the past decades,semiconductor-based photocatalysis has been received considerable attention due to its great potential to address the increasingly serious environmental pollution and energy crisis.The basic photocatalytic process relies on the interband excitation of electrons through absorbing the renewable solar energy.However,due to the wide bandgaps of most semiconductors and severe carrier recombination,the actual conversion efficiency of photocatalysis is very low.Coupling metal nanoparticles showing surface plasmon resonance(SPR)effect with traditional a wide bandgap semiconductor is an efficient strategy to improve the performance of photocatalyst including photoresponse and the carrier separation efficiency.During the decay of free electrons' collective oscillation,the plasmon-excited hot electrons could inject into the conduction band of adjacent semiconductor and prolong the lifetime of charge carriers.However,the Schottky barrier formed at the metal/semiconductor interface significantly hinders the injection of hot electrons,and the lifetime of hot electrons limits within hundreds of femtosecond due to the electron-electron scattering and electron-photon scattering occurring at the metal surface.Therefore,improving the efficiency of hot electrons injection is the key to enhance the performance of plasmonic metal/semiconductor photocatalysis.Herein,we established a new channel for hot electrons transfer by introducing Fe doping level in TiO2 to form an Ag/Fe-TiO2 plasmonic metal/semiconductor system,which dramatically improves the degradation rate of RhB solution.Also,we innovatively utilized synchrotron radiation X-ray Absorption Near Edge Structure(XANES)spectroscopy under three irradiation conditions offering direct experimental to obtain the L-edge of Ti and Fe,which unvails the mechanism of hot electrons injection in Ag/Fe-TiO2 system.Combined with the results of X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,ultraviolet-visible diffuse reflection absorption spectrum and first-principles calculation,the structure-activity relationship of Ag/Fe-TiO2 photocatalyst was established.The results show that the impurity energy level introduced by Fe ion doping not only narrows the bandgaps of TiO2 and improves the absorption in the visible region,but more importantly,it creates a new channel for the hot electrons migration induced by Ag nanoparticles.The channel effectively improves the injection efficiency of hot electrons,prolongs the life of the electrons,and significantly improves the performance of the photocatalyst in the visible light photocatalytic degradation of RhB.This dissertation is divided into four chapters as follows:The first chapter is the introduction.Firstly,it introduces the basic principle of semiconductor-based photocatalysis.Then it also introduces the principle of surface plasmon resonance and its effects on photocatalysis.At last,the purpose and content of this dissertation are introduced.The second chapter is the experimental section.The experimental details such as sample preparation,characterization instruments and photocatalytic activity measurement in this paper are detailed.The third chapter is the result and discussion.It comprehensively analyzed the results of the X-ray diffraction,X-ray photoelectron spectroscopy,transmission electron microscopy,ultraviolet-visible diffuse reflection absorption spectrum,XANES and visible light photocatalytic degradation of rhodamine B,revealing the structure-activity relationship of hot electrons transfer mechanism and photocatalytic enhancement in the Ag/Fe-TiO2 photocatalyst system.The fourth chapter is the summary and outlook.The contents and results of this work are concluded and further research works are looked ahead.