Fabrication And Photocatalytic Activity Ofa Novel Visible Light Responsivephotocatalyst

With the comprehensiveconsideration of resource,energy consumption and environmental benefits factors,it is considered the most ideal way that the solar energy is converted intohydrogen energy as the carrier of chemical energy（solar-hydrogen）process.In this process,the use of semiconductor photocatalyst by photocatalytic and photoelectrochemical water splitting is one of the most promising conversion pathways.The most core work in the process of photocatalytic/photoelectrochemical water splittingis to develop a photocatalyst with visible light response and suitable energy band structure wihch meet the needs of completely decomposed water.Sn O₂ is a kind of cheap and easily available wide band gap semiconductor material.If it can realize its visible light response,it will have important research value and practical significance.In the thesis,using Sn C l₂.2H₂O as the Sn source,the Sn O₂ photocatalysts with visible light response were prepared by hydrothermal reaction method.The photocatalytic/photoelectrochemical water splitting activity was investigated,and the photocatalytic activity and stability was improved through the load cocatalyst.This paper focuses on the development of a new type of visible light responsive photocatalyst.The experimental work has been carried out on the preparation of materials,structure characterization and photocatalytic/photochemical decomposition of water activity.The main research work and achievements are as follow:（1）Using Sn C l₂.2H₂O as Sn precursor,Sn O₂ powder with visible light response was obtained by the solvent thermal method.The absorption edge of Sn O₂samples reached 570 nm,and the band gap corresponding to 2.17 e V.The obtained samples were characterized by XRD,SEM,TG,UV-Vis and other characterization.The crystallinity,morphology and optical absorption properties of the samples were investigated under different conditions（temperature and time,drying temperature,precursor type and p H etc）.The results show that the sample obtained under this condition（dissolution of Sn C l₂.2H₂O in methanol solvent,ammonia water to regulate the p H 3.0 and then in a drying oven at 150℃crystallization 24 h.Then the results were filtered and washed,and finally dried overnight at 75℃）is the best.（2）The photocatalytic activity of the powder was tested on the self built platformunder simulated visible light,xenon lamp band band（λ>420nm）in water.The photocatalytic activity of the whole reaction in pure water,half reaction activity under electron donor（acceptor）and supported catalyst.Research results show that the whole reaction in pure water can only be produced in the whole wave band or under the visible light.This proves that that Sn O₂ has the need to meet the electrode potential of reducing water.In the case of electron acceptor,it can be made to produce oxygen half reaction,which indicates that Sn O₂ can meet the need of the electrode potential of oxidizing water.After loading the catalyst,whether in the whole reaction or semi reaction,whether the whole band or under the visible light,the hydrogen production capacity has increased significantly.The cocatalystprovides a reactive site,so that the photocatalytic activity of the catalyst is obviously improved.（3）The Sn O₂ thin films wereobtained by depositing Sn O₂ power on FTO substrate by electrophoretic deposition method in the form of three electrodes（Ag/Ag C l reference electrode,Pt electrode）,and the electrochemical decomposition of Sn O₂ electrode was tested on the electrochemical workstation.The I-T and I-V test show that:the photoelectric film prepared by photo catalytic preparation of the thin films without any further heat treatment,is not modified by any modification and supported catalyst.It shows a very clear light current under the visible light,and the photocurrent intensity is near to m A/cm².It is known that the photoelectric chemical activity can be promoted in a certain heat treatment range t hrough the heat treatment.The I-T curves show that the light anode material has a certain stability.Photoelectrochemical and photocatalytic activity showed that the prepared Sn O₂ has suitable band gap and the band edge,whichmeet the electrode potential of splitting of water needs.The visible light response mechanism is due to the divalent tin ions doping the narrowing of the band gap so that it extended to the visible region of the absorption edge in order to respond in visible light.The low price and easy to get broadband gap Sn O₂ prepared by a simple and easy method in this research works has the visible light response characteristic.