| With the development of human society economy and the increase of people's living standard,the demand for resources and energy of people quickly increased.And with the consumption of resources and energy,environmental pollution problems are becoming serious.The problem of energy shortage and environmental pollution caused by people,get more and more attention of people.As the largest developing country,our country was badly in need of solving the current severe energy shortage and environmental pollution.That is important for the sustained and rapid development of national economy of China.In many of the emerging clean energy sources,hydrogen has a high calorific value,which produces about three times as much heat as gasoline and 4.5 times as much as coke.The hydrogen itself is nontoxic,and the product of hydrogen combustion is water,which does't pollute the environment.Hydrogen can be regarded as the most potential clean energy in the 21st century.There is a method of using solar energy to convert the solar energy into chemical energy,which can decompose water into hydrogen.In the process of photochemical decomposition of hydrogen,only the sun and water are needed,and no pollutants are produced during the reaction process.Photoelectrochemical hydrolysis has a high theoretical conversion efficiency,and its theoretical can reach 30%,which is practical significance to solve the future energy crisis.It is well known that the photoconversion efficiency of hydrolysis of semiconductor photoelectrode is mainly determined by the light absorption of the photoelectrode,the separation efficiency of bulk in the semiconductor and the separation efficiency of the interface.It is very important to improve the bulk and interface separation efficiency of photoelectrochemical water splitting.In recent decades,people have done a lot of research on light absorption of photocatalysis materials,which have made great progress in photocatalysis materials.The optical absorption range of photocatalysis materials has been extended to the whole spectrum.Therefore,light absorption is not the main problem that restricts photochemical decomposition of hydrogen.Compared with the improvement of light absorption,the bulk separation efficiency and interface separation efficiency of photoelectrode are still at a low level.It is the main factor that restricts the efficiency of light conversion,and it seriously affects the further development of photochemical hydrolysis.Therefore,in order to deal with the problem of low carrier separation efficiency in photoelectrochemical hydrolysis optical conversion,it is the focus of photocatalytic research to further improve the separation efficiency of the bulk and interface of the photon-generated carrier.It is significant to further improve photoelectric conversion efficiency and promote the development of photocatalytic technology and practical life.The common reasons for the low bulk carriers separation of photocatalysis are as follows:the photoelectrode has a poor conductivity,which impedes the transmission of the photogenerated carriers;the photoelectrode has a high defect concentration,which makes the photogenerated carrier easy to compound at the defects;the carrier has a long diffusion distance and is not conducive to transmission and so on.Photogenerated carriers with low interface separation efficiency is mainly ascribe to the low water oxidation reaction rate constant,high water oxidation reaction barrier and the holes transition from electrode surface to the electrolyte difficultly.In this paper,the bulk separation efficiency and the interface separation efficiency of photoelectrode are improved by changing the surface morphology of the photoanode,doping cobalt and oriented growth.The specific research content is as follows.In the first chapter,the mechanism of photochemical decomposition water is introduced firstly,and the influence factors,application and recent development of photoelectrochemical hydrolysis are briefly introduced.Besides,the current research status and existing problems of photoelectochemical hydrolysis are summarized.In the second chapter,adding pore maker in the process of preparing BiV04 phtoanode improve the bulk and interface separation efficiency,and improve the photoelectric performance of the material.It was found that the special morphological appearance formed after adding pore maker in can effectively improve the current density of the photoelectrode.With the addition of pore maker,mesporous holes are formed on the nanoparticles of the reticulated porous structure,which can promote the separation and transmission of photogenerated electrons and holes respectively.The larger size particles reduce the number of grain boundaries and can effectively promote the transmission of photogenerated electrons to the surface of FTO glass.The mesoporation formed on the surface of nanoparticles can have good contact with the electrolyte and effectively shorten the transmission distance of the hole.The mesoporation formed on the surface of nanoparticles can possess good contact with the electrolyte and effectively shorten the transmission distance of the holes.In addition,In addition,the photoelectric hydrolysis performance can be further improved bydoping Mo in the porous photoelectrode and the further loading of the co-pi catalyst on the surface of the optical electrode.This work puts forward a new way,that adding pore maker in the precursor of BiV04 photoanode.And this way can further improve the photoelectric performance of photoelectrode,promote the development of photoelectrochemical water splitting and practical application.In the third chapter,the separation efficiency was studied by adding metal organic cobalt ions in the precursor solution to fabricate Bi VO4 photoanode.It is found that the photoelectric current density of the photoelectrode can be improved effectively by Co3+and Co2+ doping BiVO4 photoelectrode.At the same time,the structure,morphology and optical properties of BiV04 photoelectrode doped with cobalt ions were characterized.It is found that doping cobalt in BiVO4 photoelectrode can effectively improve the separation efficiency of photogenerated carrier and improve the efficiency of photoelectric conversion.Doping cobalt in photoanode possess the similar properties with loading Co-Pi on the surface of photoanode.Cobalt ion doping can better scattered in the photoelectrode and exists in the paotoanode with the form of CoOx.That reduces the defect on the surface of the electrode,reduces recombination on the interface,and improve the transmission of the carrier.In the forth chapter,this paper summarizes the main content and innovation points of the thesis,analyzes the problems of the current work,and plans the next work contents.Through the above study,this paper can effectively promotes the photochemical carrier separation in the process of photoelectrochemical water splitting by controlling the morphology,doping and crystallization of the BiVO4 photoelectrode.That improves the activity of the photoelectrochemical water splitting,and provides a new preparation method and design for the design and preparation of high efficiency photoelectrochemical water splitting of the photoelectrode.It is of great significance to promote the development of Photoelectrochemical water splitting technology and its practical application. |
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