Preparation And Photocatalytic Properties Of Bismuth Based Photocatalysts

In recent years,due to the rapid development of industry,the excessive use of fossil fuels has resulted in excessive waste water and carbon dioxide emissions.In response to the strategic goals of"carbon peaking"and"carbon neutrality"proposed by the state,and to better achieve environmental pollution control,photocatalytic technology came into being.Photocatalytic degradation technology can use sunlight and photocatalysts to degrade organic pollutants to produce non-toxic and harmless water and carbon dioxide;photocatalytic carbon dioxide reduction technology can convert carbon dioxide into solar fuel using solar irradiation and high-efficiency photocatalysts,which has important implications for energy sustainability and"carbon neutrality".Among many photocatalysts,bismuth-based photocatalysts stand out due to a series of excellent properties,such as a suitable energy band structure,stable physicochemical properties,and abundant existence on earth and so on.However,due to the faster recombination of bulk carriers and fewer active sites,the photocatalytic activity is affected.Therefore,many methods have been explored to solve these problems,such as morphology control,construction of heterostructures,construction of defects,ion doping,introduction of plasmonic effects,etc.This dissertation takes bismuth-based catalyst as the research object,and systematically expounds how to improve the photocatalytic degradation and photocatalytic carbon dioxide reduction ability and stability of the system by means of interfacial recombination,surface modification and defect engineering.The specific research contents are as follows:1.In this study,Bi VO₄-based semiconductor products were synthesized by hydrothermal method and self-deposition method.Firstly,block Bi VO₄ was synthesized by hydrothermal method using ammonium metavanadate and bismuth nitrate pentahydrate as precursors,and then Ag₃VO₄ was grown in situ by self-deposition method to form S-scheme heterojunction Bi VO₄/Ag₃VO₄ composite.The results of degradation performance,photocurrent,and XPS showed that the introduction of Ag₃VO₄ can form a special structure in line with the S-scheme charge transfer mechanism with Bi VO₄,which can effectively promote the separation of photogenerated electron-hole pairs on the interface contact surface and have high redox potential,so that the photocatalytic system with S-scheme charge transfer mechanism has strong redox energy,so as to improve the performance and stability of photocatalytic degradation.2.The plasma effect of metals is widely introduced into the photocatalytic system because of its special optical properties to improve the charge transfer ability.In this study,Bi₂Mo O₆ with high stability and high oxidation ability was synthesized by ordinary hydrothermal method.Then,by adding organic solvent DETA,α-Mn S with strong redox ability was synthesized in situ to formα-Mn S/Bi₂Mo O₆（M/BMO）with strong redox ability;Further,we added an appropriate amount of glucose during the synthesis process to reduce Bi in situ to form Bi-M/BMO with plasmonic resonance effect.The plasmonic effect of Bi can effectively absorb visible light and generate a large amount of plasma,which can promote the charge separation efficiency of the system,and further improve the photocatalytic carbon dioxide reduction performance of the Bi-M/BMO composite.3.Surface engineering and defect engineering have been widely introduced into the photocatalytic system by many researchers because they can up-regulate the optical and electrical properties of photocatalysts from primitives.In this study,we used a cell crusher to peel off the pre-synthesized Bi spheres,and passed through a high-speed centrifuge for multiple centrifugations to obtain an ultrathin two-dimensional structure—Bismuthene.Then we introduced oxygen vacancies into Bi₂Mo O₆ during the synthesis of ultrathin nanosheet self-assembled nanoflowers Bi₂Mo O₆ by adding glyoxal（OVs-BMO）.By adding an appropriate amount of Bismuthene,OVs-Bi/BMO with Ohmic contact was synthesized.Due to the dielectric effect and electron trap effect near the oxygen vacancy,the transferred electrons can be greatly increased;Ohmic contact can realize nearly zero resistance charge transfer between Bismuthene and OVs-BMO,which can effectively promote the charge transfer efficiency,so as to further promote the improvement of catalytic activity and stability.