Preparation And Study On Photocatalytic Hydrogen Precipitation Performance Of Layered Double Hydroxide (Bimetallic Oxide) High-efficiency Photocatalysts

With the increasing update of science and technology,the development process is often accompanied by problems such as environmental pollution and ecological damage.Therefore,people have paid great attention to new and pollution-free new energy sources.Among them,photocatalytic technology can convert solar energy into chemical energy such as hydrogen energy through photoelectric conversion,and has a good application prospect.Photocatalytic technology is a green,energy-saving and environmentally friendly technology.In the process of photocatalytic water splitting to generate hydrogen,the participation of semiconductor catalytic materials is essential.The core of photocatalytic water splitting to generate hydrogen is the preparation of photocatalyst.With the development of physics,chemistry and materials science,the improvement of synthesis methods,and the emergence of a large number of advanced characterization and detection methods,new progress has been made in the research of photocatalytic water splitting to generate hydrogen.The preparation of new composite photocatalytic materials helps to significantly improve the activity of monomer catalysts.In order to promote the effective separation of photogenerated carriers,this subject Layered Double Hydroxide（bimetallic oxide）with metal semiconductors.By regulating the transfer path of electrons,different types of heterojunctions are constructed,so that the photocatalytic activity of the composite material is improved.The main work content is as follows:（1）The composite photocatalyst was prepared by a hydrothermal method,consisting of spherical CoS_x and layered nanosheets of MgAl-LDH,the hydrogen production rate was5120μmol/g/h.The composite photocatalyst not only retained the advantage of high utilisation of visible light by CoS_x,but also effectively prevented photocorrosion caused by sulphide,and effectively avoided the complexation of photogenerated electron-hole pairs,showing good photocatalytic activity and stability.（2）The p-n heterojunction constructed by the layered nanosheet MgAl-LDH and the metal-semiconductor material Co₃O₄ was further explored.The construction of the heterojunction allowed the generation of an internal electric field on the surface of the material,which accelerated the transport of photogenerated carriers and thus improved the photocatalytic performance of the material.Through the optimization of the system,the hydrogen production reached 140μmol in 5h when the addition amount of the composite catalyst was 0.01 g,showing good visible light response and photoelectrochemical performance,as well as efficient and stable hydrogen evolution performance.（3）Ni Al-LDH was prepared by changing the composition of the cations in the bimetallic hydroxide through the addition of different drugs,and the S-scheme heterojunction of Mo S₂ with Ni Al-LDH in nanoflower form was constructed by electrostatic adsorption.The hydrogen production rate of the composite catalyst is 4590μmol/g/h,which significantly improves the photocatalytic activity of the composite catalyst compared with the monomer catalyst.（4）The combination of ultrasound and electrostatic force enabled the successful coupling of ZnCo₂O₄ and CdS semiconductors by electrostatic self-assembly,and effectively avoided the serious phenomenon of sulfide photocorrosion.Under the condition of simulating sunlight irradiation,the composite catalyst showed good photocatalytic activity,and the hydrogen production rate reached 16142μmol/g/h.Combined with the position of the valence band and the XPS data,it can be concluded that the composite catalyst formed an S-scheme heterojunction induced by the built-in electric field at the contact interface,resulting in a significant increase in photocatalytic activity.（5）By electrostatic self-assembly,NiCo₂O₄ and CuS were coupled,and the S-scheme heterojunction induced by the internal electric field was successfully constructed.At the same time,under the simulated visible light irradiation,the complex catalyst can quickly decompose the aqueous solution of triethanolamine to produce hydrogen at the rate of3600μmol/g/h.The composite catalyst showed high photocatalytic activity and long-lasting and efficient hydrogen production.Through the study on the photogenerated carrier separation and transfer of the catalyst.The results show that the composite catalysts can accelerate the separation and transfer of photogenerated carriers,allowing them to participate in the photocatalytic reaction more quickly.