Design And Synthesis Of Polymetallic Selenide Based High-Efficiency Photocatalyst

At present,the world's main energy supply is still fossil fuels,but the use of fossil fuels has brought many problems.How to solve the problem of depletion of fossil fuels and the environmental problems caused by fossil fuels have been major problems facing researchers since the 20 th century One of the challenges.At present,there are many renewable and non-renewable ways to obtain energy to alleviate the crisis of fossil fuels.The currently available ways of obtaining energy are hydrogen,nuclear,wind,tidal,geothermal and so on.Hydrogen energy stands out from many energy sources due to its high heating value,wide sources,environmental protection and harmlessness,and excellent combustion performance.At present,the acquisition of hydrogen energy still depends on fossil energy,and the cost is relatively large.Finding feasible ways to obtain hydrogen energy is also a problem that researchers need to solve urgently.Photocatalysis of water using solar energy as a light source is one of the important methods for obtaining hydrogen energy.However,semiconductor photocatalytic materials have the problems of carrier recombination,low quantum efficiency,and narrow light response range,which are the problems that researchers currently need to solve.Therefore,solving the above problems is the driving force for scientific researchers.CdSe crystal is an n-type semiconductor material with excellent band gap in the range of1.65 eV to 1.8 eV.It has two stable crystal structures of sphalerite and wurtzite,and other inorganic or organic materials have unique optical properties compared to sensors,solar cells,bio-fluorescent probes,and catalysis.They are widely used because of the small size,large specific surface area,strong light response,and uniqueness of cadmium selenide materials.Excellent electronic properties.Based on these excellent properties,cadmium selenide has become a research hotspot in the field of photocatalysis.Therefore,in the first chapter,this article expounds the development status and development trend of photocatalytic hydrogen-producing materials in recent years.At the same time,it briefly introduces the advantages of cadmium selenide photo as a photocatalyst,the preparation method and how to improve the photocatalytic activity.In the second chapter,an aqueous solution method was used to synthesize cadmium selenide nanomaterials with mercaptopropionic acid?MPA?as a modifier,and MPA-CdSe photocatalytic hydrogen-producing materials were obtained.The method is simple to prepare,the raw materials are cheap,and the participation of explosive and highly toxic reagents in the traditional synthesis method is reduced.Based on MPA-CdSe synthesis,PEG-CdSe photocatalytic hydrogen-producing materials were obtained by adding polyethylene glycol?PEG?.By analyzing the structures and morphologies of MPA-CdSe and PEG-CdSe,the two catalysts were compared under visible light.The types and amounts of different sacrificial agents?electron donors?,types and amounts of co-catalysts,hydrogen production performance under various conditions and catalytic environment,and their catalytic stability.It was found that PEG-CdSe was promoted by NiCl₂·6H₂O.Using ethanol as a sacrificial agent,it has a higher catalytic hydrogen production effect and better stability than MPA-CdSe in a near-neutral environment.The comparison of UV-Visible light test,fluorescence test,impedance and photocurrent test explored PEG-The reason for the high hydrogen-producing activity of CdSe.In the third chapter,based on the synthesis of MPA-CdSe in Chapter 2,W₁₈O₄₉9 was added by in situ growth method to obtain W₁₈O₄₉-CdSe complex.By controlling the ratio of W₁₈O₄₉9 to MPA-CdSe during the synthesis,different ratios of composites were obtained.By comparing the hydrogen production effect of W₁₈O₄₉-CdSe composite with single-phase MPA-CdSe under full light,and without the help of cocatalyst and sacrificial agent,the synthesized hydrogen production effect of W₁₈O₄₉-CdSe composite is MPA-CdSe This is mainly due to the formation of a Z-type photocatalytic system between W₁₈O₄₉9 and MPA-CdSe,which promotes the separation of electrons and holes.