Study Of Metallic And Nonmetallic Plasmonic Structures Construction And Their Photocatalytic Performance

Due to the growing demands for energy and the shortage of fossil fuel,renewable energy which can be substitute of fossil fuel is expected strongly.Solar energy is an ideal renewable clean energy,therefore,its utilization is great significance for the sustainable and healthy development of human beings.Among various solar energy technologies,semiconductor photocatalysis can directly convert solar energy to chemical energy for applications of water splitting,artificial organic synthesis and environmental pollution treatment.However,the traditional semiconductor photocatalysis has two main issues:1)broad band gap and and 2)quantum efficiency.Noble metal nanoparticles?Ag,Au?generally exhibit the local surface plasmonic resonance?LSPR?optical phenomenon,and which is the free electrons oscillation under incident of light,resulting in strong light absorption.LSPR is sensitive to various parameters and can be tuned by the shape,size,composition and surrounding environment of noble metal.Therefore,LSPR can be used to broaden the light absorption of widen semiconductor in visible region,and improving their photocatalytic efficiency.By now,applications of LSPR in photocatalysis have attracted more attentions and become hot spot in research area of plasmonic photocatalysis.Noble metal have been used as important catalysts for electrochemical methanol oxidation,but most of the noble metals with high activity in catalysis show weak LSPR,while the noble metals with strong LSPR usually show weak catalytic performance.Therefore,the bimetal catalysts with high catalytic activity and strong LSPR are expected for photo-enhanced catalysis.Meanwhile,the enhancement mechanism of LSPR on catalytic performance is great significance for constructing highly efficient plasmonic photocatalytic materials.In chapter two of this thesis,Pt-Au nanodisks?Pt-Au NDs?with bimetallic heterojunction were synthesized as catalysts for photoelectrochemical methanol oxidation.Au NDs with strong LSPR is used to absorb visible-near-infrared light and enhance the electrochemical methanol oxidation?MORs?on Pt surface.Compared with the reaction in dark,the reaction rate has a three times enhancement under visible-near-infrared light.Meanwhile,the influence of different size and structure of NDs on LSPR,and the correlation of optical wavelength and current intensity were studied.It was proved that the enhancement of catalytic reaction was attributed to the LSPR of Au NDs.In addition,the mechanism of plasmonic induced hot electron transfer was studied.It was proved that the dipolar surface plasmon resonance mode?DSPR?of the Au NDs was the main channel for hot electron transfer by single particle fluorescence image and spectrumThe traditional LSPR materials are mainly noble metal with few reserves and high price,which limits the large-scale application of LSPR.Therefore,the exploration and preparation of non-metallic plasmonic materials with abundant reserves and low prices will have significant effect on the development and application of LSPR.It is found that the electronic concentration(10¹⁹-10²¹cm^-3)can also be adjusted by doping,photochemistry or electrochemistry,so that the non-metallic semiconductor can also possess LSPR.At present,among many non-metallic semiconductors,non-stoichiometric WO_3-x has attracted wide attention due to its advantages such as facile synthesis,large number of oxygen vacancies?OVs?,and intense LSPR in visible-near-infrared region.In this thesis,WO_3-x was prepared using a solvothermal method,and studied its high activity and selectivity in the dehydration of ethanol to ethylene.The effects of WCl₆ precursor with different mass concentration on the oxygen vacancy of WO_3-x,and the effects of different atmosphere and light wavelength region on the selectivity of catalytic products were analyzed.The optimized conditions show that the prepared WO_3-x-5 has strong LSPR and most oxygen vacancies.Under nitrogen and full spectrum,it has the highest catalytic activity and product selectivity in the reaction of ethanol dehydration to ethylene.Through mechanism research,it was proved that the oxygen vacancy and the LSPR can greatly enhance the absorption of light,accelerate the surface reaction rate,and provide the catalytic activity of WO_3-x.In general,it is proved that the LSPR can effectively enhance light absorption,broaden the spectral range,and improve the catalytic activity of photocatalytic materials.Meanwhile,this study also proves that the construction of bimetallic and non-metallic plasmonic materials can expand the plasmonic materials system and application fields,which is of great significance for the development of plasmonic photocatalysis.