Preparation And Photocatalytic Performance Study Of Highly Efficient And Cheap Metal Induced Semiconductor Composite Materials

With the increasing need for energy and shortage of fossil fuels in the world,there is a growing desire to develop effective strategies for the conversion of solar energy into hydrogen gas,hydrocarbon fuels or other energy forms.Photocatalytic techniques have received widespread attention due to their significant advantages in solving the above problems.However,most of the semiconductors used in photocatalysis are wide-bandgap semiconductors.For example,strontium titanate,a common semiconductor,has a forbidden band width of 3.2 eV.It can only utilize the UV portion,and does not have any visible-light response.However,UV light accounts for only 5% of the total sunlight energy,while visible light accounts for 43%.Therefore,to achieve the visible light response of semiconductor materials is of great significance for the research of photocatalysis.So far,researchers have tried many methods,such as doping,surface treatment,dye sensitization and so on,but these methods also face the problems of instability,inefficiency and high cost.Over the past several years,coinage metal(Au,Ag,Cu)photosensitized semiconductors via their visible-light absorption offer a promising strategy for this issue.However,most of the researches are still focused on noble metals,such as gold and silver.While copper has received less attention due to its oxidability nature.From previous work in our group,we have known that interband-transition(from the d orbital to the sp orbital)is the main driving force,rather than the LSPR.The interband transitiononset of coppoer is only 1.9 eV,which is much lower than 2.4 eV for Au.As a result,the study towards Cu is hopeful for solving the problems of high cost and low efficiency.To further reduce the cost and improve the reaction efficiency,we try to achieve more excellent hydrogen evolution activity in visible light by using only copper as the plasmonic metal introduced by using a self-designed reaction system in this experiment.First of all,the use of a combination of a constant pressure funnel and a water-splitting jar achieves seamless integration of the photo-deposition synthesis and testing,which avoids copper oxidation in the air.Secondly,we obtained the optimal activity of 15.3 ?mol/h and the apparent quantum yield of 0.86% at 420 nm monochromatic plate by controlling the loading amount and the deposition steps.Subsequently,we speculated that the two factors that cause the change of activity are the interaction between Fano interference and metal particle surface area by using TEM characterization and UV-Vis absorption spectrum analysis.On the one hand,as the size of copper nanoparticles increases,the decoupling between the LSPR model and the band-to-band transition model gets enhanced,resulting in longer lifetime of the carriers and higher efficiency of interfacial electron mobility.On the other hand,the growth of metal particles causes a reduction of the surface area.However,under visible light irradiation,the metal particles exist as stimulators.The reduction of the surface area leads to the reduction of the active reaction site,which leads to the decrease of the activity.Therefore,based on the above two factors,the activity will have a result of a valley curve as the particle size changes.In addition,we also compared the effects of several different preparation methods,and analyzed whether the coexistence of large particles and small particles would help to further enhance the hydrogen production activity.In summary,this work has important research value and application significance for the research and development of metal-induced semiconductor photocatalyst system,which provides a good reference for cheap and efficient catalyst preparation and analysis method.