Study On The Construction And Photocatalytic Performance Of Different Kinds Of Co-catalyst/Semiconductor Materials

Energy and environment are very important for the daily life of human being.Since the industrial revolution,mankind has become increasingly dependent on fossil energy.Although coal,oil and natural gas can currently meet the energy needs of our industrial development,such traditional fossil energy will be exhausted soon.Besides,the exhaust gas generated from the process of fossil energy consumption would cause huge damage to the environment without applying scientific exhaust gas treatment method.This situation makes us urgently look for solutions to environmental pollution and energy crisis.The effective way to solve these problems is to reduce the environmental pollution caused by the usage of fossil energy with advanced environmental protection technology,and to improve utilization rate of fossil energy which is helpful for alleviating the urgent situation of energy storage.In this context,scientists focusing on ecological environment,new energy and other industries began to pay attention to semiconductor photocatalysis technology.This technology uses light energy to decompose water to produce hydrogen and organic fuel,which can alleviate the energy crisis.Besides,light energy can be used to degrade organic pollutants,reduce heavy metal ions,and protect natural resources which makes contribution to the ecological environment.Among numerous semiconductor catalysts,the outstanding catalytic properties of g-C3N4 and ZnIn2S4 have attracted more and more attention.g-C3N4 has the advantages of chemical stability,wide absorption spectrum and unique photoelectric properties,but the high electron hole recombination rste and small specific surface area of pure g-C3N4 restrict its further development.ZnIn2S4 is one of the ideal photocatalysts for hydrogen production because of its unique optical properties and wide solar energy collection capability.However,due to the low visible light absorption rate and low cycle life,ZnIn2S4 can not meet the needs of practical application.In this dissertation,different kinds of cocatalysts(non precious metals,carbon materials,bimetallic phosphides)are introduced into the semiconductor system by solvothermal method and hydrothermal method.g-C3N4 and ZnIn2S4 will be optimized in this process with improved photocatalysis hydrogen production and degradation activity.Next the author will explore and summarize the photocatalytic mechanism of composite materialsThe main contents of this dissertation are as follows:(1)Bi nanoparticles were reduced in situ on the surface of g-C3N4 by applying hydrothermal method.Then,XRD,XPS,SEM,TEM and DRS were utilized to analyze the surface and structure of Bi/g-C3N4.Then,the visible light catalytic performance of Bi/g-C3N4 was evaluated by the degradation efficiency of rhodamine B(RhB)and the rate of hydrogen evolution.Next,the influence of different Bi loading on the photocatalytic activity of the composite was tested.The results show that Bi-CN-10 has high photocatalytic activity and stability for RhB degradation under visible light,whose Kapp value was 0.12357 min-1,about 30%higher than that of pure g-C3N4.Besides,Bi-CN-10 also shows the highest hydrogen generation rate,which is twice that of pure g-C3N4.Lastly,the photocatalytic mechanism of Bi/g-C3N4 composites was proposed by studying the reactive groups and examining the band position(2)ZnIn2S4 and N-CQDs/ZnIn2S4 were synthesized by hydrothermal method.The synthesized product was identified by X-ray diffraction(XRD),and the surface of the photocatalyst was identified by transmission electron microscopy(TEM).In the hydrogen production performance evaluation experiments of composites,the photocatalytic activity of N-CQDs/ZnIn2S4 composites is much higher than that of pure ZnIn2S4.Besides,6%-N-CQDs/ZnIn2S4 can show H2 evolution rate as high as 387 μmol/h/g,approximately 5.02 times of pure ZnIn2S4.Moreover,it was found that the photoelectrochemistry(PEC)of the N-CQDs/ZnIn2S4 hybrid photocatalyst has lower impedance and smaller Tafel slope,which indicates that N-CQDs/ZnIn2S4 has a better reaction interface to generate hydrogen and can participate in photocatalytic reactions more efficiently.(3)Preparation of Ni1.8Cu0.2P/g-C3N4 composite photocatalyst and study of its photocurrent performance.By optimizing the synthesis process,the double metal phosphide was purified.The bimetal phosphide(Ni1.8Cu0.2P)was loaded on the surface of g-C3N4 by hydrothermal method,and its XRD and photocurrent were characterized Experimental results indicate that with the addition of the catalyst,the photocurrent responsivity of the composite has been significantly improved.