Preparaiton And Catalytic Application Of Sliver Modified Semiconductor Light-active Nanomaterials

With the increasingly updating and development of the social science, the demand fornew energy sources is increasing. There are two big problems in recent years, one is that thefossil energy leading to the environment pollution is more and more serious, another is how toreasonable use the pollution-free new energy. The solar energy as a new energy resourcescreates a new situation in the new energy field. Semiconductor photocatalyst which hasunique photochemical stability and the resistance to chemical corrosion, becomes a kind ofenvironmentally-friendly photocatalyst and occupies a very important position in the field ofphotocatalysis. Due to its stability, low cost, non-toxic and the good performance forphotocatalytic, the semiconductor photocatalyst has a promising prospect application in thesewage disposal. But the semiconductor photocatalyst also has its own disadvantages, such asa larger band gap width, which limits the visible light absorption ability. This is a bigstumbling block for its widespread use.Taking different categories together to realize the nanomaterials more functional is animportant research direction in the field of synthesis compound. And the research scholarstake great interest in pulling the semiconductor and metal composite materials together intosomething useful. In this article, by studying the semiconductor composite materialsphotocatalyst which was modified by the noble metal nanoparticle, we not only improved thesemiconductor photocatalytic performance of the catalyst, also had realized the visible lightdegradation of organic pollutants in the water.The main research of the article is as follows:1. The silver modified the zinc oxide to obtain the ZnO-Ag semiconductor nanocompositephotocatalyst.On the basis of previous studies，herein we use an economical and large-scale one-potsynthesis to prepare the single ZnO and different proportions of ZnO-Ag semiconductornanocomposite photocatalyst. Then combining with XRD, UV-Vis, photocatalytic reactionand its dynamics results we screen all the catalysts to get the best performance catalyst (Zn:Ag=1:1). The TEM results of ZnO-Ag semiconductor nanocomposite photocatalyst showthat ZnO nanorods surrounded by the Ag nanoparticles. Through further inquiry experimentsand the Raman results, we know that the ammonia acts as a bridge to take Ag and ZnOclosely together, and there exists an an positive synergy between the Ag nanoparticles andZnO nanorods. Owing to the surface plasmon resonance effect of the Ag nanoparticles thecatalyst can use of the visible light. The Ag nanoparticles and ZnO semiconductor formed anew Fermi level which changed the catalyst surface charge distribution and raised theseparation production rate of the photon-electrons-holes of nanocomposite photocatalyst.Then we take the terephthalic acid as a fluorescence probe to detect the production of OH inthe catalytic process and discusse the OH role in the photocatalytic process. Through thefurther experiment we prove that OH is a major oxidation species during the photocatalytic.2. Take Ag as a bridge to connect AgBr and BiOBr and preparare the AgBr-Ag-BiOBrnanocomposite photocatalyst. In order to breakthrough the limitation of single material catalytic activity, at the sametime using their respective advantages of p-type and n-type semiconductor, herein we usehydrothermal method to preparare the single BiOBr and the different amount of Ag dopingBiOBr nanocomposites. Then combining with XRD, UV-Vis, photocatalytic reaction and itsdynamics results we filter to get the best comprehensive properties of the catalyst (Ag: Bi=1:1), we named it as AgBr-Ag-BiOBr. And the SEM, Raman and TGA results show thatAgBr-Ag-BiOBr catalyst of nanocomposite structure is that the Ag nanoparticles and AgBrload on the BiOBr nanometer film. And through the further experiment we concluded that,during the photocatalytic process the Ag nanoparticles not only plays the role of the surfaceplasmon resonance effect, its another important role is the bridge connecting twosemiconductor which formes the Schottky barrier on the semiconductor contact interface. Thestructure of P-M-N causes the separation of photon-electrons-holes timely then creates the OH and O2-two oxidative species. We futher verified the two oxidative species that both ofthem have played very important roles in the process of photocatalytic degradation ofpollutants.3. The Bi2WO6was modified by the Ag nanoparticles to form AgBi(WO4)2photocatalystnanomaterials.On the basis of the first two system research, in order to further breakthroughs in noblemetals simple load and doping, we use hydrothermal method by fine adjustment of eachcomponent to get the single Bi2WO6and AgBi(WO4)2photocatalyst nanomaterials. Thesenanocomposites are characterized by XRD. The results indicate that Ag doped Bi2WO6nanocomposite is not only a simple loading, but replaces the lattice oxygen vacancy positionof the Bi2WO6to form AgBi(WO4)2nanomaterials. Through UV-Vis, photocatalyticdegradation and its dynamics performance results, we obtained the best photocatalyst. And wetake a series of experiments to explore the OH and O2-oxidation species in the process ofphotocatalytic, then explain AgBi(WO4)2nanomaterials make full use of thephoton-electrons-holes during the photocatalytic process. Through a series of stability testing,AgBi(WO4)2nanomaterial has very good stability and repeated use. It is the improvement ofsemiconductor material for noble metals simple load experiment. It is important for thepreparation of photocatalyst with good stability and high activity.