| With the rapid development of the global economy and technology, environmental pollution has becomeone of the increasingly prominent problems, water pollutants has caused more and more attention. ZnO as anexcellent semiconductor photocatalyst in environmental management and protection have a good applicationprospect. Because of ZnO photocatalytic performance have a very close relationship with its morphology, sizeand surface defect. Therefore, improve the photocatalytic properties of materials by ZnO morphology controlhas become a hot topic recently. This article used the different preparation methods to obtain differentmorphology of ZnO materials, and its photocatalytic performance has carried out detailed research work,focusing on the influence of the material morphology on its photocatalytic properties. Work can be divided intothe following several parts:(1) Using hydrothermal method under150oC temperature synthesize of three different morphologies ofZnO powder, which morphologies by SEM were lamellar structure, short rod and rod structure, respectively.Through the study of photocatalytic degradation of methyl orange experiments，Compared with other two kindsof structure lamellar structure of ZnO its degradation of performance is better. Analysis shows its goodphotocatalytic performance mainly comes from the crystal orientation of material.(2) Added sodium citrate as a surfactant in solution, and synthesised sheet and spherical nanometer ZnOstill using ammonia (NH3·H2O) as a precipitating agent. We studied the influence of reaction time,concentration on the synthesis of ZnO morphology. In the process of reaction, sodium citrate and ammoniadirectly affect the synthesis of nano ZnO morphology. Citrate ions and zinc ions can form a chelate, inhibitingthe production of ZnO along (0001) crystal plane, leading to generate nano-layers ZnO. And ammonia and zincions can form Zn(OH)2-4complex ions, result in sodium citrate and ammonia generate spherical ZnO. Bycontrolling the amout of sodium citrate and ammonia in the experiments, achieved mutual convension betweenispherical, short column and lamellar structure, and both concentration directly affected the morphologychanges and size dimensions. Finally, studied the photocatalytic properties of two different morphologies ofZnO, it was found that the ZnO lamellar structure has better photocatalytic performance than the sphericalstructure, which main can be laminated structure of ZnO powder particle size is small, specific surface area islarger, the surface of the photocatalytic activity point is more, lead to its high catalytic efficiency.(3) Using ammonia (NH3·H2O) as a precipitating agent, without adding any surfactant, the flower-like of ZnO structure was prepared using chemical precipitation. By controlling the amount of ammonia added, andthen controlling the pH of the solution, the pH of the solution can acheve a series of continuous change, andZnO powder with different sizes and morphologies has obtained. At the same time, paper studied the effects ofreaction time and concentration on the morphology of ZnO. By XRD, SEM and TEM to determine the crystalstructure and morphology, it can be seen from the XRD, crystallinity of ZnO with the increase of pH isgradually increased. As seen from the PL, the peak intensity gradually decreases with the increase of pH,thereby the surface defects gradually reduced. Then doing a study of seven different morphologies of ZnOpowder for photocatalytic degradation of methyl orange, through the experiments discovered the synthesisedZnO has the best degradation efficiency at pH10.60, at the time of120min the degradation of methyl orange isclose to one hundred percent. Finally, paper studied the influence of the amount of ZnO powder to activity ofphotocatalytic degradation，the results found the existence of an optimal addition amount, the degradation ofZnO powder has the best efficiency. |
PDF Full Text Request