Application of ZnO Nanowires in Photocatalysis
Autor: | Chang, Jan Hau, 張展豪 |
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Rok vydání: | 2014 |
Druh dokumentu: | 學位論文 ; thesis |
Popis: | 102 This thesis aims to investigate approaches to enhance the photocatalytic activity of substrate-supported ZnO nanowires (NWs). The employed NWs are grown on various substrates by thermal evaporation and have similar surface area. The NW photocatalytic activity is evaluated by degrading 50 uM rhodamine B with the use of UV light. These results in the first part of thesis reveal that the photocatalytic activity can be enhanced by using a conductive substrate and NWs with less defects. In the second part of thesis, the degradation kinetics has also been analyzed and indicates a combined zeroth-order and first-order reaction with a threshold concentration of 10 uM. The degradation constants of as-grown ZnO NWs are 0.58 uMmin-1 (zeroth-order) and 0.028 min-1 (first-order) and outperform reported values obtained from similar NWs. In the third part of thesis is for an investigation of the photocatalytic activity of substrate-supported ZnO nanowires with Ag modification and induced bending. By degrading a 50 uM rhodamine B solution, it is found that the zeroth-order kinetic constant of Ag modified bent NWs is 1.4 and 2.2 times as high as that of Ag modified unbent NWs and unmodified as-grown NWs, respectively. The improvement due to bending is related to the piezoelectric property of ZnO that facilitates charge separation. This work demonstrates the usefulness of piezoelectricity for photocatalysis. In the last part of the thesis, the photocatalytic activity of hydrogenated ZnO NWs is studied. Also, by degrading a 50 uM rhodamine B solution, it is found that the zeroth-order constant of hydrogenated ZnO NWs is around 2.5 times as high as that of as-grown ZnO NWs and the advantage of a low density of oxygen vacancies in ZnO NWs is apparent. Consequently, hydrogenated ZnO NWs enhance the photocatalytic activity significantly. |
Databáze: | Networked Digital Library of Theses & Dissertations |
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