| As a new type of nanometer materials, Ti O2 nanotubes have attracted much attention in recent years because of their large specific surface area, stable chemical properties, good photocatalytic performance and low cost advantages. However, Ti O2 nanotubes without modification only absorb the ultraviolet area of sunlight energy,which greatly limits their application in the field of photocatalysis. Therefore, further research on the preparation and modification of Ti O2 nanotubes is of important significance.In this thesis, the ethylene glycol electrolyte system was modified by weak acid,and the anodic oxidation method was also shifted from the conventional anodic oxidation to three anodic oxidation. In the weak acid electrolytic system, the effect of anodic oxidation parameters(time, voltage and temperature) on the morphology and structure of the Ti O2 nanotubes was investigated. On the basis of the best anodic oxidation parameters, Ag nanoparticles were deposited on the Ti O2 nanotube arrays.The surface morphology and phase structure were characterized by using the methods of SEM, TEM and XRD. Moreover, the photocatalytic activity of the Ag/TNAs composite materials in the degradation of methyl orange was evaluated. The specific research consequences are listed as follows:Citric acid, formic acid and lactic acid was added to modify the ethylene glycol electrolyte. The results showed that the citric acid mainly improved the specific surface area, but scarcely changed the length and diameter. However, the effect of lactic acid and formic acid were dramatic under the same reaction conditions. The length of Ti O2 nanotubes could reach 11.92 μm and 10.76 μm, respectively. Therefore,lactic acid presented the best performance in the three kinds of weak acids. The length and inner diameter of the Ti O2 nanotubes were related linearly with the anodic oxidation voltage. Moreover, temperature could increase the inner diameter of the nanotubes at low temperature, but decreased the inner diameter at high temperature.The best morphology of the Ti O2 nanotubes were achieved under the condition of 0.3wt% NH4 F + 2 vol% water + 1.5 mol/L lactic acid ethylene glycol solution, 60 V and40℃.The influence of the crystallization temperature on crystal structure, phase composition and photocatalytic performance of the Ti O2 nanotubes was also studied.It was found that the Ti O2 nanotubes were amorphous type without crystallizationprocessing, while they were transformed from anatase phase to rutile phase after the crystallization. The kinetics of photocatalytic degradation of the crystallized Ti O2 nanotubes on the methyl orange was the first order reaction, and the Ti O2 nanotubes sintered at 400℃ showed the best photocatalytic activity.The Ag-TNAs composite photocatalyst was prepared by the photoelectric reduction method. The Ag nanoparticles with about 4-10 nm in diameter were found to scatter on the inner or outside wall of the Ti O2 nanotubes, and the nanotubes maintained integrity. Because of the SPR effect of Ag, the energy level structure of the Ti O2 nanotubes was changed, and the absorption edge of the Ag-TNAs red shifted in different degrees by varying the deposit amount of Ag, which enhanced the ability to absorb visible light. In the photocatalytic degradation of Ag-TNAs with different depositions, the photocatalytic activity of Ag-TNAs were related with the deposit amount of Ag. The photocatalytic activity increased first, reached the best value and then began to decrease. The best photocatalytic activity was obtained when 2.5 wt%of Ag was deposited. |
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