【作者】 刘伟；

【导师】 王鹏；

【作者基本信息】 中国矿业大学 ， 材料加工， 2015， 硕士

【摘要】 Ti O2纳米管作为一种新型的纳米材料,由于其较大的比表面积、稳定的化学性能、良好的光催化性能以及成本较低等优点,近年来受到广泛关注。然而,未经修饰的Ti O2纳米管对太阳光利用率很低,只能吸收太阳光中紫外光区的能量,极大限制了其在光催化领域的应用。因此,对Ti O2纳米管的制备及改性进行系统深入的研究具有重要的意义。本文在弱酸改良的乙二醇电解液中,采用三步阳极氧化法制备了Ti O2纳米管,研究阳极氧化参数(时间、电压和温度)对Ti O2纳米管形貌结构的影响,并在形貌结构最佳的Ti O2纳米管阵列上,进行Ag纳米颗粒负载改性,利用SEM、TEM、XRD等方法表征其表面形貌、物相结构,以及研究Ag/TNAs复合结构材料对甲基橙的光催化降解效果,具体研究结果如下:添加柠檬酸、甲酸和乳酸改良乙二醇电解液,柠檬酸的添加主要提高其比表面积,但管长和管径无明显变化,乳酸和甲酸的效果明显,同等反应条件下制备的Ti O2纳米管的管长可以达到11.92μm和10.76μm,选择的三种弱酸中,乳酸表现最佳。Ti O2纳米管的管长、管内径与阳极氧化电压呈线性相关关系;较低温度时,温度升高可以增大纳米管的内径,较高温度时,温度升高纳米管内径反而变窄。效果最佳的工艺组合是电解液0.3wt%NH4F+2vol%水+1.5mol/L乳酸的乙二醇溶液下,60V、40℃制备的Ti O2纳米管。研究晶化温度对Ti O2纳米管晶体结构、物相成分以及光催化性能的影响发现,未晶化处理的Ti O2纳米管是无定型态,经过晶化处理后,Ti O2纳米管从锐钛矿相转变为金红石相。晶化处理后的Ti O2纳米管对甲基橙的光催化降解反应动力学表现为一级反应,且400℃晶化处理的Ti O2纳米管具有最佳的光催化活性。采用光电还原法制备Ag-TNAs复合光催化剂,Ag纳米颗粒呈直径约4-10nm的球型分散在纳米管的内壁或者外壁上,且纳米管结构保持着完整性。由于Ag的SPR效应,Ti O2纳米管的能级结构被改变,Ag-TNAs随着沉积量的差别均不同程度地发生吸收边红移,增强了对可见光的吸收能力。在不同沉积量的Ag-TNAs对甲基橙光催化降解中,Ag-TNAs的光催化活性随着Ag的沉积量先增大,达到一最佳值后开始减小,2.5wt%沉积量的光催化活性效果最佳。更多还原

【Abstract】 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.更多还原