导　　师： 彭峰

学科专业： 081705

授予学位： 博士

作　　者： ;

机构地区： 华南理工大学

摘　　要： 过去的20多年里，由于高度有序、比表面大、方便回收和稳定性好等优点，阳极氧化法制备的TiO/_2纳米管阵列被广泛的应用于在光催化剂、气体传感技术、环境监测、生物医药以及太阳能转换中等方面。然而，TiO/_2具有较宽的能带隙（3.0-3.2eV），只能在紫外光作用下发生响应，催化剂表面光生电子与空穴复合和量子产率等问题严重制约了TiO/_2纳米管阵列光催化的广泛应用。因此，通过对TiO/_2纳米管阵列进行制备方法的改进，以及对其进行合理的改性从而促进其可见光光催化活性，促进TiO/_2纳米管阵列广泛实际应用具有重要意义。本论文采用新的制备工艺合成一种新型分层结构TiO/_2纳米管阵列，考察光催化分解水和有机物性能，探讨了其形成机理；使用电化学沉积法制备分散均匀的多面体Cu2O和TiO/_2纳米管阵列复合，考察了其可见光催化活性和杀菌消毒能力；利用负载贵金属Ag和氮掺杂进行改性，提高TiO/_2纳米管阵列在可见光下的光催化活性，深入探讨了修饰后的TiO/_2纳米管阵列在可见光下的光催化机理，并通过光电化学性能实验揭示了光生电子和空穴的转移与复合，考察了不同因素对光催化效率的影响。主要内容如下： （1）将金属钛喷射在FTO导电玻璃上，采用阳极氧化法制备出具有上下双层结构的TiO/_2纳米管阵列（HST），此阵列由上下两层组成，总长度约为2.0μm，上层厚度大约0.3μm，由多孔TiO/_2纳米颗粒组成，下层厚度大约1.7μm，由TiO/_2纳米管阵列组成，纳米管的外直径约为150nm。X-射线粉末衍射（XRD）分析表明，在空气氛围中500°C下退火2h所得样品锐钛矿的含量约为76/%。合成的HST膜和用传统方法制备的TiO/_2纳米管阵列（TNA）作为光阳极用于氧化水和有机物（如：葡萄糖）。实验结果表明，新型HST的光催化活性明显高于TNA，这一结果归因于HST是由具有大比表面积的多孔结构纳米粒子的上层和具有良好电子传递性能规则的纳米管阵列的下层组成，且两层具有很好的结合。两种纳米结构膜的光生电子的传输性能（固有电阻R0）通过简单的光电化学方法表征和计算。结果表明，虽然HST膜的R/_0（85.5Ω）大于TNA膜（65.5Ω），但上层多孔纳米结构有效的增加光催化活性面，进而促进光催化活性。 （2）用阳极氧化法制备的TNA在NH/_3气氛中500°C退火4h，得到N掺杂TNA（N-TNA）。在含有EDTA的AgNO/_3溶液中，通过电化学沉积方法将纳米Ag与N-TNA组装在一起得到Ag负载的N掺杂TiO/_2纳米管阵列（Ag//N-TNA）。采用场致发射扫描电镜（FESEM）、X-射线光电子能谱（XPS）、紫外-可见光谱漫反射光谱（DRS）、XRD等方法对所得样品进行了表征，发现电化学沉积时间对纳米Ag的形貌有很大的影响。实验考察了不同电化学沉积时间对光催化的影响，结果表明，当电化学沉积纳米Ag时间为5s时的可见光催化效果最好。此时Ag//N-TNA的平均光电流密度和光催化降解酸性甲基橙染料效率分别是普通TiO/_2纳米管的6.0和6.8倍。Ag//N-TNA是一种优良的可见光光催化降解有机污染物材料。 （3）使用电化学沉积方法将纳米尺寸的多晶面Cu/_2O均匀负载在整个TiO/_2纳米管阵列结构上，获得复合纳米材料可见光催化剂Cu/_2O//TNA。通过FESEM、XRD、XPS和DRS等方法对Cu/_2O//TNA进行表征。结果表明，纳米管的长度约为900nm、内径约为100nm，壁厚约为20nm。实验考察了沉积电量对光催化效果的影响，随着沉积电量增加，沉积在TNA上的Cu/_2O量越来越多，形貌由球形纳米颗粒逐渐转向具有多晶面Cu/_2O晶体。当沉积电量为500mC时，多面体Cu/_2O每个面的长度大约80nm。此Cu/_2O//TNA在可见光下光分解水和光催化使酸性甲基橙II（AO-II）脱色的效果最好，分别是TNA的35.5和18.2倍。因此，多晶面Cu/_2O修饰的TNA在太阳能转化和有机物降解上将是一种很有前途的可见光催化材料。 （4）使用无毒Cu/_2O//TNA薄膜作为高性能可见光杀菌光催化剂进行了研究，结果表明Cu/_2O//TNA薄膜光催化剂在可见光的照射下，20min之内，便可以将高浓度的大肠杆菌（5×10~7CFU//mL）试样完全失活。经过可见光照射20min后，Cu/_2O//TNA的对大肠杆菌的杀菌效率分别是同等光照条件下TNA的20.2倍和无光处理的Cu/_2O//TNA的6.6倍。Cu/_2O//TNA具有优越的可见光杀菌性能主要是由于Cu/_2O狭窄能带隙使它能够吸收可见光，分别在导带和价带产生光生电子和空穴。光生电子从Cu/_2O的导带转移到TiO/_2的导带促进了电荷分离，产生更多的羟基自由基和活性氧物种。 Over the past decade, because of its high regulation, large surface areas, high recycleefficiency and excellent controllability, highly ordered TiO/_2nanotube arrays /(TNA/) byanodization have attracted great attention on photocatalysis, gas sensing, biomedicine,environmental monitoring, and solar energy conversion. However, the band gap of TiO/_2isvery wide /(3.0-3.2eV/) leading to its absorption only in UV light, otherwise, catalyst surfacephotoinduced charges recombination and lower IPCE limit the applicability of TNA. In orderto promote its visible light photocatalytic activity, many researches on the improved methodfor preparing TNA, reasonable modification were developed, which is great significance onthe wide range of practical applications. In this paper, a new hierarchically structured TiO/_2/(HST/) film was prepared. The resultant HST films as photoanodes were evaluated byphotocatalytic oxidation of water or organics. The formation mechanism was investigated.Highly dispersed and nano-size polyhedral Cu/_2O loaded on TiO/_2nanotube arrays /(Cu/_2O//TNA/)were successfully prepared by an electrodeposition method, which exhibited excellentphotocatalytic and good bactericidal activity under visible light. Ag nanoparticles loadedN-doped TiO/_2nanotube arrays /(Ag//N-TNA/) were successfully synthesized, improved visiblelight photocatalytic activities were observed. The main contents are as follow: Transparent TiO/_2nanostructured films composed of porous TiO/_2nanoparticle top layer andhighly ordered TiO/_2nanotube bottom layer were successfully fabricated onto metal titaniumdeposited FTO conducting substrates by anodization technique. For the hierarchicallystructured TiO/_2/(HST/) film, the top porous nanoparticle film had a thickness of ca.300nm,and the bottom nanotubes have a mean length of1.7μm and a mean outer diameter of150nm.The total thickness of the hierarchically structured TiO/_2film was around2.0μm. XRDanalysis revealed that the fabricated hierarchically structured TiO/_2film after calcination at500°C was predominantly consisted of anatase /(76/%/). The resultant HST films asphotoanodes were evaluated by photocatalytic oxidation of water or organics /(i.e., glucose/).The experimental results indicated that the HST film photoanodes exhibited higherphotocatalytic activity than the TNA film fabricated on titanium foil substrates as the samelength, which is due to larger photocatalytic activity area supplied by the top nanoparticleporous layer and excellent photoelectron transport in bottom nanotube layer of the HST filmcompared to the single nanotube film /(TNA/). Photoelectron transport property /(reflected byconstant resistance, R0/) in two nanostructured films were characterized by a simplephotoelectrochemical method. Although the constant resistance of HST film /(R0=85.5Ω/) is larger than that of TNA film /(R0=65.5Ω/), the porous nanoparticle top layer for the HST filmcould effectively enhance the photocatalytic activity area, and thus significantly improvingthe resultant photocatalytic activity compared to the TNA film. The highly ordered TiO/_2nanotube array /(TNA/) films were fabricated on titanium foilsubstrates by anodization, and then annealed at500℃for4h under ammonia, N-TNA wasprepared. Ag loaded N-doped TiO/_2nanotube arrays /(Ag//N-TNA/) were fabricated by anelectrodeposition method. The Ag//N-TNA was characterized by Field-emission scanningelectron microscopy /(FESEM/), X-ray diffraction /(XRD/), X-ray photoelectron spectroscopy/(XPS/), UV-vis diffusion refection spectroscopy /(DRS/). The effect of differentelectrochemical deposition time on photocatalytic activity was investigated. The resultsshowed the best depositon of time was5s. The average photocurrent density andphotocatalytic degradation efficiency of the Ag//N-TNA obtained from the degradation ofAcid Orange II（AO-II）weree6.0and6.8times higher than those of pure TNA, respectively.This bestows the Ag//N-TNA as a promising photocatalytic material for organic pollutantdegradation under visible light. Highly dispersed and nano-size polyhedral Cu/_2O loaded on TiO/_2nanotube arrays/(Cu/_2O//TNA/) were successfully fabricated by an electrodeposition method. The obtainedsamples were characterized by FESEM, XRD, XPS and UV-vis diffusion refectionspectroscopy /(DRS/). The results showed nanotubes had a mean length of900nm, a meaninter diameter of100nm and the wall thickness of approximately20nm. The content of Cu/_2Oloaded on the arrays was controlled by changing the deposition coulombs. The results showedthe photocurrent density and photocatalytic degradation efficiency of Cu/_2O//TNA obtainedwhen the deposition coulombs arrived500mC were about35.5and18.2times as that of pureTiO/_2nanotube arrays under visible light, respectively. The polycrystalline Cu/_2O surfacemodified TNA will be a promising visible-light photocatalytic material in solar energyconversion and degradation of organic pollution. Using a non-toxic nanocrystal Cu/_2O-loaded TiO/_2nanotube array /(Cu/_2O//TNA/) film washigh performance visible light bactericidal photocatalyst. This Cu/_2O//TNA film photocatalystwas capable of complete inactivation of high concentration E. coli /(5×10~7CFU//mL/) within arecord short disinfection time of20min under visible light irradiation. The averagebactericidal percentage of the Cu/_2O//TNA for E. coli under visible light irradiation were20times and6.6times higher than those of TNA under the same conditions and Cu/_2O//TNAwithout light, respectively. This superior bacterial performance is mainly attributed to the high ability to produce OH radicals by both photogenerated electron and hole of the preparedphotocatalyst under visible light.

关 键 词： 二氧化钛纳米管陈列 双层 纳米薄膜 电化学沉积 修饰 可见光催化性能

分 类 号： [TB383.1]

领　　域： [一般工业技术]