【作者】 王秋红；

【导师】 卢小泉； 秦冬冬；

【作者基本信息】 西北师范大学 ， 分析化学， 2017， 硕士

【摘要】 二十一世纪随着人口数量的快速増长和社会工业化进程的迅速发展,资源短缺、环境保护、人口数量和社会的可持续发展成为各国所面临和亟待解决的首要问题。节能和环保成为生态保护的核心问题,在众多能源开发和环保高效的新型能源提高战略上,以半导体氧化物为催化剂的光催化是一种绿色环保技术,其特点主要有;反应条件简单便于操作,使用范围广阔,反应的原料廉价易得,反应后不会不产生二次污染物。除此之外,光催化技术是一种可直接利用太阳光作为光源,用过半导体吸收光子来活化催化剂,并驱动氧化还原反应进行。它研究引起了人们广泛关注。二氧化钛（TiO₂）既是一种过渡金属氧化物又是一种半导体材料,因其具有化学稳定性好、光催化能力强、无毒、廉价等优在太阳能电池,生物医学,污水治理以及空气净化等领域都有很大应用潜力。但是,由于TiO₂的禁带宽度大（Eg=3.0 e V-3.2 e V）,限制了它对可见光吸收的能力。TiO₂仅仅会被波长小于387 nm紫外光激发起到催化作用,但整个太阳光中紫外光却不到4%,对太阳光的利用率很低。除此之外,单一的TiO₂受光激发后产生的光生载流子极易复合,使得它的光催化量子效率很低。这两方面的缺点在很大程度上限制了纳米TiO₂的广泛使用。研究表明改变TiO₂形貌和对其进行掺杂改性可以有效的解决以上两个问题。TiO₂纳米管作为TiO₂纳米材料中的一种,与TiO₂纳米粒子相比较TiO₂纳米管具有更高光催化活性。这是由于TiO₂纳米管具有更多优势,比如;比表面积更大和吸附能力更强。为实现TiO₂在自然光条件下的催化应用,研究者采用多种方法对纳米TiO₂进行改性研究,如贵金属的沉积、元素的掺杂、半导体的复合、光敏材料的敏化等等。本文是针对克服TiO₂的上述缺点而开展的,通过掺杂或者半导体复合的方法来制备具有高的催化活性的TiO₂纳米管光催化材料。本文以钛片作为基底材料,采用阳极氧化的方法制备出了垂直生长在基底上的高度有序的TiO₂纳米管（TiO₂ NTs）阵列,分别研究了Ti3+掺杂TiO₂（B）NSs-TiO₂ NTs、P5+掺杂TiO₂ NTs及P5+和Cr3+共掺杂Sr TiO₃-TiO₂ NTs纳米异质结的光电化学性能。使用SEM和TEM对样品的表面的形貌和内部的结构进行了表征。采用XRD、UV-vis、XPS、紫外光电子能谱（UPS）、线性扫描伏安法（LSV）、开路电压衰减（VOC）、强制调节光电流（IMPS）等等手段对掺杂前后TiO₂纳米管进行了结构、光学性能及光电化学性能进行了研究。本论文主要研究结果如下:（1）Ti3+-TiO₂（B）NSs/TiO₂ NTs薄膜的制备:以Ti箔作为基底通过水热法,首先在Ti箔上制备了H2Ti3O7纳米片的薄膜,然后通过离子交换和阳极氧化结合的方法退火得到TiO₂（B）NSs/TiO₂ NTs。并以硼氢化钠（Na BH4）作为还原剂,N2作为保护气体,400℃退火2 h,得到Ti3+-TiO₂（B）NSs/TiO₂ NTs薄膜。SEM和XRD结果表明所制备的Ti3+-TiO₂（B）NSs/TiO₂ NTs薄膜TiO₂（B）NSs生长在TiO₂ NTs的顶部,其中TiO₂（B）NSs的厚度约30 nm,TiO₂ NTs管长度约为3.5μm。Ti3+-TiO₂（B）NSs/TiO₂NTs薄膜光电流密度达到0.34 m A·cm-2（1.23 V vs RHE）,与TiO₂（B）NSs和TiO₂ NTs相比光电化学性能明显有所提高。（2）P-TiO₂ NTs薄膜的制备:通过阳极氧化的方法制备了不同氧化时间的高度有序TiO₂ NTs。以PH3作为磷源,保护气体是N2。低温煅烧处理制备出了P-TiO₂ NTs。分别研究了低浓度和高浓度的PH3对TiO₂ NTs的掺杂情况和对掺杂后的光电化学性能提高的程度。研究的结果表明P掺杂对TiO₂ NTs的形貌和结构并没有明显的影响。P掺杂TiO₂ NTs与单一的TiO₂ NTs对比发现,P-TiO₂ NTs后的紫外可见吸收光谱图中吸收强度增大,光催化性能也得到了明显的提高。实验结果表明采用阳极氧化法制备的7 h TiO₂ NTs薄膜得样品在500℃空气中退火后的光电流达到1.0 m A·cm-2（1.23V vs RHE）,经过掺杂改性以后,它的光电流可以达到2.5 m A·cm-2（1.23 V vs RHE）。（3）P-Cr-Sr TiO₃/TiO₂ NTs异质结的制备:以Ti箔为基底采用水热法和阳极氧化结合的方法成功制备了Sr TiO₃/TiO₂ NTs纳米异质结。以硝酸铬（Cr（NO3）3·9H2O）作为Cr3+掺杂剂,在水热过程中实现Cr3+的原位掺杂。实验结果表明P、Cr共掺杂对Sr TiO₃/TiO₂ NTs异质结形貌没有明显影响,光电化学性能得到明显提高;一方面可能是由于P、Cr共掺杂能够形成杂质能级,减小了Sr TiO₃/TiO₂ NTs异质结禁带宽度;另一方面可能是由于Cr3+的原位掺杂掺杂降低了电子-空穴对的复合。最后将样品在AM 1.5 G,用光强100 m W/cm2的氙灯照射,在室温条件下对样品进行了光电流密度的测试研究,在全光下P-Cr-Sr TiO₃/TiO₂ NTs的光电流密度为2.0 m A·cm-2（1.23 V vs RHE）。更多还原

【Abstract】 In the 21 century,with the rapid growth of population and the rapid development of social industrialization,the sustainable development of resources,environment,population and human society has become an urgent problem to be solved.Energy conservation and environmental protection become the core problem of ecological protection,In many energy development and environmental protection and efficient new energy improvement strategies,photocatalysis with semiconductor oxide as catalyst is a kind of green environmental protection technology,which is characterized by: mild reaction conditions and application Wide range of direct use of sunlight as a light source to activate the catalyst and drive the redox reaction and other unique properties,its research has aroused widespread concern.Titanium dioxide（TiO₂）is not only a transition metal oxide but also a semiconductor material,because of its good chemical stability,good photocatalytic capacity,non-toxic,cheap and other properties,which have great potential applications in the solar cells,biomedical,sewage treatment,air purificationand and other fields.However,the band gap of TiO₂ is large（Eg =3.0 e V-3.2 e V）,which limits its visible light absorption capacity.TiO₂ can only be the wavelength of less than 387 nm ultraviolet excitation to play a catalytic role,and these light only 4% of the whole sunlight the sun,the utilization of sunlight is very low.In addition,the photogenerated electrons and hole pairs generated by pritine TiO₂ are easily recombined,which leads to low photocatalytic quantum efficiency.These two aspects of the shortcomings to a large extent limit the widely use of nano-TiO₂.The results show that changing the morphology of TiO₂ and modifying TiO₂ which can solve the above two problems.Compared with TiO₂ nanoparticles,TiO₂ nanotubes have greater specific surface area,stronger adsorption capacity and higher photocatalytic activity.In order to achieve the catalytic application under natural light conditions,the researchers used a variety of methods to modify nano TiO₂,such as precious metal deposition,metal ion doping,non-metallic doping,semiconductor recombination,photo-sensitization.In order to overcome the above shortcomings of TiO₂,the aim of this study is to prepare doped TiO₂ nanotube photocatalytic materials with high catalytic activity in the ultraviolet and visible regions.In this paper,a highly ordered array of TiO₂ NTs was prepared by anodic oxidation method using titanium as the substrate.The photoelectrochemical properties of Ti3+ doped TiO₂（B）NSs-TiO₂ NTs,P5+doped TiO₂ NTs and P5+ and Cr3+ co-doped Sr TiO₃-TiO₂ NTs nanocomposites were investigated.The morphology,structure,optical properties and photoelectrochemical properties of TiO₂ nanotubes before and after doping were studied by SEM,TEM,XRD,UV-vis,XPS,UPS,LSV,VOC,IMPS and so on.The main results of this paper are as follows:（1）Preparation of Ti3+-TiO₂（B）NSs/TiO₂ NTs films: First of all,the H2Ti3O7 nanosheet films were prepared on Ti foil by hydrothermal method,and then TiO₂（B）NSs/TiO₂ NTs were obtained by ion exchange after annealing and anodic oxidation of the H2Ti3O7 nanosheet.Na BH4 as the reducing agent,N2 as the protective gas and annealed at 400℃ for 2 h to obtain Ti3+-TiO₂（B）NSs/TiO₂ NTs film.The SEM and XRD results show that in the Ti3+-TiO₂（B）NSs /TiO₂ NTs films TiO₂（B）NSs are grown on the top of TiO₂ NTs.The thickness of TiO₂（B）NSs is about 30 nm and the length of TiO₂ NTs is about 3.5 μm.The Photonic current density of Ti3+-TiO₂（B）NSs/TiO₂ NTs films is 0.34 m A·cm-2（1.23 V vs RHE）,and the photoelectrochemical properties are obviously improved.（2）Preparation of P-TiO₂ NTs films: Anodic oxidation method was used to prepare highly ordered TiO₂ NTs arrays with different oxidation times.Sodium hypophosphite as a phosphorus source,N2 as protective gas.P-TiO₂ NTs were prepared by low temperature calcination.The effects of different concentrations of PH3 on the photocatalytic activity of P-TiO₂ NTs were investigated.The results show that P doping has no obvious effect on the morphology and structure of TiO₂ NTs.Compared with pristine TiO₂ NTs,the absorption intensity of doped TiO₂ is improved obviously.The experimental results show that the photocurrent density of anodic oxidation of 7 h TiO₂ NTs film annealing in air at 500℃ was 1.0 m A·cm-2（1.23 V vs RHE）,and its photocurrent density can reach 2.5 m A·cm-2 after doping（1.23 V vs RHE）.（3）Preparation of P-Cr-Sr TiO₃/TiO₂ NTs heterojunctions: Sr TiO₃/TiO₂ NTs heterojunctions were successfully prepared by hydrothermal method and anodic oxidation method using Ti foil as substrate.Cr（NO3）3·9H2O as Cr3+ dopant,in situ heat treatment of Cr3+ in situ doping.The experimental results show that P and Cr co-doping has no obvious effect on the heterojunction morphology of Sr TiO₃/TiO₂ NTs,and the photoelectrochemical properties can be improved obviously.On the one hand,P and Cr co-doped can form impurity energy level and reduce Sr TiO₃/TiO₂ NTs heterojunction band gap;on the other hand,it is possible to suppress the recombination of Cr3+ by in situ doping.The photocurrent density of P-Cr-Sr TiO₃/TiO₂ NTs was 2.0 m A·cm-2 under the condition of AM 1.5 G and light intensity of 100 m W/cm2（1.23 V vs RHE）.更多还原