【作者】 侯健；

【导师】 张敏； 杨建军；

【作者基本信息】 河南大学 ， 物理化学， 2012， 硕士

【摘要】 随着能源以及污染问题的日趋严重，在众多可以利用太阳能光催化降解污染物的半导体氧化物中，TiO₂以其强氧化性、化学稳定性好、环境友好、无毒廉价等优势脱颖而出，吸引了研究人员的大量关注。然而TiO₂存在着两个制约其广泛应用的瓶颈因素：禁带较宽，约3.2eV，仅能受占太阳光4%⁵%的紫外光激发；另一方面，光生载流子的高复合率也严重制约了其对于所吸收能量的利用，阻碍了TiO₂在实际中的广泛应用。贵金属沉积是一种有效改善半导体光生电子空穴对分离效率的一种传统方法。本文采用阳极氧化法制备得到了TiO₂纳米管阵列薄膜，并在其上修饰了贵金属Pt，研究了制备方法及后处理条件等对光催化活性和光电性能的影响。采用水热法和光还原法两种不同方法制备了Pt-TiO₂，经过表征发现Pt修饰可以很大程度地提高半导体催化剂TiO₂的光催化降解和光电响应能力；光还原法制备的Pt-TiO₂，由于Pt颗粒在半导体表面分散均匀，具有更高的光催化活性。考察了光照还原时间、贵金属沉积量、后处理退火温度和气氛等制备条件对Pt-TiO₂光催化活性的影响，发现Pt的沉积量及沉积形式是影响Pt-TiO₂光催化活性的重要因素。氢气气氛下不同温度处理Pt-TiO₂的光催化研究结果表明，沉积的Pt表现出不同的存在形式对光催化活性具有较大的影响。场发射扫描电镜（FE-SEM）显示TiO₂纳米管阵列薄膜在沉积Pt之后仍保持管状结构，从高分辨电镜（HR-TEM）以及FE-SEM所拍摄的侧面图中均可看到有Pt颗粒的存在且随温度的升高逐渐增大；XRD显示TiO₂晶型随处理温度的升高而趋于更加规整。XPS证实了确实有Pt沉积于TiO₂，但不同条件下处理后的Pt具有不同的价态。光催化降解甲基橙和光电化学响应的实验表明，经过氢气气氛中200oC处理之后以零价和（Ⅱ）价存在的Pt具有最佳的光催化效率和光电化学响应。氢气气氛下500oC处理之后的Pt颗粒仅以零价的单质形式存在；但Pt颗粒在高温下发生团聚，以至于比表面积减小，反应活性位减少，光催化活性有明显降低。更多还原

【Abstract】 Rencently, pollution has been increasingly serious due to masses of home scrap and industrial waste.Among numbers of pollutant-degrading semiconductors, TiO₂array nanostructures, particularly TiO₂nanotube arrays fabricated by anode oxidation, have draw much attention owing to their strong oxidbillity,excellent mechanical and chemical stability, environmental innocuity and low cost. At the same time, as alarge-band-gap semiconductor, TiO₂can only be excited by UV irradiation wavelength under400nm, andthe recombination rate of photogenerated electron–hole pairs is high, which limit their further applicationto a great extent.For the aim of extending the photoresponse and reducing the recombination rate of TiO₂, many effortshave been put on modification. Nobel metal deposition is one of the most widespreaded method. In thiswork, we deposit nobel metal onto the catalysis, and the photocatalytic activities as well as photoelectricresponsibility were tested.Firstly, Pt-TiO₂were prepared respectively by hydrothermal method and photoassisted method. Theresult showed that Pt modification by photoassisted can largely enhance photodegradation rate andphotoresponsibility of semiconductor; comparing to that, modification by sol-gel distribute Ptnanoparticles less evenly than former method. So the activities of photoassisted is better than that ofsol-gel method. According to this, we take photoassisted as the deposition method in the follow-up tests.Secondly, series parameters such as photoassisted time, amount of deposition, heattreat temperature,and calcination atmosphere were generally investigated.Nevertheless, after annealed under different atmospheres at different temperatures, Pt nanoparticlesdeposited on TiO₂exhibited distinct form of existences which played an important role of catalyticactivities of TiO₂. Viewed from SEM, FE-SEM and HR-TEM, TiO₂still maintained tube-structure after Ptdeposition; on the HR-TEM and the sideview of FE-SEM it can be seen that Pt nanoparticles graduallygrowed along with calcination temperature arises; and XRD tests displayed that crystal form also tend tobecome more regular. XPS confirmed that Pt was indeed deposited onto TiO₂and existed in variousvalence states after annealed under hydrogen at different temperatures, yet the existence form of Pt varies with different treatments. Experiments of photocatalytic methyl orange （MO） degradation andphotoelectric responsibility further improved XPS analysis and indicated that sample with nulvalent anddivalent Pt formed by hydrogen heattreat under200oC presented the best catalytic activities. After heatedat500oC under hydrogen Pt nanoparticles existed by nulvalent and aggregated together, resulting specificsurface decreased and so did the active spot; thereby, photocatalytic activities lowered down significantly.更多还原