TiO₂基薄膜的制备及其对气相甲酸的光催化降解研究

【作者】 杨洋；

【导师】 赖敏；

【作者基本信息】 南京信息工程大学 ， 材料科学与工程， 2022， 硕士

【摘要】 室内外空气污染已经成为现代社会普遍关注的问题。尽管在过去的几十年中,世界范围内颁布了许多关于空气质量的政策和法规,但空气污染仍然在对人类健康产生负面影响。挥发性有机化合物（Volatile Organic Compounds）是大气污染之一,它的治理问题引起了研究者的关注。二氧化钛（TiO₂）半导体光催化材料具备高效无毒、稳定性好、经济环保等优势,因此使用TiO₂作为光催化剂降解污染物是解决大气污染的有效方法。然而,TiO₂的禁带宽度较宽,对可见光吸收能力差;单一的TiO₂光生载流子分离效率较低,这使得其应用受到了较大局限。本论文通过半导体复合对TiO₂进行了改性,以二氧化钛/氧化锌（Zn O）纳米棒二元异质结为主体,通过三元复合所具有的协同效应,拓宽材料的光响应范围,抑制光生电子空穴的复合,实现对单一光催化材料可见光催化性能的改善。通过实验,对材料的结构与光催化性能进行了表征测试与分析。具体的研究内容如下:（1）以不锈钢网为基底,采用改进提拉法制备了TiO₂薄膜,采用水热法在TiO₂材料上制备了Zn O纳米棒,并用XRD、SEM、TEM、UV-Vis技术对薄膜进行了表征。然后通过光催化降解挥发性有机化合物气相甲酸来评估制备材料的光催化性能,研究表明,甲酸的光催化降解过程符合一级动力学反应模型,并研究了光催化降解的反应机理。（2）通过调控反应过程中的生长反应温度、反应时间等参数,制备出具有不同微观结构的Zn O纳米棒,探讨了不同的工艺因素对Zn O微观结构和光催化性能的影响。当生长温度为95℃、生长时间为4 h时,TiO₂/Zn O复合薄膜在紫外光下具有最佳的光催化性能,降解效率达到94.42%。同时,探讨了相对湿度与光照强度对气相甲酸光催化降解效率的影响:甲酸的降解过程中存在最合适的相对湿度,随着光照强度的增加,甲酸的降解效率随之提高。并且制备的光催化材料具有良好的稳定性和可重复利用性。（3）以TiO₂/Zn O为基底,采用煅烧法在TiO₂/Zn O二元异质结表面修饰了g-C₃N₄材料,发现TiO₂/Zn O/g-C₃N₄复合薄膜在可见光范围内具有较好的光催化性能,且修饰了1层g-C₃N₄的复合材料具有最佳的光催化性能,对气相甲酸的降解效率可达到93.86%。这是由于窄禁带宽度半导体g-C₃N₄能有效地拓宽光吸收范围,且异质结的形成抑制了光生电子空穴对的复合,从而增强了复合薄膜的光催化性能。制备的光催化剂具有良好的稳定性,并且利于回收利用。更多还原

【Abstract】 Indoor and outdoor air pollution has become a common concern in modern society.Although many policies and regulations regarding air quality have been enacted around the world over the past few decades,air pollution still has a negative impact on human health.As the main component of air pollution,the effective treatment of volatile organic compounds（VOCs）has attracted extensive attention of researchers.Titanium dioxide（TiO₂）semiconductor photocatalytic material has the advantages of high efficiency,non-toxicity,good stability,economy and environmental protection,etc.Therefore,using TiO₂ as a photocatalyst to degrade pollutants is an effective method to solve air pollution.However,TiO₂ has a wide band gap and poor absorption of visible light and single TiO₂ has a low separation efficiency of photogenerated carriers,which limits its application.In this paper,TiO₂ was modified by semiconductor compounding.With the binary heterojunction of titanium dioxide/zinc oxide（Zn O）nanorods as the main body,through the synergistic effect of ternary composite,the optical response range of the material is widened,the recombination rate of photogenerated electron holes is reduced,and the visible photocatalytic performance of a single photocatalytic material is improved.Through experiments,the structure and photocatalytic properties of the materials were characterized and tested.The main research contents of this paper are as follows:（1）First,TiO₂ thin films were prepared on stainless steel mesh by the improved pulling method,and Zn O nanorod thin films were prepared on TiO₂ by hydrothermal method.The thin films were characterized by XRD,SEM,TEM and UV-Vis techniques.Then,the photocatalytic performance of the prepared materials was evaluated by photocatalytic degradation of volatile organic compound gas-phase formic acid.The study shows that the photocatalytic degradation process of formic acid conformed to the first-order kinetic reaction model,and the reaction mechanism of photocatalytic degradation was studied.（2）Zn O nanorods with different microstructures were prepared by adjusting the growth reaction temperature,reaction time and other parameters in the chemical reaction process,and the effects of process factors on the microstructure and photocatalytic performance of Zn O were discussed.When the growth temperature is 95℃and the growth time is 4 h,the TiO₂/Zn O composite film has the best photocatalytic performance under ultraviolet light,and the degradation rate reaches 94.42%.At the same time,the effects of relative humidity and light intensity on the photocatalytic degradation efficiency of gas-phase formic acid have been discussed:there is an optimum relative humidity during the degradation of formic acid,and the degradation efficiency of formic acid increases with the increase of light intensity.In repeated experiments,the prepared photocatalytic material has good stability.（3）The g-C₃N₄ material was modified on the surface of TiO₂/Zn O binary heterojunction by calcination method.It was found that the TiO₂/Zn O/g-C₃N₄ composite film had excellent photocatalytic activity in the visible light band,and the composite modified with a layer of g-C₃N₄ had the best photocatalytic performance.The degradation rate of gas-phase formic acid can reach 93.86%.This is because the narrow band gap semiconductor g-C₃N₄ can effectively broaden the light absorption range.At the same time,the formation of heterojunction reduces the recombination rate of photogenerated electron-hole pairs and enhances the photocatalytic performance of the composite film.The composite film has high stability and is conducive to recycling.更多还原