【作者】 刘晓霞；

【导师】 樊彩梅；

【作者基本信息】 太原理工大学 ， 应用化学， 2012， 硕士

【摘要】 BiOX(X=Cl, Br, I)是一系列间接带隙半导体材料,由[Bi202]层与卤原子层交错形成层状四方氟氯铅矿(PbFCl)结构,为一类新型的光催化材料。BiOX有许多优点,如光催化活性好,性能稳定,所得产品比表面积较大,光催化水处理过程用量少、毒性小,与有机基体的相容性较好,可吸收太阳光等。因此,近年来BiOX吸引了研究者们的广泛关注。为了解决粉末催化剂固液分离难、回收利用难和实际应用难等问题,本文采用简单、实用、能耗低的固定化方法合成了BiOCl薄膜光催化剂,并考察了制备过程参数对薄膜光催化剂活性的影响,期望为光催化降解水中有机污染物技术的实际应用提供基础数据。分别采用醇解-涂覆法和电化学方法在低温条件下制备了BiOCl薄膜光催化剂,通过X-射线衍射(XRD)、扫描电子显微镜(SEM)、X-射线能谱分析(EDS)、X-射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-vis DRS)等手段对薄膜的性质和形貌进行了表征；并以甲基橙为目标降解物,用紫外灯为光源,研究了制备条件对薄膜光催化活性的影响,得到如下研究结果：一、花球状BiOCl薄膜的醇解-涂覆法制备和光催化性能1.采用醇解-涂覆法制得了花球状BiOCl薄膜光催化剂,所制备的样品呈四方相晶体结构,无其他杂质为BiOCl纯相,表面呈现由纳米薄片组装而成的花球状微观结构,样品由Bi、0及C1三种元素构成,且元素组成比例与BiOCl的化学计量比相似,样品对紫外光有良好的吸收,该制备过程简单且无需高温焙烧。2.以甲基橙为目标降解物,在紫外光照射下考察了薄膜的光催化活性和稳定性。当醇解温度为60℃,采用乙二醇为溶剂,未经高温焙烧时制得的BiOCl薄膜催化剂具有最佳光催化活性,150min内对甲基橙的光催化降解率可达97%,重复使用4次之后,降解率仍大于94%,使用前后样品的XRD谱图也未发生明显改变,说明所制BiOCl薄膜光催化剂在紫外光下具有良好且稳定的光催化活性。3.通过对形成机理的简单推测,我们认为乙二醇溶剂可能有助于花球状结构的形成。通过考察外加捕获剂对BiOCl薄膜光催化活性的影响,得到在光催化降解甲基橙过程中,空穴(h+)可能起到关键作用。二、 BiOCl薄膜的室温电化学法制备及其光催化性能1.在室温条件下,先后通过阴极电沉积和阳极氧化法在Ti基体上制得了BiOCl薄膜；所制薄膜由四方相BiOCl构成,呈现交错的片状结构,对紫外光有良好的吸收；样品由Bi、O及Cl三种元素构成,且元素组成比例与BiOCl的化学计量比相似。2.不同的氧化电压和氧化时间对BiOCl的晶格取向、形貌、光催化活性和稳定性都有一定的影响。当氧化电压为2.0V,氧化时间为60min时,所制薄膜具有最佳光催化活性,此时薄膜的晶相结构有明显的110取向,呈现均匀整齐的片状结构；150min内对甲基橙的降解率可达98%,且制成的薄膜不易脱落。3.通过对降解过程中甲基橙溶液的紫外-可见全波扫描曲线的测定以及光解、吸附和光催化实验的对比研究,发现降解过程中所制BiOCl薄膜的光催化作用占主导地位,所制BiOCl薄膜经过5次循环使用,在紫外光下对甲基橙的降解活性仍可达90%,表明薄膜具有稳定的光催化活性。另外,所制薄膜在模拟太阳光下对甲基橙也有降解作用。更多还原

【Abstract】 BiOX (X=Cl, Br, I), a series of indirect band gap semiconductor, is composed of a tetragonal PbFCl structure containing [Bi2O2] layer and X layer. It is a kind of novel photocatalyst. BiOX has many advantages, such as, high photocatalytic activity, stable chemical property, large specific surface area, low consumption in photocatalytic process, low toxicity, good compatibility to organic substance, excellent absorption to the sun light and so on. Therefore BiOX attracted more and more attentions in recent years. The powder catalyst expresses poor dispersion in solution and difficulties in separation and reuse, especially tiny particles with micro-nano structure. In order to solve the problems about the powder catalyst, we prepared BiOCl thin film photocatalyst in a simple, practical and low energy consumption method, tested the effects of the parameters in preparation process on the catalytic activity of BiOCl thin film, and expected to provide basic data to the practical application of photocatalytic degradation organic pollutants.BiOCl thin film was prepared by the alcoholysis-coating method and electrochemical method at low temperature. The obtained thin film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electronic energy spectrum (EDS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic activities of BiOCl thin films prepared in different conditions were also evaluated by the degradation of methyl orange (MO) in water under UV light irradiation. All the obtained results are listed as follows:Part I The preparation of flower-like BiOCl thin film via alcoholysis-coating method and its photocatalytic activity1. Flower-like BiOCl thin film was prepared in the alcoholysis-coating method, which is simple and does not need calcination. And the results showed that the obtained BiOCl film without calcination was composed of flower-like sphere structure with tetragonal phase and had a good absorption to ultraviolet. The sample was composed by Bi, O and Cl three elements, and had a ratio close to the stoichiometric ratio of BiOCl.2. The photocatalytic activity and stability of BiOCl thin film was evaluated by the degradation of MO in water under UV light irradiation. The degradation experimental results confirmed that the thin film prepared at low temperature expresses a high photocatalytic activity and can achieve a97%degradation to10mg/L MO solution after150min UV light irradiation. The photocatalytic activity still remained an above94%removal of MO after used four cycles, and the XRD spectra of the sample before and after use were not changed, which showed that the obtained BiOCl thin film expressed a good stability. 3. A possible formation mechanism of BiOCl thin film was also inferred and the results suggested that the ethylene glycol solvent may contribute to the formation of flower-like sphere structure. Through investigate the influence of capture agent on the photocatalytic activity of BiOCl thin film, we get that hole (h+) may play the key role in photocatalytic degradation process of MO. Part II The preparation of BiOCl thin film at room temperature via electrochemical method and its photocatalytic activity1. BiOCl thin film was prepared on the Ti substrate through the cathodic deposition and anodic oxidation method at room temperature. The BiOCl thin film obtained at the best preparation condition was composed by nanoplates with tetragonal phase and had a good absorption to UV irradiation. The sample was composed by Bi, O and Cl three elements, and had a ratio close to the stoichiometric ratio of BiOCl.2. The oxidation voltage and oxidation time had the effect on the lattice orientation, morphology, photocatalytic activity and stability of BiOCl thin film. The results showed that when the Film1was oxided at2.0V for60min the obtained BiOCl thin film had an obvious110orientation, was composed by interlaced nanoplates, and performed the best photocatalytic activity (about98%in150min) and stability.3. In the degradation process, the UV-vis whole wave scanning curves of MO solution were determined. We also compared the roles of photolysis, adsorption and photocatalysis in the photocatalytic process. The results indicated that the MO in the solution was decomposed gradually in the photocatalytic process. The photocatalysis played the predominant role. The photocatalytic activity of the prepared BiOCl thin film still remained an about90%removal of MO after used five cycles, which showed the good stability of the BiOCl thin film. In addition, the MO could be decomposed slightly in presence of BiOCl thin film under the similated sunlight.更多还原