铋系纳米光催化剂的制备、表征及光催化性能研究

【作者】 黄倩倩；

【导师】 周泊；

【作者基本信息】 南京师范大学 ， 物理化学， 2011， 硕士

【摘要】 铋系光催化剂具有良好的催化性能,它们在可见光区均存在明显的吸收,这表明这些物质均可以响应可见光,因而具有可见光催化氧化处理有机污染物的能力。如何改善铋系光催化剂的制备方法,开发它们的良好性能是目前迫切需要解决的问题。Bi203是一类新型的光催化剂,与Ti02相比报道的比较少。由于Bi203的禁带宽度较窄(2.8 eV),可以吸收可见光受激发产生光生电子和空穴,可以被用来降解有机污染物。卤氧化铋BiOX (X=F、Cl、Br、I)是一种新型的半导体材料,它具有独特的电子结构、良好的光性能和催化性能。目前关于它的光催化应用方面的报道较少,研究表明卤氧化铋BiOX的光催化活性普遍优于商品TiO2(P25)的光催化活性,并且随着卤素原子序数的增加光催化活性也随之增强,即铋氧化碘BiOI的活性最高。基于此,本文首次选用微波法合成了不同晶型的Bi203及BiOI光催化剂,并系统的研究了光催化剂的制备及其光催化降解有机污染物的能力,主要包括以下几个方面的内容：一、利用微波法的反应速率快,效率高的特点合成前驱体微波产物,并利用X-射线衍射(XRD)、透射电镜扫描(TEM)、紫外可见漫反射光谱(DRS)对产物进行表征。XRD结果表明,通过不同温度煅烧提高产物结晶度,合成了不同晶型纳米级Bi203,煅烧温度300℃是合成β-Bi203的适宜温度,且随着煅烧温度的升高,更容易得到α-Bi2O3。TEM结果表明,热处理后结晶度改善。DRS谱图结果表明,a-Bi203带隙值为2.84 eV,p-Bi203的带隙值为2.77 eV,因此β相能够较好的利用可见光。以可见光下罗丹明B的降解为模型反应,研究了产物的光催化性能,证明β-Bi203的光催化活性比a-Bi203强。以Bi(NO3)3·5H2O和KI为主要原料,乙二醇与水为溶剂,在微波条件下合成由纳米片组成的微球BiOI光催化剂,以罗丹明B为模型污染物,研究其光催化性能。运用XRD、SEM、TEM、IR、DRS等技术对光催化剂的结构、形貌和光学性能进行研究,并与其光催化活性进行关联。首先将常温合成法作为对照实验,通过光催化性能测试证明微波产物性能高于常温搅拌产物。然后在不同溶剂体系中合成BiOI催化剂,选择最佳溶剂体系,在以上基础上分别对其中的实验参数如反应物摩尔配比、反应时间、反应功率等进行调整实验,探索合成BiOI光催化剂的最佳条件以获得最优性能的催化剂,同时研究了光催化反应的最佳用量。实验表明,微波合成BiOI较佳实验条件为,KI与Bi(NO3)3·5H2O的摩尔比为0.5：1,醇水配比为1：1,微波功率300 W,辐射10 min,通过简单快速的反应合成微球结构球状BiOI催化剂,微球由纳米片交叠而成,片层厚约为20nm,片的边长约为200nm,样品具有较大的比表面积,在可见光照射下2h对罗丹明B的降解率可达96%,光催化性能优越。更多还原

【Abstract】 Bismuth-radicle nano-structural oxides have good catalytic properties, they have obvious absorption in the visible region, suggesting that these substances are able to respond to visible light, which deal with the visible light oxidation of organic pollutants. It is necessary to improve the preparation of bismuth-radicle nano-structural oxides and their development of good performance. Bi2O3 is a new type of photocatalyst, compared with TiO2.Since the narrow band gap of Bi2O3 (2.8 eV), absorb visible light generated by the photo-excited electrons and holes, Bi2O3 can be used to degrade organic pollutants. Halogen bismuth oxide BiOX (X=F, Cl, Br, I) are new type of semiconductor materials, which has a unique electronic structure, good optical properties and catalytic performance. The photocatalytic properties of BiOX riding better than commodities TiO2 (P25). With the atomic number of halogen photocatalytic activity gradually increased, the activity of bismuth oxide iodide BiOI is the highest in recent years, it hardly reported in the literature.In summary, microwave heating is an assisted-synthesis method to prepare Bi2O3 and BiOI powder photocatalyst, we examined their photocatalytic properties. This dissertation mainly includes:Bi2O3 have been successfully prepared by microwave irradiation process and subsequent thermal treatment. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy (DRS). The XRD results showed that the sample is well crystallized as the calcining temperature increased, the products changed fromβ-Bi2O3 to pure a-Bi2O3, so the calcination temperature 300℃is the appropriate temperature to synthesisβ-Bi2O3. The products are flaky, and the diameter become longer as the calcining temperature increased and the photocatalytic activities of the different crystal Bi2O3 were evaluated by the extent of decolorization of Rhodamine B under visible-light. The DRS spectra shows,α-Bi2O3 band gap is 2.84 eV,β-Bi2O3 band gap is 2.77 eV. The result shows that the photocatalytic activity ofβ-Bi2O3 is higher than a-Bi2O3.Nonospheres of BiOI photocatalyst were prepared by microwave irradiation method using Bi(NO3)3·5H2O and KI as the starting raw material, glycol and water as the solvent. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (TEM), Scanning electron microscope (SEM), UV-visible diffuse reflectance spectroscopy (DRS). At first, the room temperature mixing method as a control experiment, the photocatalytic performance tested by the product performance is higher than room temperature mixing of microwave products. Synthesized in different solvent system to select the best solvent system, above each of them on the basis of processing parameters such as molar ratio, reaction time, reaction to adjust the power and other experiments to explore the synthesis BiOI the best conditions for photocatalytic optimal performance of the catalyst. Photocatalytic reaction was also studied the optimum amount. Microwave Synthesis BiOI better experimental conditions, KI and Bi(NO3)3·5H2O molar ratio of 0.5:1, 1:1 alcohol-water ratio, microwave power 300 W, radiation 10 min. The microspheres are composed of nano-films, thickness of the film was about 20 nm, the length was about 200 nm. The result showed that BiOI has high catalytic activities towards the degradation of RhB under visible light irradiation.更多还原