【作者】 姜楠；

【导师】 郝霄鹏； 吴拥中；

【作者基本信息】 山东大学 ， 材料学， 2013， 硕士

【摘要】 环境污染和能源短缺是21世纪人类面临的两大难题,光催化技术因其反应速度快、条件温、效率高和直接利用取之不尽的太阳能来源驱动反应等独特性质,而成为解决这两大难题的一种新型的绿色技术。Ⅱ-Ⅵ族硫化物中的CdS、 ZnS作为典型的半导体材料,成为研究重点,CdS为窄带隙半导体(2.42eV),能响应可见光,但其自身光生电子-空穴对分离效率低,并且存在光腐蚀现象,限制了其光催化活性；ZnS较宽的带隙(3.7eV),仅能被紫外光激发,限制了其可见光的响应,从而限制了其对太阳能的利用率。因此,以CdS和ZnS为基础开发具有高效率、高稳定性的可见光催化剂成为本论文的研究目标。本文利用还原氧化石墨烯复合硫化镉(RGO/CdS)、还原氧化石墨烯复合硫化锌(RGO/ZnS)和ZnxCd1-xS三元固溶体等体系来提高该体系材料的可见光催化性能。1)采用微波法一步反应制备了还原氧化石墨烯复合硫化镉(RGO/CdS)纳米材料,利用XRD、 SEM、 TEM、 EDS、 DRS、 Raman、 XPS、 FTIR等手段对样品进行了结构、成分、形貌表征和光电流测试。研究结果证明反应得到了还原氧化石墨烯(RGO)片层与CdS纳米颗粒的复合材料,CdS纳米颗粒均匀分布在RGO表面。以RGO/CdS为光催化剂,利用可见光降解罗丹明B测试结果表明RGO/CdS纳米复合材料的光催化效率明显高于纯CdS,其中当RGO复合量为10%时光催化效率最高,在80min内将Rh B几乎完全降解,循环试验证明样品具有良好的稳定性。实验表明RGO的加入使得CdS纳米颗粒的尺寸变小,拓宽了材料的光响应范围、增大了吸收强度、抑制了光生电子-空穴对的复合,从而提高了样品的光催化活性和稳定性。2)采用微波法一步反应制备了还原氧化石墨烯复合硫化锌(RGO/ZnS)纳米材料,利用XRD、 SEM、 TEM、 EDS、 DRS、 FTIR、 Raman、电化学等手段对样品进行了结构、成分、形貌表征和光电流测试。结果证明复合材料中ZnS纳米颗粒为六方纤锌矿结构,反应过程中GO被还原,直径在50nm左右的ZnS纳米球均匀分布在RGO片层表面。RGO/ZnS复合材料光电流的显著增强说明RGO片层与ZnS颗粒之间存在光生电子的有效传递。以RGO/ZnS为光催化剂,紫外光下降解Rh B。实验证明RGO/ZnS具有较高的光催化效率,其中当复合物中RGO含量为8%时样品具有最高的光催化效率,循环实验证明材料具有较好的稳定性,探讨了RGO/ZnS光催化机理。3)在室温离子液体1-丁基-3-甲基咪唑硫氰酸盐中,以硫氰酸锌为锌源,硫钒酸锌为锌源,采用微波法成功制备了ZnxCd1-xS固溶体纳米材料,改变反应物中Zn/Cd比来制备不同组分的固溶体。利用XRD、 SEM、 TEM、 EDS、 DRS等手段对样品进行行了结构、成分、形貌表征和光电流测试,结果表明得到的系列复合材料均为六方纤锌矿结构,并且ZnxCd1-xS样品德吸收带边均位于可见光区。尽管具有类似的尺寸和结构,不同组分的ZnxCd1-xS固溶体光催化剂在可见光下对甲基橙(MO)溶液表现出不同的催化效率,其中Zn0.36Cd0.64S具有最高的光催化效率,可见光下照射4h后降解率达到85%,明显优于纯的CdS和ZnS,研究发现在光催化过程中穴主要起着氧化剂的作用。更多还原

【Abstract】 The increasingly serious environmental pollution and energy shortages have become the two major problems in the21st century. Photocatalysis technology has been considered as a novel "green" approach to solve these problems due to its mild reaction conditions, high efficiency and the inexhaustible solar resource. The typically binary II-VI sulfide, especially CdS and ZnS, have attracted much attention and become the focus of our research. CdS has a narrow band gap (2.42eV), and can respond to the visible light. But the low separation efficiency of electron-hole pairs and photocorrosion limit its photocatalytic activity. The relatively large band gap of3.7eV for ZnS limits its photoresponse to the visible light region, and thus limits the utilization of solar energy. Therefore, Based on CdS and ZnS, the way to efficiently exploit novel photocatalysts with high efficiency and high stability is the goal of our study. According to the above analysis, we successfully prepared Reduced Graphene Oxide/CdS(RGO/CdS), Reduced Graphene Oxide/ZnS(RGO/ZnS) and ZnxCd1-xS solid solution to improve its photocatalytic performance.1) The RGO/CdS nanocomposites were successfully prepared by a microwave method and the structure, composition and morphology of the synthesized products were systematically characterized by X-ray powder (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), UV-vis diffuse reflectance spectra (DRS), Raman scattering, X-rays photoelectron spectroscopy (XPS), fourier transformation infrared spectroscopy (FTIR) and photocurrent test. The results indicated that CdS nanoparticles distributed evenly on the reduced graphene sheets. Using the degradation of rhodamine B as model reactions in the aqueous phase under visible light, the sample RGO/CdS-10%possessed the best activity and good stability after3-cycle experiments under same condition. The conversion of RhB degradation was almost to100%after80min of irradiation. The significant enhancement in photoactivity can be ascribed to be the smaller morphology of CdS nanoparticles in the nanocomposites and the introduction of graphene which reinforced the adsorptivity of the photocatalysts, suppressed the electron-hole pair recombination, and extended the light absorption range in the as-synthesized RGO/CdS nanocomposite photocatalyst.2) The RGO/ZnS nanocomposites were successfully prepared by a microwave method and the structure, composition and morphology of the synthesized products were systematically characterized by X-ray powder (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), UV-vis diffuse reflectance spectra (DRS), fourier transformation infrared spectroscopy (FTIR), Raman scattering and photocurrent test. The results indicated that ZnS has hexagonal wurtzite structure and GO has been successfully reduced to RGO sheets. RGO sheets have been successfully decorated by dense ZnS nanoballs with a mean diameter of50nm composed of many smaller self-assembled ZnS nanoparticles. The obvious enhancement observed from photocurrent spectroscopy suggests that there is photoinduced electron-transfer between ZnS nanoparticles and RGO sheets. The as-prepared RGO/ZnS nanocomposites show an excellent photocatalytic activity toward the photodegradation of rhodamine B and the sample RGO/ZnS-8%possessed the best activity. Frthermore, the mechanism of photocatalytic process of new graphene-based material is discussed briefly in this study.3) ZnxCd1-xS nanoparticles were successfully synthesized by microwave method in ethylene glycol with1-butyl-3-methylimidazolium thiocyanate ([BMIMJSCN) cadmium thiocyanate (Cd(SCN)2) as the cadmium resource and zinc thiocyanate (Zn(SCN)2) as the zinc resource. The composition of the solid solution was adjusted by controlling the Zn/Cd molar ratios. The prepared nanoparticle was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), UV-vis diffuse reflectance spectra (DRS) and photocurrent test to analyse its structure, composition and morphology. The results showed that all of the prepared samples were wurtzite phase and the absorption onsets were in visible light range. Despite the analogous size and configuration, the solid solution with different Zn/Cd molar ratio exhibit composition-dependent photocatalytic efficiencies for degradation of Methyl Orange solution under visible light illumination. Among all the photocatalysts, the sample Zn0.36Cd0.64S possessed the best activity, consistenting with the results of photocurrent test. The conversion of MO degradation was up to85%after4h of irradiation which was obviously superior to CdS and ZnS under identical conditions. At the same time, we found that in the photocatalytic process under visible light, holes contributed to the degradation.更多还原