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作为一类新兴的光催化材料,钼酸盐纳米材料具有高表面能、多活性位点和高选择性等优点,在可见光催化降解污染物方面有着重要应用,近年来受到广泛关注.作为钼酸盐家族重要的一员,钼酸银在杀菌、表面增强拉曼光谱、气敏材料等方面均有重要应用,但其光催化性能却鲜见报道.这是由于它的光谱响应范围窄和广生载流子分离效率低所致.虽然近来有少量基于钼酸银的复合材料的光催化研究,但催化效果不佳.众所周知,作为自由电子体系,诸多金属纳米粒子,如贵金属、碱金属等,存在表面等离子体共振效应(SPR),使得贵金属,特别是Ag,Au等纳米粒子在可见区域有较强的吸收.利用这一特性,Awazu等将Ag纳米颗粒沉积在TiO_2表面,创造性地将SPR应用于光催化反应,开发出在可见光谱区具有宽光谱吸收特征的Ag/TiO_2.随后陆续合成出基于SPR效应的Ag@AgCl,Ag/Ag_3PO_4材料均具有良好的光催化性能.基于此,本文在十二烷基硫酸钠(SDS)的存在下,采用水热法一步合成了具有SPR效应的Ag/Ag_2MoO_4可见光催化材料,并利用X射线粉末衍射(XRD)、紫外可见漫反射(DRS)、X射线光电子能谱(XPS)和扫描电子显微镜(SEM)等技术对材料进行了表征.系统地探讨了体系pH值、反应时间、表面活性剂用量对产物的晶相和微观形貌等的影响.此外,还利用罗丹明B降解实验考察了上述合成条件对材料可见光催化活性的影响,并通过捕获剂实验深入地研究了起催化作用的活性物种.XRD结果表明,体系的pH值对材料的晶型有极大影响,随着pH由酸性变至中性、碱性,最终得到的钼酸银也由Ag_2Mo_2O_7过渡到Ag_2MoO_4.SEM图显示在最优条件(pH为7,加入0.5g SDS,160℃下水热14 h)下制得的钼酸银为八面体的Ag_2MoO_4,且其表面均匀地分布着Ag纳米颗粒,与XPS图谱结果一致.另外表面活性剂SDS的用量对所合成材料的形貌影响很大.本文可一步得到以八面体Ag_2MoO_4为主的Ag/Ag_2MoO_4复合材料,是因为SDS的疏水长链可以诱导Ag_2MoO_4的各向异性生长.DRS结果表明,Ag_2MoO_4八面体上Ag颗粒的引入使其在可见光区的吸收明显加强,因而它在可见光下催化降解罗丹明B降解反应活性增加.捕获剂实验结果表明,起决定性作用的活性物种是光生空穴,另外·OH也起了一定作用.
As a new type of photocatalytic material, molybdate nanomaterials have many advantages, such as high surface energy, multi-active sites and high selectivity. They are important applications in the visible light photocatalytic degradation of pollutants and have drawn much attention in recent years. An important member of the salt family, silver molybdate in sterilization, surface enhanced Raman spectroscopy, gas sensitive materials have important applications, but its photocatalytic properties are rarely reported.This is because of its narrow spectral response and wide However, the photocatalytic activity of a small amount of silver molybdate-based composites has been deteriorated, but the catalytic effect is poor.As a free electron system, many metal nanoparticles, such as noble metals, alkali metals, etc. , There is a surface plasmon resonance (SPR) effect, which makes the noble metal, especially Ag, Au and other nanoparticles have strong absorption in the visible region.With this feature, Awazu et al deposited Ag nanoparticles on the surface of TiO 2, creatively SPR was applied to photocatalytic reaction to develop Ag / TiO 2 with broad spectral absorption in the visible region.Afterwards, Ag @ AgCl and Ag / Ag 3 PO 4 based on SPR were synthesized successfully Good photocatalytic performance.According to this, the Ag / Ag 2 MoO 4 visible light photocatalytic material with SPR effect was synthesized in one step by hydrothermal method in the presence of sodium dodecyl sulfate (SDS), and characterized by X-ray powder diffraction ), UV-Visible Diffuse Reflectance (DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize the material.The pH value, reaction time and the amount of surfactant The crystal phase and the micro-morphology, etc. In addition, Rhodamine B degradation experiments were also used to investigate the synthesis conditions on the photocatalytic activity of the material, and through the capture agent in-depth study of catalytic activity of the species. XRD The results show that the pH value of the system has a great influence on the crystal form of the material. As the pH changes from acidic to neutral and alkaline, the silver molybdate eventually transitions from Ag_2Mo_2O_7 to Ag_2MoO_4.SEM images show that under optimal conditions (pH7, adding 0.5g SDS, hydrothermal at 160 ℃ for 14h), the silver molybdate is octahedral Ag_2MoO_4 and its surface is uniformly distributed with Ag nanoparticles, which is consistent with the results of XPS. The amount of SDS dosage on the combination The morphology of the material has a great influence on the Ag2MoO4 composites.The Ag / Ag2MoO4 composites dominated by octahedral Ag2MoO4 can be obtained in this paper because the hydrophobic long chains of SDS can induce the anisotropic growth of Ag2MoO4.The results of DRS show that Ag2MoO4 octahedra The introduction of Ag particles in the visible region of the absorption was significantly enhanced, so it under visible light catalytic degradation of Rhodamine B degradation reaction increased capture agent results show that the decisive role of the active species is photogenerated holes, in addition · OH Played a role.