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作为一种绿色技术,半导体光催化氧化广泛应用于环境污染物治理和太阳能转化领域.高效、稳定、可回收利用催化剂的开发是光催化技术发展的一个重要方向.Ag系半导体光催化剂因在可见光分解水制氢及降解有机污染物等方面表现出优异的催化性能而广受关注.然而,该催化剂失活快,制约了其应用.因此,提高Ag系半导体材料的光催化稳定性成为近年研究热点.在各种Ag基光催化剂中,Ag_3PO_4光催化剂因其在可见光下光氧化水产生O_2以及有机染料的光催化分解中有着高的量子效率,引起了人们广泛关注.如何进一步提升Ag_3PO_4光催化剂性能及在光催化过程中的稳定性成为研究焦点,包括Ag_3PO_4光催化剂的特殊形貌和晶体结构控制生长以及复合材料控制制备.但是Z型Ag_3PO_4基可见光催化剂的构筑仍然是一个挑战.本文利用Ag_2MoO_4和Ag_3PO_4的溶液相反应法合成了Z型Ag_3PO_4/Ag_2MoO_4复合光催化剂,通过Ag_3PO_4/Ag_2MoO_4异质结光催化剂在可见光下降解罗丹明B(RhB)、亚甲基橙(MO)、亚甲基蓝(MB)和苯酚研究了其光催化性能,采用X射线衍射(XRD)、能谱、傅立叶变换红外光谱(FT-IR)、拉曼光谱、场发射扫描电子显微镜(FE-SEM)以及紫外可见漫反射光谱(UV-vis)等手段表征了该催化剂.XRD,FTIR和拉曼光谱结果表明,复合材料由Ag_3PO_4,Ag_2MoO_4和单质银组成,表面成功合成了Z构型Ag_3PO_4/Ag/Ag_2MoO_4复合材料.SEM结果发现纯Ag_3PO_4是规则的球状,纯Ag_2MoO_4则是多面体状块的颗粒,在Ag_3PO_4/Ag_2MoO_4复合材料中可以看到规则的球状体Ag_3PO_4和Ag_2MoO_4纳米颗粒,并且随着Ag_2MoO_4含量的增加,Ag_3PO_4颗粒的尺寸逐渐减小.UV-vis结果发现Ag_2MoO_4的加入拓展了复合材料对可见光的吸收范围.光催化性能测试结果表明,8%Ag_2MoO_4/Ag_3PO_4在可见光下具有优异的光催化性能:可见光照射5 min,RhB,MO和MB的降解效率分别可达95%,97%和90%.复合材料样品经过4个循环实验后,其降解RhB的效率仍然保持在84%,证明了其具有较高的稳定性.为了进一步研究Ag_3PO_4/Ag_2MoO_4的光催化机理,我们用对苯醌、乙二胺四乙酸二钠和丁醇进行了捕捉剂实验.结果表明,超氧自由基和光生空穴在降解有机染料过程中起主要作用.通过光电流测试、复合材料价带导带位置计算以及循环过程样品XRD分析并结合文献结果认为,Z构型Ag_3PO_4/Ag/Ag_2MoO_4异质结光催化体系以及可见光照射初期金属Ag纳米颗粒的生成是其具有高光催化活性和稳定性的原因.
As a green technology, semiconductor photocatalytic oxidation is widely used in the field of environmental pollutant treatment and solar energy conversion.Efficient, stable, recyclable catalyst development is an important direction for the development of photocatalytic technology.Ag-based semiconductor photocatalyst due to visible light Decomposition of water to hydrogen and degradation of organic pollutants and other aspects of the performance of the excellent catalytic performance and widespread attention However, the catalyst deactivation, restricting its application.Therefore, to improve the Ag-based semiconductor photocatalyst stability has become a research Hot spots.A variety of Ag-based photocatalysts, Ag 3 PO 4 photocatalyst due to its visible light photocatalytic oxidation of water to produce O 2 and organic dyes photocatalytic decomposition has a high quantum efficiency, aroused widespread concern.How to further enhance the Ag_3PO_4 photocatalyst And the stability in the photocatalytic process have become the focus of research, including the special morphology and crystal structure controlled growth of Ag 3 PO 4 photocatalysts and the controlled preparation of composite materials. However, the construction of Z-Ag 3 PO 4 based visible light photocatalysts remains a challenge.In this paper, Ag 2 MoO 4 And Ag_3PO_4 solution phase reaction synthesis of Z-type Ag_3PO_4 / A g_2MoO_4 composite photocatalyst, the photocatalytic activity of Ag_3PO_4 / Ag_2MoO_4 heterojunction photocatalyst was studied under visible light degradation of RhB, MB, and MB. The photocatalytic properties of the composite photocatalyst were characterized by X-ray diffraction The catalysts were characterized by XRD, EDS, FT-IR, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and UV-vis spectroscopy. The results of FTIR and Raman spectroscopy show that the composites consist of Ag_3PO_4, Ag_2MoO_4 and elemental silver, and the Ag / Ag_2MoO_4 composites with Z configuration were synthesized successfully. The SEM results showed that the pure Ag_3PO_4 was spherical and Ag_2MoO_4 was polyhedron In the Ag_3PO_4 / Ag_2MoO_4 composite, regular spherical Ag_3PO_4 and Ag_2MoO_4 nanoparticles can be seen, and with the increase of Ag_2MoO_4 content, the size of Ag_3PO_4 particles gradually decreases.UV-vis results showed that the addition of Ag_2MoO_4 The range of visible light absorption of the composites was measured.The results of photocatalytic activity showed that 8% Ag 2 MoO 4 / Ag 3 PO 4 had excellent photocatalytic activity in visible light: visible light irradiation for 5 min, RhB , The degradation efficiencies of MO and MB were 95%, 97% and 90%, respectively.After four cycles of the composite samples, the efficiency of degrading RhB remains at 84%, which proves its high stability. In order to further study the photocatalytic mechanism of Ag_3PO_4 / Ag_2MoO_4, we carried out the trapping experiments with p-benzoquinone, disodium ethylenediaminetetraacetate and butanol.The results showed that in the process of degradation of organic dyes, superoxide radicals and photogenerated holes Plays a major role.According to the photocurrent test, the calculation of the conduction band position of the valence band in the composite material and the XRD analysis of the sample during the cycling process, the results show that the photocatalytic activity of the Ag-Ag nanoparticle in the Z-configuration Ag_3PO_4 / Ag / Ag_2MoO_4 heterostructures and the initial Ag Particle formation is responsible for its high photocatalytic activity and stability.