三氧化钨/氧化银复合材料的水热法合成及其光催化降解性能研究

染料污染是水污染中最严重的问题之一,吸引了很多科学家的关注.人们尝试了很多方法去解决该问题,如化学氧化法、物理吸附法、光催化降解法和生物降解法等.与其他几种方法相比,光催化法有着低能耗、环保以及高效等优势.三氧化钨是常见的半导体材料,具有独特的光学性能,近年来受到了广泛的研究.本文以钨酸钠和硫脲为前驱体,通过水热法制备了三氧化钨/氧化银(WO_3/Ag_2O)复合材料,并用光催化降解亚甲基蓝来分析其光催化性能.通过X射线光电子能谱、X射线衍射、透射电子显微镜、扫描电子显微镜、紫外可见吸收光谱等表征手段对样品的形貌、晶格结构和光催化的性能进行表征.氧化银的带宽为1.2 e V,对可见光很敏感,三氧化钨和氧化银的复合使材料在可见光下的光催化活性显著增强,在可见光下对亚甲基蓝染料的光降解率可以达到98%.实验结果表明,复合材料中的三氧化钨纳米棒为六方相,其平均直径约为200 nm,平均长度约为4μm.而复合材料中的氧化银纳米颗粒为六方相,附着在氧化钨纳米棒的表面,平均晶粒尺寸为20 nm.氧化银的存在为复合材料提供了更多的反应活性位点.相较于单一组分,复合材料在可见光下的光吸收度更高,这说明三氧化钨和氧化银的复合改变了材料的能带结构.研究发现,三氧化钨和氧化银之间形成的异质结构是其优良光催化性能的来源.此外,三氧化钨和氧化银复合材料还具有良好的催化稳定性和化学稳定性.本文结果表明,可以通过给宽带隙的半导体材料复合一些带隙合适的金属氧化物以提升其光催化活性.

Photocatalytic activity of tungsten trioxide/silver oxide composite under visible light irradiation for methylene blue degradation

Dye pollution,one of the most serious problems in water pollution,has attracted the attention of scientists.There are many methods,such as chemical oxidation,physical adsorption,biodegradation,photocatalysis,etc.,that have been adopted to handle the crisis of dye polultion. Compared with other strategies,photocatalysis has its unique advantages including low energy consumption,environment amicableness and high efficiency.Tungsten trioxide (WO₃),a semiconductor with a band gap of 2.8 eV,has unique physical and chemical properties,and it has been applied to the area of photocatalysis to solve the problem of water pollution in recent years.However,the photocatalytic efficiency of bulk tungsten oxide fails to reach the expected.In this paper,a one-dimensional complex of tungstun trioxide and silver oxide (WO₃/Ag₂O) is synthesized via a simple hydrothermal method for photocatalytic degradation of methylene blue.The crystal structure,morphology and photocatalytic degradation ability towards methylene blue are characterized and analyzed via X-ray diffraction,scanning electron microscopy,transmission electron microscope,X-ray photoelectron spectroscopy,and UV-Vis spectrophotometer.Silver oxide (Ag₂O),with a band gap of 1.2 eV,is found to be sensitive to visible light.The combination of tungsten trioxide and silver oxide promotes its photocatalytic efficiency dramatically under visible light illumination. Results show that WO₃ nanorods in the composite possess a one-dimensional,hexagonal structure with an average length of 4μm and a diameter of 200 nm.The Ag₂O attached to WO₃ nanorods forms hexagonal nanoparticles and their average diameter reaches 20 nm.It is observed that WO₃/Ag₂O composite displays a loose structure and a high specific surface area,which provides more reactive sites.Comparing with single component,UV-Vis spectrophotometry shows that the composite has a highabsorbance in the range of visible light.The combination of tungsten trioxide and silver oxide can change the band gap of the photocatalyst whereas the photocatalytic efficiency of the composite reaches 98% in 60 min under visible light.Therefore,the synergistic effect of WO₃ and Ag₂O plays a vital role in enhancing the photocatalytic performance.Moreover,the stability of photocatalyst is one of the most important indicators of its recycling and long-term effectiveness,and the present WO₃/Ag₂O composite has good catalytic and chemical stability.This investigation proves that the combination of wide bandgap photocatalysts with visible-light sensitive metal oxide with large specific area will improve photocatalytic activity efficiently under visible light.