Preparation And Performance Analysis Of Compound Semiconductor Photocatalyst Based On Bi₂S₃

A large number of toxic and pollutants enter the space of people’s lives without meeting the standard in recent years. Those contaminants are difficult to degrade and they will lead to deterioration of water quality and chemical pollution incident. Ministry of Water Resources noted that "80% of the groundwater is undrinkable" in "Groundwater Dynamic Report" in January of this year. Photocatalytic technology based on semiconductor photocatalyst had won the attention and concern of many researchers at home and abroad because it was an environmentally friendly and cost-effective health technologies. Compared with the traditional pollution control methods, photocatalytic technology has some advantages of clean, no secondary pollution, without introducing additional chemical species such as H2O₂ and O₃ and photocatalyst can utilize cheap solar as an alternative light source to drive photocatalytic degradation of organic pollutants. Titania nanomaterials as one of most important photocatalyst is widely used in environmental governance, photolysis of water into hydrogen, solar cells, sensors and so on. Titanium dioxide with 3.2eV band gap can only absorb the UV light accounts for 5% of sunlight and majority of the sunlight can not be utilized. So how to make full use of sunlight and improve visible light absorption of photocatalyst attracted more and more people’s attention.Nowadays studies on construction of special structure and morphology of TiO₂ nanomaterials is increasing. TiO₂ nanowires and nanotubes with special structure were prepard by hydrothermal method and anodic oxidation on a metal titanium plate which as titanium source and the substrate. We also prepared compound semiconductor catalyst with visible light catalytic activity. Then we prepared WO₃ photocatalyst on the FTO conductive glass and WO₃ composite semiconductor, and further expand the production method of TiO₂ photocatalytic composite material. Using FE-SEM, XRD, TEM, XPS and DRS, PL characterized structure/morphology and optical properties of photocatalytic nanomaterials. Details are as follows.Firstly, we prepared TiO₂ nanowires and nanotubes by hydrothermal and anodic oxidation, and briefly analyzed morphology, composition and optical properties of TiO₂ nanotubes and nanowires. We found that T-TNW on Ti foil intertwined to form a cross-network structure, while T-TNT vertically grown on Ti foil and arranged with a highly ordered between the tubes. XRD pattern of T-TNW and T-TNT showed that T-TNW prepared by hydrothermal method is anatase TiO₂ with higher activity and T-TNT crystals prepared by anodic oxidation were mixed crystals of anatase and rutile. Different preparation methods and conditions may result in different material morphology, crystal type, crystal surface and the crystal axis angle, etc. According to these differences, we analyzed the formation mechanism of TiO₂ nanowires and nanotubes.Secondly, in order to make full use of sunlight and improve visible absorption of TiO₂ precursor, we compounded bismuth sulfide semiconductor which has a narrow bandgap. Bi₂S₃ was deposited on TiO₂ precursor by continuous circulation impregnation method which is simple in operation. Taking TiO₂ nanowires as an example, We analyzed SEM, TEM, XRD, XPS, DRS, PL of circulating impregnated Bi₂S₃/TiO₂ compound semiconductor in detailed. And found black Bi₂S₃ particles successfully deposited on the outside of TiO₂ nanowires the diameter of which between 20nm⁵0nm. With the increase of deposition times, size and quantity of particle also increased. DRS figure of Bi₂S₃/TiO₂ nanowires showed visible light absorption of nanowires enhanced, and PL indicated the composite energy loss of Bi₂S₃/TiO₂ reduced. We evaluated the activity of the catalyst by degradation of Acid orangeⅡand found that Bi₂S₃/TiO₂（10）’s degradation efficiency was increased by 11.77% under visible light, while degradation rate of which reached 85.46 % in the sunlight.In addition, we investigated the general applicability of the cycle impregnation on preparation of compound semiconductor photocatalytic material and further prepared the circulation impregnated Bi₂S₃/WO₃ composite photocatalyst. Short plank-shaped WO₃ was synthesized on FTO（F-doped SnO₂） conductive glass at the beginning by hydrothermal method, width of which is between a few nanometers to several microns. Then Bi₂S₃ particles successfully deposited on the surface the plank-shaped WO₃ by cyclic immersion method. Since energy band structure and location of WO₃ and Bi₂S₃ match each other, composite of Bi₂S₃ and WO₃ was advantageous to transfer and separate of photo-generated carriers. As compared to a monolayer of WO₃ and Bi₂S₃ film, Bi₂S₃/WO₃ heterojunction film has better photoelectrochemical properties.Research work of this paper can provide a certain reference for future design, fabrication, characterization and study of photocatalytic material. It also offers basis for design and development of new product.