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Controllable Synthesis Of New Semiconductor Photocatalyst And Preparation Of Semiconductor/Porous Carbon Composite Materials

Posted on:2013-02-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:C Y LiFull Text:PDF
GTID:1111330374971431Subject:Forest Chemical Processing Engineering
Abstract/Summary:PDF Full Text Request
The environmental pollution is increasingly serious with the development of human society so that the pollution of the environment, especially in door, caused the attention of people increasingly. It has been well known that majority of people spend approximately70%of their time in the indoor environments, such as residences, public buildings and offices. The levels of indoor air pollutants can be several hundred times higher than that of outdoor ones. The volatile organic compounds (VOCs) are widely used in industrial process and domestic activities. These extensive uses lead to water and air pollution, particularly in indoor pollution. The photocatalytic oxidation technology has increasingly been paid great attention to in recent years because photocatalysts in the removal of environmental pollution have a lot of advantages.Titanium dioxide(TiO2) have been extensively studied for environmental purification applications, due to its good characteristics of powerful oxidation strength, chemicalstability, nontoxicity and inexpensiveness. However, there are certain shortcomings associated with conventional TiO2powders catalysts, including an inefficient use of light, difficulty experienced during both stirring and separation of the catalyst from the reaction medium, rapidly losed activation, and the occurrence of low-concentration contamination near TiO2during the photocatalytic process. It may be a good strategy to extend the research using other classes of photocatalysts for improvement of the system efficiency or using the new composite materials.The main research contents and results were summarized as follows:1.Visible-light response Cu-Cu2+1O metal-semiconductor nanocrystals composites were successfully synthesized by using hydrothermal synthesis methods with Cu(NO3)2as starting materials, ethylene glycol (EG) as the solvent and reducing agent, and polyvinypyrrolidone k30(PVP) as surfactant. The photocatalytic performance was tested through the degradation of phenol under xenon lamp irradiation. The characterization results showed that the products were composed of two different sizes of particles. The larger particle with the diameter of50nm was Cu and the smaller particle with the diameter of20nm was Cu2+1O. The content of Cu2+1O was decreased and that of Cu was improverd when PVP was added. The distribution and integration of Cu and CU2+1O particles were also affected so that the photocatalytic activity was affected. Activity results showed that Cu-Cu2+1O particles could degrade phenol and the kinetics fits a first-order reaction. Cu2O/AC (porous activated carbon) composite photocatalysts were also prepared by an insitu method with Cu(NO3)2as starting materials, glutin as dispersant, and AC as a carrier of Cu2O. The crystal structure, spectra characteristics, and surface properties of the obtained catalysts were characterize in order to study the influence of AC on the composite photocatalysts. The results showed that the adding of actived carbon can affect the phase structure of composite photocatalysts. The energy band of Cu2O was had no effect on when actived carbon was added. The photocatalytic activity of the prepare Cu2O/AC and Cu2O for phenol degradation were investigated under visible light irradiation. The results showed the photocatalytic activity of the prepare Cu2O/AC was higher than that of the prepare CU2O/AC under visible light irradiation. It was attributed to the synergistic effect between porous activated carbon and Cu2O.2. The single-crystalline nickel oxide (NiO) mesoporous nanosheets and the flowerlike nickel oxide (NiO) were prepared, respectively. At first, the mesoporous nanosheets of single-crystalline β-nickel hydroxide (β-Ni(OH)2) were successfully synthesized via a facile hydrothermal method using Ni(NO3)2·6H2O as precursor in a mixed solution of sodium hydroxide (NaOH) and sodium dodecylbenzenesulfonate (SDBS). Then, single-crystalline nickel oxide (NiO) mesoporous nanosheets could be obtained through a thermal decomposition method using β-Ni(OH)2mesoporous nanosheets as precursor. The prepared NiO was body centred cubic structure.The prepared NiO was single-crystalline and its specific surface area was85.98m2/g. The photocatalytic degradation of phenol showed that the prepared NiO has the photocatalytic activity but it lose catalytic activity soon. The flowerlike nickel oxide (NiO) was also synthesized. The flowerlike a-nickel hydroxide (Ni(OH)2), being used as the precursor of the nickel oxide, was successfully synthesized by homogeneous precipitation method without using any templates or surfactants. Flowerlike nickel oxide (NiO) with the similar flowerlike structure can be obtained by further calcination of the prepared Ni(OH)2at400℃for2h. The results showed that the specific surface area of flowerlike NiO was125.2m2/g and the band gap energy of it was4.43eV. The flowerlike NiO have higher photocatalytic property to decompose Methyl orange pollutant.3. The morphology-and size-controlled ln(OH)3and ln(OH)3/AC (porous activated carbon) composite photocatalysts were successfully prepared. First, Mesoporous indium hydroxide nanorods were successfully synthesized by a mild one-step one-pot method.There are some pores in the samples, which are mainly composed of rod-like shapes with length of300nm and diameter of90nm. N2adsorption/desorption measurements confirmed that the prepared powder is mesoporous with average pore diameter of3.1nm. The ultraviolet-visible absorption spectroscopy analysis indicated that the band gap energy of the samples is5.15eV. Photoluminescence spectrum showed that there are two stronger emissions under ultraviolet light irradiation. The growth mechanism of indium hydroxide nanorods and the role of cetyltrimethyl ammonium bromide were also discussed. Then, the morphology-and size-controlled In(OH)3nanocrystals have been synthesized via a novel, low-cost and low-temperature(70℃) route without using CTAB as surfactant. The morphology and size of In(OH)3nanostructures can be controlled by adjusting the reaction conditions, such as the reaction time, concentration of the alkali and the alkaline source. A possible mechanism for the evolution of the morphology-and size-controlled In(OH)3was proposed. The photocatalytic degradation of phene showed that the ln(OH)3have higher photocatalytic activity than TiO2(p-25). Mesoporous nanosheets of ln(OH)3with high specific surface area were also successfully synthesized via a facile hydrothermal method using In(NO3)3and hexamethylene tetramine(HMT) as raw materials. The photocatalyst sample is highly photoactive and stable for gas-phase removal of toluene under UV irradiation.In the end, In(OH)3/AC (porous activated carbon) composite photocatalysts were prepared via a facile hydrothermal method using In(NO3)3and hexamethylene tetramine(HMT) as raw materials and AC as a carrier. The results showed that the doped of actived carbon can affect the crystal structure and the size of In(OH)3. TEM results showed that the morphology of In(OH)3were not affected when actived carbon was added.The DRS results showed that the energy band of In(OH)3was had no effect on when actived carbon was added. Results of FT-IR showed that the AC and In(OH)3were connected by chemical bond. The photocatalytic degradation of toluene showed that In(OH)3/AC catalysts with optimal AC content3%exhibited higher activity than other In(OH)3/AC catalysts,4. The TiO2/ACF composite photocatalyst was prepared by using the screen printed technology. The results of XRD showed the TiO2/ACF composite photocatalyst is confirmed anatase as the only phase present and ACF has no effects on the phase structures of TiO2. The results of SEM showed that TiO2can form thin film on ACF surface. Benzene was chosen as the model of the volatile organic compounds (VOCs) to investigate the capability of TiO2/ACF composite photocatalyst. The results showed that the TiO2/ACF composite photocatalyst have higher activity for benzene removal than only TiO2photocatalyst.
Keywords/Search Tags:Photocatalyzer, Cu2O, NiO, In(OH)3, porous Activated carbon
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