| In recent years, with application of TiO2nanomaterials increasing, some potentialtechniques are based on TiO2nanomaterials in some key areas, such as energyproduction, accumulation, preservation, and degradation of environmental pollutants.TiO2as an n-type semiconductor material has attracted wide interest of scientist, dueto the special nature of the optical response. Especially the low-dimensional size TiO2nanomaterial, such as nanowires and nanotube, has been greatly concerned. TiO2nanowires array, which have unique physical, chemical, optical and electricalproperties depended on the topography has important significance in the treatment ofenvironmental persistent organic pollutant. In this work, the specific content are listedbelow.(1) TiO2nanowires array grown in the surface of FTO conductive glass wassuccessfully achieved by two-step solvothermal synthesis. It was indicated that theTiO2nanowire arrays was rutile with high vertical orientation and good adhesion onFTO. Length of TiO2nanowires was0.4-0.8μm; the diameter was10nm-20nm. BETtest showed that TiO2nanowires synthesized by this method had a greater specificsurface area than P25. So TiO2nanowires array had better adsorption capacity, whichwould contribute to the photocatalytic reaction in the surface of TiO2nanowires(2) Ag/TiO2nanowires composites on FTO conductive glass was successfullysynthesized by photoreduction. It can be observed that Ag nanoparticles which had asize of less than10nm were uniformly distributed on the surface of TiO2nanowires inthe TEM image. EDX and XPS proved that elemental Ag and Ag+were co-existing onthe surface of TiO2nanowires. In UV-visible diffuse reflectance absorption, compositematerials had an absorption peak in region of visible light, which was induced by theplasma resonance effect of Ag nanoparticles and indicated that the composite materialhad good photosensitivity. while composites showed a superior photocatalytic activityin Cr (VI) photoreduction applications. When the concentration of tartrate acid was24mM in the system, the Cr (VI) photoreduction rate of composite material was476.2μg/L min-1cm-2under visible light irradiation; and when the concentration of tartrateacid was80mM, the reaction rate reached a saturation value of1000μg/L min-1cm-2.Experiments indicated that the composite material showed a high photocatalyticactivity for Cr (VI) under strongly acidic environment (pH=2); on the contrary,composite materials had any light catalytic reduction activity for Cr (VI) in an alkaline environment. In addition, the high ionic strength also significantly inhibitedphotocatalytic reduction activity of composite materials. Kinetic studies showed thatCr (VI) photocatalytic reduction on composite materials obeyed the pseudo first-orderkinetics model. But the reaction was divided into two stages in comparison withuniform dispersion of the powder, and the rate constant was much larger than theinitial stage. In the study of the mechanism of photocatalytic, by experiments andanalysis of the structure of small organic molecules, we found that tartrate acid havinga symmetrical structure, caused p-π-conjugated effect, made the composites show thehighest photocatalytic activity and established the corresponding photocatalyticmechanism model. The test showed that the Ag/TiO2composites nanowires arraygrown on the FTO conductive glass had a good recycling properties.（3） An Ag3PO4/TiO2nanowires array composite on FTO was successfullysynthesized by H2O2oxidation in situ. In the TEM image, we can observed thatAg3PO4nanoparticl8which had an extremely small size of only about2nm wereevenly distributed on the surface of TiO2nanowires. The EDX characterizationproved that the very small particle in the presence of TiO2nanowires was Ag3PO4.The Mott-schottky curve in electrochemical tests indicated the nature of thecomposite film was a p-type semiconductor. In test of photocurrent, compositematerial had a greater photocurrent density (0.06mA/cm2) compared to pure TiO2nanowires, Meanwhile, the absorption edge of composite material showed obviousred shift in diffuse reflectance UV-visible absorption tests, which indicated that thecomposite material had a smaller band gap energy (2.7ev) and higher photosensitivity.It was possible to produce more light carriers. Choose RhB to characterize thephotocatalytic properties of Ag3PO4/TiO2nanowire array composites. Experimentsshowed that: strong acidic environment was beneficial for RhB photocatalyticoxidation on composite materials. In24mM tartrate acid system, composite materialsshowed very higher photocatalytic activity than without tartrate acid. Kinetic studiesshowed that the photocatalytic oxidation of RhB obeyed the pseudo first-order kineticmodel, and the reaction rate constant was three times when tartaric acid existed.Eventually, the test showed that the Ag3PO4/TiO2composite nanowires array grownon the FTO glass substrate had excellent recycling properties. |
PDF Full Text Request