| Titania is one of the most common semiconductor materials, in which electrons and holes with high redox ability are excited under light irradiation. When its size is decreased to nanoscale, an excellent photoelectric conversion efficiency can be obtained for it. So in face of more and more serious challenges in energy and environment, nanometer titania has attracted more and more attention from scientists thanks to its high efficiency in degradation of organic pollutants and photocatalytic water splitting, cheap cost, nontoxicity and stable physicochemical properties. However, pure titania can only make use of ultraviolet light due to its wide bandgap. In the passing decades, scientists have developed a series of methods to improve the properties of nanometer titania materials, and in-depth studies on the photocatalysis mechanism of nanometer titania have been conducted.In view of these previous researches, in this paper, we have conducted some further investigations on AgI/TiO2nanocomposite visible light photocatalysts and hydrogenation of a commercial nanostructured titania photocatalyst (P25), which are listed as follows:AgI/TiO2nanocomposite were prepared through a deposition precipitation method, then we modified it with PdCl2. The visible light photocatalytic performance was characterized through degrading methylene blue, and the results indicated that the modification had dramatically increased the efficiency of the nanocomposite photocatalysts. XRD analyses showed that some chemical reactions had happened in the process of modification, and the products were proposed responsible for the enhancement of the visible light photocatalytic performance.AgI/TiO2nanocomposite were used repeatedly to degrade methyl orange and methylene blue, and the photocatalytic efficiency was found to decrease obviously after the first cycle. XRD and SEM analyses revealed a significant light-induced crystalline growth of AgI in AgI/TiO2, which was considered to have resulted in the dramatic decrease in the visible light photocatalytic efficiency of the photocatalyst. AgI/TiO2nanocomposite was also immersed in solutions with different PH values for some periods of time and we found the nanocomposite exhibited a higher stability in alkali solutions than in acidic solutions.Nanostructured titania photocatalyst, P25, was electrchemically hydrgenated by being placed in0.01M NaOH solution to act as the cathode to electrolyze water. After the hydrogenation, the color of P25changed from white to blue, UV-vis absorbance spectra showed its absorption in visible light was highly enhanced, and at meanwhile its solar-driven photocatalytic activity was found to be dramatically improved in the photo-degradation of rhodamine B and methylene blue. XPS spectra measurement was conducted and the photocurrent was measured, which indicated that oxygen vacancies and Ti3+were formed, and the separation efficiency of photo-activated holes and electrons was increased in electrochemically hydrogenated P25.To study in-depth the reaction between atomic hydrogen and TiO2at room temperature,(001) rutile single crystals were electrochemically hydrogenated and analyzed. XRD, infrared absorption spectra, UV-vis absorbance spectra analyses,and electric transport measurement revealed two distinct states of hydrogen inside the lattice:one is as protons bonded with oxygen ions by the strong O-H bonds (marked as (OH)o), while the other one is highly unstable and mobile (marked as H'm). Both of their concentrations decrease with increasing aging time, while the latter one exists only for several hours in the lattice. |
PDF Full Text Request