Preparation And Photocatalytic Activities Of Transition Metal Modified Titanium Dioxide In The Photocatalytic Reduction Of CO2

Photocatalysis has been found to be an effective method to convert CO2into organic energy materials. In this paper, using the silver nitrate, copper nitrate and nickel nitrate as the modifiers, tetrabutyl titanate as the precursor, the amount of0,0.5,1.0,3.0,5.0,7.0wt%metal modified TiO2catalyst (Ag-TiO2, Cu-TiO2and Ni-TiO2) were prepared. The physical and chemical properties of pure TiO2and Ag-TiO2, Cu-TiO2and Ni-TiO2samples such as the crystal structure of the catalysts, the status of metals, particle size, surface area and optical domain were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), BET (BET) and UV-visible diffuse reflectance spectroscopy (UV-vis). And the relationship between the physical and chemical properties and its photocatalytic activity of powders was also satudied. In addition, the activities of the catalysts were investigated in the photocatalytic experiments conducted under irradiation from Hg lamps in a CO2/NaOH aqueous solution.The catalyst powders of Ag-TiO2, Cu-TiO2and the Ni-TiO2were obtained by means of a hydrolysis method followed by calcination at450℃. With the help of XRD and XPS, we concluded that all catalyst TiO2polymorphs are anatase, and the metal elements were present on the surface of TiO2particles as Ag+, Cu2+and Ni2+. Schottky junction or p-n junction was formed in the powders because of the interaction between the metal and TiO2particles. The results revealed that the photoreduction of CO2with water, catalyzed by Ag-TiO2, Cu-TiO2and Ni-TiO2, can yield H2, CO, HCHO, CH3OH and CH4. CH4was identified as the major products. In addition, Ag-TiO2, Cu-TiO2and Ni-TiO2shows greater light utilization capacity and carbon conversion capability compared with pure TiO2. The optimal amount of metal modification was determined to be1.0wt%,1.0wt%and3.0wt%, respectively. The yields of the products using Ag-TiO2and Cu-TiO2followed the order H2> CH4> CH3OH> CO> HCHO, yet using Ni-TiO2followed the order H2> CH4> CH3OH> HCHO> CO. Under the same condition, the photocatalytic activity of CO2photoreduction followed the order:Ni-TiO2> Cu-TiO2> Ag-TiO2.