Prpation And Photocalytic Mechanism Of CdS-TiO₂Nano-composite Strcture

The photocatalytic reaction is the reaction of a non-polluting,environmentally friendly, naturally occurring in the normal temperature andpressure. Photocatalyst can promote the chemical reaction of substances.Photocatalyst has antibacterial, air purification, odor, and prevents mold andalgae, as well as anti-fouling and self-cleaning effect; and safety and durability.At present, the most studied photocatalyst is titanium dioxide nanoparticles.Itis a cheap, toxic pollution, but because of the titania band gap width is toolarge （3.2ev）, especially when it reaches the nanometer level, the absorptionwill further blue shift, so it is only used in ultraviolet. However, only3%⁴%ultraviolet sunlight can reach the earth surface. Therefore, the efficiency of itsuse of solar energy is extremely low. Therefore, we must develop new bandgap width of narrow semiconductor optical catalyst to more use of sunlight.Band gap of CdS is2.5eV, but TiO₂is3.2eV, which is wider than TiO₂,and can be excited in the visible. Previous studies have shown that thepresence of defects conducive to the improvement of the CdS photocatalyticproperties, but will lead to the CdS catalyst corrosion. In this thesis, we use organic density gradient separation techniques toachieve CdS with different defects, and by adjusting the reaction atmosphere,successful control of the growth of the defect.The defect is easy to generate inthe Oxygen conditions,and the defect restrained in the nitrogen conditions, andsuccessfully prepared nono defects CdS-TiO₂composite catalyst. Studies haveshown that the composite photocatalytic efficiency increases with the increaseof CdS amount.By comparison of the photocatalytic, we Analysis of the photocatalyticmechanism of defects CdS, none defects CdS and CdS-TiO₂compositecatalyst. The photocatalytic reaction in none defects CdS rely mainly onhydroxyl radicals, which is produced by electron reduction of oxygen.Thephotocatalytic reaction in defects CdS rely mainly on hydroxyl radicals, whichis produced by Cavity cavity oxidation of water. The composite catalyst isgenerated by both.