Preparation Of Hollow CdS@TiO₂ Double-shelled Pholocatalyst And Their Application For Water Treatment

The photocatalytic reaction is the reaction of a non-polluting,environmentally friendly, naturally occurring in the normal temperature and pressure. CdS, due to its small band-gap（2.42 e V）, preferable photoconductivity and high electron affinity, has been widely studied. Pure CdS nanoparticles has better catalytic efficiency under visible light, but its light corrosion phenomenon leading to the reduction of the catalytic efficiency and the generation of secondary pollution. Titanium dioxide（TiO2） as one of the most promising semiconductor photocatalysts is extensively utilized for waste streams remediation because of its superior photocatalytic activity, biological and chemical inertness, low cost, long-term stability,nontoxicity and no secondary pollution. However, It has been found that pure TiO₂ photocatalyst by itself is not efficient enough unless it is associated with a some narrow-bandgap semiconductors like CdS,ZnO and V2O5 et al. We can obtain a composite material with high photocatalytic activity under visible light via combining CdS with TiO2. At the same time, in order to increase the catalytic efficiency of photocatalysis, core-shell structure is introduced. CdS@TiO₂ core-shell structure has a widely application because it can not only increase the specific surface area（SSA） of pholocatalyst,but also reduce Cd²⁺ run off due to protect by TiO₂ layer. The optimal material is prepared via further increaseing SSA by introducing hollow structure.This paper prepared PS@CdS core-shell material by a series of methods and compared with the different ways which attempted to different reaction conditions and different types of reagents.Finally,we synthetised various target materials and obtained pholocatalyst with the smooth layer, favourable monodispersion and high mechanical strength.And then TiO₂ coated on PS@CdS core-shell nanoparticles by using sol-gel, hydrothermal and wet-chemical methods to obtain PS@CdS@TiO₂ core-shell-shell material.After a calcination, hollow CdS@TiO₂ double-shelled was perpared.Our experiments revealed that as-prepared pholocatalyst had a promotion effect in photocatalysis compared with PS@CdS and pure CdS.