Preparation of Ag/AgCl-TiO2 Hollow Nanoparticles by Co-precipitation and Their Photocatalytic Property

Anionic polystyrene(PSt) latex particles were prepared through emulsion polymerization of methacrylic acid and styrene(St). The PSt particles were surface-treated using vinyl trimethoxysilane in a mixed solvent of ethanol and water. PSt-AgCl-TiO2 composite particles were then prepared through hydrolysis of tetrabutyl titanate and the reaction of AgNO3 with NaCl using the surface treated PSt particles as templates. Ag/AgCl-TiO2 hollow particles were obtained by pre-treating the PSt-AgCl-TiO2 composite microspheres at 180 degrees C followed by drying and calcination at 500 degrees C for 4 h. XRD characterization of the final Ag/AgCl-TiO2 particles reveals that anatase crystal structure in pure TiO2 is unchanged with AgCl doping. EDS analysis shows that part of the added AgCl is transformed to Ag element, leading to the formation of the hollow Ag/AgCl doped TiO2 composite particles. Surface area test indicates that average pore size in the Ag/AgCl-TiO2 particles is about 12 nm with a specific surface varied from 125 m(2)/g to 190 m2/g, depending on the amount of AgCl. These specific surface values are much higher than that observed in commercial TiO2, P25 for instance. Photocatalytic activity of the Ag/AgCl-TiO2 hollow particles in degradation of Rhodamine B(RhB) was tested under UV and visible light. The results show that, compared with RhB degradation with pure TiO2 hollow particles under UV light, RhB degradation at 30 min increases by about 13% when Ag/AgCl-TiO2 particles with Ag content at n(Ag)/n(Ti) = 0. 1% is used as the catalyst; whereas an increase of about 38% is observed under visible light with Ag/AgCl-TiO2 composite particles [n(Ag)/n(TO= 2. 0%] at 120 min of the photodegradation. In addition, the photocatalytic activity of the Ag/AgCl-TiO2 particles under visible light is increasing with Ag amount up to n(Ag)/n (Ti) = 2. 0%, and this catalytic activity starts to decrease when Ag amount reaches n(Ag)/n(Ti)= 4. 0%. Nevertheless, all the Ag/AgCl-TiO2 particles demonstrate a higher photocatalytic performance than P25, regardless of their AgCl content. The photocatalysis mechanism of the Ag/AgClTiO2 particles was provided, and the results were interpreted based on the mechanism.