共沉淀法制备Ag/AgCl-TiO2空心复合纳米微球及其光催化性能

通过甲基丙烯酸与苯乙烯聚合制备了表面负电性的聚苯乙烯(PSt)纳米乳胶粒. 在乙醇与水的混合溶剂中, 用硅烷偶联剂乙烯基三甲氧基硅烷对其进行表面改性后加入钛酸四丁酯、 氯化钠和硝酸银, 以PSt乳胶粒为模板采用共沉淀法制备了PSt-AgCl-TiO₂复合微球. 在180 ℃对其进行液相预处理及煅烧去除PSt模板后制备了Ag/AgCl-TiO₂空心复合粒子. 对各阶段产物的形貌、 晶体结构和比表面积等进行了表征. 结果表明, 所得产物为Ag/AgCl与锐钛矿型TiO₂复合的空心粒子, 其比表面远大于商品TiO₂(P25). 考察了Ag/AgCl-TiO₂复合粒子在紫外光与可见光下对罗丹明B(RhB)降解的催化活性. 结果表明, 在紫外光下n(Ag)/n(Ti)=0.1%的Ag/AgCl-TiO₂复合粒子活性最高, 30 min时对RhB的降解率比不含Ag/AgCl的TiO₂空心微球提高了13%; 虽然Ag/AgCl-TiO₂在可见光下的催化活性远比紫外光下低, 但与纯TiO₂空心纳米微球相比其催化活性仍明显增强. n(Ag)/n(Ti)=2.0%的Ag/AgCl-TiO₂复合粒子催化活性最高, 120 min时对RhB的降解率比不含Ag/AgCl的TiO₂空心微球提高了38%.

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 ℃ followed by drying and calcination at 500 ℃ 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 m²/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(Ti)=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/AgCl-TiO₂ particles was provided, and the results were interpreted based on the mechanism.