静电自组装制备纳米TiO2/SiO2光催化材料

采用静电自组装方法制备了纳米TiO2/SiO2光催化材料。采用巯丙基三甲氧基硅烷偶联剂对SiO2进行干法改性,采用双氧水/冰醋酸将偶联剂巯基基团氧化为磺酸基基团。在正负电荷的吸引下,带负电荷的SiO2与带正电荷的钛聚合阳离子自发地组装在一起,经一定温度热处理得到纳米TiO2/SiO2光催化材料。采用XRD、FTIR、PL、UV-Vis DRS、SEM和ICP等对材料进行了分析和表征。采用甲基橙溶液评价材料的光催化性能。结果表明:SiO2促使锐钛矿的形成,抑制锐钛矿向金红石的转变,减小TiO2的晶粒尺寸,使得TiO2光吸收波长发生蓝移。TiO2与SiO2通过Si-O-Ti键发生结合。采用静电自组装方法制备的材料中TiO2的含量高于传统方法,导致材料的光催化性能有所提高。

Preparation of Nano TiO2/SiO2 Photocatalysts by Electrostatic Self-assembly Method

The nano TiO₂/SiO₂ photocatalysts were prepared by electrostatic self-assembly method (ESAM). Silane coupling agent of (OCH₃)₃Si(CH₂)₃SH was used to modify the surface of SiO₂ powders by dry process. Sulfhydryl group (-SH) of the silane was oxidized to easy ionized sulfonyl(-SO₃H) by 30% H₂O₂/HOAc oxidant. The electronegative SiO₂ was assembled with titanium polycation by electrostatic attraction. The as-prepared compounds were calcined under certain temperature to obtain the nano TiO₂/SiO₂ photocatalysts. The materials were characterized by XRD, FTIR, photoluminescence (PL), UV-Vis DRS, SEM and ICP. The photocatalytic activity was evaluated by the degradation of methyl orange in aqueous solution. The results show that SiO₂ facilitates the formation of anatase, restrains the transformation of anatase to rutile, decreases the crystallite size of TiO₂ and causes the absorption edge of TiO₂ to shift to higher energy region. TiO₂ combines with SiO₂ by the formation of Si-O-Ti chemical bond. Photocatalysts prepared by ESAM method exhibit higher photocatalytic activity than that of traditional method attributed to the higher content of TiO₂ in the samples.