石墨烯/纳米TiO_2复合材料的制备及光催化还原性能

为探索超声辅助下利用紫外光及耦合热还原工艺制备RGO/纳米TiO_2复合材料的方法,并对其在缺氧水体中的光催化还原特性进行研究,首先,以鳞片石墨为原料,采用改进的Hummers法制备了氧化石墨烯(GO),进而通过超声/紫外光还原工艺制备了还原氧化石墨烯(RGO);然后,以钛酸丁脂和RGO为前驱物,采用溶胶-凝胶法并在氮气保护下高温加热制备了RGO/纳米TiO_2复合光催化材料;接着,利用FTIR、XRD、BET及紫外-可见光谱等对RGO/纳米TiO_2复合材料进行了结构性能表征;最后,以2,4-二氯苯氧乙酸(2,4-D)为探针物,研究了RGO/纳米TiO_2在缺氧水体中的光催化特性与2,4-D降解机制。结果表明:采用低温氧化Hummers法制备的GO六碳环上生成的活性基团较少,采用超声/紫外光还原工艺及耦合高温热还原工艺可使环状结构得到良好的修复;所制备的RGO/纳米TiO_2复合材料具有良好的2,4-D降解能力,在缺氧状态下,2,4-D主要发生光催化还原反应,脱除苯环上的氯,产生氯酚、邻苯三酚及间苯三酚等中间产物,部分2,4-D被氧化降解生成CO_2和H_2O。制备的RGO/纳米TiO_2复合材料具有良好的光催化还原性能。

Preparation and photocatalytic reduction performance of graphene/nanoTiO2 composites

In order to explore the method of using ultraviolet light and coupled thermal reduction process to prepare RGO/nanoTiO₂ composites under the assistance of ultrasonic and investigate the photocatalytic reduction performance in the anoxic water, graphene oxide (GO) was prepared by improved Hummers method using flake graphite as raw material, and reduced graphene oxide (RGO) was prepared by ultrasonic/ultraviolet light reduction process firstly. Then, butyl titanate ester and RGO were used as precursors, RGO/nanoTiO₂ composite photocatalytic materials were prepared by the method of sol-gel and high temperature heating under nitrogen protection. After that, the structure and properties of RGO/nanoTiO₂ composites were characterized by FTIR, XRD, BET and ultraviolet-visible spectroscopy. Finally, 2,4-dichlorphenoxyacetic acid (2,4-D) was used as probe, the photocatalytic properties of RGO/nanoTiO₂ composites in anoxic water and the degradation mechanics of 2,4-D were studied. The results show that less reactive groups are generated on six carbon ring of GO when adopting the Hummers method of low temperature oxidation, the rings structure can be well repaired by using ultrasonic/ultraviolet light reduction process and the coupled high temperature thermal reduction process. The prepared RGO/nanoTiO₂ composites have good performances of 2,4-D degradation, under the anoxic condition, 2,4-D mainly conducts photocatalytic reduction reaction, the chlorines on benzene ring are removed and produces middle products such as chlorophenol, pyrogallol, phloroglucinol and so on, part of the 2,4-D is oxydative degraded to generate CO₂ and H₂O. The obtained conclusions indicate that the prepared RGO/nanoTiO₂ composites have good photocatalytic reduction performances.