两步水热法制备还原氧化石墨烯/纳米TiO_2复合材料及其光催化性能

Preparation of reduced graphene oxide/nano TiO_2 composites by two-step hydrothermal method and their photocatalytic properties

为研究由还原氧化石墨烯(RGO)和具有高活性晶面的TiO_2组成的复合材料的制备方法及其光催化性能,首先采用两步水热法制备了RGO/纳米TiO_2复合材料:第1步为合成暴露高活性晶面的纳米TiO_2;第2步为将合成的纳米TiO_2与氧化石墨烯(GO)复合,形成RGO/纳米TiO_2复合材料。然后,利用XRD、SEM、X射线光电子能谱仪和紫外-可见漫反射光谱等手段对制备的暴露不同晶面的纳米TiO_2和RGO/纳米TiO_2复合材料进行了表征,评价了其光催化性能。结果表明:在水热法的第1步中,通过调节HF的浓度能可控制备出具有高活性的(001)和(101)晶面的纳米TiO_2,氟原子在纳米TiO_2中以物理吸附态和化学结合态这2种形态存在;在第2步后,GO与纳米TiO_2复合形成RGO/纳米TiO_2复合材料,同时在此过程中GO被转化成RGO。在紫外光照射下,两步水热法合成的RGO/纳米TiO_2复合材料具有很好的光催化性能,明显优于商用TiO_2(P25)和纳米TiO_2的。RGO/纳米TiO_2复合材料的光催化性能有明显的提高,RGO和TiO_2暴露的晶面对光催化活性有影响。

In order to investigate the preparation method and photocatalytic properties of composites comprised by reduced graphene oxide （RGO） and TiO2 with high activity facets, RGO/nano TiO2 composites were prepared by two-step hydrothermal method., the 1st step was the synthesis of nano TiO2 exposed with high activity facets; the 2nd step was the recombination of as-synthesized nano TiO2 and graphene oxide （GO）, thus RGO/nano TiO2 com- posites were formed. Then, the prepared nano TiO2 with different exposed facets and RGO/nano TiO2 composites were characterized by means of XRD, SEM, X-ray photoelectron spectrometer, ultraviolet-visible diffuse reflectance spectroscopy and so on, and the photocatalytic properties were evaluated. The results show that during the 1st step of hydrothermal method, nano TiO2 which has high activity （001） and （101） facets can be controllably prepared by adjusting the concentration of HF. Fluorine atoms exist in nano TiO2 by two states of physically adsorbing state and chemically binding state. After the 2nd step, GO recombines with nano TiO2 to form RGO/nano TiO2 composite, and GO is transformed to RGO simultaneously in the process. RGO/nano TiO2 composites synthesized by two-step hydrothermal method have favorable photocatalytic performances under ultraviolet illumination, which outperform those of commercial TiO2 （P25） and nano TiO2. The photocatalytic properties of RGO/nano TiO2 composites have remarkable improvement. RGO and exposed facets of TiO2 have effects on the photocatalytic activity.