(001)晶面主导的TiO_2纳米片表面的F^-对其光催化性能的影响

Effect of F^- on the Photocatalytic Properties of TiO_2 Nanosheets Dominated with( 001) Facet

采用水热法以HF为晶面控制剂制备了TiO2纳米片,并用NaOH溶液对其处理,以甲基橙、甲基紫、罗丹明B和亚甲基蓝四种染料为降解对象,研究了处理前后TiO2纳米片的光催化性能并提出了机理。通过X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)等测试对处理前后TiO2纳米片的结构、形貌以及表面组成进行了表征。结果表明用NaOH溶液处理前后,样品均为边长24nm、厚度6~7nm、(001)晶面含量为84%的锐钛矿TiO2纳米片,但是处理后的样品表面F-、表面羟基和吸附水的数量都减少了,而且处理后样品的光催化活性降低。未经NaOH溶液处理的样品具有更高的光催化活性,归因于氟较氧更强的电负性可使TiO2表面吸附更多的水,促进了价带空穴对水的氧化,从而生成更多的羟基自由基。

Ti O2 nanosheets were prepared by hydrothermal method using HF as crystal facets controlling reagent. The Ti O2 nanosheets were further treated with Na OH solution. The photocatalytic activity of Ti O2 before and after treated with Na OH solution was investigated by photodegradation of methyl orange（ MO）,methyl violet,rhodamine B and methylene blue. And the mechanism of F-effecting on photocatalytic activity was proposed. The structure,morphology and surface composition of the Ti O2 nanosheets were characterized by X-ray diffraction（ XRD）,transmission electron microscopy（ TEM） and X-ray photoelectron spectra（ XPS）,respectively. The results show that the samples before and after treated with Na OH solution are Ti O2 nanosheets with 24 nm length,6-7 nm width and 84% of（ 001）facet. The amount of F-,OH-and adsorbed H2 O on the surface decreases and the photocatalytic activity reduces after the sample being treated with Na OH solution. The higher photocatalytic activity of the Ti O2 nanosheets not treated with Na OH solution is attributed to the strong electronegativity of fluorine which enchances the adsorption of H2 O on the surface. The more F-adsorbed on the surface,the more H2 O isoxidized by valence holes,which results in more hydroxyl radical generating. Therefore,surface fluorine is of great importance on effectively ameliorating photocatalytic activity of Ti O2.