氟掺杂纳米TiO2粉体的合成及光催化活性研究

以钛酸四丁酯为前驱体,以三氟乙酸为掺杂剂,采用溶胶凝胶法于450℃煅烧2 h合成了F-掺杂的纳米TiO2粉体,利用XRD,XPS,EDS,BET等手段进行测试和表征,以次甲基蓝的降解评价其光催化活性。XPS测试表明,F-以掺入晶体中的F-和表面化学吸附F-2种形式存在。XRD及BET测试发现,设计摩尔比n(F)/n(Ti)=0.05时纳米粉体粒径由10.6 nm增大到12.9 nm,比表面积由110.3 m2/g降低到102 m2/g,但光催化活性提高,可将次甲基蓝1 h降解率由73.2%提高到83.1%,这是由于掺入F-后部分Ti4+形成Ti3+,Ti3+在TiO2的禁带间形成施主能级,更易吸收光生电子。

Preparation and photocatalytic activities of F-doped nano-TiO_2 powder

Nano-F-/TiO2 powders were prepared by hydrolysis of titanium tetraisopropoxide in a mixed CF3COOH-H2O solution.The F——doped TiO2 powders were characterized by means of XRD,XPS,EDS and BET,etc.The photocatalytic degradation of methylene blue in aqueous solution was used to evaluate their photocatalytic activities.The XPS spectra show that there are fluorine atoms in TiO2 with two forms.One is physically adsorbed on the surface of TiO2,and the other is embedded into TiO2 crystal lattice.The results of photocatalytic degradation of methylene blue show that the appropriate designed doping amount of fluorine element is n(F)/n(TiO2)=0.05.The XRD and BET results show that the grain size increases from 10.6 nm to 12.9 nm and BET surface area decreases from 110.3 m2/g to 102 m2/g when the ratio of n(F) to n(TiO2) increases from 0 to 0.05.The F-doping could help to enhance TiO2 photocatalytic activity and improve the degradation rate of methylene blue from 73.2% to 83.1% for 1 h photoirradiation.The reason is that the formation of Ti3+ from Ti4+ by F-doping,and Ti3+ forms the donor level in the forbidden band of TiO2 and makes it easier absorb photoinduced electrons.