S掺杂纳米TiO2的可见光响应机制

Mechanism of sulfur-doping on TiO_2 photo-response under visible light

以硫脲为S的源物质,以钛酸丁酯为TiO2的前驱体,采用溶胶-凝胶法制备S-TiO2光催化剂。利用XRD,XPS和FTIR等技术分析S掺杂对TiO2晶格结构的影响,并探讨元素S在TiO2晶格中的化学状态以及所形成的化学键的类型。结果表明:掺杂的S以S4+进入TiO2晶格中取代部分Ti4+,形成Ti1-xSxO2催化剂;S4+在TiO2的价带上形成1个电子占据能级,价带上的电子占据能级的价带顶位主要由S3p态构成,同时S3p也有助于形成1个由Ti3d和O2p态构成的导带,S3p态与价带的交叉使价带变宽,导致能带变窄,从而改善TiO2的光谱响应,使吸收边缘扩展到可见光的区域。对亚甲基蓝的光降解实验结果证实硫掺杂明显提高了光催化活性。

S-TiO2 photocatalysts, with thiourea as source substance of S and titanium tetrabutoxide （Ti（OC4H9）4 as precursor of titanium dioxide, were prepared by sol-gel method. The effects of sulfur-doping on TiO2 crystal structure, the chemical states of S atom in TiO2 crystals and the chemical bonds formed in TiO2 were analyzed by XRD, XPS and FTIR. The results show that S atom as the state of S4＋ in TiO2 crystal lattices substitutes part of Ti atoms and form Ti1-xSxO2 catalyst, and S4＋ forms an electron-occupied level in valence band （VB）, and the electron occupies level above the VB consists of S3p states, at the same time, the S3p states contribute to the formation of a conduction band with Ti3d and O2p states, the chiasma of S3p states and the VB make VB broaden and result in energy gap narrow down, and then improve the optical response of TiO2 and extend its absorption edge into the visible-light region.