Surface Structural Reconstruction for Optical Response in Iodine-Modified TiO2 Photocatalyst System

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• 作者：Linjuan Zhang ; Jing Zhou ; Jiong Li ; Gang Liu ; Xiao Lin ; Baohua Mao ; Renduo Liu ; Shuo Zhang ; Jian-Qiang Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 26, 2014
• 年：2014
• 卷：118
• 期：25
• 页码：13726-13732
• 全文大小：521K
• ISSN：1932-7455

文摘

We report an alternative mechanism for the optical response of an iodine-modified anatase TiO₂ photocatalyst material. Unlike the general realization that the iodine atom provides impurity levels within the optical band gap, we suggest that a distorted surface structure plays a dominant role. Anatase pure TiO₂ and iodine-modified TiO₂ (I-TiO₂) nanocrystals were synthesized by a simple solvothermal method, and I-TiO₂ exhibited an extended absorption edge up to 550 nm. Employing iodine K-edge X-ray absorption fine structure (XAFS), we demonstrate that iodine is not incorporated into the nanoparticle interior but exists in the form of IO₃^{鈥?/sup> groups at the surface. Furthermore, this IO₃鈥?/sup> cluster adsorption largely induces a disordered structure, as revealed by Ti 2p_3/2 X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and Ti K-edge XAFS data fitting. Density functional theory calculation indicates that this distorted structure can form a midgap state, which should be responsible for its excellent optical property. This finding represents a promising route for improving the optical response of the nanophotocatalyst system via surface treatment.}