Defect-Induced Yellow Color in Nb-Doped TiO2 and Its Impact on Visible-Light Photocatalysis

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• 作者：Lina Kong ; Changhua Wang ; Han Zheng ; Xintong Zhang ; Yichun Liu
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 23, 2015
• 年：2015
• 卷：119
• 期：29
• 页码：16623-16632
• 全文大小：634K
• ISSN：1932-7455

文摘

Doping TiO₂ photocatalysts with foreign ions has been deemed an effective method to enhance visible light absorption and thus increase their photocatalytic performance. Herein, we report that Nb-doped TiO₂ porous microspheres prepared by ultrasonic spray pyrolysis of peroxide precursor solution are yellow, and the yellow coloration becomes increasingly conspicuous with increasing Nb dopant concentration. Comprehensive spectral analyses show that both surface peroxo species and bulk Ti³⁺ are introduced into TiO₂ microsphere samples together by charge compensation with Nb⁵⁺ dopant and are responsible for the coloration of TiO₂. The Nb-doped microspheres show higher photocatalytic rates than undoped TiO₂ for the degradation of gaseous acetaldehyde under visible irradiation but slower rates under ultraviolet light. Moreover, the photocatalytic mineralization rates of acetaldehyde to CO₂ are lowered with Nb doping under both visible and UV irradiation. Correlation between the results of surface photovoltage spectroscopic (SPS) characterizations and photocatalytic tests suggests that surface peroxo states are relevant to the visible-light-stimulated charge separation and photocatalytic reactions, albeit holes trapped in these states have lower reactivity than in valence band. On the other hand, the enhanced photoluminescence in the near-infrared region, reduced SPS response in the UV region, and photochromic phenomena during photocatalytic process indicated that Ti³⁺ defects serve as charge carrier recombination centers and display adverse effect to photocatalytic activity of Nb-doped TiO₂, especially under UV irradiation.