Boron Environments in B-Doped and (B, N)-Codoped TiO2 Photocatalysts: A Combined Solid-State NMR and Theoretical Calculation Study

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• 作者：Ningdong Feng ; Anmin Zheng ; Qiang Wang ; Pingping Ren ; Xiuzhi Gao ; Shang-Bin Liu ; Zhurui Shen ; Tiehong Chen ; Feng Deng
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：February 17, 2011
• 年：2011
• 卷：115
• 期：6
• 页码：2709-2719
• 全文大小：1117K
• 年卷期：v.115,no.6(February 17, 2011)
• ISSN：1932-7455

文摘

The structures and local environments of boron species in B-doped and (B, N)-codoped TiO₂ photocatalysts have been investigated by solid-state ¹¹B NMR spectroscopy in conjunction with density functional theory (DFT) calculations. Up to seven different boron sites were identified in the B-doped anatase TiO₂, which may be classified into three categories, including interstitial, bulk BO_3/2 polymer, and surface boron species, and has been supported by results obtained from FT-IR and XPS spectroscopy as well as from DFT calculations. Two types of interstitial borons, namely the tricoordinated (T*)- and pseudotetrahedral-coordinated (Q*) borons, were observed in addition to the two types of bulk BO_3/2 polymer and three types of surface B, in good agreement with experimental data. Further density of state analyses revealed that, compared to undoped TiO₂, the T* species in boron-doped TiO₂ are solely responsible for the observed increase in energy band gap, whereas the presence of Q* species tend to lead to a decrease in band gap and hence are more favorable for the absorption in the visible-light region. In comparison with B- and N-doped TiO₂, (B, N)-codoped TiO₂ tends to exhibit a much higher visible-light photocatalytic activity for the oxidation of rhodamine B. Accordingly, a photochemical mechanism of the (B, N)-codoped TiO₂ under visible-light irradiation is proposed.