Evaluating the Mechanism of Visible Light Activity for N,F-TiO2 Using Photoelectrochemistry

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• 作者：Jeremy W.J. Hamilton ; J. Anthony Byrne ; Patrick S.M. Dunlop ; Dionysios D. Dionysiou ; Miguel Pelaez ; Kevin O鈥橲hea ; Damian Synnott ; Suresh C. Pillai
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 12, 2014
• 年：2014
• 卷：118
• 期：23
• 页码：12206-12215
• 全文大小：472K
• 年卷期：v.118,no.23(June 12, 2014)
• ISSN：1932-7455

文摘

The improvement of the solar efficiency of photocatalytic materials is important for solar driven environmental remediation and solar energy harvesting applications. Photoelectrochemical characterization of nitrogen and fluorine codoped titanium dioxide (N,F-TiO₂) was used to probe the mechanism of visible light activity. The spectral photocurrent response under visible irradiation did not correlate with the optical absorption spectrum of the N,F-TiO₂; however, open-circuit photopotential measurements provided better correlation to the optical absorption spectra. These observations suggest that electrons excited to the conduction band from the N-induced midgap state are rapidly trapped by defect levels below the conduction band. Reactive oxygen species (ROS) can be produced via the reduction of molecular oxygen by conduction band electrons leading to the oxidative degradation of organic pollutants, and singlet oxygen may play a role. If there is no loss in the band gap activity, as compared to undoped titania, then any additional visible light activity may give an overall improvement in the solar efficiency. The photocurrent response should not be used as a direct measure of photocatalytic activity for doped titania as the oxygen reduction pathway is vitally important for the generation of ROS, whereas hole transfer from dopant midgap states may not be so critical.