Photogenerated Charge Carriers and Paramagnetic Species in (W,N)-Codoped TiO2 Photocatalysts under Visible-Light Irradiation: An EPR Study

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• 作者：Andrea Folli ; Jonathan Z. Bloh ; Eva-Panduleni Beukes ; Russell F. Howe ; Donald E. Macphee
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 24, 2013
• 年：2013
• 卷：117
• 期：42
• 页码：22149-22155
• 全文大小：350K
• 年卷期：v.117,no.42(October 24, 2013)
• ISSN：1932-7455

文摘

(W,N)-codoped TiO₂ has recently attracted interest due to substantial band gap narrowing in conjunction with good visible-light photocatalytic activities. A complete picture of the fundamental mechanism at the origin of their photoactivity is, however, far from being understood. We present an EPR study on (W,N)-codoped titanias by recording spectra in the dark and under 550 nm visible-light irradiation to identify the major species involved in the formation and migration of photogenerated charge carriers. Interstitial N鈥搇attice O (formally NO^{2鈥?/sup>) paramagnetic groups with and without a specific close range coupling interaction with a neighboring W, that is, [N_iO]_W鈼?/sup> and [N_iO]鈼?/sup>, respectively, are observed when visible light excites electrons from diamagnetic intraband gap states located at 2.30 V versus RHE (formally NO3鈥?/sup>) to the conductance band at around 鈭?.05 V versus RHE. The [N_iO]_W鈼?/sup> EPR signal, reported here for the first time, is characterized by a much stronger hyperfine interaction between the unpaired electron and the 14N nucleus than ordinary [N_iO]鈼?/sup> found in N-doped TiO₂, leading to a much higher spin density on the N center. The overall signal also contains superhyperfine coupling of the unpaired electron with the 183W nuclide (natural abundance 14.31%), the only naturally occurring nuclide of W with a nonzero nuclear spin.}