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Photogenerated charge carriers and paramagnetic species in (W,N)-codoped TiO2 photocatalysts under visible-light irradiation: An EPR study

Folli, Andrea, Bloh, Jonathan Z., Beukes, Eva-Panduleni, Howe, Russell F. and Macphee, Donald E. 2013. Photogenerated charge carriers and paramagnetic species in (W,N)-codoped TiO2 photocatalysts under visible-light irradiation: An EPR study. Journal of Physical Chemistry C 117 (42) , p. 22149. 10.1021/jp408181r

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Abstract

(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–lattice O (formally NO2–) paramagnetic groups with and without a specific close range coupling interaction with a neighboring W, that is, [NiO]W● and [NiO]●, respectively, are observed when visible light excites electrons from diamagnetic intraband gap states located at ∼2.30 V versus RHE (formally NO3–) to the conductance band at around −0.05 V versus RHE. The [NiO]W● 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 [NiO]● 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: American Chemical Society
ISSN: 1932-7447
Last Modified: 28 Jan 2020 10:45
URI: http://orca-mwe.cf.ac.uk/id/eprint/129036

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