Knut, R. and Lagerqvist, U. and Palmgren, P. and Pal, P. and Svedlindh, P. and Pohl, A. and Karis, O. (2015) Photoinduced reduction of surface states in Fe:ZnO. Journal of Chemical Physics , 140 (20). 204703-1-204703-8. ISSN 0021-9606

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We report on the electronic structure of nano-crystalline Fe:ZnO, which has recently been found to be an efficient photocatalyst. Using resonant photoemission spectroscopy, we determine the binding energy of Fe 3d states corresponding to different valencies and coordination of the Fe atoms. The photo-activity of ZnO reduces Fe from 3+ to 2+ in the surface region of the nano-crystalline material due to the formation of oxygen vacancies. Electronic states corresponding to low-spin Fe2+ are observed and attributed to crystal field modification at the surface. These states are potentially important for the photocatalytic sensitivity to visible light due to their location deep in the ZnO bandgap. X-ray absorption and x-ray photoemission spectroscopy suggest that Fe is only homogeneously distributed for concentrations up to 3%. Increased concentrations does not result in a higher concentration of Fe ions in the surface region. This is limiting the photocatalytic functionality of ZnO, where the most efficient Fe doping concentration has been shown to be 1%-4%.

Item Type: Article
Subjects: Chemistry > Physical Chemistry
Physics > Atomic and Molecular Physics
Depositing User: Dr. Rajpal Walke
Date Deposited: 06 Oct 2016 06:19
Last Modified: 06 Oct 2016 06:19

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