Photoinduced reduction of surface states in Fe:ZnO

Journal Article · Thu May 28 00:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4921570· OSTI ID:22415879

Palmgren, P.; Lagerqvist, U.; Pohl, A. ^[1]; Pal, P. ^[2]; Svedlindh, P. ^[3]

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1. Department of Chemistry Ångström, Uppsala University, P.O. Box 538, SE-751 21 Uppsala (Sweden)
2. MAX-Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)
3. Department of Engineering Sciences, Uppsala University, P.O. Box 534, SE-75121 Uppsala (Sweden)

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 Fe{sup 2+} 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%.

• OSTI ID: 22415879
• Journal Information: Journal of Chemical Physics, Vol. 142, Issue 20; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ATOMS
BINDING ENERGY
CONCENTRATION RATIO
CRYSTAL FIELD
ELECTRONIC STRUCTURE
IRON IONS
MODIFICATIONS
NANOSTRUCTURES
OXYGEN
PHOTOCATALYSIS
PHOTOELECTRON SPECTROSCOPY
POTENTIALS
REDUCTION
SPIN
SURFACES
VACANCIES
VALENCE
VISIBLE RADIATION
X RADIATION
ZINC OXIDES