Direct atomic-scale observation of redox-induced cation dynamics in an oxide-supported monolayer catalyst : WO{sub x}/{alpha}-Fe{sub 2}O{sub 3}(0001).
For the case of one-third of a monolayer of tungsten grown by atomic layer deposition on a hematite {alpha}-Fe{sub 2}O{sub 3}(0001) surface, we report direct atomic-scale observations of the structural and chemical changes that occur as this model interfacial system evolves from the as-deposited state to the oxidized state, then to the reduced state, and finally back to the oxidized state. In situ X-ray standing-wave atomic images relative to the hematite lattice show dramatic (but redox-reversible) changes to the W cation locations with respect to the occupied and unoccupied Fe surface sites. These structural changes are concurrent with X-ray photoelectron spectroscopy chemical shift changes, where W is observed to go from the 6+ to 5+ oxidation state. These novel observations of redox-induced cation dynamics in an oxide-supported catalyst are explained by models that account for W incorporation at the interface in Fe sites with various coordination schemes. Our proposed structure models are supported by our X-ray absorption fine structure measurements.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 991618
- Report Number(s):
- ANL/XSD/JA-68211; JACSAT; TRN: US201021%%254
- Journal Information:
- JACS Comm., Vol. 131, Issue 2009; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- ENGLISH
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