Probing Defect Sites on TiO_2 with H_3 Re_3 (CO)_12 : Spectroscopic Characterization of the Surface Species
Samples of the anatase phase of titania were treated under vacuum to create Ti3+ surface-defect sites and surface O- and O2- species (indicated by electron paramagnetic resonance (EPR) spectra), accompanied by the disappearance of bridging surface OH groups and the formation of terminal Ti3+OH groups (indicated by IR spectra). EPR spectra showed that the probe molecule [Re3(CO)12H3] reacted preferentially with the Ti3+ sites, forming Ti4+ sites with OH groups as the [Re3(CO)12H3] was adsorbed. Extended X-ray absorption fine structure (EXAFS) spectra showed that these clusters were deprotonated upon adsorption, with the triangular metal frame remaining intact; EPR spectra demonstrated the simultaneous removal of surface O- and O2- species. The data determined by the three complementary techniques form the basis of a schematic representation of the surface chemistry. According to this picture, during evacuation at 773 K, defect sites are formed on hydroxylated titania as a bridging OH group is removed, forming two neighboring Ti3+ sites, or, when a Ti4+O bond is cleaved, forming a Ti3+ site and an O- species, with the Ti4+OH group being converted into a Ti3+OH group. When the probe molecule [Re3(CO)12H3] is adsorbed on a titania surface with Ti3+ defect sites, it reacts preferentially with these sites, becoming deprotonated, removing most of the oxygen radicals, and healing the defect sites.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959656
- Report Number(s):
- BNL-82642-2009-JA; TRN: US201016%%800
- Journal Information:
- Chemistry - A European Journal, Vol. 14
- Country of Publication:
- United States
- Language:
- English
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