期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 14, 期 5, 页码 1402-1414出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200701514
关键词
anatase; EPR spectroscopy; EXAFS spectroscopy; rhenium; surface chemistry
资金
- NIGMS NIH HHS [GM 73789, GM 48242] Funding Source: Medline
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM048242, R01GM073789, R29GM048242] Funding Source: NIH RePORTER
Samples of the anatase phase of titania were treated under vacuum to create Ti3+ surface-defect sites and surface O- and O-2(-) species (indicated by electron paramagnetic resonance (EPR) spectra), accompanied by the disappearance of bridging surface OH groups and the formation of terminal Ti-3(+)-OH groups (indicated by IR spectra). EPR spectra showed that the probe molecule [Re-3(CO)(12)H-3] reacted preferentially with the Ti3+ sites, forming Ti4+ sites with OH groups as the [Re-3(CO)(12)H-3] was adsorbed. Extended X-ray absorption fine structure (EXAFS) spectra showed that these clusters were deprotonated upon adsorption, with the triangular metal frame remainina intact; EPR spectra demonstrated the simultaneous removal of surface O- and O-2(-) 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 [Re-3(CO)(12)H-3] 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.
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