Premium
Probing Defect Sites on TiO 2 with [Re 3 (CO) 12 H 3 ]: Spectroscopic Characterization of the Surface Species
Author(s) -
Suriye Kongkiat,
LoboLapidus Rodrigo J.,
Yeagle Gregory J.,
Praserthdam Piyasan,
Britt R. David,
Gates Bruce C.
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701514
Subject(s) - electron paramagnetic resonance , deprotonation , crystallography , anatase , extended x ray absorption fine structure , chemistry , molecule , adsorption , spectral line , radical , absorption spectroscopy , catalysis , photocatalysis , nuclear magnetic resonance , organic chemistry , ion , physics , quantum mechanics , astronomy
Samples of the anatase phase of titania were treated under vacuum to create Ti 3+ 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 Ti 3+ sites, forming Ti 4+ 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 remaining 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 Ti 3+ sites, or, when a Ti 4+ O bond is cleaved, forming a Ti 3+ site and an O − species, with the Ti 4+ OH group being converted into a Ti 3+ OH group. When the probe molecule [Re 3 (CO) 12 H 3 ] is adsorbed on a titania surface with Ti 3+ defect sites, it reacts preferentially with these sites, becoming deprotonated, removing most of the oxygen radicals, and healing the defect sites.