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Infrared Spectra of Photoinduced Species on Hydroxylated Titania Surfaces

Szczepankiewicz, Steven H. and Colussi, A. J. and Hoffmann, Michael R. (2000) Infrared Spectra of Photoinduced Species on Hydroxylated Titania Surfaces. Journal of Physical Chemistry B, 104 (42). pp. 9842-9850. ISSN 1520-6106. http://resolver.caltech.edu/CaltechAUTHORS:20150623-154758942

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Abstract

We detect transient and persistent diffuse reflectance infrared signals from surface intermediates generated by band gap irradiation of polycrystalline, hydroxylated TiO_2 under controlled atmospheres. Irradiation in vacuo or in the presence of CD_3OD(ads) leads to a new absorbance at 3716 cm^(-1), the decline of a 3647 cm^(-1) band, and a reflectivity loss. Overall reflectivity, which gauges mobile charge, partially recovers in the dark after a few minutes but fully recovers upon exposure to O_2. The 3716 cm^(-1) feature persists for days in a vacuum or dry O_2 but is bleached by the action of (O_2 + H_2O + hν). It is assigned to a Ti(III)O−H^- vibration resulting from electron trapping at acidic Ti(IV)OH centers. Irradiation under O_2 yields a new band at 3683 cm^(-1), ascribed to surface-bound OH radicals that last indefinitely in a vacuum. None of the above events occur on thermally generated TiO_(2-γ) specimens subsequently exposed to H_2O(g). We infer that (1) O_2 is an efficient scavenger of conduction band electrons at the gas−solid interface, (2) the competition for holes between lattice oxygen photodesorption and OH^- oxidation depends on gas pressure and composition, and (3) the trapped carrier buildup eventually results in extended surface reconstruction involving Ti−OH functionalities, giving rise to restructuring hysteresis.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp0007890DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp0007890PublisherArticle
ORCID:
AuthorORCID
Colussi, A. J.0000-0002-3400-4101
Hoffmann, Michael R.0000-0002-0432-6564
Additional Information:© 2000 American Chemical Society. Received: March 1, 2000; In Final Form: July 21, 2000. We thank J. A. Moss for assistance with experimental design. This work was funded by grants from the NSF and DARPA (through a cooperative program with the Northrop-Grumman Corporation).
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Funding AgencyGrant Number
NSFUNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Northrop-Grumman CorporationUNSPECIFIED
Record Number:CaltechAUTHORS:20150623-154758942
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150623-154758942
Official Citation:Infrared Spectra of Photoinduced Species on Hydroxylated Titania Surfaces Steven H. Szczepankiewicz, A. J. Colussi, and Michael R. Hoffmann The Journal of Physical Chemistry B 2000 104 (42), 9842-9850 DOI: 10.1021/jp0007890
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58488
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Jul 2015 20:05
Last Modified:14 Dec 2015 21:46

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