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. https://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.
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| 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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| Issue or Number: | 42 | |||||||||
| Record Number: | CaltechAUTHORS:20150623-154758942 | |||||||||
| Persistent URL: | https://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: | 03 Mar 2020 13:01 |
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