Unexpected Nondissociative Binding of N2O on Oxygen Vacancies on a Rutile TiO2(110)-1×1
The interaction of N{sub 2}O with oxygen vacancies (V{sub O}'s) on a partially-reduced rutile TiO{sub 2}(110)-1 x 1 surface was investigated using temperature-programmed desorption (TPD). Contrary to a common belief that V{sub O} on a rutile TiO{sub 2}(110) is a dissociation site for N{sub 2}O, our results indicate that N{sub 2}O does not dissociate to form N{sub 2}(g) and O(a). In TPD, N{sub 2}O desorption shows two peaks with maxima at 135 and 175 K that are assigned to N{sub 2}O desorption from Ti{sup 4+} and V{sub O} sites, respectively, with absolute coverages determined to be 5.1 x 10{sup 14} N{sub 2}O/cm{sup -2} and 2.6 x 10{sup 13} cm{sup -2}, respectively. When V{sub O}'s are passivated by dissociative adsorption of H{sub 2}O, the N{sub 2}O desorption peak at 175 K disappears, evidencing that the peak is related to V{sub O}-bonded N{sub 2}O. The absence of N{sub 2}O dissociation on V{sub O}'s is supported by a number of observations. First, the integrated amount of N{sub 2}O desorbed from the substrate during TPD vs. the amount of N{sub 2}O dosed at 70 K shows a straight line with no offset indicating no loss of N{sub 2}O due to the N{sub 2} formation. Second, N{sub 2}O scattering experiments at 300-350 K indicate no change in the V{sub O} concentration as determined from the H{sub 2}O TPD spectra. Third, N{sub 2}O uptake experiments at 70-90 K show that the N{sub 2} desorption feature is observed from TiO{sub 2}(110) surfaces without V{sub O}'s, suggesting a possible contribution from background N{sub 2} adsorption. Based on the above observations, we conclude that N{sub 2}O does not dissociate on V{sub O} sites on TiO{sub 2}(110) in contrast with the currently accepted view.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1036059
- Report Number(s):
- PNNL-SA-83511; 39940; KC0302010; TRN: US201205%%576
- Journal Information:
- Journal of Physical Chemistry C, Vol. 116, Issue 1; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
Similar Records
Temperature-programmed desorption study of NO reactions on rutile TiO2(110)-1×1
Interaction of Formaldehyde with the Rutile TiO 2 (110) Surface: A Combined Experimental and Theoretical Study