Atomic structure of active sites in O{sub 2} reduction on Au(111)/Tl{sub ad} electrodes in acid and alkaline solutions

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Surface x-ray scattering has been used to determine the structure of Tl adlayers on the Au(111) electrode surface during the course of 0{sub 2} reduction. 0. reduction is considerably catalyzed by Ti adlayers on Au(111). The half-wave potential is shifted to more positive values in the presence of the Ti adlayer. In both, acid and alkaline solutions TI causes a change in the reaction mechanism from a 2-ereduction to a 4e-reduction in a limited potential range. The in-plane X-ray diffraction measurements revealed that the close-packed rotated-hexagonal Ti phase, which exists in the potential range between -0.4V and the bulk TI ... continued below

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12 p.

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Adzic, R.R. & Wang, J.X. December 31, 1995.

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Surface x-ray scattering has been used to determine the structure of Tl adlayers on the Au(111) electrode surface during the course of 0{sub 2} reduction. 0. reduction is considerably catalyzed by Ti adlayers on Au(111). The half-wave potential is shifted to more positive values in the presence of the Ti adlayer. In both, acid and alkaline solutions TI causes a change in the reaction mechanism from a 2-ereduction to a 4e-reduction in a limited potential range. The in-plane X-ray diffraction measurements revealed that the close-packed rotated-hexagonal Ti phase, which exists in the potential range between -0.4V and the bulk TI deposition at {approx}{minus} 0.7V, has a lower activity for 0. reduction than the low-coverage phases in both solutions. It supports a 2e-reduction.0{sub 2} reduction does not change the TI coverage in this phase but causes a significant decrease of the in-plane diffracted intensity. The lower coverage phases which exist at more positive potentials, viz., aligned hexagonal in alkaline solution and patches of the (2 {times} 2)TI phase in acid solution, are conducive to a 4e-reduction. The diffraction intensity from these two phases, however, vanishes quickly during O{sub 2} reduction. It appears that the TI coverage remains on the surface unchanged. These observations indicate that the O{sub 2} molecules interact directly with the Tl adatoms prior to the charge transfer. This provides the most direct evidence that the outer sphere charge transfer mechanism in 0{sub 2} reduction is not operative for some surfaces. H{sub 2}0{sub 2} reduction is facile on the surface covered with the low-coverage TI phases, while it is almost completely suppressed by the rotated-hexagonal phase.

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12 p.

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OSTI as DE96004590

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  • 188. meeting of the Electrochemical Society, Chicago, IL (United States), 8-13 Oct 1995

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  • Other: DE96004590
  • Report No.: BNL--62495
  • Report No.: CONF-951007--14
  • Grant Number: AC02-76CH00016
  • Office of Scientific & Technical Information Report Number: 204121
  • Archival Resource Key: ark:/67531/metadc666728

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  • December 31, 1995

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  • June 29, 2015, 9:42 p.m.

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  • Nov. 30, 2015, 3:48 p.m.

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Adzic, R.R. & Wang, J.X. Atomic structure of active sites in O{sub 2} reduction on Au(111)/Tl{sub ad} electrodes in acid and alkaline solutions, article, December 31, 1995; Upton, New York. (digital.library.unt.edu/ark:/67531/metadc666728/: accessed September 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.