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Title: Nature of the Oxygen Species at Ni(110) and Ni(100) Surfaces Revealed by Exposure to Oxygen and Oxygen-Ammonia Mixtures : Evidence for the Surface Reactivity of O- Type Species
Authors: Kulkarni, G U
Rao, C N R
Roberts, M W
Keywords: Metal-Surfaces
Issue Date: 9-Mar-1995
Publisher: American Chemical Society
Citation: Journal of Physical Chemistry 99(10), 3310-3316 (1995)
Abstract: Adsorption of dioxygen at clean Ni(110) and Ni(100) surfaces gives rise to two prominent features in the O(1s) spectra at 530 and 531 eV due to O2- and O- type species, respectively. Interaction of ammonia with a Ni(100)-O surface where theta(oxygen) < 0.1 ML favors the dissociation of NH3 giving NHn, (n = 1, 2) and N(a) species. This is accompanied by a decrease in the intensity of the 531 eV feature. On the other hand. a Ni(100)-O surface where the oxygen species are mainly of the O2- type is unreactive, Coadsorption studies of NH3-O-2 mixtures show that at Ni(110) surfaces the uptake of both oxygen and ammonia increase with the proportion of oxygen in the NH3-O-2 mixture. The surface concentrations of the O- species and the NHn species also increase with the increase in the O-2/NH3 ratio while the slope of the plot of sigma(N) versus sigma(O-) is around unity. The results demonstrate the high surface reactivity of the O- species and its role in the dissociation of ammonia. Based on these observations, the possibility of the formation of a surface complex between ammonia and oxygen (specifically O-) is suggested. Results from vibrational spectroscopic studies of the coadsorption of NH3-O-2 mixtures are consistent with those from core-level spectroscopic studies.
Description: Restricted Access
Other Identifiers: 0022-3654
Appears in Collections:Research Papers (Prof. C.N.R. Rao)

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