Carbonate formation by reacting CO2 with an O2 layer on Ag(110) studied by high resolution electron energy loss spectroscopy

The coadsorption and reaction of CO2 with a layer of molecular oxygen preadsorbed on a Ag(110) surface have been studied with high resolution electron energy loss spectroscopy (HREELS). Clear evidence has been found for a direct reaction of CO2 and O-2 to CO3 at 100 K, resulting in a product coverage higher than attainable with atomic oxygen in the (2 x 1)O reconstruction. All internal modes of CO3 have been detected, including the in-plane bend and the asymmetric stretch modes, which are degenerate at intermediate but split at saturation coverages. An intermediate species has been observed to be stable only in coadsorption with molecular oxygen, and has been tentatively assigned to a CO4- anion. The quantitative analysis of the isotopic shift observed with (CO2)-C-13-O-16, (CO2)-C-12-O-18 and O-18(2) is consistent with a planar adsorption geometry of a structurally unmodified CO3 anion bound via the central carbon atom. (C) 1999 Elsevier Science B.V. All rights reserved.