ISOTOPIC-SUBSTITUTION EVIDENCE AGAINST THE FORMATION OF (H3O+) AD FROM COADSORPTION OF HYDROGEN AND WATER ON CU(110)

We present both high resolution electron energy loss spectra (HREELS) and thermal desorption spectra (TDS) for hydrogen plus water coadsorption on Cu(110). Hydrogen adsorbed at 100 K. increases the desorption temperature of water by {reversed tilde} 10 K., indicating a fairly weak interaction. This stabilised water is associated with dramatic changes in the HREELS spectra: the scissor mode at 1600 cm-1 is attenuated and a new vibration is observed at 1150 cm-1. The assignment of this mode to the symmetric bend of an (H3O+)ad species as recently reported for Pt(111), therefore seemed plausible also for Cu(110). However, TDS showed no isotopic exchange which indicates that a reaction between (H)ad and (H2O)ad does not occur on Cu(110). The different origin of the 1150 cm-1 mode on Cu(110) is briefly discussed. © 1990.