ACTIVATION OF CARBON-DIOXIDE BY AMMONIA AT CU(100) AND ZN(0001) SURFACES LEADING TO THE FORMATION OF A SURFACE CARBAMATE

The coadsorption of carbon dioxide and ammonia at Cu(100) and Zn(0001) surfaces has been investigated using a combination of X-ray photoelectron (XP) and vibrational (HREEL) spectroscopies. The spectroscopic features characteristic of CO2(a), NH3(a) and ND3(a) have been obtained in the temperature range 80-298 K together with the spectra of species generated as a result of the coadsorption of CO2 and NH3. XP spectra enable the surface concentrations of the species revealed by HREELS to be calculated. At both Cu(100) and Zn(0001) surfaces evidence is obtained for the formation of a chemisorbed carbamate. The latter is suggested to form via a weakly adsorbed NH3-CO2 complex. Coadsorption of carbon dioxide with water does not lead to activation at the Cu(100) surface.