Activation of carbon dioxide by ammonia at Cu(100) and Zn(0001) surfaces leading to the formation of a surface carbamate

Abstract

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) 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.