FTIR Spectroscopy Combined with Isotope Labeling and Quantum Chemical Calculations to Investigate Adsorbed Bicarbonate Formation Following Reaction of Carbon Dioxide with Surface Hydroxyl Groups on Fe2O3 and Al2O3.

FTIR spectroscopy combined with isotope labeling expts. and quantum chem. calcns. is used to investigate the adsorption of carbon dioxide on hydroxylated metal oxide surfaces. In particular, transmission FTIR spectra following CO2 adsorption on hydroxylated nanoparticulate Fe2O3, α-Al2O3, and γ-Al2O3 particles at 296 K are reported. As expected, reaction of CO2 with these surfaces results in the formation of adsorbed bicarbonate and carbonate. In this study, the vibrational spectrum of the bicarbonate product is analyzed in detail through the use of isotope labeling expts. and quantum chem. calcns. The exptl. and calcd. vibrational frequencies of adsorbed HC16O3-, DC16O3-, HC18O3-, HC16O18O2-, and HC18O16O2- indicate that bicarbonate bonds to the surface in a bridged structure. There is some evidence from the mixed isotope expts. that following initial nucleophilic attack of OH, the formation of the final bicarbonate structure involves a proton transfer. On the basis of energetic considerations, the proton transfer mechanism most likely occurs through an intermol. process involving either coadsorbed hydroxyl groups and/or carbonate. [on SciFinder(R)]