Vibrational properties of CO2 adsorbed on the Fe3O4 (111) surface: Insights gained from DFT

By virtue of density functional theory calculations, this work discusses several carbonate, carboxylate, and bicarbonate species on two thermodynamically relevant metal terminations of the (111) surface of magnetite, Fe3O4. We present adsorption energies and vibrational wavenumbers and conclude in assigning the observed infrared reflection-absorption spectroscopy bands. CO2 prefers to adsorb molecularly on the Fetet1 terminated Fe3O4(111) surface, a finding consistent with observation. Calculations compared with the experiment lead to interpreting results in favor of the Fetet1 (single metal) terminated Fe3O4(111) surface as the regular surface termination. Formation of carbonate and bicarbonate requires metal impurities on that surface. Such impurities exist, for instance, on the Feoct2 (double metal) termination, which can thus be used as a model for “metal-rich terminations” of more complex surfaces.