Effects of Surface Orientations of Cr2O3 on CO2 Adsorption: a DFT approach

Abstract In the context of corrosion of stainless steel being in contact with supercritical CO2, during the transportation step of CO2 sequestration process, we have studied the adsorption of CO2 molecule on different Cr2O3 surfaces terminations: ( 0001 ), ( 01 1 ¯ 2 ) and ( 10 1 ¯ 2 ) using density functional calculations. Upon CO2 adsorption, the formation of physisorbed and chemisorbed species are found to be dependent on different surface terminations. The analyses of the optimized geometrical parameters, vibrational frequencies and atomic charges revealed the formation of a carboxylate species and a carbonate on O layer terminated-( 0001 ), ( 10 1 ¯ 2 ) and a carbonate species on Cr layer-( 01 1 - 2 ) facets, respectively. The chemical bonding analysis depicts the formation of a covalent bond between the carbon and surface oxygen (Os) atom and between the oxygen atom of the CO2 molecule and Cr atom. Additionally, the electron density distributions (calculated from Bader’s theory) show a net electron transfer from the surface to the CO2 molecule, turning the latter into an ionic species. The calculated adsorption energies and C-Os vibrational frequencies are in good agreement with the available experimental data and emphasize the formation of carbonates for non-( 0001 ) surface termination.