Mechanistic insights to CO2 adsorption and activation on hydroxylated chromia (0001) surface

In the context of stainless -steel corrosion encountered during the transportation of CO2 in carbon capture, utilization and sequestration (CCUS), an attempt is made to apprehend the role of the hydroxylation of the surface of the chromia passive layer concerning the anhydrous Cr2O3 surface. A computational investigation is carried out for the CO2 interaction with chromia (0001) surface in the presence of water using periodic DFT+U methods. Different hydroxylation models (dissociated and molecularly adsorbed) of the chromia (0001) surface, and the mechanistic pathway for CO2 adsorption on hydroxylated chromia (0001), and further its protonation to form bicarbonate have been explored. Because of its high activation energy and endothermicity, the protonation of carbonate to bicarbonate species appears kinetically unfavorable at room temperature. However, the overall reaction profile for bicarbonate formation on hydroxylated chromia is exothermic. The charge density difference analysis of the charge transfer from the surface Cr atom to the O atoms of the CO2 molecule is followed by vibrational analysis to characterize the formation of adsorbed species. Moreover, preadsorbed water on the chromia surface enhances the surface activity for the adsorption of CO2. This study will serve as a basis to further investigate CO2 corrosion via point defect mechanism.