The Adsorption Behaviors of CO and H₂ to FeO onto CaO Surfaces: A Density Functional Theory Study

The adsorption behaviors of CO and H₂ to FeO onto CaO surfaces have been studied using the density functional theory (DFT) to determine the reactions of FeO by CO and H₂. The adsorption mechanisms of FeO clusters on the CaO(100) and CaO(110) surfaces were calculated first. The structure of the Ca(110) surface renders it highly chemically reactive compared with the Ca(100) surface because of low coordination. After gas adsorption, CO bonds to the O atom of FeO, forming CO₂ compounds in both configurations through the C atom. H₂ favors the O atom of FeO, forming H₂O compounds and breaking the Fe-O bond. Comparing the adsorption behavior of two reducing gases to FeO on the Ca surface, the reaction of the CO molecule being adsorbed to generate CO₂ compounds is exothermic. The reaction of H₂ molecule adsorption to generate H₂O compounds is endothermic. This property is essential for the inertial-collision stage of the reduction. However, the dissociation of the CO₂ compound from the reaction interface will overcome a high energy barrier and slow down the reduction. The H₂O compound dissociates from the surface more easily, which can accelerate the reduction.