Density Functional Theory Study on the Carbon-Adhering Reaction on Fe₃O₄(111) Surface

The density functional theory (DFT) has been employed to investigate the carbon-adhering reaction on Fe₃O₄(111) surface, which consists of two steps: (1) the adsorption of CO onto the Fe₃O₄(111) surface and (2) the second CO seizes an O atom from CO, which adsorbed on the surface, to form a CO₂ molecule and the C atom left behind adheres onto the Fe₃O₄(111) surface. At step 1, there are five stable configurations of CO adsorbed onto Fe_oct2-terminated Fe₃O₄(111) surface and four stable formations of CO adsorbed onto the Fe_tet1-terminated Fe₃O₄(111) surface. The top configurations of these two surfaces are most stable. Moreover, a density of the state (DOS) analysis is used to investigate the bonding mechanism of CO adsorbed onto these two surfaces. The results reveal the new C-O bonds generation on two surfaces, which is important and necessary for the formation of a CO₂ molecule. Besides, the transition states (TS) are searched to analyze the energy barrier in the process of CO₂ desorption from two surfaces. The result indicates that the oxidation reaction of adsorbed CO molecule and surface O atom is feasible. For step 2, the result shows that the carbon-adhering reaction occurs only on the top site of Fe_oct2 atom and the magnetite plays a catalytic role in the carbon-adhering reaction process.