Structures and energetics of CO₂ adsorption on the Fe₃O₄ (111) surface

Density functional theory calculations were used to investigate CO₂ adsorption behaviors on Fe_tet1-and Fe_oct2-terminated surface of Fe₃O₄ (111). The results indicated that on the Fe_tet1-terminated surface, the linear CO₂ is favored at 1/5 monolayer (ML), whereas the bent CO₂ bonded to surface O, i.e. carbonate structure, becomes possible at higher coverage. On the Fe_oct2-terminated surface, the bent CO₂ is favored; both carbonate and carboxylate structure are formed at both 1/6 and 1/3 ML. Meanwhile, the Fe_tet1-terminated Fe₃O₄(111) surface has weak coverage effects, whereas the Fe_oct2-terminated Fe₃O₄(111) surface has strong coverage effects; the Fe_oct2-terminated surface is thermodynamically more favorable than the Fe_tet1-terminated surface for CO₂ adsorption.