Coverage dependent water dissociative adsorption on Fe(110) from DFT computation.
Using density functional theory calculations and ab initio atomistic thermodynamics, H2O adsorption and dissociation on the Fe(110) p(4 × 4) surface at different coverages have been computed. At the lowest coverage, the adsorbed H2O, OH, O and H species can migrate easily on the surface. For (H2O)n adsorption, H2O molecules donating H atoms for H-bonding adsorb more strongly than those accepting H atoms for H-bonding. Monomeric H2O dissociation is favored both thermodynamically and kinetically. On nO pre-covered Fe(110) surfaces (n = 1-8), H2O dissociation is accessible for nO + H2O (n = 1-7) both kinetically and thermodynamically, while H2O desorption instead of dissociation occurs at n = 8. With the increased number of surface O atoms, H2 dissociative adsorption energies vary in a narrow range for n = 1-4 and decrease for n = 5-7, while at n = 8, the surface does not adsorb H2. At low OH coverage (n = 2, 4), OH groups are perpendicularly adsorbed without H-bonding, while for n≥ 6, adsorbed OH groups are linearly arranged and stabilized by H-bonding. The maximal OH coverage (n = 12) is 0.75 ML and the reasonable O coverage (n = 7) is 0.44 ML, in line with the experiment. The calculated desorption temperatures of H2O and H2 agree well with the available experimental data. These results provide fundamental insights into water-involved reactions catalyzed by iron and interaction mechanisms of water interaction with metal surfaces.
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, 030001, China.
Shaoli
S
Liu
Xinxin
X
Tian
Tao
T
Wang
Xiaodong
X
Wen
Yong-Wang
YW
Li
Jianguo
J
Wang
Haijun
H
Jiao