Research On The Equilibrium Geometric Structure And Electronic Structure In The Interface Of Metal Iron And The Solution

With regard to the metal corrosion behavior in aqueous solution, the dissolution process of metal atoms on the surface is the most fundamental problem. In the electrical double layer interface, the geometry and electronic structure of water molecules and anion adsorption particles would directly affect the dissolution of the metal atoms on the surface. Therefore, it is of important practical significance to reveal the scientific mechanism of the initial electrochemical corrosion from the point of view of the geometric and electronic structure in atomic scale, for it would provide a theoretical basis for anti-corrosion study. This research belongs to one of the cutting-edge problems in the cross science field of the interface science and corrosion science.By means of experiment and first principles methods, the geometric and electronic structures of Fe/solution interface were investigated. On the aspect of experimental research, by using electrochemical scanning tunneling spectroscopy technology, the electronic states of Fe/H₂O, Fe/ (H₂O+Cl) and the electronic states of Fe/H₂O exposed with the surface excess charges were elucidated. The results indicated that the energy of surface electrons increases and Fermi level shifts upwards under the interplay of H₂O adsorption layer with Fe (110) surface; Secondly, the coadsorption effect of H₂O adsorption layer and adsorption Cl on Fe (110) surface makes the electronic energy shift to higer level, which induces the surface electron energy increase and the Fermi level shift upwards. The electrons on the surface become more active; thirdly, the surface excess charges have the significant impact on the interface electronic states, which promote the energy of the electronic density to shift and affect the stability of the surface electrons.On the aspect of theory research, the interface gerometric and electronic structure of Fe/H₂O and Fe/ (H₂O+Cl) were studied by the first principle method based on the density functional theory. Additionally, the effects of surface excess charges on the interface geometric and electronic structure were investigated. The results showed that the equilibrium geometry structure of monomer H₂O or Cl and H₂O coadsorption on Fe single crystal surface is that H₂O is on the atop site of substrate Fe atoms, Cl is on the hollow site of substrate Fe atoms and H₂O is lying on the substrate surface; Secondly, both Cl and the surface excess charges have the significant impact on the orientation structure of H₂O in the electrical double layer; Thirdly, H₂O, Cl, as well as the surface excess charges all make the Fe surface atoms relaxation and reconstruction occur in different degrees. Fourthly, the dissociation products of H₂O on the Fe surface are double OH and double H, which significanly affect the arrangment structure and the adsorption density in the interface. Fifthly, the interaction of H₂O with Fe surface is through coaction of the 1b₁ and 3a₁ of H₂O and Fe 3p, Fe 3d orbtials. Thus, the interplay of H₂O with Fe is the electrostatic interaction of the inner orbits combined with the covalent bond effect of outer orbits. These results are useful for guiding the researches of the inner reaction of metal iron and solution interface and would provide the scientific basis for anti-corrosion study.