Interaction of Water Molecule with Au(111) and Au(110) Surfaces under the Influence of an External Electric Field

Abstract

The interaction of water monomers with a gold surface is investigated using density functional theory (DFT) to develop a better understanding of the response of a water molecule to an imposed electric field at the surface. Two gold surface orientations, Au(111) and Au(110), are studied. Multiple unique stable adsorption positions of water molecules are identified for each surface orientation, and the results are validated against existing theoretical and experimental data. The values of the adsorption energies do not vary by more than 0.06 eV, which suggests that the potential energy surface of the water molecule interacting with the gold electrode is relatively smooth. The projected density of states and the difference charge density analyses reveal that the interaction mechanism between the water molecule and the gold electrode is a partial exchange of charge rather than a chemical bonding. A normal electric field of magnitude between ±5.0 × 109 V/m is applied and its effect on the geometry and orientation of the water molecule is analyzed. The change in the geometry of the water molecule in response to the applied electric field shows a strong nonlinearity and asymmetry with respect to the magnitude and direction of the applied field. The interaction between the water monomer and Au electrode with/without the electric field is explained in terms of the interplay of Au–O, Au–OH, and electrostatic interactions. There is a significant difference between the dielectric response of the water molecule on the Au(111) and Au(110) surface that is related to the strength of the adsorption energy of the water monomer to both surfaces.

Interaction of H2O and H2S with Cu(111) and the impact of the electric field: the rotating & translating adsorbate, and the rippled surface

“…The rotation of H 2 O also shows that it is asymmetric with respect to the direction of the electric fieldit is more sensitive to a negative electric field. The asymmetry and greater rotation for a negative electric field agrees with the previously observed pattern for a water molecule adsorbed on gold 9 and copper 32 electrodes.…”

“…2 that the lone-pair orbitals display the most significant interaction with the 3d orbitals of the surface Cu atoms and also the most change (e.g., peak PDOS value, energy shifting and broadening) upon adsorption compared to other states at lower energies. This reveals that the Cu-χ interaction is the strongest interaction for both H 2 O and H 2 S. The stronger Cu-χ interaction is in agreement with the prediction that a small α value corresponds to a strong interaction between χ and the electrode [8][9][10]38 . Additionally, the PDOS change of the lone-pair orbitals is slightly greater for H 2 S, suggesting that the Cu-χ interaction is stronger for H 2 S than for H 2 O.…”

“…A copper electrode with (111) surface, Cu(111), was selected for the electrode because it has a similar electronic structure to that of gold but displays significantly different interfacial characteristics such as chemical reactivity and mechanical rigidity. In particular, the gold electrodes remained structurally insensitive to adsorption and the applied electric field 9 . The lack of a large structural change of the gold surfaces aligns well with the comparison made by Michaelides 10 where gold was one of the least structurally sensitive metals to water adsorption among the following matals: Ru, Rh, Pd, Pt, Cu, Ag and Au.…”

“…The dipole moment is expected to play an increasing role when an electric field is applied. The dipolefield interaction is the greatest contributor to the electrostatic interaction in the presence of the electric field and it increases as the magnitude of the electric field increases 9 . (111) is hydrogen production using a water gas shift reaction where a copper-based catalyst is widely used 15,16 .…”

THz-Pulse-Induced Selective Catalytic CO Oxidation on Ru

“…More recently, calculations have shown that strong external electric fields perpendicular to the surface and of the same order of magnitude (1 V/nm), as used in this study, have the potential to push or pull an entire layer of water molecules adsorbed on Au by as much as 0.5 Å [15]. It has been suggested that such effects can be enhanced at protrusions in the surface, such as step sites, where the electric fields can be enhanced by as much as a factor of 5 [16].…”