Quantum Chemical Modeling of Hydroxide Ion Adsorption on Group IB Metals from Aqueous Solutions

I. V. Nechaev and A. V. Vvedenskii

Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia

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Received July 9, 2008

Abstract — Interactions between hydroxide ions and (001), (011), and (111) faces of Cu, Ag, and Au in the gas phase and in an infinitely diluted aqueous solution are nonempirically studied with the density functional method (DFT) with the use of B3LYP functional. Adsorption surfaces are modeled by n-atomic clusters (n =10–18). The presence of solvent is taken into account in terms of the combined molecular–continuum model, and the effect of polarizable dielectric is estimated with the use of self-consistent solvent reaction field COSMO model. The composition and structure of hydrated hydroxide ion are found and the hydration energy is estimated in satisfactory agreement with the experimental data. Relative effects of the metal nature, crystal face orientation, and adsorption site on the adsorption characteristics are determined, and the geometrical parame-ters of the chemisorption bond and the degree of the partial charge transfer are estimated. A comparative analysis of the results obtained shows that the adsorption on-top position, which is energetically unfavorable in the gas phase, becomes prevailing in an aqueous solution, which can be explained by the increased stability of the on-top adsorption complex.

PACS numbers: 68.43.-h