Computational Insights into the Relationship Between Solution Concentration and Adsorption Energy

TL;DR

This study explores how solution concentration affects ion adsorption on metal surfaces, revealing that higher concentrations slightly increase work function and strengthen adsorption interactions.

Contribution

The novel contribution is the systematic calculation of adsorption energy and work function changes with concentration, mediated by dielectric properties.

Findings

Surface coverage remains largely unchanged at higher concentrations due to electrostatic shielding.

Work function increases by 20–90 meV with concentration, depending on metal type and surface orientation.

Adsorption energy changes are not statistically significant despite increased solution concentration.

Abstract

The electrochemical interaction between aggressive ions and metals plays a key role in corrosion failure processes. The Langmuir adsorption isotherm equation was employed to reveal that surface coverage remains largely unchanged at higher concentrations, with the concentration effect partially mediated by the dielectric properties of the solution. The work function and adsorption energy of two typical corrosive elements, Cl and S, adsorbed on the surfaces of two metals (Al and Cu) were systematically calculated. By adjusting solubilization parameters in different implicit solvent models, variations in dielectric properties at similar surface coverage under different concentrations were simulated. It was observed that as the solution concentration increased, the electrostatic shielding effect of the surface solution was enhanced, while the changes in adsorption energy were not statistically significant. However, the work function was found to increase by approximately 20–90 meV with increasing concentration, with the magnitude of this increase dependent on the metal type and surface orientation. This enhancement further strengthened the adsorbate–substrate interaction, thereby influencing the electrochemical reaction kinetics of the surface material.

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