Demystifying the Stern layer at a metal-electrolyte interface: Local dielectric constant, specific ion adsorption,...

Area of Science:

• Electrochemistry
• Surface Science
• Computational Chemistry

Background:

• The electric double layer (EDL) is fundamental to electrochemistry, influencing applications like energy storage.
• Existing models struggle to predict electrode-electrolyte interface properties from a molecular viewpoint.

Purpose of the Study:

• Investigate the charging behavior of a silver (111) electrode in sodium fluoride solutions.
• Clarify the molecular mechanisms governing ion adsorption and charge transfer at the electrode-electrolyte interface.

Main Methods:

• Combined experimental results with theoretical calculations.
• Employed classical density functional theory for ion distributions.
• Utilized joint density functional theory (JDFT) for electronic structure analysis.

Main Results:

• Surface charge density at negative electrode potentials is explained by a neutral Stern layer with field-dependent dielectric properties.
• Fluoride ion adsorption at positive potentials involves both physical and chemical interactions.
• JDFT confirms fluoride binding and partial charge transfer, with binding energy increasing with voltage.

Conclusions:

• Molecular insights into the Stern layer and adsorbed species behavior extend conventional EDL models.
• Specific ion adsorption, particularly fluoride, is crucial for accurate interface modeling.
• Findings enhance understanding of electrochemical interfaces for improved device design.