Density-Potential Functional Theory with Explicit Solvation and Desolvation for Electrical Double Layers.

Area of Science:

• Physical Chemistry
• Computational Electrochemistry
• Materials Science

Background:

• Electrical double layers (EDLs) are critical at electrochemical interfaces.
• Existing models often lack molecular detail on solvation/desolvation effects.
• Realistic modeling requires integrating electrostatics with molecular solvent behavior.

Purpose of the Study:

• To develop an advanced theoretical framework, DPFTsol, for modeling EDLs.
• To incorporate explicit ion-solvent binding and entropy into EDL theory.
• To accurately predict EDL structure and capacitance under realistic conditions.

Main Methods:

• Developed DPFTsol, an extended density-potential functional theory.
• Incorporated explicit ion-solvent binding energies and configurational mixing entropy.
• Validated against experimental differential capacitance data for Ag(111)-KPF6 solutions.

Main Results:

• DPFTsol quantitatively reproduces experimental capacitance curves across concentrations.
• Revealed potential-dependent ion desolvation, solvent layering, and dielectric changes.
• Demonstrated the influence of solvation parameters on capacitance and electric fields.

Conclusions:

• Explicitly accounting for solvation/desolvation is essential for accurate EDL predictions.
• DPFTsol provides a robust framework for understanding and designing electrochemical interfaces.
• The model enables prediction of phenomena like secondary capacitance peaks due to solvation.