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Near-electrode anion dehydration and field-dependent dielectric response govern double-layer capacitance.
Hari R Sudhakar1, Ankur Gupta2, Ananth Govind Rajan3
1Indian Institute of Technology Bombay, Department of Chemical Engineering, Powai, Mumbai, Maharashtra 400076, India.
Physical Review. E
|December 23, 2025
Summary
This study presents a new classical framework for predicting electrical double-layer (EDL) capacitance without fitting parameters. The model highlights ion-specific hydration as key to EDL capacitance, improving electrochemical predictions.
Area of Science:
- Physical Chemistry
- Computational Electrochemistry
- Materials Science
Background:
- Predicting electrical double-layer (EDL) capacitance from continuum theories without fitting parameters is a significant challenge.
- Incomplete understanding of interfacial electrostatics hinders accurate theoretical predictions.
Purpose of the Study:
- To develop a classical framework for predicting EDL capacitance without fitting parameters.
- To identify the key physical mechanisms governing EDL capacitance.
Main Methods:
- Construction of a classical, first-principles framework for EDL capacitance prediction.
- Validation against experimental data for three distinct electrolytes across various concentrations.
Main Results:
- Achieved favorable agreement with experimental data without employing fitting parameters.
- Identified ion-specific hydration as the dominant mechanism for EDL capacitance.
- Demonstrated the significant influence of field-dependent dielectric response and ion-specific dielectric decrement.
- Uncovered the modest, yet structurally significant, role of excluded-volume electrostatics.
Conclusions:
- The developed classical framework successfully predicts EDL capacitance, demystifying electrochemical phenomena.
- Near-electrode ion-specific hydration is the primary determinant of EDL capacitance.
- The framework can be integrated into implicit solvation models for quantum-mechanical calculations.
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