Half-Cell Ion Concentration Polarization on Nafion-Coated Electrode

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Ion concentration polarization (ICP) typically involves paired ion enrichment and depletion zones at ion-selective membranes under an electric field.
• Understanding and controlling ICP is crucial for electrochemical systems, sensing, and energy applications.

Purpose of the Study:

• To demonstrate and characterize the phenomenon of solitary ion concentration polarization (half-cell ICP) on a Nafion-coated electrode.
• To investigate the current-voltage characteristics and potential applications of this novel ICP behavior.

Main Methods:

• Fabrication of a Nafion-coated electrode.
• Electrochemical measurements including current-voltage-time responses and conductance measurements.
• In situ visualization of pH and ion concentration changes.

Main Results:

• Successful demonstration of solitary ion enrichment or ion depletion (half-cell ICP) on the electrode, deviating from traditional paired ICP.
• Observation of diode-like current rectification with a high rectification factor (up to 500) even at high voltages (<±200 V).
• Correlation between ion depletion hindering flux and ion enrichment facilitating flux.

Conclusions:

• The study provides a deeper understanding of ICP phenomena at electrode interfaces.
• The demonstrated half-cell ICP opens possibilities for developing high-voltage ionic diodes.
• Potential applications in advanced sensing and energy conversion devices are highlighted.