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Published on: January 19, 2018
Probing the extended space charge by harmonic disturbances
Isaak Rubinstein1, Boris Zaltzman
1Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, 84990, Israel. robinst@bgu.ac.il
Summary
Probing the electric double layer at permeable interfaces with high-frequency signals is challenging under bias. The quasielectroneutral bulk dominates, but extended space charge can be studied using impedance spectroscopy or anomalous rectification.
Area of Science:
- Electrochemistry
- Surface Science
- Physical Chemistry
Background:
- Permeable interfaces with charge-selective properties, like ion-exchange membranes, are crucial in various electrochemical systems.
- Understanding the electric double layer (EDL) at these interfaces is key to controlling ion transport and device performance.
- Previous studies focused on zero-bias conditions, leaving the behavior under applied voltage less understood.
Purpose of the Study:
- To investigate the feasibility of probing the diffuse electric double layer (EDL) at permeable, charge-selective interfaces under a finite steady-state current-voltage bias.
- To determine if high-frequency current-voltage disturbances can effectively probe the EDL under non-zero bias conditions.
- To compare different methods for studying the EDL, particularly the extended space charge region.
Main Methods:
- Applying small harmonic high-frequency current-voltage disturbances to permeable charge-selective interfaces.
- Analyzing the system's high-frequency response under a finite steady-state current-voltage bias.
- Comparing the efficacy of electric impedance spectroscopy (EIS) and anomalous rectification effects for probing the EDL.
Main Results:
- The diffuse electric double layer (EDL) at permeable interfaces under finite underlimiting bias is not effectively probed by high-frequency disturbances.
- The high-frequency response is dominated by the quasielectroneutral bulk, similar to the zero-bias case.
- Extended space charge within the EDL can be probed using both linear (EIS) and nonlinear (anomalous rectification) responses.
Conclusions:
- High-frequency probing of the EDL under finite bias is limited due to bulk dominance.
- Anomalous rectification offers a more promising experimental approach than electric impedance spectroscopy for studying nonequilibrium EDLs.
- The findings provide insights into the limitations and possibilities of characterizing EDLs in electrochemical systems under operating conditions.
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