AC-Modulated XPS Enables to Externally Control the Electrical Field Distributions on Metal Electrode/Ionic Liquid...

Area of Science:

• Electrochemistry
• Materials Science
• Spectroscopy

Background:

• Ionic liquids (ILs) exhibit complex charging dynamics and form electrical double layers (EDLs) at interfaces.
• Understanding these processes is crucial for designing advanced electrochemical devices.
• X-Ray Photoelectron Spectroscopy (XPS) offers a surface-sensitive probe for investigating electrochemical interfaces.

Purpose of the Study:

• To extract local electrical potential profiles in an ionic liquid electrolyte using AC-modulated XPS.
• To investigate the charging/discharging processes and electrical double layer formation within an electrochemical system.
• To develop a more realistic equivalent circuit model for the investigated electrochemical system.

Main Methods:

• Utilized AC square-wave (SQW) bias at 10 kHz and 0.1 Hz to modulate an electrochemical system.
• Performed *in operando* XPS measurements simultaneously with current measurements.
• Analyzed F 1s binding energy shifts in the IL anion to determine local potential profiles and IR drops.

Main Results:

• Successfully extracted local electrical potential profiles by correlating binding energy shifts with AC bias.
• Quantified AC currents, system impedance, and potential variations due to IR drops.
• Developed and validated a realistic equivalent circuit model using LT-Spice simulations.

Conclusions:

• AC-modulated XPS is a powerful technique for probing dynamic electrochemical processes and local potential variations.
• The study provides insights into the complex behavior of ionic liquids in electrochemical devices.
• Demonstrated the ability to controllably induce and reverse local electrical field developments within the device.