Real-Space Charge Density Profiling of Electrode-Electrolyte Interfaces with Angstrom Depth Resolution

Area of Science:

• Electrochemistry
• Surface Science
• Nanotechnology

Background:

• Interfacial charge accumulation and depletion are fundamental to electrochemical processes.
• Understanding the spatial charge distribution at electrode-electrolyte interfaces is challenging.
• Existing methods lack the resolution to probe charge profiles with angstrom precision.

Purpose of the Study:

• To develop and validate a novel technique for experimentally quantifying real-space charge distribution at electrode-electrolyte interfaces.
• To investigate the charge profiles of electric double layers (EDLs) with angstrom depth resolution.
• To explore charge variations in emergent electrolytes like ionic liquids and highly concentrated aqueous solutions.

Main Methods:

• Development of charge profiling three-dimensional atomic force microscopy (CP-3D-AFM).
• Measurement of 3D force maps at varying electrode potentials using electrochemical 3D-AFM.
• Application of statistical analysis, peak deconvolution, and electrostatic calculations to derive local charge density profiles.

Main Results:

• CP-3D-AFM successfully quantified the real-space charge distribution of electrode surfaces and EDLs.
• Pronounced sub-nanometer charge variations were observed in ionic liquids and highly concentrated aqueous solutions.
• Integrated charge densities derived from CP-3D-AFM agreed with macroscopic electrochemical measurements.

Conclusions:

• CP-3D-AFM provides unprecedented angstrom-depth resolution for probing interfacial charge profiles.
• The technique offers new insights into the structure of EDLs in various electrolyte systems.
• This method advances the understanding of charge dynamics critical for electrochemical applications.