Galvani Potential-Dependent Single Collision/Fusion Impacts at Liquid/Liquid Interface: Faradic or Capacitive?

Area of Science:

• Physical Chemistry
• Electrochemistry
• Surface Science

Background:

• Understanding the electric double layer (EDL) at liquid/liquid interfaces (LLI) is crucial for various electrochemical applications.
• Non-faradaic processes at LLIs, particularly those involving droplet impacts, are not fully characterized.
• Existing methods for characterizing micro/nanoscale heterogeneous media often require catalytic or charge-transfer activity.

Purpose of the Study:

• To report a novel subtype of nano-impacts occurring at the LLI due to EDL reorganization.
• To investigate the non-faradaic characteristics of these single fusion impacts and their dependence on the potential of zero charge (PZC).
• To explore the potential application of these impact experiments for characterizing micro/nanoscale heterogeneous media.

Main Methods:

• Utilized micropipette-supported liquid/liquid interface (ITIES) to study emulsion droplet impacts.
• Measured transient currents (anodic, bipolar, cathodic) generated during single fusion impacts.
• Analyzed the dependence of these currents on the potential of zero charge (PZC) and supporting electrolyte concentration.

Main Results:

• Identified a new subtype of nano-impacts characterized by transient currents dependent on PZC, confirming their non-faradaic nature.
• Demonstrated that the integrated mean charge is proportional to the Galvani potential, suggesting adherence to the discrete Helmholtz model for EDL.
• Observed differences in PZC values for MgCl2 droplets versus pure water, attributed to specific ion absorption at the interface.

Conclusions:

• The study provides significant physicochemical insights into the EDL structure and behavior at micropipette-supported LLIs.
• The findings indicate that EDL at the LLI may follow the discrete Helmholtz model.
• This work presents a novel approach for micro/nanoscale heterogeneous media characterization using impact experiments at LLIs, applicable even for non-catalytic or non-reactive systems.