Electrical Double Layer Spillover Drives Coupled Electron- and Phase-Transfer Reactions at Electrode/Toluene/Water...

Area of Science:

• Electrochemistry
• Physical Chemistry
• Interface Science

Background:

• Coupled electron- and phase-transfer reactions (CEPhT) are crucial in various chemical processes.
• Understanding CEPhT at three-phase interfaces (solid electrode, insulating organic solvent, aqueous electrolyte) is challenging.
• Electric double layer (EDL) spillover is a proposed driving force for CEPhT.

Purpose of the Study:

• To propose and investigate a concerted mechanism for CEPhT at three-phase interfaces.
• To elucidate the role of EDL spillover in driving CEPhT.
• To correlate experimental findings with theoretical simulations.

Main Methods:

• Scanning electrochemical cell microscopy (SECCM) was used to study ferrocene oxidation.
• Finite element method (FEM) simulations were employed to model electrostatic potential and species concentration.
• Analysis of current-voltage (i-E) curves incorporating mass transport, electron transfer, and phase transfer.

Main Results:

• Experimental and simulated i-E curves showed good agreement, validating the proposed mechanism.
• EDL spillover was confirmed as the driving force for CEPhT, creating unique interfacial microenvironments.
• Reaction kinetics unexpectedly depended on the supporting electrolyte concentration due to EDL spillover.

Conclusions:

• The study provides the first experimental and simulation evidence for a concerted CEPhT mechanism.
• EDL spillover facilitates CEPhT by enabling electron transfer and solvent shell replacement at the interface.
• This understanding can be used to engineer electrochemical systems for reactions in challenging media.