Adiabatic versus non-adiabatic electron transfer at 2D electrode materials.

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• Two-dimensional (2D) electrode materials on conductive supports are crucial for electrochemical applications.
• Understanding electron transfer at these interfaces is essential for optimizing electrochemical processes.

Purpose of the Study:

• To investigate the fundamental electronic interactions governing outer-sphere electron transfer (OS-ET) at graphene grown on copper electrodes.
• To quantify the effect of graphene layering on electrochemical kinetics.

Main Methods:

• Integrated experimental-theoretical approach combining scanning electrochemical cell microscopy (SECCM) and structural microscopy.
• Development of rate theory based on the Schmickler-Newns-Anderson model Hamiltonian.
• Parameterization using constant potential density functional theory (DFT) calculations.

Main Results:

• Observed electron transfer (ET) kinetics trend for hexaamineruthenium (III/II) couple: monolayer > bilayer > multilayer graphene.
• Quantitatively rationalized the observed trend using a developed rate theory model.
• Demonstrated that increasing graphene layers enhances contact potential, raising the effective ET barrier.

Conclusions:

• The electron transfer mechanism at graphene/copper interfaces is predominantly adiabatic.
• Graphene layering significantly influences electrochemical reaction rates by modifying interfacial electronic properties.
• The findings provide fundamental insights into designing 2D material-based electrodes for electrochemistry.