Collision Dynamics during the Electrooxidation of Individual Silver Nanoparticles

Area of Science:

• Electrochemistry
• Nanoparticle Science
• Physical Chemistry

Background:

• Nanoparticles exhibit complex electrochemical behavior due to their high surface area.
• Understanding electron transfer kinetics at the nanoscale is crucial for catalysis and sensing.

Purpose of the Study:

• To simulate and explain the multi-current peak phenomenon observed during silver nanoparticle oxidation at a gold electrode.
• To quantify the electron transfer rate constant and collision dynamics in nanoparticle-electrode interactions.

Main Methods:

• High-bandwidth electrochemical recordings of silver nanoparticle (Ag NP) oxidation.
• Computational simulations of random nanoparticle motion and diffusion.
• Coupling simulations with electrochemical kinetic parameters and literature data for Ag/Ag+ redox system.

Main Results:

• Simulations quantitatively reproduced the experimentally observed multi-current peak behavior.
• Each experimental peak results from thousands of unobservable, short-duration (∼6 ns) particle-electrode collisions.
• Estimated instantaneous current density during collision: 500-1000 A/cm².
• Electron transfer rate constant estimated at 5-10 cm/s, limited by nanoparticle thermal velocity.

Conclusions:

• Brownian motion and collision frequency are critical factors in interpreting heterogeneous electron transfer reactions involving nanoparticles.
• Only a small fraction (∼1%) of Ag NP surface atoms are oxidized per collision.
• The study provides a framework for understanding nanoscale electrochemical processes.