Zinc Plating on Copper Proceeds via Breakdown of a Capacitive Electric Double Layer

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• The electric double layer (EDL) at solid-liquid interfaces is crucial for electrochemical processes like plating and catalysis.
• Atomistic dynamics of the EDL remain poorly understood, hindering control over interfacial phenomena.

Purpose of the Study:

• To directly visualize the atomistic dynamics of EDL formation, growth, and collapse during zinc electroplating.
• To elucidate the mechanism behind rough morphologies in plated films and its broader implications.

Main Methods:

• Operando atomic-resolution transmission electron microscopy (TEM) was employed to observe the EDL in real-time.
• Zinc electroplating on copper in an ionic liquid electrolyte under galvanostatic conditions was studied.

Main Results:

• EDL growth via charge accumulation was observed, followed by substrate erosion and nucleation of transient metallic nanoparticles.
• Particle enlargement led to dielectric breakdown, heat generation, and Cu/Zn alloy deposition in recurrent cycles.
• Spontaneous brass nanoparticle formation at room temperature highlights the role of interfacial energy.

Conclusions:

• Electroplating proceeds via a breakdown-driven mechanism, characterized by discontinuity, chemical reactivity, and electrostatic instability.
• The dielectric breakdown of chemically active EDLs is a general phenomenon relevant to plating, energy storage, and catalysis.
• This mechanism provides a unifying explanation for rough plated film morphologies.