Palladium Electrodeposition onto Pt(100): Two-Layer Underpotential Deposition.

Area of Science:

• Electrochemistry
• Surface Science
• Materials Science

Background:

• Understanding the initial stages of metal electrodeposition is crucial for developing advanced materials.
• Platinum (Pt) and palladium (Pd) are catalytically important metals with applications in various fields.

Purpose of the Study:

• To investigate the initial stages of palladium electrodeposition onto a Pt(100) surface.
• To characterize the structural and electrochemical properties of ultrathin palladium films.

Main Methods:

• Cyclic voltammetry at a low scan rate (0.1 mV·s⁻¹) was employed to study the deposition process.
• Ex situ Atomic Force Microscopy (AFM) was used for surface morphology characterization.
• Electrochemical characterization was performed in 0.1 M H₂SO₄ solution.

Main Results:

• The deposition of the first two Pd layers onto Pt(100) was found to be underpotential, occurring via a two-step mechanism, each step forming a complete atomic layer.
• Thicker Pd deposits (above 10 monolayers) showed increased irreversibility and peak broadening in cyclic voltammetry, indicating reduced ordered flat areas.
• AFM analysis confirmed rougher thick deposits and the formation of (100)-oriented rectangular islands aligned with specific Pt surface directions.

Conclusions:

• The study provides the first evidence of an underpotential deposition mechanism for the initial Pd layers on Pt(100).
• The growth mode transitions from layer-by-layer deposition to rougher island growth for thicker films.
• The findings offer insights into controlling nanostructure formation during electrodeposition for potential catalytic applications.