Density Functional Theory Study of Pd Aggregation on a Pyridine-Terminated Self-Assembled Monolayer

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Self-assembled monolayers (SAMs) are crucial for controlling metal nucleation.
• Understanding metal-SAM interactions is key to electrodeposition mechanisms.
• Atomic-level insights into metal cluster formation are needed.

Purpose of the Study:

• Investigate initial palladium (Pd) cluster formation on a pyridine-terminated SAM on Au(111).
• Elucidate Pd-SAM and Pd-Pd interactions at the liquid/solid interface.
• Gain insight into metal nucleation mechanisms during electrodeposition.

Main Methods:

• Density functional theory (DFT) calculations.
• Ab initio molecular dynamics (AIMD) simulations.
• Nudged elastic band (NEB) calculations.

Main Results:

• Identified a stable SAM conformation (planar, herringbone packing) for Pd adsorption.
• Discovered two binding sites for Pd atoms on the pyridine end group.
• Observed spontaneous Pd dimerisation with an energetic driving force of ~-0.3 eV/atom.
• Determined a low energy barrier (0.10 eV) for Pd diffusion and dimerisation.

Conclusions:

• SAM functionalisation significantly influences metal nucleation.
• Strong Pd-pyridine interactions drive cluster formation.
• DFT and AIMD provide atomic-level understanding of electrodeposition initiation.