Dynamical Study of Adsorbate-Induced Restructuring Kinetics in Bimetallic Catalysts Using the PdAu(111) Model System

Area of Science:

• Surface Science
• Catalysis
• Materials Science

Background:

• Bimetallic catalysts are crucial for chemical reactions, with their activity depending on dynamic surface restructuring.
• Tuning catalyst surfaces with agents like carbon monoxide (CO) and oxygen is an effective strategy.
• Understanding the mechanisms and kinetics of restructuring is vital but challenging due to complex variables.

Purpose of the Study:

• To investigate the in situ restructuring dynamics of palladium (Pd) on gold (Au)(111) using advanced techniques.
• To uncover previously unidentified timescale and kinetic parameters of CO-induced restructuring in Pd/Au systems.
• To provide a mechanistic understanding for fine-tuning bimetallic catalyst surfaces.

Main Methods:

• Time-resolved temperature-programmed infrared reflection absorption spectroscopy (TP-IRAS).
• Ab initio thermodynamics calculations.
• Machine-learning molecular dynamics (MLMD) simulations.

Main Results:

• Pd monomers repopulated the surface upon CO exposure up to 373 K.
• Complete Pd dissolution into the subsurface occurred above 473 K.
• Apparent activation energies for dissolution were determined as 0.14 eV and 0.48 eV, with restructuring occurring over ~1000 s.

Conclusions:

• CO acts as both a probe and an agent for restructuring Pd/Au(111) surfaces.
• The study elucidates the fluxional nature of alloy catalysts at the atomic level.
• Identified kinetic parameters offer opportunities for controlled surface modification under moderate conditions.