Modelling adsorbate coverage on complex alloy surfaces

Area of Science:

• Materials Science
• Theoretical Chemistry
• Surface Science

Background:

• Extending catalysis theory to complex alloys and multiple adsorbates is computationally challenging due to numerous surface site-adsorbate combinations.
• Existing models often struggle to accurately predict adsorbate behavior on alloy surfaces.

Purpose of the Study:

• To develop a simplified approach for catalysis theory applicable to complex alloys and multiple adsorbates.
• To investigate the impact of adsorbate-adsorbate interaction rules on surface coverage and catalytic activity.
• To predict the performance of Palladium-Silver (PdAg) alloys in the oxygen reduction reaction.

Main Methods:

• Defining blocking rules for disallowed local adsorbate-adsorbate configurations.
• Conducting simple simulations to test the effect of different interaction rules.
• Applying the simulation approach to PdAg intermetallic and solid solutions, and to Ag14Ir16Pd30Pt14Ru26 high-entropy alloys.

Main Results:

• In PdAg alloys, Silver (Ag) atoms prevent full oxygen (O*) coverage, allowing adsorbed hydroxyl (*OH) species formation.
• Adsorbed *OH species are predicted to enhance oxygen reduction reaction activity, reaching optimal adsorption energies.
• The influence of interaction rules on oxygen reduction was less distinct in high-entropy alloys compared to binary PdAg alloys.

Conclusions:

• The developed adsorbate-adsorbate interaction rules provide a viable method for studying complex alloy catalysis.
• The findings offer experimental guidance for distinguishing PdAg(111) alloy surface structures and understanding adsorbate coverage.
• The approach highlights the potential of *OH species for improving oxygen reduction reaction activity in PdAg systems.