OH formation and H₂ adsorption at the liquid water-Pt(111) interface

Area of Science:

• Surface Science
• Computational Chemistry
• Electrochemistry

Background:

• Understanding the liquid water-Pt(111) interface is crucial for catalytic reactions, such as the oxygen reduction reaction in proton-exchange membrane (PEM) fuel cells.
• Previous models often used static water layers, potentially misrepresenting dynamic interfacial processes.

Purpose of the Study:

• To investigate the influence of liquid water dynamics on the structure and energetics of hydroxyls at the Pt(111) interface using ab initio molecular dynamics.
• To compare hydroxyl formation in dynamic liquid water environments with static water layer and bare surface models.

Main Methods:

• Constant temperature ab initio molecular dynamics simulations.
• Analysis of hydroxyl coverages, Pt site availability, and atomic surface oxygen stability.
• Investigation of hydrogen adsorption competition with water molecules.

Main Results:

• Hydroxyls at the dynamic liquid water-Pt(111) interface exhibit different structures and energetics compared to static models.
• Particularly stable hydroxyl coverages (1/12, 5/12, 2/3 ML) were identified, featuring adjacent uncovered Pt sites.
• Atomic surface oxygen is unstable in liquid water, contrasting with static simulations.
• Hydrogen adsorption requires a negatively charged Pt(111) surface for accurate modeling.

Conclusions:

• Liquid water dynamics are essential for accurately modeling the Pt(111) interface and its role in catalytic reactions.
• The findings provide improved understanding of hydroxide and surface oxide formation during cyclic voltammetry.
• A negatively charged Pt(111) surface is necessary to reconcile hydrogen adsorption simulations with experimental observations.