Tailoring the active site for the oxygen evolution reaction on a Pt electrode

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• Highly active electrocatalysts are crucial for efficient water electrolysis.
• The oxygen evolution reaction (OER) is a key process in water splitting.
• Understanding active sites on electrocatalysts like platinum (Pt) is essential for improving performance.

Purpose of the Study:

• To investigate the properties of OER active sites on single-crystal Pt electrodes.
• To understand how potential cycling affects OER activity on Pt(111) surfaces.
• To identify the structural origins of OER enhancement.

Main Methods:

• Electrochemical measurements of OER activity.
• Repeated oxidative and reductive potential cycling on Pt(111) electrodes.
• X-ray diffraction (XRD) for structural analysis.
• Surface morphology characterization.

Main Results:

• OER activity on Pt(111) is significantly enhanced after potential cycling, reaching nine times higher activity by the third cycle.
• OER activation is dependent on the terrace width of the Pt(111) surface, with wider terraces showing greater enhancement.
• Potential cycling creates atomic-sized vacancies and defects in the second subsurface Pt layer.
• Surface roughening, forming bowl-shaped cavities with high-coordination Pt atoms, is induced by potential cycling and correlates with OER activation.

Conclusions:

• Repeated potential cycling effectively activates Pt(111) surfaces for the oxygen evolution reaction.
• Defects, particularly vacancies in the subsurface layer and specific surface morphologies, are identified as the active sites responsible for enhanced OER.
• The findings provide insights into designing and optimizing electrocatalysts for water electrolysis.