Platinum oxide formation under oxygen evolution reaction conditions.

Area of Science:

• Electrochemistry
• Materials Science
• Surface Science

Background:

• Electrocatalyst degradation impedes the widespread adoption of electrolyzers and fuel cells.
• Understanding catalyst surface behavior under reaction conditions is vital for developing durable catalysts.
• Oxidative degradation is a primary failure mechanism for electrocatalysts.

Purpose of the Study:

• To investigate the atomic-level structural changes of a platinum (Pt)(111) model electrode during the oxygen evolution reaction (OER).
• To elucidate the mechanism of platinum electrocatalyst oxidation under operando conditions.
• To compare electrochemical oxidation with thermal oxidation processes.

Main Methods:

• Operando High-Energy Surface X-ray Diffraction (HE-SXRD) combined with a Rotating Disk Electrode (RDE) setup.
• Ex situ X-ray Reflectivity (XRR) and X-ray Photoelectron Spectroscopy (XPS) for surface characterization.
• Studying the electrode-electrolyte interface under unexplored potential regimes during OER.

Main Results:

• The Pt(111) surface undergoes electro-oxidation in a distinct layer-by-layer manner.
• A sub-nanometer thick platinum dioxide (PtO2) film forms on the surface.
• The formed oxide film leads to catalyst deactivation and surface roughening.

Conclusions:

• The study provides critical insights into the electrochemical oxidation mechanisms of platinum electrocatalysts.
• Layer-by-layer oxidation and subsequent PtO2 formation are key to catalyst deactivation.
• Significant differences exist between electrochemical and thermal oxidation pathways for platinum.