Surface dynamics at well-defined single crystal microfacetted Pt(111) electrodes: in situ optical studies

Area of Science:

• Electrochemistry
• Surface Science
• Spectroscopy

Background:

• Understanding carbon monoxide (CO) oxidation on platinum (Pt) is crucial for catalysis.
• Well-defined adlayers on Pt(111) microfacets provide model systems for studying surface reactions.

Purpose of the Study:

• To investigate the electrochemical oxidation of CO adlayers on Pt(111) microfacets.
• To compare the oxidation rates of different CO adlayer phases (c(2 x 2)-3CO and square root of 19 x square root of 19R23.4 degrees -13CO).
• To elucidate the role of surface structure and defects in CO oxidation kinetics.

Main Methods:

• Simultaneous in situ reflectance spectroscopy (RS) and second harmonic generation (SHG).
• Potential step and linear scan voltammetry.
• Study of CO adlayers on Pt(111) microfacets in aqueous H2SO4.

Main Results:

• The c(2 x 2)-3CO phase exhibits significantly slower oxidation rates than the square root of 19 x square root of 19R23.4 degrees -13CO phase.
• Slower oxidation of c(2 x 2)-3CO is attributed to the lack of vacant sites required for CO oxidation.
• Continuous CO adsorption-oxidation cycles accelerate the oxidation rate of the c(2 x 2)-3CO phase.
• Emergence of defects on the Pt(111) facet acts as nucleation sites for CO oxidation.

Conclusions:

• Surface structure and adlayer phase significantly influence CO oxidation kinetics on Pt(111).
• Defect sites play a critical role in facilitating CO oxidation, especially for more ordered adlayers.
• Understanding these surface phenomena is key for designing efficient electrocatalysts.