CO Oxidation on Pt(100): New Insights based on Combined Voltammetric, Microscopic and Spectroscopic Experiments

• Active sites for COb oxidation are located at Pt adislands and clusters on Pt(100).
• During COb preignition, CO forms less-compressed adlayer on (100) terraces.
• COb oxidation leads to restructuring of Pt adisland edges.
• Potentially active sites are blocked with CO during COb oxidation.
• History of CO adlayer formation determines the electro-oxidation mechanism.

We present an experimental study of the CO electro-oxidation on Pt(100)-(1 × 1) electrodes employing electrochemical methods in combination with in situ scanning tunneling microscopy (STM) and shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). We discussed the nature and stability of the active sites in the preignition region in the presence of dissolved CO (COb) and monitored substrate structure changes during the COb electro-oxidation process. We corroborated that the electro-oxidation kinetics is determined decisively by the history of CO adlayer formation. A new mechanism was proposed for Pt(100) electrode deactivation in the preignition region after excursion of electrode potential to COb ignition region. We believe that this mechanism takes place on Pt surfaces independently on their crystallographic orientation.

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