Anodic Oxidation of COads Derived from Methanol on Pt Electrocatalysts Linked to the Bonding Type and Adsorption Site

A newly formulated four-component modified Butler-Volmer model has been developed to evaluate global oxidation kinetic parameters for the various types of carbon monoxide adsorbates (COads) on a nanoparticle Pt surface determined by the type of bonding as well as the local structure of the adsorption site. Partial coverages of COads were prepared by potentiostatic adsorption of methanol followed by potentiostatic partial oxidation at various elevated potentials and for various durations. Anodic linear sweep voltammetry was then performed, and the COads oxidation peaks were fitted with the model to analyze the kinetics. According to the model, preferential oxidation with respect to COads bonding and Pt substrate structure can be achieved dependent upon the potential and extent of oxidation. Partial oxidation at 450 mV vs. RHE for 60 min. resulted in a majority population of linearly bonded COads on cubic-packed Pt sites; whereas partial oxidation at 650 mV vs. RHE for 220 sec. resulted in a majority population of bridged-bonded COads on close-packed Pt sites.