Evolution of adsorbed CO on Pt and Pt/Au surface

DEL-GIUDICE, GABRIELA; TESIO, ALVARO Y.; CAPPELLARI, PAULA S.; PALACIOS, RODRIGO E.; PLANES, GABRIEL A.

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2018 vol. 270 p. 48 - 53

0013-4686

In this work, we studied in detail one of thepossible limiting-steps during CO oxidation at Pt and Pt/Au electrodes, namelyCO adsorption and diffusion at the electrode´s surface. With this aim, we usedan electroless method for Pt surface modification, which entails thespontaneous deposition of gold at Pt electrodes. We also use a home-madefast-response (four electrodes) flow cell that allows an accurate control ofthe electrode exposition time to CO (tad)and of the time interval (tw) before stripping of the adsorbed CO (COad).Thus two key experimental parameters of the electro-oxidation process can be independentlymodified and the results evaluated. Our results are consistent with a mechanismin which CO is initially adsorbed onto active sites and then moves away bysurface diffusion. As a result, the subsequent oxidative stripping eliminationof CO starts with COad far away from the most active sites. Theexperiments carried out for Pt/Au electrodes with different fraction of electrodearea covered by CO (qCO) demonstratethat Au acts as a barrier, hindering the surface diffusion of CO from/to theactive sites, giving raise to the multiple pecks observed when twis low.