An electrochemical and XPS study of Ag-Pb binary alloys incorporated in Nafion® coatings

Abstract

Glassy carbon electrodes coated with thin films of Nafion® metalized with silver and lead species were investigated by cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS). Metalization of Nafion® film was accomplished by dipping the coated electrodes in 3 mM AgNO3 + 3mM Pb(NO3)2 solution for 10 min. The resulting chemically modified electrodes were electrochemically characterized toward the oxidation of amino compounds in carbonate solutions buffered at pH 10. Under chronoamperometric experiments carried out at a constant applied potential of 0.95 V vs SCE, the linear range (r2>0.995) was determined to be at least three decades and the limit of detection range from 26μM (ethylamine) and 65μM (tert-butylamine), for the investigated amino compounds. The perm-selective properties of the Nafion® film with respect to anion species were investigated toward the electrooxidation of ethylamine in presence of large concentration of chloride ions. The XPS analysis revealed heterogeneous distribution of the catalytic species dispersed in the metalized Nafion® film. Thus, a comparison of the spectra of Ag3d and Pb4f acquired at various take-off angles, indicates an increase in the atomic ratio Ag:Pb and a notable enrichment of lead oxide species in the outer surface of the film when compared with the bulk membrane coated electrode.