Adsorption and Electrooxidation of Carbon Monoxide on Silver

The adsorption and electrooxidation of CO on polycrystalline Ag at pH 13, 9.2, 7, and 0.3 have been studied by cyclic voltammetry and Fourier transform infrared spectroscopy (FTIRS). At the four pH values the cyclic voltammograms (CVs) showed the formation and electroreduction of underpotential (UP) Ag oxides, i.e., oxides formed at potentials lower than the equilibrium potential of the Ag/Ag2O couple. Two pairs of peaks of UP oxides appeared at pH 13 and 9.2, but only one pair at pH 7 and 0.3. At pH 13 and 9.2 the current density of the anodic peak of the UP oxide appearing at the more positive potential increased if the solution was saturated with CO, and its peak potential increased (pH 13) or remained the same (pH 9.2), indicating the electrooxidation of adsorbed CO. Both at pH 7 and 0.3 the anodic peak in the presence of CO appeared at potentials 0.2 V more negative than that in the corresponding base electrolyte. Only at pH 13 did the CO adsorbed on Ag remain adsorbed after eliminating the dissolved...