Cyclic voltammetry on Ag(111) and Ag(100) faces in sodium hydroxide solutions

The electrochemical behavior of silver (100) and (111) single crystal surfaces was examined by cyclic voltammetry in aqueous NaOH solution. In the `double layer' region (between −1.2 and 0.1 V (SCE)) adsorption of OH⁻ ions followed by phase transformation into an Ag–OH monolayer was found to take place. The difference in peak potentials recorded in 0.1 and 0.01 mol dm⁻³ NaOH solutions of about 60 mV indicates that one electron is exchanged in the overall electrochemical reaction, implying a complete charge transfer between OH⁻ ions and the silver surface. The adsorption process has been modeled to a Frumkin adsorption isotherm. Further oxidation of silver into Ag₂O takes place at more positive potentials. The formation of bulk Ag₂O results in considerable change to the original single crystal surface. This is likely to be due to roughening of the silver surface as a consequence of the formation and reduction of the oxide.