Electrochemical behavior of Ag-Cu alloy in alkaline media

Abstract

Results of the investigation of electrochemical behaviour of Ag-Cu alloy containing 50 mass% Ag and 50 mass% Cu are presented in this paper. Pure silver and copper were investigated, too. Working electrodes were prepared by metallurgical process. 1 mol dm-3 and 0.5 mol dm-3 solutions of NaOH are chosen as the electrolyte. On the cyclic voltammograms, some current waves corresponding to number and quantity of phases present in the investigated electrodes appeared and they can be used for characterization of investigated alloy. On the voltammogram recorded for pure silver, two anodic and two cathodic peaks appeared. First peak consisted of two joined current waves which can be ascribed to the formation of the two different types of silver(I) oxide, Ag2O. Second peak should correspond to the formation of silver(II) oxide, AgO. Voltammogram obtained for pure copper exhibits one broad current wave corresponding to the formation of copper oxides, followed by a wide potential area in which copper is completely passive. At 0.4 V vs. SCE, current starts to increase again due to oxygen evolution and probably due to simultaneous dissolution of copper with formation of CuO22- as a product. In alkaline solutions copper has no significant influence on the shape and current values of the voltammograms recorded for Ag-Cu alloy; however, it has an influence only on the anodic and cathodic peak potentials, which are shifted to more negative values in comparison to Ag. It could mean an easier formation of oxides and their harder reduction. Comparing voltammograms recorded for Ag-Cu alloy in 0.5 moldm-3 NaOH and in 1 moldm-3 NaOH solutions, one can see that current waves appear at more positive potentials on the voltammograms obtained in the solution of lower concentration and with much higher current densities than those on the voltammograms obtained in the solution of higher concentration

Study of the catalytic activity of copper substrates coated with gold and silver foam in alcohol-alkaline media

“…Under cathode polarization, similar peaks are observed, respectively, for the reduction of these compounds to Ag and Cu. It was shown in [30] that the presence of copper in the alloy contributed to the shift of the anodic and cathode peaks of silver oxidation to more negative potentials. This facilitated the formation of oxides, but hindered their reduction.…”