Double layer on silver single-crystal electrodes in contact with electrolytes having anions which present a slight specific adsorption Part I. The (110) face

Abstract

Differential capacity-potential curves have been studied at the interfaces between a (110) silver face and the aqueous electrolytes, NaF, NaClO 4 , KBF 4 and KPF 6 . From the variation of the potential of the minimum capacity as a function of electrolyte concentration, it is found that the anionic specific adsorption strength varies in the following order: F − >ClO 4 − >BF 4 − =PF 6 − ≥0 The inverse order, in comparison with mercury, is explained by a local adsorption on surface defects. With KPF 6 , specific adsorption is quite negligible and the minimum potential is identified with the potential of zero charge. The (110) Ag pzc without specific adsorption is −0.975±0.005 V (SCE). For the KPF 6 /(110)Ag system, the electrical double-layer model without specific adsorption accounts for capacity-potential curves at different concentrations. The particular ideal atomic distribution of the (110)face is taken into account, and its effect on the array of water molecules may explain the high inner-layer capacities. The inner-layer capacity-electrode charge curve is discussed.