Deposition and stripping processes of tin on gold film electrodes studied by surface conductance

Abstract

The CV and surface conductance (SC) responses of tin species adsorbed on evaporated gold film electrodes were studied as a function of the potential window and the potential sweep rate. Sn adatoms were generated either, by reducing Sn(II) present in the solution (u p d) or by first irreversibly adsorbing Sn(II) and then reducing it in the supporting electrolyte alone. The experimental results show that at potentials about E ≈ −0.25 V(versus SCE), all the Sn(II) is reduced to Sn(0) and this species is adsorbed on the electrode surface. The subsequent oxidation of Sn(0) leads to Sn(II)ad, adsorbed on the electrode. This species desorbs only when the Sn(II)ad is further oxidised to soluble Sn(IV). The number of electrons involved in the reduction of Sn(II) to Sn(0) and vice versa is two. On the other hand, the analysis of the resistance measurements at low coverage is made by applying the surface Linde’s rule. This leads to the conclusion that the Sn(0) behaves as an interstitial impurity. SC experiments, made in the potential region corresponding to Sn bulk deposition, suggest the formation of a bulk Sn–Au alloy.