The triangular potential sweep voltammetric studies on pure tin in concentrated sodium hydroxide solutions

Abstract

The triangular potential sweep voltammetric studies were carried out on pure tin (99.9999%) in NaOH solutions (1–10 N). The forward scan revealed two distinguished peaks in the region −1.12 to −0.9 V vs sce and at faster sweep rates a single peak appeared. Oscillations were observed in the E-i curve in the potential regions of Sn/Sn(OH) 2 or Sn(OH) 2/Sn(OH) 4 in the forward scan; and increase of stannite concentration increased the oscillations. The non-stoichiometric nature of the passive oxide film is responsible for these oscillations. The first anodic peak potential and current dependencies on sweep rates revealed that a “pore resistance model” holds good. The appearance of a single cathodic peak at far negative potentials, compared to the anodic peak observed at higher sweep rate, was understood to be due to irreversible reduction of oxidised species formed on the forward scan. The fractional dependence of cathodic peak current and potential on stannite ion concentration, at constant OH − ion concentration and a Tafel slope of 60 mV decade −1, suggests the reduction of stannite involves activated adsorption of Sn(OH) obeying the Temkin isotherm with its discharge as a rate-determining step.