Electrochemical Investigation for Cu²⁺ Oscillatory Phenomena at the Liquid/Liquid Interface with a Specific Adsorption of Ion Pair Model

Abstract

In this paper, a novel current oscillatory phenomenon for Cu2+ at the water/1,2‐dichloroethane interface is reported with cyclic voltammetry and potential‐step chronoamperometry. The small irregular current spikes were only observed near the site of the oxidation peak of CuCl2− and were mainly related to the Cu2+concentration in the aqueous phase. Our experimental results demonstrated that the current oscillation is caused by specific adsorption of ion pairs at the W/DCE interface between Cu2+ in the aqueous phase and TPB− in the organic phase. Therefore, a specific adsorption of ion pair model has been formulated for the current oscillation at the liquid/liquid interface. The DFT calculation method was used to explain the mechanism of ion pair formation. The calculation results suggested that the TPB−Cu2+TPB− ion pair has the lowest‐energy state, thus providing qualitative support for the ion pair model. A probable mechanism for the observed current oscillation was also discussed in this paper. At the same time, a spectrophotometric experiment was performed to evidence a strong attractive interaction between Cu2+ and TPB−.

Galvani Potential-Dependent Single Collision/Fusion Impacts at Liquid/Liquid Interface: Faradic or Capacitive?

“…It showed that rare current spikes could be observed in the chronoamperograms and OCP curve (Figure S7 in the Supporting Information). These experiments were designed to prevent interference arising from the potential generation of ion pairs , and the formation of water clusters, that is, ionosomes, which were formed by the presence of extra hydrophilic ions in the organic phase . It should be emphasized that the ion pairs between Mg 2+ and TB – probably existed during our experimental process.…”