Investigation of the electrochemical processes related to IT coupling with ET by hydrophilic droplet electrodes

The electrochemical processes of ion transfer (IT) at a water/1,2-dichloroethane (W/DCE) interface coupling with electron transfer (ET) at an aqueous solution/Pt interface have been investigated systematically by hydrophilic droplet electrodes with cyclic voltammetry and Osteryoung square wave voltammetry. Here a disk Pt electrode is covered fully with an aqueous droplet containing redox couple of K3Fe(CN)6 and K4Fe(CN)6, and this assembly is immersed into the DCE phase. Based on this simple three-electrode setup, we can observe that the reduction of K3Fe(CN)6 and the oxidation of K4Fe(CN)6 on the Pt electrode are coupled with respective Cl− and K+ transfer processes at the W/DCE interface. The complicated mechanism of coupling processes has been discussed and evaluated by the analysis of several influence factors, such as, concentrations and ratios of redox couple in the aqueous droplet, and phase volume ratios. In addition, the Gibbs energies of different ions transfer at the W/DCE interface have been accurately determined by OSWV with K+ or Cl− as the internal reference ion. This method has also been demonstrated to be a useful tool to detect several ions simultaneously.

► Effects of several factors on IT coupling with ET processes have been studied.
► The complicated mechanism of coupling processes has been discussed and evaluated.
► A simple way of determining Gibbs energies of ion transfer is developed.
► This method can be used to detect ion transfers in a mixed solution simultaneously.