Kinetic analysis of the picrate ion transfer across the interface between two immiscible electrolyte solutions from impedance measurements at the equilibrium potential

Abstract

The kinetics of the picrate ion transfer across the water/nitrobenzene interface was analysed at the equilibrium (Nernst) potential by using a faradaic impedance method with a four-electrode cell system. The potential-dependent apparent ionic rate constant ( K 0 app= 8.3 × 10 −2 cm s −1 at the standard potential E 0 pi(vs. TBA += 0.318 ±0.002 V) and the apparent charge transfer coefficient (α app=0.56) were corrected for the ion distribution in the electrical double layer and the true charge transfer coefficient α t = 0.6±0.1 was determined. The conclusion was drawn that the kinetic measurements at the ITIES, which are based on the application of a small signal exciting the system in the thermodynamic equilibrium, offer more reliable data than measurements involving large potential sweeps or variations.