Effect of temperature on the ion transfer across an interfaces between two immiscible electrolyte solution. Ion transfer dynamics

The effect of temperature on ion transfer across the water-nitrobenzene interface was studied for a series of six quaternary ammonium and phosphonium cations and two anions using cyclic voltammetry and the faradaic impedance method at the equilibrium potential. Structure-breaking properties of small ions and enhancement of water structure in the presence of larger cations were manifested in both entropic and enthalpic contributions to the standard Gibbs energy of ion transfer. At the phase boundary, the ion is forced to overcome a relatively low potential barrier of about 5 kJ mol-1, but the ion transfer rate is lowered considerably owing to hydrodynamic friction. The hydrodynamic factor of about 10(-4) reflects a drop in ion mobility in the transition state, which in turn makes the translational part of the activation entropy more negative. The stochastic method has provided a consistent theory for experimentally observed effects of interfacial potential difference, standard Gibbs energy of ion transfer (Bronsted correlation). viscosity and temperature.