Adsorption and Instability of ITIES

Mechanical instability of ITIES due to adsorption and chemical desorption of surfactants has been known for many years. For example, Aral et al. studied the instability of the water-octanol interface caused by the adsorption of sodium dodecylsulfate by potentiometry and could relate interfacial polarization and oscillations [79]. The early work has been thoroughly reviewed by Kihara and Maeda [80]. In 2001, Maeda et al. demonstrated that self-sustained oscillations could be studied for a systan comprising cetyltrimethylammonium in water and picric acid in nitrobenzene [81]. 

In 2002, Kakiuchi et al. proposed a thermodynamic theory that showed that, upon coupled adsorption and transfer of surfactants, the electrocapillary curve may have a positive curvature, as opposed to a negative curvature in classical electrocapillary theory. This implies that the double-layer capacitance would be 

FIGURE 1.5 Schematic representation of the potential profiles across the ITIES in the absence (dashed line) and presence (solid line) of specific adsorption of anionic species from the aqueous phase to the interface. (Su, B., N. Eugster, and H. H. Girault, 2005, J Electroanal Chem, Vol. 577, p. 187. Used with permission.) 

More recently, this topic has been revisited by Daikhin and Urbakh [88] who presented a kinetic description of ionic surfactant transfer across an ITIES that includes the charging of the interface, adsorption, and transfer as well as characteristics of the electrical circuit. This model showed that the irregular current oscillations are due to a dynamic instability induced by the interplay between the potential-dependent adsorption and direct transfer across the interface. In particular, this model showed that current anomalies occur in a potential range close to the standard ion-transfer potential. 

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