Determination of the capacitance of the double electric layer at the nitrobenzene water interface by a potentiodynamic methodстатья
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Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
Аннотация:We propose and substantiate a potentiodynamic method to measure the capacitance of the double electric layer at the interface between two immiscible electrolyte solutions when the charge of the layer is accompanied by diffusion-limited ion transfer. This faradeic process was shown to cause polarizability of such interfaces as a result of a near surface ion concentration change when there are hydrophobic ions in organic phase and hydrophilic ions in water. Migration effects were considered and conditions were discussed when they were negligible. A technique was proposed to estimate the probable error in the case of kinetic limitation of charge transfer. The experimental results at zero charge potential within a wide range of concentrations (0.2-100 mM) of tetraphenylborate tetrabutylammonium in nitrobenzene and lithium chloride in water support the validity of theoretical assumptions and conclusions. Ion transfer was shown to be limited by diffusion and inner (chargefree) layer capacitance (approximately 30 PF/cm2) to be independent of concentration. Diffusion-limited current at a concentration of over 20 mM was determined by diffusion of the tetrabutylammonium ion in water. Its distribution coefficient from water to nitrobenzene and standard transfer potential were estimated to be 2.92.10(4) and -261 mV, respectively. More diluted solutions exhibited a-prevalence of concentration-independent diffusion flow.