ADSORPTION OF SURFACTANTS - DIFFERENTIAL CAPACITANCE STUDIES USING PHASE-SENSITIVE ALTERNATING-CURRENT VOLTAMMETRY

The interfacial behavior of cetylpyridinium chloride adsorbed on a hanging mercury drop electrode has been studied using three-dimensional phase sensitive ac voltammetry (3D/AC/V). This methodology, which has recently been developed in our laboratory, possesses a very wide time window that permits a detailed study of adsorption phenomena. It is based on the reconstruction of the differential capacitance (C) versus applied potential (E) curves, sampled after many phase-sensitive ac chronoamperometric experiments. Cetylpyridinium chloride molecules, which aggregate to form a range of association structures in solution, strongly bond onto the electrode surface. They also associate into a variety of surface aggregates on mercury depending on their concentration and the applied potential. A capacitance oscillation appears at a certain potential for a wide range of concentrations.