BEHAVIOR OF PERFLUORINATED SURFACTANTS AT THE ELECTRODE SOLUTION INTERFACE/

The electrochemical behaviors of perfluorinated anionic (FSA and FC-99 ), cationic (FSD), and nonionic (FSN) surfactants at Hg and Pt electro des were studied by using the interfacial capacitance measurement and cyclovoltammogram techniques. Their behaviors were also compared with that of the analogous hydrogenated surfactants. In the potential regio n near the potential of zero charge, both types of surfactants were fo und to be adsorbed at the Hg/solution interface with their hydrophobic segments oriented toward the electrode surface. However, the surface activity of the perfluorinated surfactants is in general weaker and th e saturated adsorption layer is less compact than that of the hydrogen ated surfactants at the weakly charged Hg/solution interface. On a mor e hydrophilic Pt electrode surface and on a strongly charged surface o f Hg, both types of surfactants were found to be adsorbed at the elect rode/solution interface with their hydrophilic end-groups or segments situated at the interface. On the basis of these results, basic princi ples for application of perfluorinated surfactants in electrochemical systems were postulated.