COMPARATIVE STUDY OF DODECANETHIOL SELF-ASSEMBLY ON THE OXIDE-FREE SURFACE OF NI AND CO ELECTRODES UNDER ELECTROCHEMICAL CONTROL

Electrochemical methods in combination with the technique of electrode surface renewal by cutting in dilute aqueous solutions of 0.1 M NaClO4 with the addition of dodecanethiol (DDT) at controlled potential were used in the work. This made it possible not only to overcome the problem of obtaining an oxide-free metal surface but also to carry out in situ investigation of the formation dynamics and properties of the resulting DDT layers by voltammetry and chronoamperometry, and to determine the conditions for the rapid formation of strong insulating nanofilms on nickel and cobalt. The trends in the influence of various factors (the nature of electrode metal, DDT concentration, the presence of oxygen in solution, the addition of ethanol) on the kinetics of formation and blocking properties of DDT nanofilms are established. The processes of adsorption on Co and Ni were determined to be similar, but adsorption on nickel is slower. For instance, at the dodecanethiol concentration of 10-3 mol/L, nanofilm formation on Ni lasts for ~30 min, and on Co for ~10 min. It is shown that the adsorption behaviour of DDT on these metals strongly depends on the concentration of DDT and ethanol in solution and less significantly on the presence of oxygen in the solution. The presence of oxygen in the solution slows down this process and slightly reduces the inhibitory properties of nanofilms. The introduction of ethanol into a DDT-containing solution of sodium perchlorate leads to significant acceleration of the process of dodecanethiol self-assembly on nickel and cobalt in a wide ethanol concentration range. The best insulating properties of monolayers are obtained in water-ethanol solutions with ethanol concentration 40-60 % on DDT/Ni electrodes and 20-50 % on DDT/Co electrodes.