Charge effects on the behavior of CTAB adsorbed on Au(111) electrodes in aqueous solutions

Abstract

The behavior of adsorbed CTAB on Au(111) electrodes has been studied using electrochemical and FTIR experiments in different aqueous solutions. The results show that the adsorbed layer is stable in acidic solutions in the whole potential range of study. The observed electrochemical and FTIR behavior is compatible with the formation of a membrane of CTA+ on the electrode surface with the polar amino groups in contact with the surface. When the electrode charge is negative, the polar groups are attracted to the surface, so that the capacitance of the electrode is smaller than that recorded for the unmodified Au(111) electrode. As the charge becomes positive, the membrane detaches from the surface and water molecules permeate through it, changing the capacitance of the electrode and giving rise to characteristic peaks in the voltammetric profile. At potentials higher than these peaks, the behavior of the electrode is comparable to that observed for the unmodified electrode. The stability of the membrane is facilitated by the incorporation of anions of the supporting electrolyte. Those anions remain on the membrane even when the electrode is transferred to a different solution, as the electrochemical behavior shows.