Role of the doping ions for the electrocrystallization of silver on poly(3,4-ethylenedyoxythiophene)-modified electrodes

Тhe aim of the present study is to reveal the role of organic anions-induced characteristics of poly(3,4-ethylenedioxythiophene) (PEDOT) for metal electrocrystallization. PEDOT layers are obtained in the presence of perchlorate ions and one of the two organic anions, polystyrene sulfonate (PSS) or dodecyl sulfate (DDS). Potentiostatic current transients of silver electrodeposition are measured in the course of several consecutive deposition/dissolution experiments on both PEDOT/PSS- and PEDOT/DDS-coated electrodes. It is found that the metal nucleation and growth is markedly influenced by the type of organic ions used, with PEDOT/DDS providing conditions for more intense metal electrodeposition in comparison to PEDOT/PSS. The latter type of layers shows also an effect of deactivation in the course of several consecutive measurements. Experimental current transients obtained in the PEDOT/PSS case are interpreted by means of Scharifker model for multiple nucleation and growth. The seeming deactivation of the PEDOT/PSS layers is considered to occur at the expense of decrease in both number of active sites for nucleation and nucleation rate per active site. These results are commented in terms of the appearance of concentration gradient in the polymer bulk of the more hydrophilic PEDOT/PSS resulting in a lower effective overpotential for electrochemical nucleation and growth than the formally calculated one.