THEORETICAL INVESTIGATION OF THE ELECTROCHEMICAL DEPOSITION OF METAL INVOLVING ADSORPTION AND DESORPTION STEPS

The objective of this work is the study of a reactional pathway charac teristic of an electrodeposition process with adsorption. It involves five limiting steps. The determination of the impedance expression cor responding to this mechanism leads us to give an electrical equivalent circuit. The expression of the real part of the diffusion impedance c an be negative when there is adsorption of a competitive species at th e electrode. In this case, the shape of the impedance diagram is quite special because the real part of the impedance leads to negative valu es. The experimental diagrams were realized during the reduction of Te (IV) into Te(0). These diagrams were simulated and the good agreement obtained between the experimental and calculated curves confirms the r ate determining steps involved in the reactional pathway proposed.