Lead deposition onto fractured vitreous carbon: influence of electrochemical pretreated electrode

We evaluated the electrochemical deposition of Pb(II) onto Fractured Vitreo us Carbon (FVC) electrodes from solutions containing very low concentration s of lead in different electrolytes (sulfate or chloride). To examine how t he FVC surface state influences the lead deposition efficiency, the electro des were subjected to different electrochemical pretreatments prior to the actual deposition process. The FVC electrode was used as a representative m odel of the vitreous carbon (VC) bulk, avoiding the polishing procedure tha t could change the surface. Electrochemical pretreatment was carried out by cyclic voltammetry in electrolytes containing chloride or nitrate anions a nd in some cases: ferrocyanide. Before and after the electrochemical pretre atment, the electrode surface morphology was assessed using Atomic Force Mi croscopy (AFM) imaging. The quantity of lead deposited on the FVC electrode surface (lead deposition efficiency) in each experiment was estimated from the charge under the lead anodic; dissolution peak. Electrochemical pretre atment of electrodes in chloride or nitrate electrolytic baths consistently reduced the lead deposition efficiency. A detailed analysis, correlating l ead deposition efficiencies to surface roughness and fractal dimension of t he freshly prepared and electrochemically pretreated FVC electrodes, indica ted that the decrease in efficiency corresponded to the change in electrode surface geometry. The greater efficiency of lead deposition observed in th e chloride-containing electrolyte was due to the interaction between chlori de and deposited lead rather than a chloride interaction with the FVC subst rate. (C) 2000 Elsevier Science B.V. All rights reserved.