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

We evaluated the electrochemical deposition of Pb(II) onto Fractured Vitreous Carbon (FVC) electrodes from solutions containing very low concentrations of lead in different electrolytes (sulfate or chloride). To examine how the FVC surface state influences the lead deposition efficiency, the electrodes were subjected to different electrochemical pretreatments prior to the actual deposition process. The FVC electrode was used as a representative model of the vitreous carbon (VC) bulk, avoiding the polishing procedure that could change the surface. Electrochemical pretreatment was carried out by cyclic voltammetry in electrolytes containing chloride or nitrate anions and in some cases, ferrocyanide. Before and after the electrochemical pretreatment, the electrode surface morphology was assessed using Atomic Force Microscopy (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 pretreatment of electrodes in chloride or nitrate electrolytic baths consistently reduced the lead deposition efficiency. A detailed analysis, correlating lead deposition efficiencies to surface roughness and fractal dimension of the freshly prepared and electrochemically pretreated FVC electrodes, indicated that the decrease in efficiency corresponded to the change in electrode surface geometry. The greater efficiency of lead deposition observed in the chloride-containing electrolyte was due to the interaction between chloride and deposited lead rather than a chloride interaction with the FVC substrate.