Real-Time Staircase Cyclic Voltammetry Fourier Transform Electrochemical Impedance Spectroscopic Studies on Underpotential Deposition of Lead on Gold

Abstract

We report results of detailed studies on the underpotential deposition of lead (Pb UPD) and effects of specifically adsorbed halide anions on the UPD reaction at polycrystalline gold electrodes employing real-time staircase cyclic voltammetry Fourier transform electrochemical impedance spectroscopy (SCV-FTEIS). Potential shifts observed during the Pb UPD in the presence of halide ions are partially attributed to the chemical interaction of halide ions with Pb2+ as well as the physical obstruction by the preadsorbed halide ions. More importantly, the presorbed halides, oil the top of which Pb2+ ions are adsorbed, form it pseudocapacitor on the gold surface, and its electrical discharge leads to the Ph UPD. Real-time SCV-FTEIS measurements in a chloride solution without Pb2+ reveal that the voltammetric currents arise from charging both the double-layer and pseudocapacitors formed due to the presorption of halide ions at the surface, indicating that the capacitors formed upon adsorption of halide ions oil the electrode surface play a critical role in the Pb UPD.