Potentiodynamic electrochemical impedance spectroscopy: Lead underpotential deposition on tellurium

Lead underpotential deposition (upd) on tellurium and the effect of halides (iodide, bromide and chloride) in the upd and the monolayer anodic oxidation have been investigated with potentiodynamic electrochemical impedance spectroscopy (PDEIS). PDEIS gives, with a virtual spectrometer, the ac and dc responses of the electrochemical interface along the trajectory of a potential scan. The built-in analyser decomposes the total response into the constituents related to the elements of the equivalent electric circuit and gives the dependences on the potential of the double layer capacitance C_dl and the parameters of the Faraday impedance. No adsorption capacitance was found in the equivalent circuit of Pb upd on tellurium. Pb upd manifests itself in the increase of the double layer capacitance in the negative scan, additional C _dl increase in the positive scan below the oxidation potential of Pb adatoms and the decrease in C_dl observed during monolayer anodic stripping from the tellurium surface. The most significant halide effect has been found for iodide. Iodide stabilises the monolayer against the anodic oxidation.