Abstract
The composition of lead chloride complex ions adsorbed during the underpotential deposition of lead on a polycrystalline gold electrode in 
was studied by X‐ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (TOF-SIMS). Gold electrodes were emersed at 0.3, −0.29, and −0.42 V vs. saturated calomel electrode. Then, either before or after rinsing, the surface concentrations of various species were analyzed using the two vacuum spectroscopic techniques. An adsorbed species with the stoichiometry of 
was present on the polycrystalline gold electrode just before the underpotential deposition (UPD) region at +0.3 V. The ejection of some adsorbed 
and Pb(II) occurred during the UPD Pb discharge process. A mechanism of Pb(II) adsorption and UPD is proposed which is consistent with a parallel electrochemical study. [J. Electrochem. Soc., 146, 2555 (1999)] Strong adsorption of nitrate ions was detected. © 1999 The Electrochemical Society. All rights reserved.