Underpotential metal deposition on gold, monitored in situ with a quartz microbalance

Abstract

The underpotential deposition (UPD) of Pb, Bi, Cu, and Cd has been examined on polycrystalline Au in 0.1 M HClO 4 . The Au film electrode was attached to an oscillating quartz crystal microbalance (QCM) mounted in an electrochemical cell. The coverage of the UPD layer on the Au surface is calculated from the frequency change of the QCM as a function of potential. Coverages are in good agreement with previous estimates obtained using other techniques. The electrosorption valencies (γ) have been calculated from the charge to coverage ratios obtained from the QCM. Values for the four metals, Pb (γ = 2.0), Bi (γ = 2.7), Cu (γ =1.4). and Cd (γ = 1.6 to 2.0), are similar to those previously reported. These experiments indicate that the QCM is a quantitative tool for examining monolayer and sub-monolayer metal deposits.