In-situ photoacoustic investigation of thallium underpotential deposition on polycrystalline copper electrodes

Abstract

Photoacoustic spectrometry (PAS) was used as an ancillary in-situ technique for the investigation of underpotential deposition (UPD) of thallium on polycrystalline copper. The PAS signal generated by 605 nm radiation was found to increase upon deposition of Tl on Cu. Since underpotential deposition is generally a monolayer event, the limit of detection obtained for this technique was estimated to be 0.05 of a monolayer. The PAS results support the conclusion that the second UPD peak is due to a second discrete monolayer rather than a filling-in of vacant sites in the first monolayer. The use of PAS to study the thallium system at pH 12 confirmed that removal of Cu2O from the electrode surface occurred at a sufficient rate that it did not interfere with the UPD of thallium.