X-ray photoelectron spectroscopic evidence of distinctive underpotential deposition states of Ag and Cu on Pt substrates

The underpotential deposition (u.p.d.) of copper and silver ions on platinum electrodes has been studied using X-ray photoelectron spectroscopy (x.p.s.). A significant chemical shift of the x.p.s. binding energies of the u.p.d. copper and silver atoms relative to bulk copper and silver metal is obtained. Analogous spectral results are obtained for in situ vapor deposition of copper and silver atoms on clean platinum substrates which reveal the metallic nature of the u.p.d. species.