A SERS investigation of the electrodeposition of Ag-Au alloys from free-cyanide solutions

In this paper we investigated the electrodeposition of Ag-Au alloys from cyanide baths by in situ surface-enhanced Raman spectroscopy. The spectroelectrochemical investigation is complemented by electrochemical experiments (cyclic voltammetry and potentiostatic electrodeposition) and structural (X-ray diffraction), morphological (scanning electron microscopy) and compositional (energy dispersive spectroscopy) characterisation of the alloys. Electrochemical and spectroelectrochemical results on singlemetal electrodeposition baths of otherwise identical composition are reported for comparison. Single-phase deposits of composition ranging from 13% to 75% Au were obtained potentiostatically. The voltammetric behaviour was correlated to the vibrational characteristics of adsorbed ligands. Quantitative and qualitative differences in interfacial chemistry as a function of applied potential were assessed and explained on the basis of variations in the nature of cyanide-related surface species. The cyanide and metal-adsorbate stretching bands have been analysed. (C) 2003 Elsevier B.V. All rights reserved.