An in situ SERS and FTIRAS study of salicylate interaction with copper electrode

Abstract

The salicylate anion (ortho-hydroxy-benzoate-C6H4OHCOO−) interacts with common metals forming a semi-passivating layer on the surface. This semi-passivating layer allows the application of relatively high positive potentials without significant dissolution of the metal. It enables the electro-synthesis of conducting polymers (e.g. polyaniline, polypyrrole) directly on the metal surface, and such polymeric layers can act as anti-corrosion materials. Notwithstanding this characteristic, the behavior of salicylate on different metal surfaces is not yet well-understood. In the present work, the interaction of salicylate with copper (a metal of great interest in the industry) was studied. For this purpose, in situ surface enhanced raman scattering (SERS) and Fourier transform infrared absorption spectroscopy (FTIRAS) experiments were performed. The results show the formation of a copper(II) salicylate complex in the solution since low potentials (ca. 0 V vs Ag/AgCl). At higher potentials, salicylate decomposition is observed. FTIR spectra show the formation of CO2 in solution, indicating salicylate decarboxilation. The SERS experiments indicate the breakage of the benzenic ring on the surface. It is suggested that at potentials above 0.6 V, a film of insaturated aliphatic chains linked by oxygen atoms is formed on the surface.