FTIR studies of benzoate adsorption on the Au(111) electrode

Subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) has been used to examine (i) the orientation and coordination of benzoate on the Au(lll) electrode; (ii) the dependence of the IR band intensity on the surface coverage; and (iii) the chemical stability of benzoate at the Au(lll) surface. The results indicate that orientation of adsorbed benzoate changes from a nearly flat co-ordination at a negatively charged surface to a tilted position at positive charge densities. The transition in the orientation of the adsorbed molecule occurs in the vicinity of the potential of zero charge in the solution investigated, The integrated IR band intensities correlate very well with the surface concentration of benzoate obtained from chronocoulometric measurements. An overall agreement between the spectroscopic and electrochemical results is excellent. The spectroscopic data demonstrate that no decomposition or oxidation of benzoate occurred at the Au(lll) electrode surface over the potential range investigated. (C) 1999 Elsevier Science S.A. All rights reserved.