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

Subtractively normalized interfacial Fourier transform infrared spectroscop y (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 in tensity on the surface coverage; and (iii) the chemical stability of benzoa te at the Au(lll) surface. The results indicate that orientation of adsorbe d 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 p otential of zero charge in the solution investigated, The integrated IR ban d intensities correlate very well with the surface concentration of benzoat e obtained from chronocoulometric measurements. An overall agreement betwee n the spectroscopic and electrochemical results is excellent. The spectrosc opic data demonstrate that no decomposition or oxidation of benzoate occurr ed at the Au(lll) electrode surface over the potential range investigated. (C) 1999 Elsevier Science S.A. All rights reserved.