Electrochemical and FTIR studies of 4-cyanopyridine adsorption at the gold(111) vertical bar solution interface

Subtractively normalized interfacial Fourier transform infrared spectroscop y (SNIFTIRS) has been employed to study the adsorption of 4-cyanopyridine ( 4-CNPy) at the Au(111) electrode surface. The vibrational spectra have been used to study the character of surface coordination and the stability of a dsorbed 4-CNPy molecules. Our studies show that 4-CNPy molecules are totall y desorbed from the Au(111) surface at potentials lower than -0.7 V versus SCE and that they adsorb at the gold surface at more positive potentials. A t potentials lower than 0.05 V versus SCE, the adsorption has a non-dissoci ative character. The 4-CNPy molecules are initially oriented flat (pi-bonde d) on the electrode surface and reorient from the flat to a vertical State when the electrode potential approaches 0 V (SCE). When the potential is gr eater than 0.05 V versus SCE, the character of 4-CNPy adsorption becomes di ssociative and the adsorbed molecules partially hydrolyze to form isonicoti namide (INA). The IR spectra acquired at very positive potentials indicate that 4-CNPy is oxidized at E > 0.6 V versus SCE. (C) 1999 Elsevier Science S.A. All rights reserved.