An interaction of 1,10-phenantroline with the copper electrode in neutral and acidic aqueous solutions: a surface enhanced Raman scattering study

This paper presents the investigations of the Cu electrode/1,10-phenanthroline interface by using surface enhanced Raman scattering (SERS) method. Both neutral and acidic aqueous solutions of I,10-phenanthroline have been studied. In order to characterise the adsorbed film its SERS spectrum was compared with the normal Raman spectra of 1,10-phenanthroline monohydrate and its complex with copper (I) chloride in a solid state. Both frequency values and relative intensities are considerably changed in the SERS spectra in comparison to the Raman spectrum of non-adsorbed molecules. The general pattern of the SERS spectrum is similar to that of the Raman spectrum of the Cu (I)-phenanthroline complex, thus suggesting that the Cu electrode surface is modified by some kind of surface complex. This surface complex was shown to be stable in a wide range of electrode potentials (up to -1.2 V. As evidenced by electrochemical experiments (cyclic voltammetry) the modification of the Cu surface by phenanthroline molecules significantly inhibits the hydrogen evolution at negative potentials. The inhibiting effect is more pronounced in acidic solutions. The appearance of the bands assigned to the out-of-plane vibrations in the surface Raman spectrum suggests that the plane of the adsorbed molecules is tilted from the normal to the metal surface. (C) 2000 Elsevier Science B.V. All rights reserved.