Adsorption and corrosion inhibition behavior of imidazole on cobalt electrodes studied by SERS and electrochemical methods

The interaction of imidazole with Co electrodes in an electrochemical system was studied by surface-enhanced Raman scattering (SERS) and electrochemical methods. The SER spectra of Co in an imidazole solution as a function of the applied potential were analyzed and the assignment of the Raman bands was made. It was found that there were three kinds of surface species on the Co surface in different potential regions and they were interchangeable depending on the potential. In a relatively negative potential region (-1.2 to -0.9 V), imidazole was adsorbed on the surface and its orientation might change from a vertical configuration via the N-end of the pyridine ring to a tilted configuration via the C2=N3 double bond. In a more positive potential region (−0.8 to −0.7 V), the SERS signal from the adsorbed imidazole weakened and finally disappeared, meanwhile the signal from the Co and imidazole complex strengthened gradually. At the open circuit potential (−0.6 V), we detected very strong bands from the Co oxides. By comparing the Tafel curves of the Co electrode in the solution without and with imidazole, we found that imidazole has a marked effect on the corrosion inhibition of the Co electrode. This result demonstrates that we may be able to reveal the complicated interaction of surface species with metal surface at the molecular level by combining the SERS and electrochemical methods.