Potential- and pH-dependent adsorption of aniline on silver as evidenced with surface enhanced Raman spectroscopy

The potential- and pH-dependent adsorption of aniline on silver has been studied using Surface Enhanced Raman Spectroscopy. Different orientations of the adsorbed aniline depending on the composition of the electrolyte solution and the potential of the electrode have been identified based upon occurence and band-shift of characteristic Raman bands corresponding to modes of the adsorbed molecule related to the molecule-electrode interaction. In neutral electrolyte aniline is adsorbed via Ag-N interaction at potentials positive to the potential of zero charge, at potentials negative to the pzc this coordination is changed to a more edge-on one. In acidic solutions the anilinium-cation is adsorbed flat by interaction of the aromatic electron system and the electrode as well as edge-on.