Electrochemical polarization free energy change

The failure of the free-electron model to reproduce even pronounced effects in ER is demonstrated in Figure 24. Here, the ER spectra for Cu(lll) on mica are shown for 5- and / -polarization at 45° angle of incidence (solid curves). The pronounced peaks in the experimental spectra at 2.2 eV, at the onset of the interband transition in Cu, cannot be reproduced by the free-electron model alone (dashed curves). A satisfactory agreement between theory and experiment—at least for the spectral shape—was, however, achieved when a shift of the interband transition energy with electrode potential of -0.2 eV/V was included in the calculation. Although the absolute value of this potential-induced band structure change in Cu may be somewhat in question, the result certainly indicates that the electrochemical double layer can influence the electronic structure of metal surfaces. 

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