Optical spectroscopy of adsorbed intermediates in electrochemical reactions. Part 1.—Surface field effects

Abstract

The optical and electronic properties of Au and Pt electrode surfaces have been investigated by in situ electrochemical modulation spectroscopy (ECMS). The surface field is shown to have a pronounced effect on the dielectric function of the surface layer. A new bias-dependent electroreflectance (ER) theory is developed to account for field-induced plasma resonances, and the use of ER techniques for resolving critical points in the band structure of metals is demonstrated. In ECMS studies of the adsorbed hydrogen layer on Pt, ER effects have been taken into account and it is shown that both strongly- and weakly-bound forms induce a decrease in the reflectance. The broad, intense absorption of these species is attributed to photon-excited electron transitions from resonant bound-state levels to empty Pt conduction-band levels above the Fermi energy.